GIFT OF WORKS OF AUSTIN T. BYRNE, C. E., PUBLISHED BY JOHN WILEY & SONS. Inspection of the Materials and Workmanship Employed in Construction. A reference book for the use of inspectors, super- intendents, and others engaged in the construction of public and private works. i2mo, cloth, 555 pp., $3.00. A Treatise' on Highway Construction. Designed as a text-book and work of reference for all who may be engaged in the location, construction, or maintenance of roads, streets, and pavements. Fifth Edition, Revised and En- larged. Svo, cloth, 1067 pp.. $$.co. A TREATISE .; i':.;; : HIGHWAY CONSTRUCTION. DESIGNED AS A TEXT-BOOK AND WORK OF REFERENCE FOR ALL WHO MAY BE ENGAGED IN THE LOCATION, CONSTRUCTION, OE MAINTENANCE OF ROADS, STREETS, AND PAVEMENTS. BY AUSTIN T. BYRNE, C.E. FIFTH REVISED AND ENLARGED EDITION. FIRST THOUSAND. NEW YORK : JOHN WILEY & SONS. LONDON: CHAPMAN & HALL, LIMITED. 1907. ^ \<\*\ COPYRIGHT, 1892, 1900, 1907, BY AUSTIN T. BYRNE. ROBERT DRUMMOND, PRINTER, NEW YORK. PREFACE TO THE FIFTH EDITION, f IN the preparation for its fifth edition Highway Construction has undergone extensive revision; with but few exceptions all the chapters have received substantial additions, and the present edition is larger by about 120 pages than its predecessor. Among the new matter will be found an account of the im- proved methods for testing paving materials, effect of motor vehicles on roads, results of the experiments for the suppression of dust, use of asphaltic oil for the improvement of earth roads, sug- gestions for the construction of roads adapted to modern traffic, statistics of the amount of money invested in street pavements and the per capita cost of maintenance in the principal cities of the United States, and other matter designed to increase the utility and scope of the work. A. T. B. NEW YORK, April, 1907, PREFACE TO THE FOURTH EDITION. PURSUANT to the purpose of the author and the publishers to keep this work abreast of the times, a thorough revision of the Third Edition has been made, minor errors being corrected, obsolete matter expunged, and considerable new matter (some cue hundred and twenty-five pages) added. Among the chapters expanded are those on Stone Pavements, Brick Pavements, Broken-stone Pavements, and Asphaltum and Coal-tar Pavements. Included in the new matter will be found some important tables on asphalt production and manufacture, the comparative cost of laying and maintenance of pavements in various cities of this country and Europe, with other valuable data, and a number of specification forms. NEW YORK, November, 1900. iii 505887 Tl PREFACE. Callanan. Roads and Road-making. Clark. Recent Practice in the Construction of Roads and Streets (London). Cluss. Mortars and Concretes of Antiquity and Modern Times (a paper read before the American Institute of Architects). Codrington. Maintenance of Macadamized Roads. Dobson. Pioneer Engineering. Encyclopaedia Britannica. Engineering and Building Record. Engineering Magazine. Engineering News and American Railway Journal. Gillespie. The Principles and Practice of Road-making. Grillmore. Roads, Streets, and Pavements; Limes, Hydraulic Cements, and Mortars; Strength of the Building Stones in the United States. Good Roads. .Greene. The Construction and Care of Streets (a paper read before the Commonwealth Club of New York); Asphalt and its Uses (a paper read before the American Institute of Mining Engineers); Roads and Road-making (in Harper's Weekly). Harper's Weekly. Haupt. Common Roads, in Reports of the Pennsylvania Board of Agriculture; The Best Arrangement of City Streets, in Franklin Institute Journal; Importance of Good Wagon-roads, in Engineering Magazine; Engineering; Specifications and Contracts. Hay wood. Reports Addressed to the Commissioners of Sewers of the City of London. Henck. Field-book for Railroad Engineers. Herschel.The Science of Road-making. Hughes. The Roads and Walks of Central Park, New York. Hurst. Architectural Surveyor's Handbook. Jenks. Road Legislation for the American State. Journal of the Association of Engineering Societies. Journal of the Franklin Institute. Journal of the Society of Arts. Knight. American Mechanical Dictionary. Kuichling. Cement Mortars for Use in Public Works (Report to the Executive Board of the City of Rochester, New York). Law. The ^irt of Constructing Common Roads. Lippincott's Magazine. Love. Pavements and Roads. McClanahan. Roads and Road -drainage, in Report of the Illinois So- ciety of Engineers and Surveyors. Mahan. Civil Engineering. PREFACE. Vll Manuel de I'lnggnieur des Fonts et Chausse'es. Mathewson. City Streets: How to Build them and Why (a paper read before the Ohio Society of Surveyors and Civil Engineers). Molesworth. Pocketbook of Formulae and Memorandum. Morin. Aide Memoir; Experience sur le Tirage des Voitures. Moseley. Mechanics of Engineering. Nelson. Making and Mending of Country Roads, in Harper's Weekly. Newberry. The Street Pavements of New York,' in School of Mines Quarterly. North. Construction and Maintenance of Roads; Highways and Na- tional Prosperity, in Engineering Magazine. Nystrom. Pocketbook of Mechanics. Paget. Report on the Economy of Road Maintenance and Horse-draft through Steam Road-rolling. Parnell. Treatise on Roads. Paving and Municipal Engineering. Pennell. What I Know about European Roads, in Harper's Weekly. Pope. Improvement of City Streets. Potter. The Common Roads of Europe and America, in the Engineer- ing Magazine; Our Common Roads, in the Century Magazine; The Gospel of Good Roads. Proceedings of the Association of Municipal and Sanitary Engineers and Surveyors. Proceedings of the Institution of Civil Engineers. Rankine. Civil Engineering. Reports of the Engineer Department of the District of Columbia. Reports of the Pennsylvania Board of Agriculture. Reports of the Tenth and Eleventh United States Cens'us. Reports of the United States Geological Survey. Reports of Various City Civil Engineers. Rhawn.A. Plea for Better Roads. Ripley. Improved Roads (an address before the New Jersey State Board of Agriculture). School of Mines Quarterly. Scribner's Magazine. Searles. Field Engineering. Shaler. The Common Roads, in Scribner's Magazine. Shunk. Treatise on Railway Construction and Location for Young Engineers. Smith. Parks and Pleasure Grounds. Speed. The Common Roads of Europe, in Lippincott's Magazine. Spon. Dictionary of Engineering. Stone. \111 PREFACE. The Century Magazine. The Clay Worker. The Manufacturer. The Sanitarian. The Technologist. The Transit. Torrey. Pavement Construction and Economies (an address at the Street-paying Exposition, Indianapolis). Transactions of the American Society of Civil Engineers. Transactions of the Canadian Society of Civil Engineers. Trautwine. Engineer's Pocketbook. United States Consular Reports on the Streets and Highways of For- eign Countries. Vose Manual for Railroad Engineers. WaddelL General Specifications for Highway Bridges. Wellington. The Economic Theory of Railway Location. Wheeler. Repair and Maintenance of Roads. Wilkins. Mountain Roads, etc. Wright. Mechanical Dictionary. Whipple. Microscopy of Drinking-water. Wilkins. Mountain Roads, etc. Wright. Mechanical Dictionary. TABLE OF CONTENTS. CHAPTER I. PAVEMENTS. PAGE Object of pavements The qualities essential to a good pavement The interests affected in the selection of pavements Selection of suitable pavements Cost of wagon transportation Cost of railroad transpor- tation Effect of reducing the cost of wagon transportation Problem involved in the selection of the most suitable pavement Adaptability Desirability Economic desirability of pavements Tractive force re- quired on different pavements Number of horses required to move a given load on different pavements Economy of smoothness Service- ability Comparative safety Observations of Capt. Greene Observa- tions of Col. Haywood Deductions from the observations Condition of the weather and slipperiness Cause of the difference in the observa- tions of Capt. Greene and Col. Haywood Slipperiness, cure for Durability Causes affecting durability Durability of different pave- ments Cost of pavements Cheapest pavement What a good pave- ment should cost Economy and public bodies First cost Relative economies Maintenance Prevailing opinion regarding pavements Cleansing Comparison of pavements with regard to facility for clean- ing Annual cost for service Consequential damages Disadvantages of dirty and noisy pavements Gross cost Traffic census Traffic census in the United States Weights of vehicles Form of traffic census Tonnage Guaranteeing pavements Deferred payments Justifica- tion of contracts for maintenance Destruction of pavements Amount of money wasted in continually opening streets European methods ... 1 CHAPTER II. MATERIALS EMPLOYED IN THE CONSTRUCTION OF PAVEMENTS. Materials employed for paving Physical and chemical qualities Breaking and crushing tests Methods of testing durability Method of testing ix TABLE OF CONTENTS. the comparative value of paving-stones Absorptive power Descrip- tion of materials Granite Syenite Amount and value of granite used for street purposes in the United States Price of paving-blocks Various uses of granite Specific gravity, weight, and resistance to crushing of various granites Manufacture of granite blocks Sandstone "Bluestone" Commercial names of sandstone Analyses of sand- stone Specific gravity, weight, and resistance to crushing Amount and value of sandstone used for street purposes in the United States Amount and value of bluestone used in 1904 Limestone Uses of lime- stone Experience with limestone Specific gravity, weight, and re- sistance to crushing Amount and value of limestone used in 1904 Trap-rock Specific gravity, weight, and resistance to crushing Bitu- men Asphaltum Asphalt Origin Occurrence Distribution No- menclature Composition Refined asphaltum Refining asphaltum Asphaltic cement Flux for asphaltum Liquid asphalt Petroleum re- siduum Examination of Specifications for Asphaltic paving materials Bituminous limestone Manner of using bituminous limestone Analysis of European bituminous rocks Bituminous sandstones Manner of using the sandstone Trinidad asphaltum Characteristics of crude Trinidad Composition of Trinidad asphaltum Refined Trinidad asphaltum Refining Trinidad asphaltum Characteristics of refined Trinidad asphaltum Bermudez asphalt California asphaltum Buena Vista asphalt Asphalt mastic Analysis and tests of asphaltum Penetration tests Analysis of California asphaltum Prices of asphal- tum in 1906 Production and varieties of, in the United States Imports of, to the United States Percentage of the uses of asphaltum Paving-pitch Gas-tar Brick Clay Composition of clay Quality of clay required for paving-brick Manufacture of paving-brick Re- pressed brick Analyses of clay Characteristics of good paving-brick Tests of paving-brick Standard tests adopted by the National Brick Manufacturers' Association Specific gravity, weight, and resistance to crushing Absorptive power of brick Tests of Ohio paving- brick Wood Quality of wood Creosoting Specific gravity, weight, and resistance to crushing Absorptive power of wood Sand Use, price, and weight of Gravel Shingle Chert Specific gravity, weight, and resistance to crushing of various substances 24 CHAPTER III. STONE PAVEMENTS. Early stone pavements Cobblestoie pavement Specifications for Bel- gian-block pavement Specifications for Granite-block pavement Advantages and defects of granite-block pavements Quality of stone TABLE OF CONTENTS. XI PAGE for pavements Size and shape of the blocks Dressing the blocks Manner of laying the blocks Gauging the size of the blocks Founda- tion for the blocks Cushion-coat Joint-filling Bituminous cement Sandstone- block pavements Limestone- block pavements Pavements on steep grades Durability of granite blocks Wear of granite block Cost of maintaining granite- block pavements Method of paying for granite- block pavements Number of blocks to the square yard Cost of construction of granite- block pavements Cost of Belgian- block pavements Cost of sandstone- block pavements Cost of cobblestone pavements Heads of specifications for granite-block pavements 129 CHAPTER IV. WOOD PAVEMENTS. Success of, in Europe Failure of, in America Advantages of Objections to Wood pavements and death-rate Systems of wood pavements Size and form of the blocks Number of blocks per square yard Es- sentials necessary to successful construction Foundation for wood pavements Chief causes of failure Quality of the wood Chemical treatment of the wood Dimensions of the blocks Expansion of wood blocks Width of joints Filling for joints Durability of wood pave- ments Duration and life of wood pavements in European and American cities Wear of wood pavements Cost of wood pavements Cost of maintaining wood pavements Description of various systems of wood paving Heads of specifications for wood-block paving Maintenance of wood pavements by contract Specifications for cedar- block pavements Microbes in wood pavements Cedar- block pavements Karri (Austra- lian) block pavement Creosoted pine blocks Cotton wood and gum blocks Redwood block pavement Jetley's patent creo-resinate blocks Kreodone blocks 156 CHAPTER V. ASPHALTUM AND COAL-TAR PAVEMENTS. Introduction of asphalt Difference between European and American asphalt Advantages of asphalt Defects of asphalt Asphalt pave- ment injured by illuminating-gas Durability of asphalt Wear Cost of construction Extent of asphalt pavements in 1903 Cost of maintenance Foundation Asphalt-cement pavements Composition of Failure of Trinidad-asphalt pavements Composition of, preparation of Memoranda Extracts from reports of city civil engineers Experi- ments with asphalt pavements in various cities Heads of specifications for standard Trinidad-asphaltum pavement Specification for asphal turn Xll TABLE OF CONTENTS. pavements on bituminous base On hydraulic base On surface of old pavements Specifications for asphalt pavement, Washington, D. C., Maintenance of asphalt pavements under contract Bermudez asptyalt European asphalt pavements Bituminous limestone pave- ments in America Coal-tar pavements Coal-tar and asphaltum Vulcanite pavement Advantages and defects of coal-tar or distillate pavements Specifications for coal-tar distillate pavements Asphalt- bldck pavements Advantages and defects Cost of asphalt-block pave- ments American bituminous-rock pavements Specifications for Expansion of asphalt Repairs to asphalt pavements Specifications for the repairs of asphalt pavements For the condition of asphalt pavements at end of guarantee period 195 CHAPTER VI. BRICK PAVEMENTS. Advantages and defects of brick pavements Durability of Size and shape of the bricks Quality of the bricks Foundation for Sand cushion Manner of laying Joint-filling Cost of brick pavements Variety of systems Heads of specifications for brick pavement Extract from paving-brick specifications Rumbling in brick pavements Number of brick and block required per square yard Brick paving for country roads Average price of paving-brick per thousand in 1904 .258 CHAPTER VII. BROKEN-STONE PAVEMENTS. Introduction of broken-stone pavements Methods of Tresaguet, Telford, and Macadam Modern Telford and Macadam pavements Defects of Telford system Defects of Macadam system Advantages of broken- stone pavements Defects common to all broken-stone pavements Essentials requisite to successful construction Erroneous methods of construction Quality of the stone Abrasion and cementation tests of stone Size of the stones Shape of the stones Breaking of the stone Hand- breaking Cost of breaking by hand Amount broken by hand Stone-crushers Cost of operating crushers Amount of stone broken by crushers Dimensions, capacity, etc., of stone-crushers Cost of quarrying and crushing stone Voids in broken stone Weight of broken stone Area covered by a cubic yard of broken stone Thickness of the broken stone The New Jersey and Bridgeport roads Number of cubic yards of broken stone required per mile Spreading the stone Thick- ness of the layers Binding, necessity of, qualities of Injurious effects TABLE OF CONTENTS. Xlli PAGE of large amounts Practice of the French engineers Watering Com- pacting the broken stone, by traffic, by horse- rollers, by steam-rollers Defects of traffic consolidation Advantages of rolling Defects of horse- rollers Introduction of steam-rollers Advantages of steam-rolling Pressure exerted by rollers and by loaded vehicles Defects of wide rollers Objections to picks on steam-rollers Steepest grade on which a steam-roller can be operated Cost of maintaining steam-rollers Amount of rolling Manner of applying the roller Cost of rolling Cost of broken-stone pavements Cost of broken-stone roads in Massa- chusetts Difference in cost of broken-stone pavements in Europe and America Wear of broken-stone pavements Effect of climate 'on broken-stone roads Cost of maintaining broken-stone pavements Specifications of modern broken-stone roads in England Methods of construction adopted in Chicago, in Bridgeport, in St. Louis Heads of specifications for broken-stone pavements 286 CHAPTER VIII. MISCELLANEOUS PAVEMENTS. Gravel, quality of Preparing and laying the gravel Repairing gravel roads Cost of construction Weight of gravel Bituminous macadam Pre- paring and laying Concrete macadam Stone trackways, advantages of Trackways in Italy Cost of stone trackways Jasperite Artificial granite blocks Plank roads Method of construction Life and cost of plank roads Log roads Charcoal Iron Blast-furnace slag Chert Florida clay Tar-macadam Artificial stone Hydraulic cement Clinkers Glass Novaculite Destructor concrete Cork Copper-slag Steel trackways India rubber Artificial paving-stones Asphaltina Asphalt-granite pavement ..,.. 349 CHAPTER IX. FOUNDATIONS. Necessity of foundations Essentials necessary to the forming of stable foun- dations Influence of the character of the soil Defects of sand and plank foundations Blast-furnace slag as a foundation-material Con- crete, advantages of Thickness of the concrete Quality of the concrete Strength of the concrete Specific gravity of concrete Proportions Determination of voids in the broken stone Voids in sand Quantity of water, some of the usual proportions Mixing, laying, and ramming the concrete Transverse strength of concrete Compressive strength of con- crete Cost of concrete Proportions for Portland -cement concrete Limes, characteristics of Cements, natural and artificial Tests of ce- XIV TABLE OF CONTENTS. PAE merit Characteristics of Portland cement Testing cement Composi- tion of mortar Quality and quantity of sand Quantity of water Strength of mortar Effect of frost on mortar Weight of cement Specifications for concrete Specifications for the preparation of the roadbed Foundation employed in Liverpool 38 & CHAPTER X. RESISTANCE TO TRACTION. Conditions causing resistance to traction Want of uniformity of the surface Resistance of penetration Rolling resistance of wheels Experiments of M. Dupuit Friction Resistance to traction on different road-surfaces Experiments of MM. Dupuit and Morin Gravity Tractive power of horses and gradients Work done by a horse Loss of tractive power on inclines Effect of inclines on the load a horse can draw Steep grades objectionable Equivalent length of inclined and level roads Character of vehicles Width of tires Size of wheels Effect of wheels Wheel diameters 430 CHAPTER XL LOCATION OF COUNTRY ROADS. Considerations governing location Principles governing location Econ- omy of motive power Selection of best route Reconnoissance, object of Points to be attended to in making reconnoissance Configuration of the country Ridges and passes Watercourses and valleys Streams give the direction of the high ground Preliminary survey Data to be obtained on preliminary surveys Topography Map Memoir Levels Cross-levels Profile Bridge sites Principles to be observed in mak- ing final selection Examples of cases to be treated Intermediate towns Mountain roads Method of surveying mountain roads Loss of height Water on mountain roads Halting-places Alignment Curves, kind of Reduction of grade on curves Increasing wheelway on curves Excessive crookedness to be avoided Curving roads, advantages of Zigzags, objections to Final location Construction profile Gradient, definition of Determination of gradients Angle of repose, to ascertain Tractive power required in descending inclines Men and animals as- cending steep slopes Maximum grade and traffic Maximum grade to be adopted Maximum suitable for various pavements Maximum adopted by Telford Maximum adopted by the French engineers Smooth and rough surfaced inclines Determination of maximum grade To determine the most advantageous grade Cost of grades Grade of mountain roads Minimum grade Minimum grade adopted by the French engineers Undulating grades Level stretches, objections to TABLE OF CONTENTS. XY PAGB Vertical curves, application of Different methods of designating the same grades ........ 453 CHAPTER XII. WIDTH AND TRANSVERSE CONTOUR. Width of roadways Minimum width Advantage of wide roads Width of land appropriated for road purposes in various localities Width of mountain roads Number of acres required per mile for different widths Transverse contour, object of Amount of rise required for different pavements Form of transverse contour Form for streets Form for country roads Excessive rise, evils of Straight sides objectionable Concave form not desirable Contour on hillside roads 485 CHAPTER XIII. EARTHWORK. Earthwork, definition of Equalizing earthwork Transverse balancing Borrow-pits Spoil-banks Staking out of borrow-pits Shrinkage of earth Increase of rock Settlement of embankments Failure of earth- work Stability of earthwork Angle of repose of earths Angle of slopes Effect of moisture on earth Angle of slopes in rock, excavation Form of side slopes Protection of side slopes Slips Catch- water ditches Drainage of side slopes Embankments, best materials for Manner of forming embankments Slopes of embankments Drainage of embank- ments Embankments over plains Embankments across marshes Description of an embankment formed by Mr. G. Waite, C.E. Em- bankments across bogs Embankments on hillsides Roadways on rock slopes Rock excavation Blasting Quantity of rock loosened Line of least resistance Quantity of powder required Cost of excavating rock Haul Cost of earthwork Loosening earth Transport of earth Limits to which shovels, wheelbarrows, carts, scrapers, and dump- wagons may be employed Loosening and transporting by machinery Calculating amount of earthwork Calculation of half- widths and areas Examples of cross-sections of earthwork Calculation of sectional areas Formulae for the calculation of areas Table of cubic contents 491 CHAPTER XIV. DRAINAGE AND CULVERTS. Drainage, object and necessity of Methods employed for securing drainage Division of natural soils Mitre-drains Tile-drains Silt- basins Pro- tection of drain-outlets Cost of drains Fall of drains Side ditches XVI TABLE OF CONTENTS. PAGE Springs, treatment of Drainage of the surface Protection of gutters Water-breaks objectionable Catch-water ditches Culverts Area of waterway Rainfall Determination of area of waterway Catch-pools Materials for culverts Cement and earthenware pipes, dimensions and cost of Iron pipe-culverts, dimensions and cost of Box-culverts Arch-culverts Thickness of arch Thickness of abutments Dimensions and cost of drain-tile Discharging capacity of circular pipes 525 CHAPTER XV. BRIDGES, RETAINING-WALLS, PROTECTION WORKS, TUNNELS, FENCING. Bridges, importance of Care in their construction The loads for which bridges should be proportioned Materials for bridges Wood Types of timber bridges Diagrams and dimensions of timber bridges Sub- structure of bridges Retaining-walls Proportions of retaining-walls Form of retaining-walls Dry-stone retaining-walls Foundation of re- taining-walls How retaining-walls fail Coping for retaining-walls Weep-holes Formulae for calculating the thickness of retaining-walls Surcharged walls Least thickness of retaining-walls Where retaining- walls should be built Protection of roads Parapets, dimensions of Earth mounds Wooden railings afford no protection Guard-stones Roads along the seashore, margin of rivers and lakes Bulkheads and masonry walls Tunnels Fences Cost of fencing 550 CHAPTER XVI. CITY STREETS. Laying out of streets Best arrangement of streets Width of streets Street grades Grade at street-intersections Accommodation summits Transverse grade Transverse contour Sub-foundation drainage of streets Surface drainage of streets Gutters Catch-basins Street lines and monuments Street profiles Increasing the width of the car- riageway at street corners 568 CHAPTER XVII. FOOTPATHS, CURBS, GUTTERS. Footpaths, definition of Qualities required Width Cross-slope Founda- tion Surface requirements Materials employed for footpaths Stone, manner of dressing Specifications for flagstones Wood Asphalt Proportions and materials employed in Paris Number of square yards that a ton of prepared asphalt will lay Life of asphalt footways TABLE OF CONTENTS. XV11 PAGE Specifications for asphalt footway pavements Brick Specifications for brick walls Artificial stone, varieties of Formation of artificial stone Wear of artificial stone Specifications for concrete footwalks Specifications for artificial-stone footwalks Tar concrete Specifica- tions for tar-concrete footpaths Gravel, manner of constructing The Central Park walks Drainage of gravel walks General directions for the construction of gravel walks Curbstones Setting curb Specifi- cations for granite curb Specifications for bluestone curb Specifica- tions for setting curb Specifications for artificial-stone curb and gut- ter Specifications for dressing old curb Specifications for resetting curb Hollow curbs Gutters Specifications for cobble gutters Specifications for brick gutters Specifications for gutter-stones Crossing or bridge-stones Specifications for bridge-stones Specifica- tions for relaying bridge-stones Prices 595 CHAPTER XVIII. RECONSTRUCTION AND IMPROVEMENT OF COUNTRY ROADS. Rectification of alignment and grades Drainage Improvement of the sur- face Improving clay roads Improving sand roads Scraping or road machines, manner of using Cost of constructing earth roads Cost of maintaining earth roads Value of improvements, how to ascertain Data required Defects of existing roads Profit of eliminating unnec- essary grades Profit of eliminating unnecessary length Profit of im- proving the surface Annual loss occasioned by bad roads Improving with crude-oil 646 CHAPTER XIX. MAINTENANCE. REPAIRING; CLEANSING; AND WATERING. Maintenance, definition of Necessity of What good maintenance com- prises System of maintenance Maintenance of country roads Direc- tions for maintaining macadamized highways Errors commonly com- mitted in the maintenance of broken-stone roads Amount o f . water required Cost of maintenance Repair Organization of road force Instructions to roadmen System of highway maintenance adopted in France Street cleansing Intervals at which it is performed Objec- tions to dusty streets Dirt-producing causes Composition of street dust Amount of refuse collected from city streets Amount of dirt produced by different pavements Methods employed for cleansing Systems of executing the work Cost of cleansing Methods of cleansing employed in Berlin, Paris, London, Baltimore, Boston, and other Ameri- can cities Street orderly system Cost of street sweeping Amount of XV111 TABLE OF CONTENTS. PAGE surface swept by one man Amount of surface swept by a machine broom Cost of operating mechanical sweepers Brooms Carts and wagons Disposal of street dirt Removal of snow Methods employed System adopted in Milan Disposal of snow Weight of snow Street washing Street sprinkling Systems employed Quantity of water required Cost of sprinkling Sea-water for street sprinkling sanding pavements. 657 CHAPTER XX. TREES. Opinions regarding the planting of trees on roads and streets Trees on the French and Belgian roads Financial value of trees Fruit-trees in Saxony Selection of trees Qualities necessary to good road-trees Distance apart to plant trees Trees at street-intersections Protection of trees 727 CHAPTER XXI. STAKING OUT THE WORK. Object of Distance apart of stakes Straight lines and curves Side slopes Setting out culverts Length of culverts Setting out bridges Drains, setting out Setting out vertical curves Staking out transverse contour of street pavements Setting stakes for curb Setting stakes for any structure Fixing lines upon water Bench marks 732 CHAPTER XXII. SPECIFICATIONS AND CONTRACTS. Specifications, contents of Tests of materials Contracts General speci- fications for clearing Close cutting Grubbing Grading Formation of embankments Earth- work, measurement and classification Drains Catch-water ditches Off-take ditches Rip-rap Retaining, breast, slope, and parapet walls Culverts Masonry, classification of Arch- culvert masonry Centring Laying masonry in freezing weather Pointing Grouting Brick masonry Dry walls Dry box-culverts Pipe culverts Cement Cement tests Sand Mortar Concrete Foun- dation excavation Artificial foundations Timber Piles Cofferdams Wrought iron Cast iron General stipulations applicable to all con- tracts Interpretation of specifications Omissions in specifications Engineer defined Contractor defined Notice to contractor, how served Preservation of engineer's marks and stakes Dismissal of incompetent persons Spirituous liquors Quality of materials Samples Deviations from plans and specifications Right reserved to alter details Inspectors TABLE OF CONTENTS. XIX PAGE Defective work Measurement of work Excavation Overhaul Ma- sonry Timber Piles Culverts and drain-pipe Stone, brick, and pole drains Concrete Curbing Gutters Crossing or bridge -stones Catch- basins Bridges Pavements Partial payments Commencement of work Time of completion Progress of work Forfeiture of contract Damages for non-completion Evidence of payment of claims Protec- tion of persons and property Bond for faithful performance of work Power to suspend work Loss and damage Miscellaneous work Clean- ing up Personal attention of contractor Contract not to be assigned Payment of workmen Prices Payments, when made Heads of speci- fications for a highway Specifications for a bulkhead Heads of specifica- tions for grading, macadamizing, curbing, and flagging Specifications for the supply of broken stone Indemnification for patent claims In- demnity bond Right to construct sewers Old materials, disposal of Security retained for repairs Alteration of manhole covers, stopcock boxes, etc. Heads of specifications for repaving Specifications for street cleansing Instructions to bidders Form of proposal Form of agree- ment Form of bond Specifications for team labor Specifications for sprinkling Form of monthly certificate Affidavit of contractor Cer- tificate of final acceptance 739 CHAPTER XXIII. IMPLEMENTS AND PRICES. Description and prices Tools for clearing Tools for grading Mechanical graders Tools for draining Tools for rock excavation Hand-drills Steam-drills Tools for macadamizing Stone-crushers Sprinkling- carts Horse-rollers Steam-rollers Tools employed in the mainte- nance of macadam roads Tools employed for block pavements Con- crete-mixing machines Tools employed for asphalt pavements Tools used for cleansing pavements Mechanical sweepers Street patrol hand- cart Sprinkling- carts Snow- shovels and ploughs Tools employed for artificial stone pavements Catch -basins Sewer-inlets and gutter- crossings Street name-plates Direction indicators The viagraph. . . . 802 CHAPTER XXIV. MISCELLANEOUS NOTES. Comparison of European and American methods and prices Statistics of roads *in the United States Average weight of load -for horses Average cost of haulage per Ion per mile Average length of haul XX TABLE OF CONTENTS. PAGE from farms to market Average total cost per ton for the whole length of haul Pavements and horseshoes Annual cost of structures Interest and sinking-fund tables Sprinkling oil on roads Sinking funds Annual cost of pavements Relative economy of materials Suppression of dust Temperature of pavements Effect of heat on pavements State aid to road construction Roads adapted to modern traffic Statistics of the extent of pavements and cost of maintenance. . 899 APPENDIX I. Naming and Numbering Country Roads and Houses. . . . 930 APPENDIX II. Methods of Assessing the Cost of Street Paving 940 APPENDIX III. Ordinance Regulating the Width of Wagon- tires 943 APPENDIX IV. Cycle-paths 945 INDEX.. . 946 LIST OF TABLES. 1. Cost of wagon transportation on different road-surfaces 3 2. Tractive force required upon level roads of different materials 6 3. Comparison of gross cost of pavements 18 4. Comparative rank of pavements 21 5. Composition of granite rocks 31 6. Specific gravity, weight, and resistance to crushing of granites 31 7. Production and value of granite in the United States for street uses . . 32 8. Analyses of sandstones 36 9. Specific gravity, weight, and resistance to crushing of sandstones 37 10. Production and value of sandstone in the United States for street uses. . 38 11. Production and value of bluestone used for street purposes in the United States 38 12. Specific gravity, weight, and resistance to crushing of limestones 40 13. Production and value of limestone used for street purposes in the United States 40 14. Specific gravity, weight, and resistance to crushing of trap-rocks 41 14,. Value of trap-rock used for road purposes. . . .^ 42 14 V . Absorptive power of stones 48 14^. Resistance to abrasion of paving materials 52 14 4 . Resistance to abrasion and impact ,...'. 55 14-. Cementing and recementing value of rocks 60 14a. Composition of asphalt 66 15. Analyses of European bituminous rocks 76 16. Composition of Trinidad asphalt 79 16a. Comparison of Cuban and Bermudez asphalts 87 17. Prices of asphaltum 101 18. Production of asphaltum in the United States 102 18a. Varieties of asphaltum, etc., produced in the United States 102 19. Imports of asphaltum 103 20. Analyses of clay 110 21. Tests of paving-brick 115 21a. Tests of Ohio paving-brick. 116-119 xxi XXli LIST OF TABLES. 22. Absorptive power of wood 121 23. Specific gravity, weight, and resistance to crushing of wood 122 24. Specific gravity, weight, and resistance to crushing of various sub- stances 127 24a. Size of paving-blocks used in different cities 137 25. Wear and duration of granite pavements in London 146 26. Number of granite blocks to the square yard 149 27. Extent of stone-block in various cities in the United States in 1903 150 28. Extent and cost of Belgian-block in the United States in 1890 151 29. Extent and cost of sandstone- block in the United States in 1890 151 30. Extent of cobblestone pavement in the United States in 1903 152 31. Duration and cost of wood pavements in London 169 32. Wear of wood pavements 171 33. Extent and cost of wood pavements in various localities 173 34. First cost and cost of maintaining wood pavements in London 1 74 35. Extent and cost of asphalt pavements in various cities 207-209 35a. Cost of maintaining asphalt pavements 211 36. Cost of asphalt- block pavements in various cities 248 37. Cost of brick pavements 269 38. Coefficients of quality of stones 301 39. Cost of quarrying and crushing stone 309 40. Number of cubic yards of broken stone required per mile of road 313 41. Cost of broken-stone roads 328 42. Cost of broken-stone pavements in various cities 329 42a. Loss of stone on Massachusetts highways 338 43. Cost of gravel pavements 351 44. Amount of water absorbed by Portland cement 400 45. Adhesive strength of mortars '. 409 46. Shearing strength of mortars 410 47. Tensile strength of mortars 411 48. Effect of size of grain of sand on tensile strength of mortar 414 49. Character of sieves for sifting sand 414 50. Resistance to traction on different road-surfaces 437 51. Tractive force on a level 439 52. Resistance of gravity on different grades 439 53. Tractive power of horses at different velocities 442 54. Duration of a horse's daily labor and maximum velocity unloaded 442 55. Increase in tractive power 442 56. Maximum amount of labor a horse is capable of performing at different velocities 443 57. Gross load which a horse can draw on different grades 444 58. Effect of grades upon the loads a horse can draw on different pave- ments 445 59. Force required to draw loaded vehicles on inclirles and equivalent level roads. . . 447 LIST OF TABLES. XX111 NUMBER PAGE 60. Best width of wheel-tires 448 61. Coefficient of resistance for different pavements 474 62. Methods of designating grades 480 63. Number of acres required per mile for different widths of roadways .... 487 64. Amount of transverse rise for different pavements 488 65. Natural slopes of earth 495 66. Lengths and angles of slopes. ; 495 67. Amount of powder required 512 C8. Capacity of drill-holes 512 69. Coefficient for different earth-slopes 521 70. Earthwork table 523 71. Cost and weight of vitrified culvert-pipe 541 72. Cost and weight of Portland -cement pipe 541 73. Dimensions, weight, and prices of iron pipe 542 74. Dimensions of box-culverts 544 75. Thickness of arches 546 76. Thickness of abutments 548 77. Dimensions, weight, and prices of drain- tile 549 78. Discharging capacity of circular pipes 549 79. 80. Span and dimensions of bridges 554, 555 81. Coefficients for thickness of retaining-walls 560 82. Width, maximum grade, and average width of sidewalks in several cities. 576 83. Street statistics of various cities 594 84. Number of square yards that one ton of prepared rock asphalt will lay. . 598 85. Composition of dirt from paved streets 696 86. Amount of refuse collected from city streets 697 87. Average cost per capita for street maintenance in various cities 700 88. Wages in European countries 8^)9 89. The amount of one dollar at compound interest for a term of years 915 90. The annual sinking-fund that with compound interest will amount to one dollar at the end of a term of years 918 91. Extent and cost of pavements in 175 cities of the United States 928 92. Cost of street maintenance in cities having a population of over 30,000. . 929 LIST OF ILLUSTRATIONS. riOURE PAGE A. Dorrey abrasion machine 49 B. Maryland Geological Survey machine for testing abrasion 50 C. Deval abrasion machine 53 D. Page impact machine 56 E. Briquette machine 5", F. Page impact machine 58 G. Rattler for testing brick 112 1. Roman pavements . 130 2. Cobblestone pavements 130 3. Belgium-block pavement 130 4. Early granite-block pavements 130 5-7. Improved granite-block pavement 133 la. Street-intersection paved with granite blocks 136 8. Cobblestones on steep grades . . 144 9, 10. Granite block on steep grades 144 12. Section showing joint-filling 160 13. Plan of street paved with wood blocks 160 13a. Pavement of round blocks 161 14. 15, 15a, 15&. Sections of asphalt pavements 196, 197 15c, 15d. Asphalt with brick gutter 201 15e. Diagram for showing location of asphalt repairs 256 16, 17. Hale brick pavement 259 18. Section of brick pavement on concrete 259 19. Plan showing arrangement at junction 259 19a. Plan of brick paving at street intersections 264 196 Cross-section macadam road with brick trackway ' 284 19c. Cross-section brick trackway underdrained ' 284 20. Broken-stone pavements in France previous to 1775 287 21. Tresaguet's system 287 22. Telford's system 287 23. Macadam's system 287 24. Shape of stone for broken-stone pavements 306 25-28. Type sections of broken-stone pavements 346 xxv XXVI LIST OF ILLUSTRATIONS. FIGURE PAGE 29-32. Stone trackways 354-355 32a. Cross-section of steel trackway 373 32&, 32c. Steel rail for trackways 374 32d. Trackway on Murray Street, New York City 375 32e. Gibbon patent trackway 376 33. Form of briquette for testing tensile strength of cement 405 34. Clamps for holding briquette 405 35. Cement- testing machine 405 36. Diagram, resolution of forces in overcoming obstacles on roads 430 37-39. Diagrams illustrating resistance of penetration 432-433 40. Resolution of the force of gravity on inclined planes 440 41. Mechanical advantage of wheels 451 42. Contour map 457 43. Map of preliminary surveys 458 44. Preliminary profile 458 45. Diagram road between two distant towns . 463 46. Simple curve . 466 47. Compound curve 466 48. Reverse curve 466 49. Double reverse curve 466 49a. Widening wheelway on curves 467 50. Construction profile 471 51-53. Application of vertical curves 485 53a, 536. Location of roads on inclined strata 483 54. Transverse contour of streets 489 55. Transverse contour for country roads 489 56. Hillside road showing stepping of slopes and retaining- walls 498 57. Formation of embankments by end dumping 500 58. ' ' layers 501 59. Usual method of forming embankments .' 502 60. Embankments over plains 503 61. 62. Embankments on hillsides, manner of stepping the slope 507 63-65. Embankments of rock-slopes 508, 509, 510 66-68. Formation of a road in the face of a cliff 510 69. Profile of cut and fill illustrating calculation of overhaul 516 70-76. Examples of earthwork cross-sections 519 77. Examples of profile and cross-sections of earthwork 522 78. Cross-section of blind drain 528 79. ' ' pole drain 528 80. ' ' stone drain 528 81. * ' tile drain 528 82. Protection of drain-outlet 528 83. 84. Silt-basins 528 85-89. Examples of the drainage of country highways 531 90. Section of country highway 533 LIST OF ILLUSTRATIONS. XXV11 FIGURE PAOB 91. Drainage of road in embankment 533 92. " " suburban streets 533 93-96. Head-walls for pipe-culverts 538 96a. Wing abutment for single pipe-culvert 539 966. Head-wall for double pipe-culvert 539 96c. Head-wall for triple pipe-culvert 540 96d. Section of pipe-culvert 540 97-101. Examples of box-culverts 543 102-108. Examples of arch-culverts 545, 547 109-124. Types of timber bridges 552 125-132. Simple timber bridge 554, 555, 556 133-136. Examples of retaining- walls 557 137-139. " road construction along the seashore or margin of rivers 1 562, 663 140. Examples of mound and ditch fence 564 141, 142. Arrangement of city streets 570, 571, 573 143, 144. ' ' street-intersections 577, 578 145. Crowns in street gutters 580 146_148. Arrangement of streets with opposite sides at different levels. .580, 581 149. Sub- foundation drainage of streets _ 582 150-153. Examples of catch-basins 583, 584 153a. Examples of sewer inlet 587 1536. Sewer inlet without basin 588 154, 155. Surface-drainage at street-intersection 589 156. Objectionable form of water-way at street crossings 589 157. Street monument 590 158. 159. Example of widening carriageway at street-intersections 592 160. Improper method of dressing flag- and bridge-stones 597 161 . Drainage of park walks 622 162-166. Fire-clay curb 634 167. Iron curb 634 168. Granite curb, Washington, D. C 636 169. Bluestone curb 636 170. 171. Hollow curb 638 172. Arrangement of gutter-stones 639 173-176. Examples of crossings and gutters 642, 643 177. Tree-protection 731 178. Setting slope-stakes 733 179. ' ' out culverts on horizontal ground 734 180. 181. Setting out culverts on sloping ground 734 182. Setting out vertical curves 736 183. ' ' stakes for street contours 737 184. " " " curb : 737 185. " " " any structure 738 186. Bush-hooks . . .802 XXV1U LIST OF ILLUSTRATIONS. FIGURE PAGiiJ 187. Axe mattock 802 188. Pick mattock 802 189. Grading-pick 803 190. Clay-pick 803 19.1. Shovels 803 192. Grading-plough 804 193. Hardpan-plough 804 194. 195. Drag-scraper r 805 196. Pole-scraper 806 197-199. Wheeled scraper 807 200-202. Wheelbarrows 808 203. Earth-cart 809 204, 205. Dump-cars 810, 811 206, 207. Dump- wagon 813, 814 208-210. Mechanical graders or road machines 815-817 211, 212. New Era grader 818 213. Surface-grader 819 214. Road-leveller 820 214a. King log-drag 820 215. Draining-tools 821 216. Hand-drilling tools 823 217. Steam-drill 825 218. Portable boiler 827 219. Straight-edge 828 220. Roadbed-roller 829 221. Sprinkling-cart 829 222-223. Stone-crushers 834 224. The Gates crusher, exterior view 835 225. " " " sectional view 835 226. The Farrel crusher, sectional view 836 227. The Champion crusher, sectional view 836 228. Climax crusher, sectional view 837 229. The Western crusher, sectional view 837 230. The Austin crusher, sectional view 838 231. The Blake crusher, sectional view 838 232. The Reliance steel stone-crusher, mounted on skids 839 233. Portable crushing plant 839 234. Stone-screen : 840 235. 236. Engines and boilers 841, 842 237-241. Stone-crushing plants 843-845 242. Stone-distributing cart 846 243-246. Horse-rollers 846-848 247-251. Steam-rollers 851-854 251a. Scarifier ! 855' 2516. Motor roller 856 LIST OF ILLUSTRATIONS. XXIX FIGURE PAGE 2o i c. Tamping roller 856 252-254. Paving-haramers 856 255-259. Paving-rammers 857 260. Asphalt melting tank 858 261. Sand-dryer 859 262. Portable asphalt- plant 860 263. Asphalt-mixing machine 861 264. Asphalt-cutters 861 264. Asphalt-rakes 861 264. Asphalt rammers 861 264. Asphalt smoothing-iron 861 265. Portable fire-box 862 :266. Fire- pot roller 863 266a. Asphalt hand-roller 863 2666, 266c. Steam-rollers for asphalt 864 267. Surface-heater for asphalt .866 268. 268a. Portable heater for asphalt 867 2686. Hooke's asphalt- heater 868 269. Asphalt gutter- painters 868a 569a. Asphalt pouring-pots 8686 270-271. Concrete-mixing machines 869-870 272-276. Sweeping-machines 870-873 277. Scraping-machine 874 278-280. Patrol-cart 875, 876 281. Hand-scoop 876 282. Hand-sweeper 877 282a. Pick-up sweeper 877 283. 283a. Dump-carts 879 284-286. Combined sweeping- and collecting-machines 879-881 287, 2886. Street-sprinklers 882, 884 289, 290. Snow-ploughs 886 291-297. Tools for artificial stone pavements 887 298. Iron catch-basin 888 ~299-300. -Gutter-gratings 889 301. Sewer inlet-trap 890 302, 303. Inlet for broken-stone roads 890 304, 305. Gutter crossing 891 306. Gutter boxes 892 306a. Direction indicators , 895 307. The viagraph 896 308. Widening wheelway on roads 925 309. Inclination of wheelway on curves 925 INTRODUCTION. HISTORICAL SKETCH. ROADS are pathways formed through a country to facilitate the movement of persons and exchange of commodities. They are of various kinds, according to the state of civilization and wealth of the country traversed; thus, they range from rude paths, passable only by pedestrians, to the comparatively perfect modern road, passable alike by persons and vehicles. The motive for the formation of roads is found (1) in the in- quisitive spirit of man, and his desire for intercourse with his fel- lows ; (2) in the necessity of obtaining provisions for his sustenance in times of scarcity; and (3) in the desire to gratify his fancies with the products of other localities. With the progress of civilization and the congregation of men in cities and towns their wants multiply, and the products of the earth have to be collected and transported to supply them. Th?> collecting, transporting, and exchanging of products is trade or commerce, and its importance and expansion are directly propor- tional to the facilities afforded. Countries inhabited by the least civilized people whose wants are supplied by nature in the immediate vicinity of their dwellings are almost destitute of roads; hence it has come to be said that roads are the physical symbol by which to measure the progress of any age or people. " If the community is stagnant, the condition of the roads will indicate the fact ; if they have no roads, they are Although roads are the offspring of civilization, they have be- ixxi XXX11 HIGHWAY CONSTRUCTION, come the chief factors, if not indeed the means, for its advancement. Without them the invention of printing and other arts so beneficial to the welfare of men would separately be ineffectual, or productive of advantages of a very limited extent. Without roads, the inter- change of advantages, moral, intellectual, and physical, which now takes place in all highly civilized countries between the rural and urban population, could not be maintained; without them, indeed, large towns or cities could not continue to exist. The supply of the population collected in such places, with the various products of agriculture necessary to their physical existence, could not be sustained. Nor, on the other hand, would the rural population affording that supply be benefited by a return in exchange of the refinements of the town, and the various articles of luxury and necessity obtained by commerce from every part of the globe. It is frequently asserted that, since the introduction and de- velopment of railroads, the latter have assumed to a greater and greater degree the functions of the common road, and that high- ways are no longer an indication of progress. This is true to only a limited extent. Eailroads have changed the character of the traffic on the common roads, and personal travel for business or pleasure is no longer dependent upon the condition of the high- ways; but commercial intercourse as represented in the exchange of products is as much dependent upon the condition of the public road to-day as it ever was, for the reason that it is impossible to construct a railroad to the door of each producer and consumer. Hence railroads never can supersede the common road, and every ton of freight carried by them must be conveyed over a highway /at either or both terminals, and the cost of this highway transpor- tation has a marked influence not alone upon the price paid by the consumer, but also on the profit realized by the producer. If railroads may be compared to the arteries of a living body, then the common roads are the veins, and each is equally neces- ., ary in quickening and communicating life to the parts to which -, they lead. But the true relation between railroads and wagon-roads frequently seems to be lost sight of; the functions of each are quite different and in no sense rivals. The highway serves the very important purpose of effecting local intercourse and of connect- ing the local freight and passenger traffic with the railroad service. .Roads running parallel to the railroad and connecting towns al- HISTORICAL SKETCH. XXXul ready joined by t'he railroad are of but little importance, It is the roads running at an angle with the railroad and connecting it with the country to the right and left, thus acting as feeders, that re- quire attention in modern times. In Baden, Germany, this rela- tion of the roads to the railroads was early recognized by striking from the list of state roads all those that ran parallel to the rail- road or had lost their importance by its construction, in order to save funds for the support of the others; while most of those run- ning across the railroad, if they crossed at a station so that they served as feeders, were raised to the grade of state roads. The word " road " is derived from the Anglo-Saxon rad, a riding, and ridan, to ride, and as generally used it means a public high- way, although, as a generic term, it is applied to any kind of a path open to travel. The word " highway " is probably the more correct term when applied to a traveled thoroughfare, but custom has established the propriety of using the word " road." The word "highway" is used several times in the Old Testa- ment, while the word "road " is used but once. As to when paved roads were first introduced little is known;, we find here and there in the works of the ancient historians occa- sional mention of road construction. Herodotus speaks of a great Egyptian road, constructed under King Cheops, upon which 100,000 men were employed for ten years. Strabo informs us that the city of Babylon was paved about the year 2000 B.C., and that three great highways ran from there to Suza, Ecbatana, and Sardes. The highway leading from Babylon to Memphis was paved at an early date, and along it arose the cities of Nineveh, Palmyra, Damascus, Tyre, Antioch, and other great commercial cities. The importance of roads to the welfare of nations was not unknown to the ancients. The senate of Athens, the governments of Lacedaemon, Thebes, and other states of Greece, bestowed much care upon them. The Carthaginians were systematic and scientific road-makers; they built up and consolidated an empire so promi- nent in military and naval achievements and in the arts and industries of civilized life that for feur hundred years it was able to hold its own against the preponderance of Greece and Rome. XXXIV HIGHWAY CONSTRUCTION. The Romans learned the art of making paved roada from the Carthaginians, and the highways constructed by them are great monuments in this department of art. The first Roman road was constructed under the direction of the censor Appius Claudius (312 B.C.). This road, named after him the Appian Way, was frequently, on account of its excellence, called the " queen of roads." Under Augustus and Julius Caesar the Roman capital was made to communicate with all the chief towns by paved roadways, and during the last African war a road of this kind was constructed from Spain through Gaul to the Alps. Later these great lines of communication were extended through Savoy, Dauphine, and Provence ; through Germany, every part of Spain, through Gaul, and even to Constantinople; through Hungary, Macedonia, and to the mouths of the Danube. Neither did the in- terposition of seas obstruct the labor or daunt the enterprise of this great people. The lines of communication thus constructed to the shores of the continent of Europe were continued at corresponding points of the neighboring islands and continents. Sicily, Corsica, Sardinia, England, Africa, and Asia were accordingly penetrated and intersected by roads, forming the continuation of the great European lines. These gigantic works were the most solid struc- tures of their kind which have been formed in any age, and many of them still remain, often forming the foundation of modern roads and in some instances constituting the road-surface now used. Erom these remains and the accounts of ancient writers we are en- abled to follow the methods employed in their construction. The engineering appears to have been very simple. A prominent land- mark was selected in the direction desired, and the road located on an absolute straight line without reference to intervening obstacles. The roads were divided into two classes : (1) Private roads, the use of which was free, while the soil remained private property; and (2) public roads, of which the use, the management, and the soil itself were alike vested in the state. The public roads were divided into three classes. The military roads were called " prae- torian roads," being under the immediate government of praetors, or military superiors. The high roads were called " consular roads," because they were made and maintained by the authority of the consuls; and the local roads leading from the consular roads to small places were called " vicinal roads." The width of the HISTORICAL SKETCH. XXXV roads varied from 8 to 20 feet, and the method of construction was as follows: Two shallow trenches, called sulci, were first dug par- allel to each other, marking the width of the road. The space between them was excavated to solid ground; in this excavation the road materials were placed, arranged in four layers having a total thickness of about three feet : (1) The statumen, or founda- tion, consisting of two courses of large flat stones laid in lime-mor- tar, or of stones not smaller than the hand could grasp; (2) The rudus, composed of broken stones mixed with one third their quantity of lime-mortar, and forming a layer about 9 inches in thickness; (3) The nucleus, composed of fragments of brick, stones, and pottery, set in lime-mortar, and about 6 inches thick; (4) The summa crusta, or pavimentum, composed of large irregularly shaped stones about 6 inches thick, closely jointed and fitted with the utmost nicety. These roads bore uninjured the weight of columns, obelisks, and other immense blocks of stone weighing hundreds of tons; notwithstanding this, the utmost weight which each class of vehicle was permitted to carry was regulated by law, and those laws were strictly enforced. Although these roads were eminently durable, they were deficient in the other qualities requisite for a good road, and Horace states that they were " less fatiguing to people who travel slowly/' Streets were paved with large polygonal blocks, laid as described above, and footways with rectangular slabs. Specimens are still to be seen in Rome and Pompeii. The curator viarum of the Romans was an official of distinc- tion, wielding great authority, and Plutarch tells us of Caius Gracchus that when he was appointed supreme director for making roads, the people were charmed to see him go forth on his tours of road-making followed by such numbers of ambassadors, magistrates, architects, and artificers. When the Romans conquered Gaul they found many roads or trails from three to six feet wide, and the French archaeologists tell us that nearly 13,000 miles of these trails were improved by the invaders. In Peru the Incas built great roads, the remains of which attest their magnificence. Humboldt in his " Aspects of Nature " speaks of the mountain road from Quito to Cuzco as "a marvellous work, not inferior to the most imposing Roman roadways." It was from XXXIV HIGHWAY CONSTRUCTION. The Romans learned the art of making paved roada from the Carthaginians, and the highways constructed by them are great monuments in this department of art. The first Roman road was constructed under the direction of the censor Appius Claudius (312 B.C.). This road, named after him the Appian Way, was frequently, on account of its excellence, called the " queen of roads." Under Augustus and Julius Caesar the Roman capital was made to communicate with all the chief towns by paved roadways, and during the last African war a road of this kind was constructed from Spain through Gaul to the Alps. Later these great lines of communication were extended through Savoy, Dauphine, and Provence ; through Germany, every part of Spain, through Gaul, and even to Constantinople ; through Hungary, Macedonia, and to the mouths of the Danube. Neither did the in- terposition of seas obstruct the labor or daunt the enterprise of this great people. The lines of communication thus constructed to the shores of the continent of Europe were continued at corresponding points of the neighboring islands and continents. Sicily, Corsica, Sardinia, England, Africa, and Asia were accordingly penetrated a,nd intersected by roads, forming the continuation of the great European lines. These gigantic works were the most solid struc- tures of their kind which have been formed in any age, and many of them still remain, often forming the foundation of modern roads and in some instances constituting the road-surface now used. Erom these remains and the accounts of ancient writers we are en- abled to follow the methods employed in their construction. The engineering appears to have been very simple. A prominent land- mark was selected in the direction desired, and the road located on an absolute straight line without reference to intervening obstacles. The roads were divided into two classes: (1) Private roads, the use of which was free, while the soil remained private property; and (2) public roads, of which the use, the management, and the soil itself were alike vested in the state. The public roads were divided into three classes. The military roads were called " prae- torian roads," being under the immediate government of praetors, or military superiors. The high roads were called " consular roads," because they were made and maintained by the authority of the consuls; and the local roads leading from the consular roads to small places were called "vicinal roads." The width of the HISTORICAL SKETCH. XXXV roads varied from 8 to 20 feet, and the method of construction was as follows: Two shallow trenches, called sulci, were first dug par- allel to each other, marking the width of the road. The space between them was excavated to solid ground; in this excavation the road materials were placed, arranged in four layers having a total thickness of about three feet: (1) The statumen, or founda- tion, consisting of two courses of large flat stones laid in lime-mor- tar, or of stones not smaller than the hand could grasp; (2) The rudus, composed of broken stones mixed with one third their quantity of lime-mortar, and forming a layer about 9 inches in thickness; (3) The nucleus, composed of fragments of brick, stones, and pottery, set in lime-mortar, and about 6 inches thick; (4) The summa crusta, or pavimentum, composed of large irregularly shaped stones about 6 inches thick, closely jointed and fitted with the utmost nicety. These roads bore uninjured the weight of columns, obelisks, and other immense blocks of stone weighing hundreds of tons; notwithstanding this, the utmost weight which each class of vehicle was permitted to carry was regulated by law, and those laws were strictly enforced. Although these roads were eminently durable, they were deficient in the other qualities requisite for a good road, and Horace states that they were " less fatiguing to people who travel slowly." Streets were paved with large polygonal blocks, laid as described above, and footways with rectangular slabs. Specimens are still to be seen in Eome and Pompeii. The curator viarum of the Romans was an official of distinc- tion, wielding great authority, and Plutarch tells us of Caius Gracchus that when he was appointed supreme director for making roads, the people were charmed to see him go forth on his tours of road-making followed by such numbers of ambassadors, magistrates, architects, and artificers. When the Romans conquered Gaul they found many roads or trails from three to six feet wide, and the French archaeologists tell us that nearly 13,000 miles of these trails were improved by the invaders. In Peru the Incas built great roads, the remains of which attest their magnificence. Humboldt in his " Aspects of Nature " speaks of the mountain road from Quito to Cuzco as "a marvellous work, not inferior to the most imposing Roman roadways." It was from XXXVI HIGHWAY CONSTRUCTION. 1500 to 2000 miles in length, and most of it was at an elevation of over 12,000 feet above the level of the sea; it was 20 feet wide and paved with stones 10 feet square, and had a running stream and a row of shade-trees on each side. Prescott in his " History of Peru," in speaking of this road, says that "it was conducted over sierras covered with snow; galleries were cut through the living rock; rivers were crossed by means of bridges swung suspended in the air; precipices were scaled by stairways hewn out of the native bed, and ravines of hideous depth were filled up with solid masonry." In the breaking-up of society which followed the decline of the Roman Empire, the roads fell out of repair and finally into ruin. During the Dark Ages they were regarded with terror as aids to plunder, and such intercourse as was maintained took place almost exclusively by rude paths capable of being passed on foot, or at best by horses. With the reconstruction of society in Europe the roads gradually became practicable for pack-animals and the rude vehicles of the time; but no serious attempt was made to restore or replace the public highways until the middle of the eighteenth century. About this time the revival of road construction was almost simul- taneous in England and France, and shortly afterwards the other chief countries of Europe took up the matter. Among the first laws passed in England on the subject of roads is one in the year 1285, directing that all bushes and trees along the roads leading from one market to another should be cut down for 200 feet on either side, to prevent robbers lurking therein, and providing "that when any highway is worn deep and incom- modious that another shall be laid out alongside." Henry VIII. also made provision under this head by enacting "that two justices of the peace and twelve other men of wisdom and discretion shall choose fresh routes when the old ones are worn out." In 134G Edward III. authorized the first toll to be levied for the repair of the roads. In 1523 the English Parliament passed the first act relative to the improvement of the public roads. Regarding the condition of the English highways a hundred and fifty years ago, Lord Macaulay tells us that it was no uncom- mon thing for the fruits of the earth to rot in one place when a score of miles away the people were suffering from a scarcity of the very food which was spoiling and almost within their reach. The roads HISTORICAL SKETCH. XXXV11 were so wretched that the food could not be transported. At this time each parish was obliged to build and maintain the roads within its confines, and it not infrequently happened that a poor and impoverished agricultural community was expected to maintain a highway between two rich and prosperous towns. Mr. Arthur Young in his " Six Months' Tour in the North of England " gives us the following account of the state of the roads at that time (1770) : " I know not in the whole range of language terms sufficiently expressive to describe this infernal road. Let me most seriously caution all travellers who may accidentally propose to travel this terrible country to avoid it as they would the devil; for a thousand to one they break their necks or their limbs, by over- throws or breaking-downs. They will here meet with ruts, which I measured, actually four feet deep, and floating with mud only from a wet summer. What, therefore, must it be after a winter ? The only monding it receives is tumbling in some loose stones, which serve no other purpose than jolting a carriage in the most intolerable manner. These are not merely opinions, but facts; for I actually passed three carts broken down in these eighteen miles of execrable memory." England sought to improve the ill-condition of her highways by the establishment of a comprehensive system of turnpikes, and be- fore the beginning of this century thirty thousand miles of these roads had been built; but they were constructed in such an imper- fect manner that they were but little improvement on the old roads. Even as late as 1809 the roads answered the description of Mr. Young, and little improvement was effected till the advent of MacAdam and Telford. Contemporaries and in some respects ad- vocates of rival systems, to these two men England owes her present admirable system of roads; and Charles Dickens wrote: " Our shops, our horses" legs, our boots, our hearts, have all been benefited by the introduction of MacAdam." The French and the Swiss probably have the best highways of any of the European countries. Until the time of Louis XIV. the roadc of France received no more attention than did those of Eng- land. This monarch had several fine roads made in the environ.-: of Paris for his personal use and pleasure. They were very wide and paved only in the centre. Shortly after the construction of these royal roads the nation began to appreciate the advantage of good XXXV1U HIGHWAY CONSTRUCTION. roads, but it was not until the advent of the first Napoleon that the modern system of magnificent highways was inaugurated, solely for military purposes, and this object has never been lost sight of ; so that, although in modern times their use as a means of communica- tion for the people accounts for their great and increasing number, it is largely owing to their military character that the French gov- ernment expends the enormous sums it does annually on the national roads. The material and financial prosperity, thriftiness, and content- ment of the French people has long excited the admiration of the world; neither internal revolution nor defeat from abroad appears to have entailed upon them burdens too heavy for them to bear. Students of economic problems ascribe this marvellous condition to the far -reaching and splendidly maintained system of highways, on which the obstacles to economical transportation have been reduced to the minimum. In the United States the highways have not improved as rapidly as other institutions; in fact, they are very inferior to those of Europe. The reason for this may be attributed to several causes, among which may be mentioned (1) the excellence of the railroad systems and waterways; (2) the indifference of those in charge of highway maintenance; (3) the want of appreciation of the benefits of good roads and the fear of increased taxation on the part of the rural population; (4) the dispersion of the people over large areas in their search for desirable localities for residence; and (5) the ill-effects of the system requiring the personal service of the rural population on the highways. The experience of Europe in road improvement shows that the highways should be taken as much as possible out of the hands of local authorities, and administered by either national or state gov- ernments in accordance with the needs of the people who use the roads; and that as the whole public is benefited by good roads, therefore all should pay for their improvement and maintenance. This view of the subject is not new in the United States, for Wash- ington recommended in a letter to Patrick Henry that the roads of Virginia be taken away from the control of the county courts and be given to the State authorities. One of Hamilton's pet schemes was that of road improvement, and he recognized thor- oughly that roads left to local authority would never be satisfac- HISTORICAL SKETCH. XXXIX torily built. During the past ninety years there has been more or less national legislation in regard to common roads. Several very comprehensive measures have passed one or another of the Houses of the National Congress, but the only road of any consequence constructed by the government was the national road (650| miles in length, 80 feet in width, and macadamized for a width of 30 feet), which it originally was intended should go from the tide-water of the Atlantic Ocean to the Ohio River. It was built from Cumberland In Maryland to a point in Ohio several hundred miles from the Ohio River, and there it was allowed to stop, being finally donated to the States through which it passes. In this way ended the first great effort of the Federal Government to build and establish, as the Constitution of the United States contemplated, a system of post- roads all over the country. The date of the first introduction of street pavements cannot be determined with certainty. Livy informs us that in the year 584 (about 170 B.C. ) the censors caused the streets of Rome to be paved from the ox market to the temple of Venus. Streets paved with lava, having deep ruts worn by the wheels of chariots, and raised banks on each side for foot-passengers, are found at Pompeii and Hercu- laneum. Abderahman, the caliph of Cordova, Spain, caused the streets of that city to be solidly paved, A.H. 236 (A.D. 950), and a man might walk after sunset ten miles in a straight line by the light of the public lamps. The earliest reference to street pavements in the British Isles is found in the records of the city of Glasgow. In the year 1577 the council resolved to spend 200, "to big the calsayis," or, to modernize it somewhat, to build the causeways. The date of the first introduction of pavements into London is unknown, but the streets of that city were not paved at the end of the eleventh century. It is related that in the year 1190 the chucch of St. Mary-le-Bow in Cheapside was unroofed by a violent wind, and that four pillars, 26 feet in length, sunk so deep into the ground that scarcely 4 feet of them appeared above the surface of the soft earth forming the street. Holborn was first paved in 1417, and Smithfield in 1614. The first act for paving and improving the City of London was passed in 1532. The streets were described in the simply-worded statute as " vsry x l HIGHWA.Y CONSTRUCTION. foul, and full of pits and sloughs, so as to be mighty perilous and noyous, as well for all the king's subjects on horseback as on foot with carriages" (litters). The capital of France was not paved in the twelfth century, for Rigord, the physician and historian of Philip II., relates that, the king standing one day at a window of his palace near the Seine and observing that the carriages which passed threw up the dirt in such a manner that it produced u most offensive stench, his majesty resolved to remedy this intolerable nuisance by causing the streets to be paved, which was accordingly done. The orders for this purpose were issued by the government in the year 1184, and upon that occasion, it is said, the name of the city, which was then called Lutetia, on account of its dirtiness, was changed to that of Paris. Dijon, France, had paved streets as early as 1391, and it is re- marked by historians that after this was done dangerous diseases, such as dysentery, spotted fever, and others, became less frequent in that city. In the United States, Boston, Mass., appears to have been the first city to pave its streets, for when Josselyn visited that city in 1663 he found many streets paved with pebbles; and Ward said in 1699: " The buildings, like their women, being neat and handsome, and their streets, like the hearts of the male inhabitants, are paved with pebble." Drake says that the paving of the public streets began very early and was made of importance after 1700; the side- walks were also early paved with cobblestones and flags. We learn that the first regular paving of a Philadelphia street was due to an accident. A man on horseback being mired and thrown from his horse, breaking his leg, a subscription was raised and the street paved with pebbles from the river-bank. In 1719 many sidewalks were being paved with brick and the cartway with cobblestone. In 1750 the grand jury represented the great need of paved streets, " so as to remedy the extreme dirtiness and miry state of the streets;" but the first general effort worthy of mention to pave the streets was made in 1761-62, and then the only means applied to the purpose was that produced by lotteries. In New York City the first stone pavement appears to have HISTORICAL SKETCH. x ji been laid in about the year 1657 on Brower Street, between Broad and Whitehall, and known to-day as Stone Street. The division of streets into carriageways and footways appears to have been first practised in 1614, in which year the citizens of London began to pave the margins of the streets before their doors, but the middle of the streets was paved with large pebbles very unevenly. In 1761 raised footways of square granite blocks were used in Westminster and for London generally in 1766. In 1704 the Common Council of Albany, N. Y., ordered "that ye streets be paved before each inhabitant's door within this city, eight foot breadth from their houses and lotts, before ye 25th of October next ensuing, upon penalty of forfeiting the summe of 15 shillings for ye Behooffe of ye sheriffe, who is to sue for ye same." In New York the first footwalks were laid in 1790, on the west side of Broadway, from Vesey to Murray Street, and opposite for the same distance along the Bridewell fence. They were narrow pavements of brick and stone, scarcely wide enough to permit two persons to walk abreast. In 1696 the first contract for cleaning the streets of New York was made. Prior to this the work had been done by the citizens, every man being required to keep the street clean before his door. In 1697 the first attempt at lighting the streets of New York was made. This was done by hanging out a lantern with a candle in it upon the end of a pole from the window of every seventh house on the nights when there was no moon, the expense being divided equally among the several houses. Authority to construct toll-roads was first granted in England, in 1346, but their construction did not become general until 1676, and they were entirely abolished in 1878. . In the United States the first toll-road company was incorpo- rated in Pennsylania in 1792, to construct and maintain an artificial road from Philadelphia to Lancaster, a distance of about 70 miles. The framers of the act authorizing the construction of this road recognized the importance of the relation between the load and the width of the wheel-tire. The rate of toll was graded according to the width of the tire, and the maximum load to be -carried by the different widths of tire was distinctly ctated. Vehicles with tires of less breadth than four inches were not xlii HIGHWAY CONSTRUCTION. allowed to carry more than two and a half tons between the first day of December and the first day of May, and not more than three tons during the rest of the year. The act also provided for the placing of milestones and the erection of guide-posts at ail intersecting roads, with the name of the place to which they led and its approximate distance in miles. Though considerable advance in processes and machines have been made during the past hundred years, the two chief factors in the preservation of roads so ably regulated in the above mentioned act are still the same, and in many cases are the cause of the evils we suffer from in the shape of bad highways. The modern movement for the improvement of the highways of the United States was begun about the year 1885. Since then various ways and means have been adopted by several States to secure good roads. The popularity of the agitation is shown by the organization of State and National societies, the appointing of investigating commissions, holding of conventions, and the enact- ing of State-aid laws. In 1891 New Jersey enacted the first modern State-aid law. Massachusetts passed a similar law in 1893 and has been followed by Rhode Island, Connecticut, and New York. At the present time the giving of State aid is being favorably considered by the legislatures of nearly all the States. The Fifty-second Congress, in response to a memorial con- taining 150,000 signatures, made an appropriation for the purpose of investigating practical methods for the improvement of the public roads. The appropriation has been continued and in- creased, and has resulted in the establishment of the U. S. Road Inquiry Office and the U. S. Road Material Laboratory at Washing- ton, D. C., for the scientific testing of road materials. The use of State funds for road-building, now so popular, is not new in the United States. As early as 1784 Virginia built at State expense all the roads leading to the court-house in each county. In 1797 Kentucky passed a road law which with slight changes remained in force until 1894, when a new law was enacted. Under the law of 1797 many miles of earth and stone roads were built with State aid. In 1795 the State treasury paid for the construe- HISTORICAL SKETCH. tion of a road from Crab Orchard to the top of the Cumberland Mountains in the gap through which the present road to Virginia passes. In North Carolina as early as 1819 the State gave aid in the construction of roads through a State Board of Internal Improve- ments. In 1823 the engineer to the Board, Hamilton Fulton, recommended the adoption by the State of a general system of building the public roads, dividing them into three classes: 1. State roads, the cost of which was to be divided equally between the State and the counties through which they passed, the maintenance to be at the cost of the counties. 2. County roads, constructed and maintained by the counties traversed. 3. Private roads, constructed and maintained by the individuals who are benefited by them. A TEEATISE ON HIGHWAY CONSTRUCTION, CHAPTER I. PAVEMENTS. 1. General Considerations. The object of a pavement is (1) to secure a water-tight covering that will preserve the natural soil from the effects of moisture, and not, as commonly supposed, to support the vehicles, the weight of which and tha!: of the covering material must be actually borne by the natural soil. (2) To fur- nish a smooth surface on which the force of traction will be reduced to the least possible amount, and over which vehicles may pass with safety and expedition at all seasons of the year. 2. The dualities essential to a good pavement may be stated as follows : (1) It should be impervious. (2) It should afford good foothold for horses. (3) It should be hard and durable, so as to resist wear and dis- integration. (4) It should be adapted to every grade. (5) It should suit every class of traffic. (6) It should offer the minimum resistance to traction. (7) It should be noiseless. (8) It should yield neither dust nor mud. (9) It should be easily cleaned. (10) It should be cheap. HIGHWAY CONSTRUCTION. 3. Interests affected in the Selection. Of the above require- ments, numbers 2, 4, 5, and 6 affect the traffic and determine the cost of haulage by the limitations of loads, speed, wear and tear of horses and vehicles. If the surface is rough or the foothold bad, the weight of the load a horse can draw is decreased, thus necessi- tating the making of more trips or the employment of more horses and vehicles to move a given weight. A defective surface necessi- tates a reduction in the speed of movement and consequent loss of time ; it increases the wear of horses, thus decreasing their life- service, and lessens the value of their current services; it also in- creases the cost of maintaining vehicles and harness. Numbers 7, 8, and 9 affect the occupiers of the adjacent premises, who suffer from the effect of dust and noise; and second, the own- ers of said premises, whose income from rents is diminished where these disadvantages exist. Numbers 3 and 10 affect the taxpayers alone, first as to the length of time during which the covering remains serviceable, and second as to the amount of the annual repairs. Number 1 affects the adjacent occupiers principally on hygienic grounds. Numbers 7 and 8 affect both traffic and occupiers. 4. Selection of Pavements. In the selecting of the most suita- ble pavement, whether for a street or a country road, all classes of citizens are alike interested; for of all the systems of intercom- munication none is brought into more direct contact with the peo- ple than the public highway, and its effect upon the price of commodities is felt by all. Not a ton of agricultural or mechani- cal produce can reach its destination without first and last paying toll to the condition of the highway over which it has to be hauled' in the form of time, wear and tear of horses, harness, and vehicles thus enhancing its cost to the consumer without any increased benefit to the producer, who must be compensated for the cost of all unnecessary expenses of transportation due to the ill condition of the highway. 5. Cost of Wagon Transportation. It is apparent that but few people comprehend the cost of transportation by horses and wagons, or realize the amount of money annually wasted by the ill condi- tion of the roadways. Table I shows from actual observation the cost of moving a load of one ton a distance of one mile on level roadways with PAVEMENTS. different pavements in the usual condition in which they are main- tained. The excessive amount of these charges is seen when it is remembered that the same goods using the roadways are now carried by the railroads at an average cost of T % of a cent per ton- mile. TABLE I. COST OP TRANSPORTATION BY HORSES AND WAGONS PER TON-MILE ON DIFFERENT ROAD-COVERINGS. Iron rails 1.28 cents per ton-mile Asphalt 2.70 " " Stone, paving, dry and in good order 5.33 " " " ordinary condition 12.00 " " covered with mud 21.30 " Broken stone, dry and in good order 8.00 " " moist " " " 10.30 " " " ordinary condition 11.90 " " covered with mud 14.30 " " " " ruts and mud 26.00 " '* Earth, dry and hard 18.00 " ruts and mud 39.00 " " Gravel, loose 51.60 " " " compacted 12.80 " " Plank, good condition 8.80 " " Sand, wet 32.60 " " " dry 64.00 " " 6. In 1890 the railroads of the United States carried over 600,000.000 tons of freight. Most if not all of this had to be han- dled at one or both terminals in wagons. If the distance hauled was but one mile and the rate per ton-mile 22 cents, which is the average rate of haulage, the cost would be $133,500,000. The low rate of railroad transportation has been achieved by careful and scientific study, and by daily attention to every portion of the road- bed and rolling stock. Defective parts are instantly removed and new ones substituted so that the road is always in good order. But pavements once laid are left to . batter the vehicles, and the vehi- cles, in return, to pound the pavements: little or no attention being paid to them until they finally become unendurable and are entirely renewed. Moreover, on every well-managed railroad the statistics of cost of transportation are the subject of the most sci- entific study, and at the end of each year it is exactly ascertained HIGHWAY CONSTRUCTION. just how much it has cost to haul a ton of freight one mile, and what proportion of this is for train service, what for maintenance of rolling stock, what for maintenance of way, and so on; whereas very few engineers in charge of highways have attempted to find out accurately what is the relative damage done to vehicles and horses by different kinds of pavements, what is the relative amount of force required to draw a unit of weight on different surfaces, what is the relative cost of maintaining different pavements during a term of years under a unit of traffic, or what is the exact propor- tion of horses falling on different surfaces. 7. Effect of Reducing the Cost of Wagon Transportion. If the cost of wagon transportation could be reduced by the improvement of the highways to, say, five cents per ton-mile, what would be the result ? It would create an annual saving of many millions of dol- lars and it would put in motion a large tonnage of various kinds of merchandise that cannot now be handled with profit ; it would give a large margin of profit on many products which are now moved with little profit, and would directly benefit both the producer and the consumer. The cost of wagon transportation over the roads of France does not exceed one third the like expense in America, it being common in rural districts to haul three tons and in the cities from three to five tons net freight with one horse. 8. Problem involved in the Selection of Pavements. The prob- lem involved in the selection of the most suitable pavement is composed of the following factors: first, adaptability; second, desirability; third, serviceability; fourth, durability; fifth, cost. 9. Adaptability. The best pavement for any given roadway will depend altogether on local circumstances. Pavements must be adapted to the class of traffic that will use them. The pavement suitable for a road through an agricultural district will not be suitable for the streets of a manufacturing centre, nor will the covering suitable for heavy traffic be suitable for a pleasure-drive or a residential district. General experience indicates the relative fitness of the several materials as follows : For country roads, suburban streets, and pleasure-drives, broken stone. For streets having heavy and constant traffic, rectangular blocks of stone laid on a concrete foundation with the joints filled PAVEMENTS. with bituminous or Portland cement grout. For streets devoted to retail trade and where comparative noiselessness is essential, asphalt, wood, or brick. 10. Desirability. The desirability of a pavement is its posses- sion of qualities which make it satisfactory to the people using and seeing it. Between two pavements alike in cost and durability, people will have preferences arising from the condition of their health, personal prejudices, and various other intangible influences, causing them to select one rather than the other in their respective Htreets, Such selections are often made against the demonstrated economies of the case, and usually in ignorance of them. When- ever one kind of pavement is more economical and satisfactory to use than is any other, there should not be any difference of opin- ion about securing it, either as a new pavement or in the replace- ment of an old one. Popular prejudices about pavements affect the prices of real estate upon paved streets, and so help to determine their desir- ability. A stranger's impression of a city or town depends largely upon the ease with which he can go from place to place in the transaction of business or in the pursuit of pleasure, and he is pleased or displeased exactly in proportion to the smoothness of his journey or the ruggedness of his way. Massive business blocks, pretentious private residences, stately public buildings, beautiful parks and lawns, possess no attraction for one who is compelled to pick a way for his feet and keep his eyes on the ground for fear of stumbling over jagged stones or falling in the mud. To man and beast alike, the roadway that offers a few or no obstacles to easy travel is a delight which shortens the journey by mitigating the pangs of fatigue. To persons who ride for pleasure or for health, rough pave- ments cause great annoyance. The pleasure of fast driving in the parkways or roadways devoted to that purpose is defeated by the necessity of jolting over rough pavements until the driveway is reached, and in the case of invalids the rough roadways prevent the taking of air altogether in many cases. 11. The economic desirability of pavements is governed by the ease of movement over them, and is measured by the number of horses or pounds of tractive force required to move a given weight, usually one ton, over them. The following table shows the relative HIGHWAY CONSTRUCTION. tractive force required upon level roads formed of different ma- terials, asphalt being taken as the standard of excellence in this respect : TABLE II. NUMBER OP HORSES REQUIRED TO MOVE ONE TON ON DIFFERENT PAVE* MENTS. Asphalt 1.00 Stone blocks, dry and in good order 1.50 to 2.00 in fair order 2.00 ' 2.50 " " covered with mud 2 00 " 2.70 Macadam, dry and in good order 2.50 <% 3.00 in a wet state 3.30 in fair order 4.50 " covered with mud 5.50 " with the stones loose 5.00 " 8.20 See also TabJps L and LI. 12. From Table II it is seen that to move the same load at the same speed and for the same length of time, with the same fatigue to each horse, requires from 1| to 3 horses on stone block pavements, and 2^ to 8 on macadam, while for asphalt but 1 is required. If iron rails be taken .as the standard of excellence, the number of horses required will be as follows : Iron rails 1 Asphalt t li Stone block, best condition 3 " " ordinary condition 5 " bad " 8 Macadam , 5.7 to 8 Cobblestones, good.... 6.6 " 13.3 ordinary 25 Earth, dry.... 20 Sand 40 13. Economy of Smoothness. From the above table the great economy of smoothness becomes at once apparent. But it is evident that, as in all lines of transportation, the greatest resistance regu- lates the load over the rest of -the route, unless there be auxiliary power; so the continuity of the surface should remain unbroken by any other grade of material which would increase the resistance. PAVEMENTS. The advantages of smooth pavements to owners and users of horses and vehicles are enormous. With them one third greater loads could be moved ; there would be no stuck teams, fewer wor- ried, beaten horses, fewer angry, overworked drivers, and thus fewer delays and interruptions to business. 14. Serviceability. The serviceability of a pavement is its quality of fitness for use. This quality is measured by the expense caused to the traffic using it, viz., the wear and tear of horses and vehicles, loss of time, etc. No statistics are available from which to deduce the actual cost of wear and tear. It has been estimated as follows : On cobblestones 5 cents per mile travelled belgian block 4 " granite block 3 " wood 2.5 " broken stone in first-class condition... 1.2 " asphalt 1 " The serviceability of any pavement depends in a great measure upon the amount of foothold afforded by it to the horses, provided, however, that its surface be not so rough as to absorb too large a percentage of the tractive energy required to move a given load over it. Cobblestones afford excellent foothold, and for this reason are largely employed by horse-car companies for paving between the rails; but the resistance of their surface to motion requires the -expenditure of about 280 pounds of tractive energy to move a load of 1 ton. Asphalt affords the least foothold, but the tractive force required to overcome the resistance it offers to motion is only about 30 pounds per ton. 15. Comparative Safety. The comparison of pavements in this respect is the distance travelled before a horse falls. The ma- terials affording the best foothold for horses are as follows, stated in the order of their merit : (1) Earth dry and compact. (2) Gravel. * (3) Broken stone (macadam). (4) Wood. (5) Sandstone and brick. (6) Asphalt. (7) Granite blocks. 8 HIGHWAY CONSTRUCTION. 16. The most complete observations made in the United States to ascertain the prevalence of accidents on the different pavements were made under the direction of Capt. F. V. Greene, the results of which show that a horse may travel before falling on Asphalt (Trinidad) 583 miles Granite 413 " Wood 272 " 17. Observations for the same purpose were made in London under the direction of Col. Haywood. The results were as follows. The three classes of pavements, wood, asphalt, and stone, were ob- served as nearly as was possible under the same conditions of space, weather, gradients, and soundness. The result of fifty days' ob- servation showed that before meeting with an accident a horse would travel a far greater distance on wood than he could either on asphalt or stone. The following table shows the distance trav- elled by a horse before meeting with an accident : DRY-WEATHER DISTANCES. Wood 646 miles Asphalt 223 " Granite 78 " DAMP-WEATHER DISTANCE. Wood 193 miles Asphalt 125 " Granite 168 " I THOROUGHLY- WET-WEATHER DISTANCES. Wood 432 miles Asphalt. 192 " Granite 537 " Another mode of observation gave the distance travelled as follows : Wood 446 miles Asphalt...., 191 " Granite...-. . .. 132 18. The foregoing figures appear to show that (1) Asphalt was most slippery when merely damp, and safest when perfectly dry. (2) That granite was most slippery when dry and safest when wet. PAVEMENTS. (3) That wood was most slippery when damp and safest when dry. It will be noticed that only under a single condition, and that the least persistent, is granite safer than wood or asphalt, and that wood is safer than asphalt under all circumstances. Granite was least safe and wood and asphalt most safe when clean. 19. Slight rain makes asphalt and wood more slippery than they are at other times. On asphalt the slipperiness begins almost immediately the rain commences. Wood requires more rain before its worst condition ensues. The slipperiness lasts longer upon wood, on account of its absorbent nature, than it does upon the as- phalt. When dry weather comes after the rain, then asphalt is in its most slippery condition and horses fall upon it very suddenly. On wood their efforts to save themselves are more effectual. Wood is also frequently in that peculiar condition of surface in which horses slip or slide along it without falling. A small quantity of dirt on asphalt makes it very slippery. In damp weather granite blocks become very greasy and slippery; in dry weather, if of a hard variety, the surface polishes and becomes rounded and the only foothold is by the joints between the blocks. In winter, during frost, asphalt is usually dry and safe ; wood, retaining moisture, is very slippery. Under snow there is very little if any difference between the safety of asphalt and wood. 20. The difference in the results obtained by Capt. Greene and Col. Haywood may be due in the case of the wood and stone pavements to climatic causes. London is more damp and foggy than any one of the American cities in which the traffic was ob- served, and therefore its pavements would be more slippery. The difference in the asphalt returns may be accounted for by the dif- ference in the character of the material. The asphalt pavements in London are made from natural bituminous rock, which makes a very smooth, hard surface, while the American pavements are made from natural bitumen mixed with sand, which forms a rough, granular surface. Moreover, these observations were made some eighteen years ago, at a time when asphalt was a new thing and its proper ireatment very insufficiently understood. It was not then recog- nized that asphalt requires to be constantly and thoroughly cleansed in order to do justice to itself. That the number of falls on as- phalt is decreasing as its use is becoming more extended is shown by the following : 10 HIGHWAY CONSTRUCTION". In Berlin in 1885, 4403 horses fell on an area of 398,000 square yards of asphalt pavement, in 1887 the number was reduced to 2456, while the area had increased to 485,000 square yards. That asphalt is but slightly more dangerous than some kinds of stone is shown by observations made at Paris some years ago in two streets, one paved with the hard sandstone much used in that capital, and the other with asphalt. In the street paved with stone one out of every 1308 horses fell, and in that paved with asphalt one out of every 1409 fell. 21. Slipperiness can be cured on both wood and asphalt: on the asphalt by sprinkling it with sand, on the wood by sprinkling it with gravel. The result in both cases is dirt. The sand thrown on the asphalt tends to wear it out ; the gravel thrown on the wood tends to preserve it. 22. Kinds of Falls and their Causes. The commonest falls on wood are falls on the knees, which are less likely to injure the horses and are less inconvenient to the traffic than other falls. Falls on haunches are more numerous on asphalt than on wood. Of com- plete falls there are fewest on wood and most on granite. The falls on asphalt are generally due to sudden pulling up and sharp turn- ing; those on granite, to the excessive width of the blocks, which fail to afford proper foothold. 23. Durability. The durability of a pavement is its quality, which relates to the length of time during which it is serviceable and not to the length of time it has been down. The only meas- ure of the durability of a pavement is the amount of traffic tonnage it will bear before it becomes so worn that the cost of replacing it is less than the expense incurred by its use. 24. As a pavement is a construction, it necessarily follows that there is a vast difference between the durability of the pavement and the durability of the materials of which it is made. Iron is eminently durable, but as a paving material it is a failure. 25. Durability and Dirt. The durability of a paving material will vary considerably with the condition of cleanliness observed. One inch of overlying dirt will most effectually protect the pave- ment from abrasion and indefinitely prolong its life. But the dirt is expensive, it injures apparel and merchandise, and is the cause of sickness and discomfort. In the comparison of different pave- ments no traffic should be credited to the dirty one. PAVEMENTS. 11 26. A pavement so rough and insecure that the traffic is kept off the road might be a most durable one, but it certainly would be lacking in serviceability. In a general way of speaking, the value of city property depends upon the volume of the traffic in the street upon which it is located. Ordinarily a pavement is not wanted by the owners of property on the street, however durable it may be, if it lacks serviceability; and they may not want it, even when it is serviceable, if it is not popular. 27. Life of Pavements. The life or durability of the different pavements under like conditions of traffic and maintenance may be taken as follows: Granite block ........................ . ............ 12 to 30 years Sandstone .......................................... 6 " 12 Asphalt ........................... ............... 10" 14 Wood ....................... ..................... 3" 7 Limestone .......................................... 1" 3 Brick ...................................... . ....... 5" ? Macadam .......................................... ? 28. Cost. The question of cost is the one which usually ests the taxpayers, and is probably the greatest stumbling-block in the attainment of good roadways. The first cost is usually charged against the property abutting on the highway to be improved. The result is that the average property-owner is always anxious for a pavement that costs little, because he must pay for it, not caring for the fact that cheap pavements soon wear out and become a source of endless annoyance and expense. Thus false ideas of econ- omy always have stood and undoubtedly to some extent always will stand in the way of realizing that the best is the cheapest. 29. The pavement which has cost the most is not always the best, nor i.j that which has cost the least the cheapest; the one which is truly the cheapest is the one which makes the most profitable re- turns in proportion to the amount which has been expended upon it. No doubt there is a limit of cost to go beyond which would produce no practical benefit, but it will always be found more economical to spend enough to secure the best results, and it will always cost less in the long-run. One dollar well spent, is many times more effective than one half the amount injudiciously expended in the hopeless effort to reach sufficiently good results which may look as 12 HIGHWAY CONSTRUCTION. well for the time, no matter how soon it may have to be done over again. 30. A good roadway should cost more to build than a poor one, but it is often the case that the poor road costs as much as a good one would. But even when a good one is more expensive, it will be easier and cheaper to keep in repair, and will last many years longer, while its advantages and the saving to those who daily use it will much more than compensate for the extra expense they may have been put to in building it. 31. Economy and Public Bodies. The true economy for public bodies which never die is to secure the best, in the best possible manner; for the best, every essential point being considered, is the cheapest. If a cheap pavement is adopted, the cost to maintain it will be so excessive as to more than make the difference between its first cost and that of a first-class one. As an instance of the profitable results of this policy the experience of the city of Liver- pool, England, may be cited. After many years of experiment and the expenditure of vast sums of money in pavements, the corporation of Liverpool now points with justifiable pride to its 250 miles of the best paved streets in the world. The policy adopted by this corporation in the execution of public works in the best possible manner, and generally by their own workmen, has proved successful in every way ; and, by a judicious primary expenditure, the cost of maintenance of the roads, sewers, and other public works is reduced to a minimum, and the greatest economy is thereby attained. The laying of the impervious pavement which was adopted in 1872 for the carriage-ways of the city has been continued up to date without intermission, and is still in progress, resulting in nearly 1,750,000 yards, superficial, of impervious carriage-way pave- ments, and a saving by the execution of this class of work unpre- cedented in municipal experience. The financial result can best be shown by the following: " Deal- ing with the year 1879, under the present city engineer (Mr. Clem- ent Dunscombe, M.A., M. Inst. C. E.), the estimated expenditure for the general repairs to the roads in this city was 28,000 ($136,080), the mileage of adopted roads at that time being 226 miles. Concurrently with the extension of the impervious carriage-way PAVEMENTS. 13 pavements, the expenditure under this head has been reduced year by year till tne estimated cost for the current year (1889) is only 8400 ($40,824), with a street mileage under repair of 254 miles. This reduction has not been effected, as might at first sight be supposed, by an increased rate under this head, due to an aug- mented expenditure of capital requiring the provision of additional interest and sinking fund to redeem the original debt for paving and like works within 23 years (from 1870, when the loan was effected, to 1893, when it will be paid), as the amount raised on paving-rate account in the year 1879 was, approximately, 17,000 ($82,620) more than in the year 1889, although the interest and sinking fund on the debt had increased from about 13,000 ($63,180) per annum in the year 1879 to about 47,000 ($228,420) per annum in the year 1889." Permission is never given to private companies or persons to cut through the pavement in any street for any purpose. When such work is necessary, the corporatiqn will do it in its own thorough way, and the interested parties must pay the entire cost a regula- tion worth noting. With the introduction of the improved pavements, it was found absolutely necessary, in order to attain the best results, to purchase the street-railroad tracks and reconstruct them in connection with the new pavements. Accordingly the city purchased some fifty miles of street-railroad tracks, and reconstructed them in a most substantial manner, and then rented them to the several original car companies at a fixed annual rental of 10 per cent on their cost. The city keeps the tracks in good condition. The success of these lines is conclusive proof that when street-car tracks are well de- signed and properly constructed they do not form the slightest impediment even to the narrowest-wheeled vehicles. 32. Economic Benefit. The economic benefit of a good road- way is comprised in its cheaper maintenance, greater and easier facility for travelling, thus reducing the cost of transportation, less cost of repairs to vehicles, less wear of horses (thus increasing the life and time of serviceability and enhancing the value of their present service), saving of time, ease and comfort to those using it. 33. First Cost. The cost of construction is largely controlled by the locality of the place, its proximity to the particular material used, and the character of the foundation. Tables XXVII, XXVIII, 14 HIGHWAY CONSTRUCTION. XXIX, XXX, XXXV, XXXVI, XXXVII, XLI,XLII,andXLIII show the cost of different pavements in several of the principal cities of America. 34. The Relative Economies of Pavements whether of the same kind in different condition or different kinds in like good condition are sufficiently determined by summing their cost under the following headings of account : (1) Annual interest upon first cost. (2) Annual expense for maintenance. (3) Annual cost for cleaning and sprinkling. (4) Annual cost for service and use. (5) Annual cost for consequential damages. 35. First. The first cost of a pavement is like any other per- manent investment, measurable for purposes of comparison by the amount of annual interest on the sum expended. Thus, assuming the worth of money to be 4$, a pavement costing $4 per square yard entails an annual interest loss or tax of $0.16 per square yard. 36. Second. Maintenance. Under this head must be included all outlays for repairs and renewals which are made from the time when the pavement is new and at its best to a time subsequent when, by any treatment, it is again put in equally good condition. The gross sum so derived divided by the number of years which elapse between the two dates gives an average annual cost for maintenance. 37. Maintenance means the keeping of the pavement in a con- dition practically as good as when first laid. The cost will vary considerably, depending not only upon the material and manner in which it is constructed, but upon the condition of cleanliness observed, and the quantity and quality of the traffic using it. 38. The prevailing opinion that no pavement is a good one unless when once laid it will take care of itself is erroneous; there is no such pavement. All pavements are being constantly worn by traffic and the action, of the atmosphere, and if any defects which appear are not quickly repaired they soon become unsatisfactory and are destroyed. To keep them in good repair incessant atten- tion is necessary and is consistent with economy. Yet claims are made that particular pavements cost little or nothing for repairs, simply because repairs are not made, while any one can see the need of them. 39. Third. Any pavement, to be considered as properly cared PAVEMENTS. 15 for, must be kept dustless and clean. While circumstances legiti- mately determine in many cases that streets must be cleaned at daily, weekly, or semi-weekly intervals, the only admissible condi- tion for the purpose of analysis of street expenses must be that of like requirements in both or all cases subjected to comparison. 40. The cleansing of pavements both as regards its efficiency and cost depends (1) upon the character of the surface; (2) upon the nature of the material of which they are composed. Block pavements present the greatest difficulty; the joints can never be perfectly cleansed. The order of merit for facility of cleansing is (1) asphalt, (2) brick, (3) stone, (4) wood, (5) macadam. 41. Fourth. The annual cost for service is made up by com- bining several items of cost incidental to the use of the pavement for traffic ; for instance, the limitation of the speed of movement, as in cases where a bad pavement causes slow driving and the consequent loss of time; or cases where the condition of a pave- ment limits the weight of the load which the horse can haul, and so compels the making of more trips or the employment of more horses and vehicles; or cases where it causes greater wear and tear of vehicles, of equipage, and of horses. If a vehicle is run 1500 miles in a year and its maintenance costs $30 a year, then the cost of its maintenance per mile travelled is two cents. If the value of a team's time is, say, $1 for the legitimate time taken in going one mile with a load, and in consequence of bad roads it takes double that time, then the cost to traffic from having to use that one mile of bad roadway is $1 for each load. The same reasoning applies to circumstances where the weight of the load has to be reduced so as to necessitate the making of more than one trip. Again, bad pave- ments lessen not only the life-service of horses, but also the value of their current service. The unit of these accounts is obtained by first finding the cost per mile of distance travelled, which cost divided by 5.280 and multiplied by the unit -of area gives the desired result. 42. Fifth. Consequential Damages. The determination of con- sequential damages arising from the use of defective or unsuitable pavements involves the consideration of a wide array of diverse circumstances. Bough-surfaced pavements, when in their best condition, afford a lodgment for organic matter composed largely of the urine and excrement of the animals employed upon the road- 16 HIGHWAY CONSTRUCTION. way. In warm and damp weather these matters undergo putre- factive fermentation and become the most efficient agency for generating and disseminating noxious vapors and disease-germs, now recognized as the cause of a large part of the ills afflicting man- kind. Pavements formed of porous materials are objectionable on the same if not even stronger grounds. 43. Pavements productive of dust and mud are objectionable, and especially so on streets devoted to retail trade. If this particu- lar disadvantage be appraised at so small a sum per lineal foot of frontage as $1.50 per month, or six cents per day, it exceeds the cost of the best quality of pavement free from these disadvantages. Rough-surfaced pavements are noisy under traffic and insufferable to nervous invalids, and much nervous sickness is attributable to them. To all persons interested in nervous invalids this damage from noisy pavements is rated as being far greater than would be the cost of substituting the best quality of noiseless pavement; but there are, under many circumstances, specific financial losses, meas- urable in dollars and cents, dependent upon the use of rough, noisy pavements They reduce the rental value of buildings and offices situated upon streets so paved, offices devoted to pursuits wherein exhausting brain-work is required. In such locations quietness is almost indispensable, and no question about the cost of a noiseless pavement weighs against its possession. When an investigator has done the best he can to determine such a summary of costs of a pavement, he may divide the amount of annual tonnage of the street traffic by the amount of annual costs and know what number of tons of traffic are borne for each cent of the average annual cost, which is the crucial test for any comparison, as follows: (1) Annual interest upon the first cost (2) Average annual expense for maintenance and renewal. (3) Annual cost for custody (sprinkling and cleaning) (4) Annual cost of service and use (5) Annual cost of consequential damages. Amount of average annual cost Annual tonnage of traffic. Tons of traffic for each cent of cost . . 44. Gross Cost of Pavements. Since the cost of a pavement depends upon the material of which it is formed, the width of the roadway, the extent and nature of the traffic, the condition of PAVEMENTS. 17 repair and cleanliness in which it is maintained, it follows that in no two streets is the endurance or the cost the same, and the differ- ence between the highest and lowest periods of endurance and amount of cost is very considerable. The comparative cost of various street pavements in Liverpool, including interest on first cost, sinking fund, maintenance, and cleaning, when reduced to a uniform standard traffic of 100,000 tons per annum for each yard in width of the carriage-way, is given by Mr. Deacon as follows : Per Square Yard per Annum. Block paveme:;t of hard granites $0 23 "softer " o 0.28 Bituminous concrete 35 Wood pavement 0.58 Macadam, on pitch foundation 0.71 Taking the standard of traffic at 40,000 tons per annum, for each yard in width the cost for the last three pavements is : Bituminous concrete 0.27 Wood 0.41 Macadam.. 0.47 Asphalt may be placed between wood and bituminous concrete, in the above order. These comparisons show the high cost of a macadamized surface in a street where traffic is great; and however well it may be maintained, it is much dirtier and dustier than any other pavement, though it is superior to them all in safety, and to block pavements in the matter of noise. Table III shows the approximate comparative gross cost of various pavements in the United States for a period of fifty years, the pavement at the end of that period to be in as good condition as when first laid. 45. Traffic Census. Comparison of pavements in respect to their gross cost can be effected only by comparing the gross traffic tonnage which each will bear for a unit of cost. As this can be ascertained only by direct observation, it is desirable that engineers in charge of roads and streets find out accurately the traffic tonnage, the amount of force required to draw a unit of weight over differ- ent surfaces in like condition, the cost of maintaining different coverings during a given period under a unit of traffic tonnage, the 18 HIGHWAY CONSTRUCTION". TABLE III. COMPARISON OP THE GROSS COST OF PAVEMENTS FOR A PERIOD OF 50 YEARS. Cost per Square Yard. Granite Block. Asphalt. Wood. Brick. $1 00 $1 00 $1 00 $1 00 3.25 2.50 1.40 1.80 Total first cost 4 25 3.50 2 40 2 80 Interest on materials and sinking fund, 50 yrs @, 4 % . 26 00 20 00 11 20 14 40 Interest on foundation @, 4 % 2 00 2 00 2 00 2 00 2.50 4.50 7.50 2 50 Cleaning etc 50 years . . 5 00 1 00 6 00 2 50 3 renewals of surface @, $3 25 9 75 5 " " @ 2 50 12 50 12 " " @, 1.40 16.80 8 " " @ 1 80 . . . 14 40 Cost of service . (estimated at) so 66 10 00 20 00 15 00 " " consequential damages ( " ") 10.00 1.00 1.50 2.00 Total 89 50 54 50 67 40 55 60 1.00 1 00 1.00 1.00 Less value of old material 88.50 1 00 53.50 .10 66.40 54.60 .25 4-50) Annual gross cost 87.50 1 75 5:3.40 1 068 66.40 1.33 54.35 1 . 087 relative safety of different surfaces, and the damage done to vehicles and horses by different pavements. These items should be care- fully observed and recorded. As the amount of travel is variable,, the observations should be made for a certain period on con- secutive days, and should be repeated at different seasons of the year. 46. The most extensive observations on this subject in the United States were made under the direction of Capt. F. V. Greene, member of the American Society of Civil Engineers. The method of observing and recording was as follows : " The observations were made on six consecutive days (Sundays omitted) at the same place, and were continuous from 7 A.M. to 7 P.M., except when darkness prevented. No addition was made for this omission, nor for night traffic/' PAVEMENTS. 19 The printed instructions issued to each observer contained the following rules as a guide in estimating weights : Less than 1 ton. 1-horse carriages, empty or loaded. 1-horse wagons, empty or light loaded. 1-horse carts, empty. Between 1 and 3 tons. 1-horse wagons, heavy loaded. 1-horse carts, loaded. 2-horse wagons, empty or light loaded. Over 3 tons. Wagons and trucks drawn by two or more horses and heavy loadei. " Special note will be made, in the column of Remarks, of any unusually heavy loads, such as 6-horse trucks loaded with stone or iron, and an estimate given of their weight." The weight and number of the horses was disregarded, because Capt. Greene wished to make comparison with English reports in which their weight was disregarded. Their weight should ~be in- cluded in all observations, as the action of their feet is an impor- tant factor in the wear of pavements. 47. Capt. Greene assigned the following weights to each class of vehicles : Light-weight vehicles one-half ton each, including their load; medium weight two tons, and the heavy weight four tons. The weight to be assigned to each class of vehicles had better be ascertained by occasionally weighing a typical vehicle and i/ load. The weight of horses may be taken at one-half ton each. 48. Form of Traffic Census. TRAFFIC CENSUS of Street. Class of pavement Condition , Width between curbs Date of observation State of the weather Temperature i Name of observer. . . . 20 HIGHWAY CONSTRUCTION. Classification of Vehicles. Hours of Observation. 6 to 7. 7 to 8. 8 to 9. 3 to 10. 10 to 11. 11 to 12. 12tol. 1- horse light 1- loaded 2- light 2- loaded 3. light 3- loaded 4- light 4- loaded. Led horses, No. of. ... Totals Number of falls 49. To obtain tonnage, multiply the total number of vehicles in each class by the weights assigned to that class, and adding to- gether the products the total vehicular tonnage is ascertained, which divided by the width between curbs and the number of days of observation gives the average daily tonnage per foot of width. Under Condition note the state of repair and cleanliness; whether the surface is dry, damp, or greasy. Under Falls note the kind, whether on knees, haunches, or complete, and if possible the cause " The average tonnage per vehicle is an almost infallible indi- cator of the character of the street, i.e., whether devoted to resi- dential or business purposes. It ranges from 0,68 tons on Fifth Avenue, New York City, to 2.08 tons on a portion of Wabash Ave- nue, Chicago. The same character is indicated by the proportions of light and heavy vehicles in the street. On Fifth Avenue, New York, for instance, 91$ of all the vehicles weigh less than one ton, while on Wabash Avenue only 25$ of them have so little weight. The general average for all cities is as follows: Less than 1 ton, 67^; between 1 and 3, 26$', more than 3 tons, 1$. The average tonnage per foot of width in each city, so far a; here observed, varies from 151 in New York to 30 in Buffalo, and the general average is 77. For all the cities observed the average daily tonnage per foot of width is 77, and varies from 273 tons on Broadway, New York, to 7 tons on a granite street in St. Louis. The average weight per vehicle is, for all cities, 1.15 tons. The average width of the streets between curbs is 44 feet." In London the traffic on some of the asphalt- and wood-paved streets exceeds 400 tons per foot of width per day. PAVEMENTS. 21 In Liverpool granite-block pavements sustain a daily traffic tonnage per foot of width of from 400 to 500 tons. The comparative rank of pavements in the order of their merit is shown in Table IV. TABLE IV. COMPARATIVE RANK OF PAVEMENTS, NAMED IN THE ORDER OF THEIR MERIT. * Order of Merit. Durability. Service- ability. Hygienic Fitness. Service on Grades. Gross Annual Cost. Facility for Cleansing. 1 2 Granite Asphalt Asphalt Brick Asphalt Brick Granite Brick Asphalt Brick Asphalt Brick 3 Brick Wood Granite Wood Wood Granite 4 Wood Granite Wood Asphalt Granite Wood 50. Guaranteeing Pavements. To secure pavements that shall be durable and serviceable, the municipal authorities often require the contractors to guarantee their pavements for a term, usually, of five years, under provisions calling for maintenance in good condi- tion during that period of time and for final delivery in good or- der. Such contracts involve two kinds of service, that of construc- tion, and of maintenance for a limited period. In the latter the conditions are exacted indiscriminately alike on streets with heavy traffic and on those with very light traffic, and thereby become sometimes burdensome, unless the same contractor paves so many streets of all kinds as to correct the inequality by securing of fair average traffic condition. The correct policy to pursue in contract- ing for maintenance would be to measure the service of the pave- ment by the tonnage rather than by the years. To do so equitably the city needs information about the traffic, which it can obtain only by having a traffic census taken as described in Art. 45. 51. Many contracts for street pavements in some European cities have provided for the construction and the maintenance of the pavements for long terms, say of twenty years, payments to be made in equal annual instalments throughout the term. Such arrangements appeared at first to be very favorable, owing to the first payments being so much less than they otherwise would be for the whole cost of construction. The pro-rata annual payments 22 HIGHWAY CONSTRUCTION. provided for the interest and risks of various kinds, with cou trac- tors' profits thereon, in addition to the direct outlays for construc- tion and repairs, so that the final outcome was unsatisfactory to both parties to the contract. The prevailing custom in this coun- try is to pay the cost of constructien of a pavement as soon as com- pleted. Two methods of meeting the expense of maintenance are followed. In one the municipality meets the annual requirements as they occur, and in the other, under contract for a term, say, of ten or twenty years, the contractor, for equal annual payments, is required to keep the pavement and turn it over to his successor in good condition at the expiration of the contract. 52o This annual payment has to cover the contingency of the contractor's being at the expense of completely renewing the pave- ment. The equal annual amounts paid on contracts for mainte- nance, as just explained, include two funds, one of repair accounts and the other a sinking fund, intended to meet the cost of renew- ing the pavement, which must be done if the c ontract is for a long term of years. ' 53. If an attempt is made to separate, for each year, the propor- tion of the annual payment which should provide for each of the two purposes, it would be found that the earlier years would be contributing little or nothing for repairs, as, the pavement being new, they would not be required, but the proportion so applied would increase gradually and at last consume nearly all the annual payment. 54. The justification of contracts for the maintenance of pave- ments is in the fancied advantage gained from having some one admittedly responsible for their condition and more amenable to discipline than are city officials for neglect. The experience with such contracts show that they establish a high initial price, that the shifting* of the responsibility is, ineffective, and that the terms of the contract are practically unenforceable, the repairs are deferred as long as possible, and in the end the city has to pay the full price and take possession of a pavement in such a condition that it is beyond good repair. The obstacles in the way of recovering under a bond are practi- cally insuperable. An indeterminate guaranty is worth nothing in law or in equity. If the terms of a guaranty could be made so specific that it was enforceable in law, the city would have to see to it that any one of a hundred causes did not operate to vitiate it; for PAVEMENTS. 23 example, a change in the tires of the vehicles, an increase in the volume of the traffic, openings for underground work, bonfires, leaky gas-mains, and so on through a list too long for consideration, would be cause for avoiding its terms and conditions. The exacting of a guaranty bond should be discontinued and the work awarded to the lowest responsible bidder in the same man- ner as for other kinds of construction in which the materials and workmanship are furnished under the engineer's specifications, tests, and inspection. Upon completion of the work the contractor should receive full payment, this being deferred only long enough to make sure that the requirements of the specifications have been complied with. The maintenance should then be assumed by the city and become a municipal charge. 55. Destruction of Pavements. The most serious cause of the destruction of street pavements is the frequency with which they are torn up for the introduction and repairing of underground pipes, and no pavement can be designed which will withstand such frequent disturbance. The only radical remedy for this evil is a very costly one in its first inauguration, but it is one that would be economical in the end, and that is a subway or series of subways under our roadways. 56. The amount of money wasted in continually opening up the streets, digging, bracing, and refilling, is a considerable item, not counting the interference with travel and business, and would be sufficient to cover the interest on the cost of the subways. The waste, being distributed through many companies, is not sufficiently felt to cause a reconstruction. 57. Under the best municipal administrations of Europe neither corporations nor individuals are permitted to disturb the pave- ments. All removals and restorations are done by the city's own employes, upon the deposit, by the parties who require the streets to be opened, of a sufficient sum to cover the expense for each piece of paving done, at a fixed price per yard according to the kind of pavement. In New York the Department of Public Works has an organ- ized system of supervision to insure the proper restoration of the pavements torn up by private corporations. The companies or in- dividuals making the openings are required to pay the cost of in- spection as well as the cost of restoring the pavement. CHAPTER II. MATERIALS EMPLOYED IN THE CONSTRUCTION OF PAVEMENTS. 58. Selection of Paving Material. The materials most com- monly used for pavements are stone in the form of blocks and broken fragments: wood in the form of blocks and plank, as- phalt in two forms, sheet and block, and clay in the form of brick. 59. In order to determine the fitness of the different materials under given conditions of service it is necessary to know (1) the agencies causing their destruction, the extent and character of the traffic, and the topographic and climatic conditions under which they are to be used; (2) the properties which the materials must possess in order to resist the destroying agencies; and (3) the most reliable methods of ascertaining experimentally the extent to which the materials possess the required properties. 60. The agencies causing the destruction of paving materials may be classified as mechanical, chemical, physical, and organic. It is estimated that the mechanical agencies cause 80 per cent, of the destruction and the others 20 per cent. The mechanical and physical agencies exert the greatest action on the surface, while the chemical affects both the surface and substratal portions. 61. Mechanical Agencies. The mechanical agencies due to the traffic are: (a) Impact produced by the action of horses' feet; (6) The percussive and abrading action of moving wheels; (c) The crushing due to the weight of the load on the wheels. The mechanical agencies are generally applied in their most destructive form, namely, in the presence of water, thus producing 24 MATERIALS EMPLOYED IN THE CONSTRUCTION OF PAVEMENTS. 25 attrition in the presence of a .solvent, in which condition their destroying effect is most energetic. 62. Chemical Agencies. The chemical agencies are water and the various acids present in the atmosphere, and the humous acids derived from the decomposition of animal and vegetable matter. The action of the chemical agencies is very slow, and their effect may be ignored except in the case of rocks already in a state of decomposition or containing readily soluble mineral matter. The rocks that are most susceptible to the solvent action of water impregnated with acids are the limestones, calcareous sandstones, and the granites containing feldspar. 63. Physical Agencies. The physical agencies are: (a) air in the form of wind, (6) heat due to changes of temperature, and (c) ice. 63a. Air acts mechanically to remove the loosened material and transport it in the form of dust. From measurements made by the engineers of France it appears that about 7 cubic yards of material per mile per annum are removed from the road surface by the action of wind and water. 63b. Heat, through changes of temperature, causes expansions and contractions which produce a slight movement among the com- ponent particles of the material, thus breaking their cohesion and leaving them more susceptible to the destroying effect of the other agents. 63c. Ice. Water penetrates into all the materials commonly employed for paving purposes, and at the freezing temperature it acts mechanically to disrupt the material by the pressure exerted while passing from the liquid to the solid state. In the formation of ice, 100 volumes of water expands to 109 volumes of ice, and the pressure exerted on cooling the water one degree below the normal freezing-point is 144 tons per square foot. The effect of ice on the individual fragments of the material is slight, but when frequently repeated, as in alternate freezing and thawing, it hastens disintegration by weakening the cohesion of the particles and thus renders them more susceptible to the action of the other agents. The most destructive effect of ice is produced in the structure of the pavement and its foundation. If the construction is de- 26 HIGHWAY CONSTKUCTIOtf. fective and the maintenance poor, water accumulates in the body of the roadway, and on freezing either destroys the bond or weak- ens it materially. 64. Organic Agencies. The organic agencies are vegetable or fungous growths that thrive in damp, shady places. 65. Resisting Properties. The properties which the material used for paving must possess in order to resist the destroying agencies are physical and chemical. The physical properties comprise resistance to crushing, impact, and abrasion. The chemical properties consist in the ability to resist for a considerable length of time the disintegrating action of the several physical, chemical, and organic agencies due to the weather and present on the surface of the roadway; this quality is generally designated by the term durability. 65a. Resistance to Crushing. The ability to resist crushing varies with the character of the material and frequently varies to a considerable extent in the same material. In plastic or viscous materials it depends upon the strength of the cementing medium or adhesive power of the matrix; in stones, brick, etc., it depends upon the cohesion and interlocking of the component particles. Since the resistance to crushing possessed by all the materials commonly regarded as suitable for paving is in excess of that actually required in use, this property is of secondary importance in determining the enduring quality of a material, especially when it is to be placed on a good foundation. With a weak foundation high resistance to crushing and cross-breaking is essential. 65b. Resistance to Impact and Abrasion. This property de- pends upon the hardness and toughness of the material. These two properties, while closely related, are not always coincident; some materials, although extremely hard, are yet so brittle that they crush easily under pressure. Materials possessing extreme hardness polish readily under friction and thus produce a slippery and dangerous road surface. 65c. Hardness is generally denned as that property of a solid which renders it difficult to displace its parts among themselves. When applied to the materials used for paving it signifies the resistance offered by the material to wear by abrasion under the MATERIALS EMPLOYED IS THE CONSTRUCTION OF PAVEMENTS. 27 action of wheels. The definition adopted 'by the U. S. Road Ma- terial Laboratory is "the resistance which a material offers to the displacement of its particles by friction." 65d. Toughness as applied to a paving material may be defined as that property which enables it to resist fracture under the blows produced by traffic. 65e. Durability depends upon the hardness, toughness, and chemical stability of the material. Physical defects and abrasion generally cause the destruction of the material long before it is injured by chemical changes. 66. Methods of Testing Materials. The extent to which the various materials possess the required qualities is ascertained in two ways: (1) by actual use in the roadway (this method is known as the "service test"); an d (2) by investigations and experi- ments made in a laboratory. 66a. Service Tests are conducted by laying strips of the dif- ferent materials in the same roadway where they are subjected to the same amount of traffic under similar conditions for an extended period of time, observations of their behavior being made from time to time. This method is objected to on account of the large expenditure of money and the great length of time required before any definite conclusions can be drawn. Service tests have been carried out in the cities of Washington, Boston, and Detroit. 66b. A modification of the service method has been used in St. Louis, Mo. The different materials were laid in strips measur- ing 22 inches wide and 8 feet long, and a two-wheeled cart with tires 2J inches wide loaded to two tons, or 800 pounds per inch width of tire, was rolled back and forth by machinery for a length of time sufficient to cause an amount of wear equal to that of eight and one half years' use on the street. The heaviest traffic at that time in St. Louis was 75 tons per day per foot of width, and the average for business streets was 35 tons. Estimating the effect of horses' shoes at one third of this amount, 50 tons per foot were taken as a standard. The total abrasion of the fire-brick pavement was 9%, or a depth of f of an inch, but about one half of the bricks were broken. Asphaltum blocks under the same test wore 14%, and but one was 28 HIGHWAY CONSTRUCTION. brcken. Broken stone lost 1% under a traffic of 12.7 tons per foot of width. Broken stone and sand lost 1% under 16 tons per foot. Limestone blocks lost 1% under 4400 tons per foot of width. Wood blocks lost 1% under 12,900 tons per foot, and the granite blocks lost 1% under 70,000 tons. The action of the elements was not taken into consideration ; it would undoubtedly increase the wear of the several materials. 66c. Laboratory Investigations. In the laboratory, while it is difficult or impossible to reproduce the exact conditions of service, it is possible by submitting samples of the materials to similar tests under uniform conditions to determine in a comparatively short time and at a small cost the enduring value of each property and to closely predict the behavior of the material under any given conditions. 66d. The systematic testing of road-building materials was first introduced by the government engineers of France about 1865, since which time they have made extensive investigations for the purpose of determining the wearing value of stones, and have established coefficients of quality (given in Table XXXVIII) to serve as a guide in selecting new quarries. In 1881 the government engineers of Portugal undertook the systematic testing of road materials. In England and other sections of Europe but few investigations or tests have been made. In the United States the Massachusetts Highway Commission established in 1893 the first laboratory for the testing of road-builcl- ing materials; since then several State laboratories and the U. S. Road Material Laboratory have been equipped with appliances for testing such materials. 67. Description of Materials. Rocks. The rocks from which the stone for paving purposes is obtained vary in quality within wide limits, according to their geological position, physical structure, and chemical composition. Several varieties of structure are met with the same chemical constituents, this being due to the degree of crystallization of the mineral elements. These differences fit the various rocks for special purposes. The principal varieties of rock employed for paving-blocks are the granites, basalts, sandstones, and limestones, because of the MATERIALS EMPLOYED IN THE CONSTRUCTION OF PAVEMENTS. 29 facility with which they split into the desired shapes; for broken- stone pavements all varieties of rock are used, including the flints and gravels. 68. Granite is an unstratified igneous rock composed of quartz (pure silica), feldspar (silica, alumina, together with potash, soda, or lime), and either the potash mica (muscovite) or the iron- magnesia mica (biotite) or both. Hornblende may take the place of mica. In addition to these essential constituents one or more accessory minerals may be present, and in many cases the quantity of these and the manner of their aggregation determines the char- acter and quality of the granite. 68a. The durability of granite depends to a great extent upon the character of the feldspar present, some varieties being moderately stable, while others become quickly kaolinizBd. The question of the relative durability of different feldspars is not easy to solve, and much difference of opinion exists. Merrill states that in the pegmatite dykes of Delaware and Pennsylvania the microcline (potash feldspar) remains remarkably fresh and translucent, while the oligoclase rapidly weathers into a friable gritty mass. Of the micas, the white or muscovite is the most durable. The black mica, or biotite, is rich in iron oxides, and is often found in a more or less decomposed or altered state. Hornblende usually occurs in stout, fibrous prisms of dark-^reen color and gives toughness to the granite; it yields slowly to atmospheric influences, gradually breaking down into a ferruginous clayey residue. Of the accessory minerals the most detrimental are pyrites and magnetite, which are readily oxidized. 68b. The structure of granite varies considerably from coarse to fine and is termed the holocrystalline, which implies that it is made u~^ r xclusively of crystalline particles having clear, well- defined boundaries without any intervening matrix. Of the different kinds of granite, those which are compact and composed of orthoclase feldspar and muscovite are generally con- sidered the most reliable paving material; those containing an excess of mica are easily laminated ; when quartz is present in excess it renders the stone too brittle; an excess of feldspar causes the stone to decay rapidly in consequence of the action of air and water, the potash of the feldspar is removed and the residue 30 HIGHWAY CONSTRUCTION. consists of a white powder composed chiefly of silica and alu- mina. 68c. The colors of granite are white, gray, various shades of red, and occasionally green. The color depends upon the miner- als present : potash-spar communicates a red color, soda-spar pro- duces gray, while muscovite mica produces no changes; the black biotite mica darkens the color, hornblende and augite give a dark appearance, and epidote communicates a green color. 68d. Granite requires close examination to discover the altera- tion of the feldspars ; if the feldspar has been converted into kaolin, or replaced by chlorite, the hardness and cohesion of the rock will depend on the quartz alone. Such a rock is likely to break up rapidly. 68e. The term " granite" as popularly used is not restricted to rock species of this name in petrological nomenclature, but in- cludes what are known as gneisses (foliated and bedded granites), syenite, diorite, gabbro, and other crystalline rocks whose uses are the same. 681 Gneiss is similar to granite in composition, but differs from it in physical structure, which is fibrous or foliated, by reason of which it is unsuitable for blocks, and, as a rule, is too deficient in toughness for use as broken stone. 68g. Syenite differs from granite in having little or no quartz: it is a holocrystalline aggregate of orthoclase feldspar, hornblende, and a ferro-magnesian mineral, with some accessory plagioclase and possibly iron, zircon, apatite, and epidote. (It is called syenite because it was first found in the island of Syene in Egypt.) It is massive and its occurrence is like that of granite. It furnishes excellent material for paving-blocks, and is better in propor- tion to the darkness of color and the predominance of horn- blende. 68h. Diorite is the name given to rocks composed of a crystal- line mixture of oligoclase (soda and lime feldspar) and hornblende with magnetic iron and apatite. These rocks occur in an eruptive form and under conditions similar to syenite. When the com- ponent minerals are fine-grained and compact they make a very satisfactory material for broken-stone roads. When they contain labradorite (lime and soda feldspar) combined with a coarse tex- MATERIALS EMPLOYED Itf THE CONSTRUCTION OF PAVEMENTS. 31 TABLE V. PERCENTAGE COMPOSITION OF GRANITIC ROCKS. C & I 1 5 5 J" Name. "u a N fli <0 w o5 3 s | jj> C D 1 'So I M .2 J 'ft 1 . S a W " J . (Q W Granite, Mass. . 25.0 7.0 56.9 0.1 8.0 2.0 < i 75.0 20.0 5.6 . . . . . . . . 5 1 1 2 5 * * M&ss 81 5 4 5 4 1 3 Diorite, " .. 55.0 2.0 15.0 5.0 10.0 3.0 10.0 TABLE VI. SPECIFIC GRAVITY, WEIGHT, AND RESISTANCE TO CRUSHING OF VARIOUS GRANITES. Localities. Specific Gravity. Average Weight, pounds per cubic foot. Resistance to Crushing, pounds per square inch. 2.66 166 35,000 24,000 Chtiumout Bay N Y. 2 65 162 2 22 700 2.63 164.4 22250 Sharkey's Quarry, Me Richmond Va 2.72 22,125 21 250 Huron Island Mich 20 650 2 61 163 2 19750 Port Deposit, Md 19,750 Quincy Mass 2 66 166 2 19 500 Dulut.h Minn 19000 2 67 166 9 15 000 Mount Sorrel Eusrland . 2 67 167 12 800 Bay of Fundy Canada 11 916 Aberdeen, Scotland (gray) (red) 2.62 2 62 163 165 10,900 Dublin Ireland . . .... 10 450 New Haven Conn 9 750 Cornish, Wales 2 66 166 6 300 Patapsco, Md 2.64 163 5,340 HIGHWAY CONSTRUCTION. ture they quickly decompose and form large quantities of mud during wet weather. 69. Table V shows the percentage of common minerals in rocks of the granite species and will serve to indicate their gen- eral composition. Table VI shows the specific gravity, weight per cubic foot, and resistance to crushing of various granites. TABLE VII. PRODUCTION AND VALUE OF GRANITE PAVING-BLOCKS. State. 1889.* Value Thou- sand. 1904.t Value Thou- sand. Number of Blocks. Value. Number of Blocks. Value. California 7,303,321 $297,236 $40.70 5,534,250 53,150 1,464,656 366,475 6,677,265 9,808,465 983,575 5,678,562 1,004,325 697,852 60,000 1,892,260 1,246,100 330,000 417,700 190,000 677,688 1,138,190 163,825 $252,054 4,000 49,354 13,031 250,896 426,463 46,864 320,714 66,000 31,786 3,000 65,151 28,535 15,500 15,807 7,000 30,643 47,823 5,945 Colorado Connecticut. . . . Delaware 761,100 104,333 1,599,952 17,704,915 286,950 6,106,016 1,239,000 4,323,130 40,683 8,208 84,951 824,113 10,310 378,627 68,045 216,986 53.45 78.67 53.10 46.55 35.93 62.01 54.92 50.19 Georgia . Maine Maryland Massachusetts. . Minnesot a Missouri Montana New Hampshire. New Jersey New York 2,043,739 3,999,912 587,120 775,000 587,000 3,836,127 781,765 87,569 168,555 26,962 34,200 30,200 241,793 45,817 42.85 42.14 45.92 44.13 51.45 63.03 58.61 No. Carolina. . . . Oregon Pennsylvania. . . Rhode Island. . . So Carolina So Dakota 3,017,500 883,096 342,895 170,694 45,643 18,505 56.57 51.69 53.97 Vermont Virginia \V ashington 382,758 1,032,200 100,000 4,277,333 14,745 30,966 3,000 254,051 \Visconsin 5,540,000 179,075 32.32 Total 61,822,871 $2,978,172 $48.17a 44.176,629 $1,983,328 $44.89a * llth U.S. Census. f Mineral Resources of the United States, 1904. a Average. 70. Table VII shows the amount of production and value of granite blocks for street-paving throughout the United States for the years 1889 and 1904. From this table it appears that the MATERIALS EMPLOYED IN THE CONSTRUCTION" OF PAVEMENTS. 33 number of blocks used for paving in 1889 amounted to nearly 62,000,000, with a value varying from $32.22 per thousand in Wis- consin to $78.67 per thousand in Delaware. In 1904 the produc- tion was approximately 44,000,000, showing a decrease of about 20,000,000 in amount and a decrease in value of nearly $1,000,000. The price in 1904 varied from $15 per thousand to about $80 per thousand, according to siz3 and regularity of shape. 71. Value of Granite Blocks. In the most important States which produce paving blocks, namely, California, Maine, Massa- chusetts, Missouri, New Jersey, and Pennsylvania, the value varies from $40 to something over $60 per thousand. The variation in the price for these States, in all of which the production of paving- blocks has been going on for some time, is due to the quality of the stone used for these purposes, and also to the special care observed in trimming blocks to certain definite sizes. In some localities surface rock of inferior quality is broken up into paying-blocks, which are sold at low prices. In a number of cities considerable care is taken by the municipal authorities in the selection of the granite for paving material. This care is exercised both with reference to the quality of the stone and to invariability of size, and consequently the price paid is in some cases markedly higher than that paid in other cities more indifferent in regard to the material employed. 72. The following list is presented for the purpose of showing the various uses of granite for street and road construction : Paving-blocks. Basin-heads. Curbing. Crossing-stones. Flagging. Gutter-stones. Crushed for artificial stone; broken for concrete. 73. Manufacture of Granite Paving-blocks. The manufacture of paving-blocks varies in many of its details from the ordinary methods of granite-cutting. The high skill and fine workmanship of the stone-cutter are not needed, but a quickness in seeing and taking advantage of the directions of cleavage, as well as a deftness in handling the necessary tools, is requisite. The tools used for making blocks are knapping-hammers, opening-hammers, reels, chisels, and for initial splits drills, wedges, :and half-ronnds. When the block-maker quarries his own stock it is called " motion work," and the same process is used as in quarry- 34 HIGHWAY CONSTRUCTION. ing stone for other purposes, except that, as large blocks are not required, most of it can be done with plug and feather. Slabs, having been split out in the usual manner to sizes that may be easily turned over and handled by one man, are subdivided into pieces corresponding approximately to the dimensions of the required blocks. This is done by striking repeated blows upon the rock along the line of the desired break with heavy knapping and opening hammers. When a break is to be made crosswise the grain, it is frequently necessary to chisel a light groove across one face, and commonly across the adjacent sides, to guide the fracture produced by striking on the opposite surface with the opening- hammer. Good splits can, however, be made along either the rift or grain by the skilful use of the opening-hammer alone. Blocks broken out in the manner described are trimmed and finished with the reel, which is a hand-hammer having a long, flat steel head attached to a short handle. Block-makers become very expert in, die use of this tool, and without making any measurements turn out in a surprisingly short time a large number of blocks. In Maine, which is far ahead of any other State in the number of blocks made, the entire product of many quarries is used for this purpose exclusively. This is also the case in California, which comes second, though the blocks are manufactured chiefly from the surface "boulders" or detached masses of basalt so common in Sonoma County. Other quarries, however, in various parts of the country utilize only the " grout," small or irregular-shaped pieces,. for making paving-blocks, and haul the stock to the breakers, who work in sheds; but the greatest number of blocks are made on the spot where the rock is quarried, the workmen being protected during the hottest months by a temporarily spread canvas fly. Blocks are counted as they are thrown into the cart which is usually needed to haul them to the shipping point. Several paving- block quarries in Maine are situated on steep mountain-slopes so near water communication that blocks may be slid in long board chutes from the quarry directly into the hold of the vessel used for their transportation. Paving breakers seldom work by the day, but are paid a certain sum per thousand for making the blocks; the price paid in 1889 ranging from $22 to $30 according to the size of block made, kind of stone used, locality, and whether the tools were furnished and MATERIALS EMPLOYED IN THE CONSTRUCTION OF PAVEMENTS. 35 the blocks quarried by their employers. Workmen using their own tools are commonly paid one dollar more per thousand for the blocks made; and when they quarry the stock they use, from $2 to $5 per thousand is allowed in addition. 74. Sandstones are rocks made up of grains of sand which are cemented together by silicious, ferruginous, calcareous, or argilla- ceous material. From the nature of the cementing material the rocks are variously designated as ferruginous, calcareous, etc. In most cases the cementing material determines the color. The va- rious shades of red and yellow depend upon the iron oxides. The purple tints are said to be due to oxide of manganese. The gray and blue tints are produced by iron in the form of ferrous oxide or carbonate. 75. The hardness, strength, and durability depend upon the nature of the cementing material. If the cementing material be one which decomposes readily, as in the argillaceous and calcareous varieties, the whole mass is soon reduced to sand. 76. Sandstones are widely distributed, and they represent all of the geological periods, from the oldest to the most recent forma- tions. 77. The sandstones obtained from the Upper Silurian and the^ Lower Carboniferous formations are much used in the form of blocks, for street paving in the Lake and Western cities. They are durable' and do not become smooth or slippery when wet, but in the form of fragments for broken stone roads they are as a rule useless. 78. Hudson River Bluestone. The term " Hudson River blue- stone " is used to designate the blue, fine-grained, compact, and even-bedded sandstone which is so largely employed for flagging' and curbing in the cities and towns of New York and neighboring States. The color is predominantly dark gray and hence (more by con- trast with the red sandstone) a " bluestone." In texture the range is from the fine shaly or argillaceous to the highly silicious and even conglomerate rock. The best bluestone is rather fine-grained and not very plainly laminated, and its mass is nearly all silica or quartz which is ce- mented tegether by a silicious paste and contains very little argil- laceous matter. It is so compact as not to absorb moisture to any extent, and. 36 HIGHWAY CONSTRUCTION. hence soon dries after rain or ice; it has the hardness to resist abrasion and wears well; it is even-bedded and thus presents a good TABLE VIII. ANALYSIS OF SANDSTONE. Kind of Stone. Locality. 1 Oxides. c o> 1 onic Acid, r, and Loss. g | | 0- a i "o 1 a "S 33 ^ * 3 ^ PU CO D^ p. ct. p. ct. p. ct. p. ct. p. ct. p. ct. p. Ct.l p. t;t. p. ct. Manyard (E. Long-) 79.38 8.75 2.43 2.57 4.108 2.79 Worcester.. . -< meadow, > 88.89 5.95 1.79 0^41 0.27 0. 86 1.83 Kihbie ( Mass. \ 81.38 9.44 3 54 0.11 0.76 6. '28 4.49 Browns tone Portland, Conn. 69.94 J13.15 2.48 0.70 3 09 Trace 3.30 5 43 1.01 Sandstone.. Stonj* Pt., Mich. 84 57 ' 5.90 6.48 0.68 Unde ter'd 1.92 Quartzite... Buff Pipestone, Minn Amherst, Ohio. 84.52 9700 12 33 2 12 1.00 0. 31 1.15 Trace 0.11 0. 0.34 04 2.31 0.21 Berea.... 1 ... Berea, Ohio 96.90 1.68 0.55 0. 55 0.32 Euclid Bluest Euclid Co.. Ohio. 95.00 '2.50 1.00 ..'.. 1.50 Columbia... Columbia, Ohio. 96.50 i'.w .. '"o. 50'" 2.00 Red Laurel Run, Pa. 94.00 Trace i.'jw 1.10 1.00 1.92 Elyria Grafton, Ohio. 87.66 1.72 3.52 0.17 0.20 2. OS Sandstone .... Fond duLac, Mn. 78.24 10.88 3.83 0.95 1.60 1.67 '6"06 smooth natural surface, and it has a grain which prevents it from becoming slippery; it is not materially affected by freezing and thawing; it is strong and not apt to get broken if well laid. 79. Commercial Names of Sandstone. The commercial names of sandstone are usually obtained from places where it is quarried, as, Berea, Grit, Medina, etc. 80. Table VIII above, giving analysis of sandstone from a number of localities, will serve to indicate its general com- position. 81. The specific gravity, weight, and resistance to crushing of various sandstones is given in Table IX. The value of sandstone used for street purposes in the United States in 1889 and 1904 is given in Tables X and XL MATERIALS EMPLOYED IN THE CONSTRUCTION OF PAVEMENTS. 37 TABLE IX. SPECIFIC GRAVITY, WEIGHT, AND RESISTANCE TO CRUSHING OF VARIOUS SANDSTONES. Localities. Specific Gravity. Average Weight, pounds per cubic foot. Resistance to Crushing, pounds per square inch. Potsdam (red), N. Y 2 J Medina, N. Y* Maiden (bluestone), N. Y 2.75 Warsaw ( bluestone), N. Y 2 . 68 Albion, N. Y Craigleith, Scotland 2 . 45 Belleville, N. J 2.56 Kasota, Minn... Seneca, Ohio. . . Beresi, Ohio 2.57 Little Falls, N.Y. Dorchester, New Brunswick.. . . Vermilion, Ohio. Massillon, Ohio. . Cleveland, Ohio. Abroatli (pavement), England.. 2.47 Marquette, Mich 2. 53 Middletown (Portland), Conn... 2.62 North Amherst, Ohio. Oxford (bluestone), N. Y 2.71 Fond du Lac, Wis. Bristow, Va 2.61 Yorkshire, England 2 . 51 Warrensburg, Ohio. . Haverstraw, N. Y. . . Derby Grit, England 2.4 Cheshire (red), England 2.15 Nova Scotia 2.62 162.28 171.47 167.10 153 159.67 160.06 155 158.17 163.43 168.9 163 157 150 133 163.50 42,804 17,725 13,500 5,287 11,700 11,675 10,500 10,250 9,850 9,412 8,850 8,750 7,910 7,884 7,450 6,950 6,650 13,472 6,250 5,714 5,000 4,350 3,100 2,185 .38 HIGHWAY CONSTRUCTION". TABLE X. VALUE OF SANDSTONE USED FOR STREET PURPOSES IN 1904. State. 1889. 1904. Arkansas $8 215 $38 357 California 200 76 180 Colorado 509 955 123 442 Connecticut 2 250 40 Illinois 50 8048 Indiana 651 Iowa 880 370 Kansas 131,188 50,445 Kentucky 1,600 20,849 Louisiana 2 315 Maryland 2,045 -Massachusetts 40 471 155 960 Michigan 550 1,400 Minnesota 38,200 213,296 Missouri 2,512 2,130 Montana 2,999 Nevada 558 New Jersey 6,800 New Mexico 3,000 50 New York 459,158 1,084,244 Ohio 430,525 821,360 Oregon 111 Pennsylvania 175,062 574,859 So Dakota 134,379 Tennessee . . . 965 Texas . 520 Utah . 16,520 ^Washington 9,000 W Virginia 23,274 24,416 \Visconsin ... 10,662 \Vyoming . 3,250 Total $1,832,822 $3,384,176 TABLE XI. VALUE OF BLUESTONE USED FOR STREET PURPOSES. State. 1889. 1904. New Jersey $8,550 New York 475,403 $536,126 265,959 365,742 Total $749,912 $901,868 MATERIALS EMPLOYED IN THE CONSTRUCTION OF PAVEMENTS. 39 82. Limestone. Limestone is essentially carbonate of lime, but it always contains some additional constituent; the more commonly occurring impurities or accessory matters are silica in the form of quartz, clay, iron, magnesia, etc. And limestones are said to be silicious, argillaceous, ferruginous, magnesian, dolomitic, bitumi- nous, etc., according as they contain one or another of these con- stituents. Other foreign mineral matter may be found in them, and in p.uch quantity as to give character to the mass. In color there is a wide variation, depending upon the impu- rities; it ranges from the white of the more nearly pure carbonate cf lime through gray, blue, yellow, red, brown, and to black. The texture also varies greatly; it may be coarse or fine. The erms coarse-grained and fine-grained are applied when the mass resembles sandstone in its granular aggregations. Other terms, -as saccliaroidal (like sugar), oolitic, crinoidal, etc., are also used to describe the texture. The state of aggregation of the constituent particles varies greatly, and the stone may be hard and compact, almost vitreous, or loosely cemented and crumbling with slight pressure, like sugar, or, again, like chalk, dull and earthy. From this general statement of the range in composition and texture, it follows that there is an equally wide variation in hard- ness, strength, and durability of limestones. Some are hard and strong, surpassing in their resistance to crushing force many gran- ites, and nearly as durable as the best sandstone; others are friable and fall to pieces under slight pressure, or they are disintegrated rapidly by atmospheric agents. 83. The limestones are used for flagging and curbing, being- selected for these purposes on account of accessibility or cheapness. For broken-stone roads with light traffic the limestones are emi- nently suitable; they possess the quality of forming a mortar-like detritus which binds the stones together and enables them to wear better than a harder material that does not bind. For this purpose the most suitable ones are the silicious, magiissian, dolomitic, and bituminous. 84. Tte experience of all cities using paving-blocks of lime- .stone is that it wears unevenly, and in a year or two the blocks are shivered and split by the action of frost. Table XII shows the specific gravity, weight, and resistance to crushing of various limestones. Table XIII shows the value of lime- stone used for street purposes in 1890 and 1904, by States and Territories. 40 HIGHWAY CONSTRUCTION. TABLE XII. SPECIFIC GRAVITY, WEIGHT, AND RESISTANCE TO CRUSHING OP VARIOUS- LIMESTONES Localities. Specific Gravity. Averaere Weight, pounds per cubic foot. Resistance to Crushing, pounds per square inch. Joliet 111 ... 16 900 Bardstown, Ky 2 69 168 16 250 North River N Y 2 71 169 13 42") Marblehead Ohio 12 600 Glens Falls N Y 2 70 169 11 475 Marquette, Mich 8 050 Billingsville, Mo 7 250 Caen, France 8 650 Purheck England 2 6 162 9 160 Anglesea, " 7 579 Blue Lias " 2.467 154 TABLE XIII. VALUE OF THE PRODUCTION OF LIMESTONE FOR STREET USES IN THE UNITED STATES. State. 1890. 1904. Alabama $9,800 $7 915 Arkansas 500 34 580 California 1,390 5 875 Florida . . . . ... 300 Illinois ... 505,576 681 857 Indiana . ... 316,722 399 152 Iowa 53641 65 233 Kansas 97,502 79718 Kentucky 86,054 214 994 Maryland . ... 6,750 32 180 Michigan ..... 18,156 96320 Minnesota 11 778 66454 Missouri 670,351 489 843 Nebraska 86,643 16 523 New Jersey 2984 New York 197 091 441 737 No Carolina 12088 Ohio ... 183 235 778 021 6962 Oregon 150 Pennsylvania 72,512 438 357 So Carolina 125 Tennessee 3,400 67,133 Texas 32,278 23,089 Utah 5,995 Vermont . 2,098 931 Virginia 190 1,696 Washington 1,486 West Virginia 42,965 Wisconsin 27,789 276,775 Total $2,383,456 $4,289,932 MATERIALS EMPLOYED IK THE CONSTRUCTION OF PAVEMENTS. 41 85. Th3 n aterial called Ligonier " Granite," which is exten- sively used for paving, etc., is a silicious limestone from localities near Pittsburg, and is said to have a crushing strength of 23,000 pounds per square inch. 86. Trap-rock is the name commonly given to the large gru;ip of unstratified eruptive rocks known technically as basalts, diabases, and dolerites. The term trap is derived from the Swedish trappa, a stair, and is applied to those rocks because they fre- quently occur in large tabular masses rising one above the other like steps, as seen on the west shore of the Hudson River from Jersey City to Haverstraw. The trap-rocks consist essentially of feldspar, generally labra- dorite, together with augite, olivine. and magnetic or titaniferous iron, with apatite and sometimes other accessory minerals. The texture is generally close-grained and compact. The colors are either dark gray, dark green, or grayish black, the dark color being due to a large proportion of magnetite, which also contributes to the high specific gravity of these rocks. The trap-rocks are generally hard and tough, have no true cleavage, and break irregularly; they are usually difficult to work, but there is much variation in the rocks of different localities. The rock of the Palisades in New Jersey splits easily into blocks, and has been extensively used for paving in the cities of New York and New Jersey. They have also been extensively used for broken- stone pavements, and while all have not been uniformly satisfac- tory, still general experience places them the first in order of merit as a material for broken-stone roads. 87. Table XIV shows the crushing resistances, specific gravity, and weight of trap-rocks. Table XIVj shows the value of trap- rock used for street purposes in 1904. TABLE XIV. CEUSHING RESISTANCE, SPECIFIC GRAVITY, AND WEIGHT OF TRAP-ROCKS. Locality. Resistance to Crushing, pounds per square inch. Specific Gravity. Weight of one cubic foot, pounds. Staten Island, N. Y 22 2oO 2 86 178 8 Jersey City Heights N J 20 750 to 22 250 3 03 189 5 Palisades, N. J 19 700 42 HIGHWAY CONSTRUCTION. TABLE VALUE OF TRAP-ROCK PRODUCED IN THE UNITED STATES FOR ROAD PURPOSES IN 1904. State. Value. California ............................. $225,429 Connecticut ........................... 176,984 Massachusetts ......................... 203,958 New Jersey ............................ 595,214 New York ............................. 352,251 Pennsylvania .......................... 210,614 Total $1,764,450 87a. Essential Properties of Stone. The essential properties of stone to be used for paving purposes either in the form of blocks or broken fragments are (1) Hardness, (2) Toughness, (3) Uniformity of wear, (4) Maintenance of a rough surface under traffic during both dry and wet weather, (5) Durability, (6) Good cementing or binding property in the case of broken fragments. 87b. Hardness. The hardness of rocks depends upon the hard- ness of the constituent minerals: this hardness is measured by the resistance to scratching and is rated according to the scale usually employed for minerals, which is as follows: Quartz 7 Augite and other py- Feldspars 5.5-6.5 roxenes 5.0-6.0 Garnets 6.5-7.5 Dolomite 3.5-4.0 Olivine 6.5-7.0 Zeolites 3.5-5.5 Epidote 6.0-7.0 Micas 2.5-5.0 Tourmaline 7.0-7.5 Serpentine 2.5-4.0 Magnetite 5.5-6.5 Kaolinite 2.0-2.5 Pyrites 6.0-6.5 Calcite 3.0 Hornblende and other Chlorite 1 . C-2 . 5 amphiboles 5.0-6.7 Talc (steatite) 1.0-1.5 87c. The term "hard" is applied to rocks composed mainly of minerals whose hardness is 6 and upwards. The hardness of the mineral does not imply that the rock will be durable; many hard minerals are more subject to decay by atmospheric influence and solvents than those of a softer texture which possess chemical stability. The component minerals may be hard, but the rock MATERIALS EMPLOYED IN THE CONSTRUCTION OF PAVEMENTS. 43 may ba soft if the mineral particles do not adhere strongly to each other. Thus some sandstones are composed of quartz, but the grains are so weakly cemented together that the rock as a whole is soft and friable. 87d. Hardness without toughness is of little use. A stone may be very hard, but so brittle as to be crushed to powder under a heavy load, while a stone not so hard, but having a greater degree of toughness, will sustain a similar load without injury. Under the service conditions hornblende and other amphiboles display a greater resistance to abrasion than the feldspars, although the former are the softer minerals. 87e. Toughness. The toughness of rocks depends upon (1) the physical structure, texture, and coherence of the mineral grains, and varies according to the manner in which they are interlocked or bonded together, either by cohesion between themselves or by a cementing medium. With regard to the texture, fineness and evenness of grain are an advantage, coarse grain or porphyritic structure is detrimental. The structures which exhibit the great- est toughness in service are, in the order of their merit, the micropeg- matitic or micrographic, the microgranitic, and the ophitic. (2) The kind of mineral. With regard to the kind of mineral, it appears that, other things being equal, a high proportion of hornblende and quartz is the most favorable. (3) The state of freshness of the mineral. Fresh unaltered original minerals are not absolutely essential to a high capacity to resist abrasion. In attrition tests made in England by Mr. E. J. Lovegrove of the two stones which showed tb/> 7 i Driest resistance, the feldspars were decomposed, the ferro-ma" n ,sian minerals had changed to chlorite and to fibrous hornblende. Alteration of the minerals in the rocks of the granite species appears to have a toughening effect. 87f. Regarding the meaning of the terms "fresh," "altered/* and " decomposed" in their application to rocks or the minerals composing them there seems to be some confusion. The common employment of these terms is to convey ideas of goodness and badness; this is not the case when reference is made to rocks. When a mineral is referred to as being in a fresh condition it means that it possesses its inherent properties in an unimpaired state. 44 HIGHWAY CONSTRUCTION. A fresh rock is one in which the minerals that compose it are fresh. When a mineral within a rock is altered as the result of certain forces acting upon it, it breaks up into one or more new minerals, each one in its own way being as "fresh" as the original mineral It is thus possible for the alteration of a rock to make it actually stronger and more durable than before. Some of the new min- erals produced by alteration (molecular rearrangement) may be an improvement upon the original; others may be the reverse. When a rock is acted upon by surface weathering agencies it frequently happens that certain selected mineral substances are removed and the cohesion of the whole impaired or weakened or softer minerals may be introduced, as in the kaolinization of the feldspars in granite. This process is termed "chemical decomposition." The term "alteration" is also applied to the indurating, or hardening, which occurs in stone after it is removed from the quarry. In newly quarried stones the mineral constituents are often in a state of chemical instability, and the interstices are filled with quarry water; exposure to the atmosphere for a longer or shorter period allows this water to evaporate and causes the minerals to harden or pass into a chemically stable condition with- out changing their form. The rapidity with which chemical decomposition and decay takes place is influenced to a great extent by the climate: in warm climates, with rain only at long intervals, the action is slow; in humid climates, with rain at frequent intervals accompanied by variations of temperature, decay is rapid. 87g. Uniformity of Wear. In stones employed in the form of blocks it is essential to ease of traction and the avoidance of ruts that the surface should wear away evenly. Evenness of wear seems to depend upon the mineral composi- tion; rocks containing a large amount of easily weakened or soluble minerals as the carbonates, zeolites, marcasite, olivine, etc., will wear unevenly. 87h. Maintenance of a Rough Surface under Traffic. In order that the pavement afford a good foothold for horses and to aid in the manoeuvring of motor vehicles it is necessary that it maintain a rough surface under all conditions of the weather. To accom- plish this the stone must have a certain coarseness of grain or MATERIALS EMPLOYED IN THE CONSTRUCTION OF PAVEMENTS. 45 texture. The suitable degree of coarseness can only be ascertained by an examination of blocks of stone which have proved service- able. Fine-grained hard rocks wear smooth with rounded edger, and become slippery and dangerous. 87i. Durability. In order that it may prove durable the rock must possess in addition to hardness and toughness " chemical stability." The elements commonly considered unstable chem- ically ar3 fsrric oxide in the hydrated form, protoxide of iron, carbonate of calcium, and non-crystalline alumina. The chemical stability varies within wide limits and the ten- dency to decay is present in all rocks when brought under the oxidizing influence of air and water, and this tendency is still further intensified by the chemical action of the various acids found in roadways. 87j. The chemical durability of the rock-forming minerals varies considerably. Quartz, garnet, tourmaline, magnetite, and epidote are, chemically, very durable; quartz is practically un- affected by weathering or solvents. Pyrites is n6t stable and is quickly oxidized. The feldspars under weathering disintegrate or break up along cleavage lines. The white mica is chemically stable, the black unstable, but both are rapidly removed under the action of traffic. Olivine is rapidly decomposed and softened by normal atmospheric influences. 87k. Good Cementing or Binding Property. The binding power or, as it has now come to be called, the cementing value of a stone, is the property possessed by rock-dust or other finely divided material found in nature to act when moistened with water as a cement on the coarser fragments. This property varies not only with different kinds of rocks, but also with those identical in classification and chemical composition. The absence of cement- ing value is so pronounced with some varieties of rock that they cannot be made compact with the roller or by traffic. In consequence of the important influence of the binding prop- erty in the construction and maintenance of broken-stone roads it is essential to know its source and ascertain the principles or elements governing its action, so that the latter may be controlled or modified in service. From investigations made with this ob- ject by Mr. A. S. Cushman and described in Jour. Am. Chem. Soc., 46 HIGHWAY CONSTRUCTION. May, 1903, and from tests made in the U. S. Road Material Labora- tory, it appears that this property is due to the presence of amor- phous colloid (uncryst alii zed gum-like) particles, which by reason of their porous structure absorb water and become adhesive. The degree of adhesion so obtained is extremely variable even in the same rock species, and probably depends upon the amount of water present. The amount of combined or micellian water present in the colloids varies continuously with the temperature and vapor pres- sure of the atmosphere in which they are placed. Dried at high temperatures they lose nearly all the combined water, but re- absorb it when allowed to cool in free air or moist atmosphere. The process is effected without any apparent change in the physical appearance of the particles, in which it differs from the absorption of hygroscopic water, which produces a distinct appearance of wetness. The dehydration and rehydration may be repeated indefinitely unless the temperature of drying is raised too high, when the faculty is gradually lost and finally destroyed. Heat does not destroy the power of imbibing hygroscopic water. 871. It has been commonly considered that the cementing property was due to the presence of either oxide of iron, lime, or clay. The evidence obtained in the U. S. Road Material Laboratory indicates that it is not due to any particular mineral. Ccllcid preparations were made of the various minerals found in rocks, gravels, clays, and soils, such as iron, alumina, silica, and the various silicates of aluminum, calcium, iron, and magnesium; all were found to possess some degree of cementing power. The detritus of all rocks possesses the power of binding to a greater or less degree, being most marked in the traps, limestones, and sandstones and least in the slates and quartzites. 87m. In view of the fact that the dust on the surface of a road is being continually cemented, broken up, and recemented, and that clay and the dust from many rocks show an increase in cement- ing power under the prolonged action of water and kneading, ex- periments to ascertain the recementing value were made. The values obtained were generally smaller than the original cement- ing value. MATERIALS EMPLOYED IN THE CONSTRUCTION OF PAVEMENTS. 47 The cementing and recementing values of different rocks are given in Table XIVs. 87n. Methods of Testing Stone. The tests to which stones are subjected to in the laboratory are usually as follows. Stones to be used in the form of blocks are examined for: 1. Specific gravity; 2. Absorptive power; 3. Resistance to abrasion (test for hardness); 4. Resistance to abrasion with impact; 5. Resistance to impact (test for toughness); 6. Resistance to crushing (compression); 7. Petro logical analysis; 8. Chemical analysis; 9. Durability or resistance to weathering. Stones to be used in the form of broken fragments are examined as described above and in addition the dust or detritus is tested to ascertain its cementing or binding power. 87o. Specific Gravity. The specific gravity may be determined either by weighing in air and water or by a specific-gravity balance. Specific gravity and porosity are closely related. The specific gravity varies with the density or compactness of the aggrega- tion of the mineral grains forming the stone. The closer the grains the more compact and dense the stone, and the less will be the amount of interstitial space and hence the less porosity. A high specific gravity does not always imply superiority. From the specific gravity the weight per ton or cubic yard may be determined. A knowledge of the weight is useful in deciding between two otherwise equally good stones; the heavier will be the more expensive, due to increased cost of transporta- tion. On a broken-stone road it is an advantage to have a detritus with a high specific gravity, as it will not be so easily re- moved by rain and wind as one of low specific gravity. The specific gravity and weight of the various materials em- ployed are given in Tables VI, VII, VIII, XIV, XXII, and XXIV. 87p. Absorptive Power. The absorptive power of a material is usually determined by immersing a specimen in water for a cer- tain length of time. The method employed in the U. S. Road Material Laboratory and which requires the least manipulation 48 HIGHWAY CONSTKUCTIOX. and gives results sufficiently accurate for road-building purposes is as follows: A smooth stone weighing between 20 and 60 grams, and which has passed through the abrasion test, is selected and weighed in air, after which it is immersed in water and imme- diately reweighed in the water. After 96 hours of immersion it is again weighed in the water. The absorption capacity is then calculated by the formula Number of pounds of water absorbed ) by a cubic foot of rock j A B X62.5, in which A is the weight in air, B the weight in water immediately after immersion, C the weight in water after immersion for 96 hours, and 62.5 the weight of a cubic foot of water. The period of 96 hours was adopted for the reason that experi- ments showed that absorption practically ceases after about 62 hours. Table XIV2 shows the maximum and minimum amount of water absorbed by the principal rock species. Table XXI and XXIa shows the absorptive power of brick and Table XXIII gives the same for wood. TABLE XIV 2 . WATER ABSORBED BY THE PRINCIPAL ROCK SPECIES. Name of Material. Num- ber of Sam- ples. Maxi- mum Per Cent. Mini- mum Per Cent. Name of Material. Num- ber of Sam- ples. Maxi- mum Pei- Cent. Mini- mum Per Cent. Amphibolite. . . Andesite .... 6 3 6 11 2 12 7 16 2 2 1 1 6 0.32 1.30 4.34 2.72 2.43 0.48 0.59 2.95 0.04 0.20 0.13 0.05 0.18 0.10 1.16 0.06 0.25 1.60 0.05 0.11 0.04 0.03 0.01 0.13 0.05 0.05 Granite 15 46 1 4 9 7 16 3 2 2 1 1 0.89 2.84 0.14 0.82 2.40 8.84 0.59 3.07 2.57 0.30 0.11 0.18 0.06 0.03 14 0.06 0.02 0.30 0.11 0.81 0.34 0.24 0.11 0.18 Limestone .... Peridotite. . . . Quartzite Rhyolite Sandstone. . . . Schist Shale Basalt Chert Conglomerate. . Diabase Diorite . . Dolomite Eclogite Slag Felsite Flint Oabbro Slate Steatite Syenite Gneiss 87q. Resistance to Abrasion. Test for Hardness. The resist- ance which rocks, bricks, and other materials offer to abrasion MATERIALS EMPLOYED IN THE CONSTRUCTION OF PAVEMENTS. 49 without impact, as in the case of footway pavements, steps, and floors, depends upon the hardness of the component particles. This property is measured by determining the amount worn aw r ay by grinding during a given length of time. The first apparatus used for this purpose was invented by a French engineer named Dorrey, and the test is commonly referred to as the "Dorrey" test. The apparatus used in the U. S. Road Material Laboratory and shown in Fig. A consists of a circular cast-iron plate revolving horizontally FIG, A. DORREY MACHINE FOR TESTING HARDNESS. round a vertical spindle. The specimens, formed of rectangular prisms measuring 4X6X8 centimeters, are held in sliding clamps so arranged and weighted that the specimens are constantly pressed against the surface of the revolving plate, with a pressure of 250 grams per square centimeter. The wearing action is produced by feeding quartz sand of a determined quality and size to the plate as it revolves. The quantity of sand used in each test is 4 liters. The plate is rotated for two hours at the rate of 2000 50 HIGHWAY CONSTRUCTION. revolutions per hour. The height of the specimen is measured both before and after the test, and the difference is taken as the wear. The " Bauschinger " apparatus, modelled after that cf Dorrey, consists of a cast-iron plate, about 5 feet in diameter, revolving on a vertical spindle. The samples to be tested are dressed to 4 inches square, are fixed in position, and weighted with a lead cf 4 pounds per square inch. Tests are made both with and without the use of water. Fine emery is used as the abrading medium, being fed onto the plate at the rate of about 20 grams for every 10 revolu- tions. The speed is 20 revolutions per minute and 200 revolutions complete a test. FIG. B. MACHINE FOR TESTING ABRASION, MARYLAND GEOLOGICAL SURVEY. A modified form of the Dorrey machine, made and used by the Highway Division of the Maryland Geological Survey, is shown in Fig. B. The test-pieces used are cylindrical cores 1 inch in diameter, made with a diamond drill from specimens of the mate- rial to be tested. They can be prepared with much less work than is necsesary to prepare the rectangular-shaped test-pieces. The MATERIALS EMPLOYED IN THE CONSTRUCTION OF PAVEMENTS. 51 apparatus consists of a grinding-wheel W ', which may be of car- borundum or iron, to which water and sand are fed through a tube in the center, and a cross-piece, F, to which are fastened at equal distances and on opposite sides from the center two brass sleeves A which carry the brass tube B containing the cores R of the material to be tested. The sleeve A has a longitudinal slot E r through which a pin passes to the tube B, to which it is fastened and prevents it from rotating. The core is fastened in the tube B by a key D. The test is made as follows: Cores of two varieties of rock are prepared and placed in the tubes. The cores are pressed: against the face of the wearing wheel by a five-kilogram weight,, C, suspended on the pivot H at the end of a tube, G, which rests: directly on the core R. After a certain number of revolutions the amount each core has worn away is measuured by comparing their lengths before and after the test. The ratio of the differ- ence so found is the ratio of the wear sustained. Experiments made by Bauschinger to ascertain the resistance^ to abrasion show: 1. That wet grinding produces a loss about twice as great as^, dry grinding; 2. That there is no relation between crushing strength and abrasive resistance; 3. That the limestones wear about five times and the sand- stones about four times as fast as the granites, porphyries, and basalts; 4. That the clay slate shows the least loss, but only a few specimens were tested; 5. That brick and tile wear about twice as fast and the cement compositions about three times as fast as the primitive rocks; 6. That the resistance of asphalt paving to abrasion falls be- tween the cement mixtures and stands tone. The average results of Bauschinger's abrasion (without impact) tests are given in Table XIVs. Four-inch cubes of the material were pressed on an iron plate with a weight of four pounds per square inch and 20 grams of emery fed every 10 revolutions and revolved 200 times at a radius of 19.5 inches. HIGHWAY CONSTRUCTION. TABLE XIV 3 . AVERAGE RESULTS OF BAUSCHINGER'S ABRASION TESTS OF PAVING MATERIALS. Kind of Material. Aver- age Specific Average Weight per Cu. Ft. Average Compres- sive Strength Number of Re- sults How Ground, Average Loss of Ratio : Loss wet Grav- ity. Pounds. in Pounds per Sq. In. Aver- aged. Wet F in Cu. Ins. Loss dry Granite 2.63 164 22,400 f 92 D. 0.24 I i 70 I 8 W. 0.46 J L Syenite 2.27 142 lb,780 24 D. 0.28 I i on 1 1 W. 0.82 / A . *y\j Diorite 2.87 180 26,200 ( X D. 0.27 } 1.90 I 2 W. 0.68 Hornblende. . 2.82 176 21,900 2 D. 0.19 Porphyry 2.57 161 24,500 / 93 I 8 D. W. 0.20 0.24 } 1.72 Basalt 3.01 188 34,200 | 86 D. 0.19 1 2.31 I 4 W. 0.47 I Gneiss. ... . . 2.61 163 23,000 4 D. 0.21 Quartz 2.63 165 17,500 9 W. 0.19 Clay slate . . . 2.72 170 26,000 { I D. W. 0.16 0.35 J2.76 Breccia 2.61 163 22,600 10 D. 0.20 Limestone . . . 2.87 180 20,500 163 32 D. W. 1.10 1.41 1 1.60 Sandstone. . . 2.48 155 17 ; 600 44 38 D. W. 0.81 0.64 } 2.25 Brick and tile 2.98 187 105 D. 0.38 1 2.50 Artificial sto'e 34 W. 0.75 J made with Portland cement. .. . Asphalt pav- ing. . 2.36 2.33 148 146 r 20 I 4 i 2 D. W. D. 0.51 1.82 0.61 } 3 . 20 ' 1 2.68 *"& I 2 W. 1.62 } The ratios of loss given in the last column have been taken out from the wet and dry tests on identical material, and therefore are not the ratios of the two general average results in the pre- vious column. 87r. Resistance to Abrasion and Impact. The resistance offered by a material to abrasion combined with impact depends upon its toughness and not upon its hardness. Materials which yield easily to this form of disintegration produce roads which are muddy in wet weather and dusty in dry weather. MATERIALS EMPLOYED IN THE CONSTRUCTION OF PAVEMENTS. 53 The extent of, this resistance is determined by placing a known weight of the material broken into fragments in a tight drum or cylinder of cast iron which rotates about an eccentric axis so that the fragments of material roll over one another and shift from end to end of the cylinder. The machine employed to test this property was invented by Deval, a French- engineer. It consists of two or more iron cylinders measuring 20 cm. (7.9 ins.) in diameter and 34 cm. (13.4 ins.) in depth, fastened to a shaft so that the axis of each cylinder is at an angle of 30 degrees with the axis of rotation. The shaft which carries the cylinders is supported on bearings and has at one end a pulley by which the cylinders are revolved and at the other end a revolution counter. The Deval type of machine used by the U. S. Road Material- Laboratory is shown in Fig. C. The method of conducting a test is as follows: The rock to be tested is broken into fragments as nearly cubical in form as possible, with dimensions not less than 1J inches nor greater than 2 inches, measured through the corners on the long- est line of the fragment. Fragments which have thin, sharp edges, liable to break off easily are rejected. FIG. C. DEVAL MACHINE. The amount of rock used for a test is 5 kilograms, or 11 pounds, which is weighed with minute accuracy. In some cases the rock is first washed and dried before weighing. The charge is placed in the cylinder, the cover secured in place, the cylinder is then rotated at a uniform rate of 2000 revolutions per hour for five hours, or until the automatic recorder shows 10,000 revolutions; the machine is then stopped, the cylinders opened and the con- tents removed and placed on a sieve having meshes of 1/16 inch. .54 HIGHWAY 'The material which passes through this sieve is put aside for use in the cementation test. The sieve and the remaining fragments are then placed under running water until all the adhering dust is washed off. The fragments are then dried and carefully weighed ; the difference between this weight and the original 5 kilograms, or 11 pounds, shows the amount worn off during the test. The percentage which the 1/16-inch dust bears to the original Tveight may be taken as the basis of comparison or the French coefficient of wear may be determined by the formula which is Ibased upon the fact that only the best varieties of rock show^ a -wear of less than 20 grams per kilogram, or 2 per cent, of the original weight. The formula is as follows: 20 400 Coefficient of in which W is the weight in grammes of dust less than 1/16 inch per kilogram or per 2.2 pounds of rock used. To determine the amount of abrasion in the presence of water, about half a gallon of water is put into the cylinder with the stones and the test conducted as described above. In Table XIV4 are given the maximum and minimum per- centages of wear and the coefficient according to the French stand- ard for several varieties of rock tested by the U. S. Road Material Laboratory. 87s. Resistance to Impact (Test for Toughness). The resist- ance offered to fracture under blows is estimated by counting the number of blows given by a hammer of known weight to fracture the rock or reduce it to powder. The French engineers employ for this purpose a machine modelled after a pile-driver. It con- sists of vertical guides in which a hammer slides. The hammer is raised by a cord which passes over a pulley at the top of the guides, and can be released at any desired height, from which it falls upon the specimen which is held by clamps at the foot of the guides. Two hammers are employed, one weighing 42 kilograms {92.4 pounds), which is used with a fall of 100 cm. (40 ins.), and the other weighing 20 kilograms (44 pounds) is used with a fall of 80 cm. (32 ins.). The test-pieces used are 4 cm. (1.58 ins.) MATERIALS EMPLOYED THE CONSTRUCTION' OF PAVEMENTS. 55 TABLE XIV 4 . ABRASION AND IMPACT TEST COEFFICIENTS OF WEAR. Per Cent. of Wear. Coefficiem of Wear. Name of Material. Samples. Maximum. Minimum. Maximum. Minimum. Ampliibolit6 . . . 6 4 6 1 5 26 7 8 5 Andesite 3 6 4 2 6 15 2 6 3 Basalt . 6 16 6 1 7 23 6 2 4 Chert .... 10 27 9 2 7 14 6 1 4 Clay 1 19 1 19 1 2 1 2 1 Conglomerate 2 12 7 5 7 7 3 2 Diabase . ... 14 6 3 1 2 34 5 6 4 Diorite 8 3 4 1 9 20 6 11 7 Dolomite 15 18 6 2 5 16 1 2 2 Eclogite 1 2 9 2 9 13 8 13 8 Felsite 2 3 4 1 9 21 3 11 9 Field stone (erratics). . Flint 1 1 5.0 7 2 5.0 7 2 8.0 5 5 8.0 5 5 Gabbro 1 2 9 2 9 14 3 14 3 Gneiss 6 5 2 1 9 20 7 7 7 Granite 15 14.8 1.8 21.7 2 7 Limestone 46 34.2 2 8 14 2 1 2 Mixed stone 1 8 7 8 7 4 6 4 6 Peridotite 1 3.6 3 6 11 1 11 1 Quartzite 3 3 6 2 2 18 2 11 1 Rhyolite 9 9 7 1 8 22 9 4 1 Sandstone 7 31 8 3 4 11 6 1 3 Schist 16 7 1 1 9 20 6 5 7 Shale . 2 16 2 4 7 8 6 2 5 Slao- . 2 8 3 7 6 5 2 4 8 Slate 2 6 9 4 7 8 5 5 8 Syenite 1 2 8 2 8 14 4 14 4 cubes, and these cubes are used for each specimen with each hammer. The test devised by Mr. Logan Waller Page, chief of the U. S. Road Material Laboratory, is made with the machine shown in Fig;. D. The specimens used are 25 mm.x25 mm. (0.98 inch) cylinders. The test-piece is adjusted so that the center of its upper surface is tangent to the spherical end of the plunger, and the plunger is pressed firmly upon the test-piece by two spiral springs which surround the plunger guide-rods. The test-piece is held to the base of the machine by a device which prevents its rebound- ing when a blow is struck by the hammer. The hammer weighs 2 kilograms (4.4 pounds) and is raised by a sprocket-chain and 56 HIGHWAY COXSTRUCTIOH". released automatically by a concentric electro-magnet. The test consists of a 1-cm. fall of the hammer for the first blow and an increased fall of 1 cm. for each succeeding blow until the test-piece fails. The number of blows required to de- stroy it is used to represent the toughness. In England Mr. Clark of Truro has made N r impact tests with a hammer weighing 15 pounds falling 10 inches onto an anvil on which was placed 3 pounds of the stons to be tested, broken into fragments of such size as to pass in all directions through a 2^-inch ring. The blows were continued until all the stone was broken small enough to pass through a sieve having a J-inch mesh. The kind of stone tested and the number of blows required to reduce it were as follows: Kind of Stone. Number of Blows. Quartz 265 to 295 Sandstone 440 Quartzite 451 Basalt 724 Greenstone 909 87t. Resistance to Crushing (Compres- sion Test). The resistance to crushing is ascertained by submitting specimens of the material to pressure in a hydraulic press and noting the pressure at which the specimen is first cracked and afterward completely crushed. The specimens are usually 25-mm. cubes and these are used for a test. The resistance offered is obtained in kilograms per square centimeter of bearing surface, and FIG. D- PAGE IM- the average of the results furnished by the FOR T DE M TE C R H Mm E - difeent CubCS 1S USed " ING TOUGHNESS. The results obtained for the same kind MATERIALS EMPLOYED IN THE CONSTRUCTION OF PAVEMENTS. of stone frequently varies within considerable limits, this variation being due to flaws in the samples and variations in mineralogical structure. The resistance to crushing of the various materials is given in Tables VI, VII, VIII, XIV, XXI, XXIa, XXII, and XXIV. 87u. Petrographic Analysis. The microscopic examination re- veals very clearly the nature of the component minerals, their in- terlocking, decomposition, and alteration, as well as the presence of secondary products, which may affect the chemical stability. For this investigation a thin chip of the rock is ground with emery until it becomes transparent; it is then mounted upon a micrc- scope-slide and examined. 87v. Chemical Analysis. The chemical analysis is employed to supplement the petrographic examination as well as to deter- mine qualitatively and quantitatively the constituents. From the chemical analysis conclusions can usually, though not always, be drawn as to the weathering properties. 87w. Cementation Test. The binding or cementing power of rock-dust is determined by the method and machines devised by ELECTRICAL ATTACHMENTTOR OPENING AND CLOSING THREE-WAY COCK. FIG, E, BRIQUETTE MACHINE, Mr. Logan W. Page, Geologist of the Massachusetts Highway Com- mission. The test is made by wetting the dust obtained from the abrasion test in the Deval machine or purposely preparing it in a 58 HIGHWAY CONSTRUCTION. ball-mill and forming it into cylindrical briquettes 25 mm. (0.98 inch) in diameter and height. The briquettes are moulded in the machine shown in Fig. E by forcing the moist powder into a steel die under a pressure of 100 kilograms per square cm. (1.422 pounds FIG, F. PAGE IMPACT MACHINE. per sq. in.). Five briquettes are usually made from each sample. The briquettes are dried either for two weeks in a temperature of 60 to 70 F., or dried for twelve hours in air and twelve hours in a steam-bath, and then cooled in a desiccator, after which they are broken by impact in the Page machine shown in Fig. F. It con- MATERIALS EMPLOYED IN THE CONSTRUCTION OF PAVEMENTS. 50 sists cf a 1-kg. (2.2 pourids) hammer H, which is guided by two vertical rods D. The hammer H, which ends in a small cone at the top, L, is caught on the lower side of the cone by two spring- bolts, S, and is lifted by a cross-head, 7, which is joined to a crank- shaft above. A vertical rod, P, which is directly over the hammer cone, can be adjusted by thumbscrews to give a drop to the ham- mer varying from a fraction of a millimeter to 10 cm. This rod has a hollow cone at its lower end into which the cone of the ham- mer-head is thrust when the hammer is lifted by the cross-head /. When the cone of the hammer-head is brought into the cone of the adjusting-rod the hammer is exactly centered and brought free of the guide-rods D. As the cross-head 7 continues to rise, the bolts supporting the hammer, which are tapered at an angle of about 45 degrees, are thrust open by the sloping head of the adjusting cone rod P, releasing the hammer, which falls on a flat-end plunger, 7?, of 1 kg. weight, which is pressed upon the briquette, , by two light spiral springs surrounding the guide-rods, F. This plunger, B, is bolted to a cross-head, G. A small lever, .7, holding a brass pencil, K, at its free end is connected with the side of the cross- head by a link-motion arranged so that it gives a vertical move- ment to the pencil five times as great as the movement of the cross-head. The pencil is pressed against a drum, A, and its move- ment is recorded on a slip of silicated paper fastened thereon. The drum is moved automatically through a small angle at each stroke of the hammer; in this way a record is obtained of the move- ment of the cross-head during and after each blow of the hammer. To the cross-head G is fastened a steel rod R, which passes up through the cross-head 7 and through a piece of metal securely attached to the cone -rod P. At this junction a vernier scale is graduated, by means of which the height of blow of the hammer can be accurately set to 0.1 mm., and by lowering the cone rod until it rests on the hammer cone L, the height of the briquette can also be measured to 0.1 mm. The standard fall of the hammer for a test is 1 cm. (0.39 inch), and this blow is repeated until the bond of cementation of the material is destroyed. The blow producing failure is easily ascer- tained, for when the hammer falls on the plunger, if the material beneath it can withstand the blow it recovers; if not, the plunger 60 HIGHWAY CONSTRUCTION. stays at the point to which it is driven, and in either case the be- havior of the test-piece is recorded on the drum. The automatic record thus obtained from each briquette is filed for future reference. The number of blows required to destroy the bond .of cementation or resilience, as described above, is noted and the average obtained upon five briquettes is given as the cementing value. As the surface of a broken-stone road is constantly abraded and recemented, tests have been made to ascertain the value of the recementing property. The fragments from the cementation tests are pulverized, again mixed with a definite quantity of water, moulded into briquettes and tested in the same manner as for the cementation test. The tests indicate that the value of the re- cementing property is less than the cementing value except in a few cases, as with dolomitic limestone, in which it is greater. A comparison of the cementing and recementing value of several rocks is given in Table X TABLE XIV 5 . CEMENTING AND RECEMENTING VALUE OF VARIOUS ROCKS. (U. S. ROAD MATERIAL LABORATORY.) Name of Material. Cementing Value. Recementing Value. Diabase (trap). 110 89 (i 49 44 Limestone (fernisrinous) . . 158 72 ' ' (dolomitic). . 59 42 n 22 30 1 1 110 126 Gravel 11 13 Sandstone 54 23 Novaculite (chert) 24 18 Hornblende schist . . . 7 9 The value of the recementing property seems to be affected to some extent by the continued presence of water, and kneading experiments made with a dolomitic limestone indicate that the value is increased by kneading. A sample moulded and tested at once showed a value of 16; tested at the end of twenty-four hours the value was 81; kneaded for one hour and tested the value was. 190. MATERIALS EMPLOYED IN" THE CONSTRUCTION OF PAVEMENTS. 61 87x. Durability or Eesistance to Weathering. The durability of stone employed for paving purposes depends upon its resistance to chemical decomposition; this is influenced by the chemical com- position of the. constituent minerals, and to some extent by the climatic conditions under which the stone is used. It is also af- fected to a certain extent by the porosity or capability of the ma- terial to absorb water. A low absorbing capacity is a matter of much importance in cold climates. Non-porosity, however, is not always a quality synonymous with durability, for many materials that absorb water also permit of its rapid evaporation; such mate- rials are likely to prove more durable than those that absorb less water and part with it more slowly. The only reliable test of the weathering quality of stones is that of actual service under the given conditions, but as this is not always practicable certain tests have been devised which will in a comparatively short time simulate the effect produced by climatic changes during a long period of time and thus enable an estimate to be made of the probable durability and behavior of the given stone. These tests comprise the determination of the porosity or resistance to absorption, resistance to freezing, and the action of acids. 87y. Resistance to Freezing. To ascertain the probable ability of a stone to resist the expansion caused by freezing water several tests have been devised, that known as "Brard's," in which a weighed sample of the stone was immersed in a saturated solu- tion of sulphate of soda the crystallization of which in the pores of the ston"! produced a force similar to that of freezing water, has been muca used; an easier method is to reproduce the actual effect of freezing by artificially freezing the sample after prolonged immersion in water. 87z. Resistance to Acids. The resistance to the action of acids is determined by immersing a weighed sample in the required acid or in water saturated with it; the period of immersion is usually six weeks, at the end of which the sample is removed, washed in pure water, and weighed. The difference between the weights indicates the loss. 62 HIGHWAY CONSTRUCTION. 88. Bitumen, Asphaltum, Asphalt. Bitumen is the name used to denote a group of mineral substances, composed of different hy- drocarbons, found widely diffused throughout the world in a variety of forms which grade from thin volatile liquids to thick semi-fluids and solids, sometimes in a free or pure state, but more frequently intermixed with or saturating different kinds of inorganic or organic matter. 88a. To designate the condition under which bitumen is found different names are employed; thus the liquid varieties are known as naphtha and petroleum, the semi-fluid or viscous as maltha or mineral tar, and the solid or compact as asphaltum or asphalt. 89. Three distinct varieties of asphaltum are recognized, namely, the earthy, the elastic, and the hard or. compact. 89a. The earthy variety, represented by the chapopota of Mexico, Colombia, and other parts of South America, has a brown- ish-black dull color, an earthy uneven fracture, when freshly ex- cavated a strong though not unpleasant earthy odor, is soft enough to take an impression of the nail, hardens slightly on exposure to the atmosphere, and burns with a clear brisk flame, emitting a powerful odor, and depositing much soot. 89b. Elastic asphaltum is of various shades of brown; is soft, flexible, and elastic; it has an odor strongly bituminous, and is of about the density of water; it burns with a clear flame and much smoke. Like caoutchouc, it takes up pencil marks, and on this account is called mineral cauotchouc ; it has been found only at three places: in the fissures of a slaty clay at Castleton, England; at Montrelais, France; and in Massachusetts. 89c. Hard or compact asphaltum is the most useful variety; it forms large deposits in many parts of the world, and is of various degrees of quality, according to its age and the impurities mixed with it; when nearly pure its ordinary characteristics are as follows: Color brownish black and black; lustre resinous or coal-like; opaque. At temperatures below 100 F. it is brittle and breaks with a conchoidal fracture. Melts ordinarily at 190 F. to 195 F., and is liquid at about 212 F. At 212 F, it has a peculiar but agreeable aromatic odor, somewhat resembling, but still very differ- ent from, that of coal tar; at ordinary temperatures the odor is scarcely perceptible, but when rubbed it is quite strong. It kindles. MATERIALS EMPLOYED IX THE CONSTRUCTION OF PAVEMENTS. 63 readily and burns brightly with a thick smoke. Distilled by itself it yields a bituminous oil of a yellow color (consisting of hydrocar- bons mixed with oxidized matter), water, some combustible gases, and sometimes traces of ammonia. After combustion it leaves about one third of its weight of char- coal and ashes containing silica, alumina, oxide of iron, sometimes oxide of manganese, lime, and other inorganic and organic matter. Its composition and hardness are variable. Specific Gravity. Pure bitumen has a density less than water; but in consequence of the impurities mixed with it the specific gravity of asphaltum varies from 1.0 tc 1.7. Solubility : It is insoluble in water, partly or wholly soluble in chloroform and disulphide of carbon, partly or wholly in oil of turpentine and petroleum ether, and commonly partly in alcohol. 90. By different solvents asphaltum may be decomposed into three distinct though complex substances which have been named by Boussingault and other chemists who have investigated it petrolene, asplialtene, and retine. Nothing definite is known concerning these compounds or how their variable proportions and composition affect the quality of an asphaltum. In the past they have received but little attention from chemists, due probably to the limited use of asphaltum; but now, in view of its large and increasing employment for paving and other industrial purposes, their investigation offers a wide and undoubtedly profitable field for chemical research. 90a. The characteristics of these compounds, so far as known, are generally as follows : Petrolene is the compound which is considered to give the vis- cous or adhesive quality. It may be described as that portion of the bitumen which is soluble in petroleum ether. It is lighter than water, very combustible, and has a high boiling-point, pale yellow color, and peculiar odor. On evaporating off the ether it remains as a resin with a brownish-black color, which dissolves readily in the volatile oils. Its composition is carbon, hydrogen, and sulphur. The amount present in an asphaltum is variable, ranging from 3 to 70 per cent of the weight of the asphaltum.* * It has been found that a bitumen suitable for paving purposes should contain at least 70 per cent of petrolene. HIGHWAY CONSTRUCTION. Asphaltene is the compound which gives the hardness to as- phaltum. It contains the elements of petrolene, together with a quantity of oxygen, and probably arises from the oxidation of that compound. It is that portion of the bitumen which is insoluble in ether. It is dissolved out by carbon disulphide. chloroform, benzene, etc. Its color is a brilliant black; density greater than water. It burns like resins in general, leaving a very abundant coke. Like petrolene, it is composed of carbon, hydrogen, and oxygen, and the amount present in an asphaltum is as variable ranging from 1 to about 60 per cent. Retine is dissolved out by alcohol (anhydrous) from that por- tion of the asphaltum which is unaffected by the solvents above mentioned. It is a yellow resin composed of carbon, hydrogen, and sulphur What effect this compound has upon asphaltum is unknown. Some authorities claim that its presence is injurious. 91. Origin of Bitumen. The origin of bitumen is unknown. It is supposed to be the ultimate product resulting from the destruc- tion under certain conditions of the organized remains of animals and vegetables, producing (1) naphtha, (2) petroleum, (3) maltha or mineral tar, (4) asphaltum. The whole of these substances merge into each other by insensible degrees, so that it is impossible to say at what point maltha ends and asphaltum begins. Naphtha, the first of the series, is in some localities found flowing out of the earth as a clear, limpid, and colorless liquid; as such it is a mix- ture of hydrocarbons, some of which are very volatile and evapo- rate on exposure. It takes up oxygen from the air, becomes brown and thick, and in this condition it is called petroleum. 91a. The hardening of the bituminous fluids which have oozed out or been exposed by other causes upon the surface of the earth seems, in most cases at least, to have resulted from the loss of the vaporizable portions, and also from a process of oxidation which consists, first, in a loss of hydrogen, and finally in the oxygenation or evaporation of the more volatile portions, which gradually trans- forms them into mineral tar or maltha, and, still later, into solid glossy asphaltum, of which gilsonite, wurtzilite, uintahite, etc., are examples. 92. Occurrence and Distribution of Asphaltum. Deposits of asphaltum are found widely diffused throughout the world, and at MATERIALS EMPLOYED IN" THE CONSTRUCTION OF PAVEMENTS. 65 various altitudes ranging from below sea-level to thousands of feet above. It is, however, seldom found among the primitive or older rock formations, but seems to belong exclusively to the secondary and tertiary formations. Intermixed with the argillaceous stratas, it forms extensive beds or lakelike deposits on both continents, the most remarkable of which are those situated in the West Indies and South America. The most notable of these are the so-called pitch lakes on the island of Trinidad, and at Bermudez, Venezuela. 92a. Saturating the calcareous and sandstone formations, it forms large subterraneous deposits in Europe and the United States. The calcareous varieties occur more extensively in Europe than in America, and are the source of the material employed there for street-paving under the name of asphalte. The sand- stone class is found extensively in the Western and Southwestern States, especially in California, Texas, Kentucky, and the Indian Territory. 92b. In a free or nearly pure state it is found in veins and seams in the primitive rock and volcanic formations. This class of deposit is rare and the amount of asphaltum is generally insignifi- cant. A notable exception, however, are the deposits of Utah, etc. The mines from which gilsonite, wurtzilite, uintahite are produced are said to be very extensive, and the material is very nearly pure. Similar deposits are found in Mexico, Cuba, and various parts of .South America. 92c. In many localities beds of shale, sand, and cretaceous lime- stone are found saturated with maltha, from which the bitumen is extracted by boiling or macerating with water. 92d. From the variety of the deposits and their manner of occurrence it seems that asphaltum belongs to no particular era or age. Moreover, the asphaltum obtained from these different sources is not uniform either in character, appearance, hardness, or chemical composition. The ultimate composition of specimens from several localities is given in Table XIV#. 93. Nomenclature. As indicated above, the varieties of bitumen and asphaltum are as numerous as the localities producing them; hence there is a great variety of names used to designate the same substance which is oftentimes misleading, if not confusing. As an illustration of this variety the following may be mentioned: 66 HIGHWAY CONSTRUCTIOX. native pitch, mineral pitch, glance pitch, grahamite, albertite, piauzite, elaterite, gilsonite, wurtzilite, uintahite, turrellite. TABLE XlVa. COMPOSITION OF THE BITUMEN OP VAHIOUS ASPHALTS. Locality. Consistency. In Extracted Bitumen. Sulphur. Carbon. H |e d n.' ^rQgen.. Trinidad (Lake) Hard Medium Soft 6.16 6.48 6.23 9.60 8.52 1.79 3.39 1.98 1.47 1.32 5.87 82.33 82.77 83.30 80.32 80.87 89.28 84.16 85.65 87.40 85.72 82.88 10.69 10.62 9.88 10.09 10.42 8.66 11.52 12.37 11.05 11.83 10.70 0.81 0.35 0.70 0.28 0.19 0.79 1.58 6 '.65 1.21 0.75 California (Waldorf) " (La Patera) Texas (Uvalde) Cuba (Bejucal) Utah (Gilsonite) Kentucky Indian Ter. (Cbickasaw) . . . ' " (Ardmore) 93a. Sometimes the name of the locality where it is found is used as a prefix and is thus useful to indicate the source. Such names are Dead Sea bitumen, Egyptian asphalt, Cuban, Trinidad, Bermudez, Calif ornian, Kentucky, etc. 93b. The name asphalte has been adopted by the French to designate the material obtained from their bituminous limestone deposits, and is now generally employed throughout Europe to denote both the carbonate of lirne impregnated with asphaltum. and the pavement made from that material. 93c. The name lithoearbon has been recently adopted to designate a cretaceous limestone saturated with bitumen found in Texas. 93d. Some authorities apply the terms asphaltum, asphalt, and liquid asphalt to the semi-fluid and viscous bituminous substance or maltha, which by heat may be transformed into asphaltum. This application seems to be erroneous, because asphaltum techni- cally means bitumen in the solid form. Others use the same terms to designate the entire mixture of bitumen, mineral and organic -matter, while others apply them to denote the purified material. 94. The names which seem to be the most used in the United MATERIALS EMPLOYED IN THE CONSTRUCTION OF PAVEMENTS. 67* States and which are at the same time descriptive of the various; classes are as follows : Crude asplidltum or crude asphalt is applied to all mixtures of bitumen,, clay, sand, etc.; e.g., crude Trinidad asphalt. Refined asphaltum or asphalt is used to denote the asphaltum after it has been wholly or partly freed from the combined organic and inorganic matters. The limestone rocks impregnated with bitumen are called bituminous or asphaltic limestones. The term rock asphalt is also applied to the same material, the name of the source being also- used, as "Italian rock asphalt," "Val de Travers rock asphalt,"' etc. The sandstones containing bitumen are known as bituminous or- asplialtic sandstones, the name of the source being also mentioned.. The semi-fluid bitumen is designated lay the names maltha. and mineral tar. The term asphalt is also frequently but erroneously applie [ to various preparations in which the cementing material is coal tar or the residue of oil-refineries, etc. substances which are entirely dissimilar to asphaltum. though apparently possessing some of its, characteristics. The term bitumen is employed to designate the truly bitumi- nous portion of the asphaltum and its compounds.* 95. Refined Asphaltum is asphaltum freed from the combined water and accompanying inorganic and organic matter. By com- paratively simple operations the several varieties of asphaltum may? be reduced to an equal state of purity. 95a. The argillaceous varieties, such as Trinidad, Bermudez,, etc., are purified in iron vessels by the application of heat either directly from fire or indirectly by steam, the temperature em- * Manjak is the name given to the asphaltum found in the Island of Bar- badoes. Its composition is: Volatile organic matter 70.85 Non-volatile organic matter 26.97 Mineral matter 0.18 Moisture 2.00 100.00 ,68 HIGHWAY CONSTRUCTION. ployed ranges from 212 F. to 350 F. During the application of the heat, the asphaltum is liquefied the, combined water is evapor- ated, the organic^ matters rise to the surface and are skimmed off, and the inorganic settle to the bottom of the vessel; when the liberation of the impurities is completed, the liquid asphaltum is drawn off into barrels and constitutes the refined asphaltum of commerce. 95b. The calcareous and silicious varieties are purified by boil- ing or macerating them with hot water, according to the freedom with which they part with the intermixed impurities. During the action of the water the sand and other ingredients fall to the bottom of the vessel, and the bitumen rises to the surface or forms clots on the sides of the boiler, whence it is skimmed off and thrown into another boiler, where it is boiled for some time, during which the water and more volatile oils are evaporated, and the mineral matters still retained fall to the bottom, leaving the bitumen in the form of a thick viscid substance, in which state it is used in several of the arts. By continuing the boiling for a considerable time or by increasing the temperature to about 250 F. the volatile portions are driven off and the viscid bitumen is brought to a condition which upon cooling causes it to become solid. 95c. The operation of refining or purifying, while exceedingly simple, requires to be performed with much care, for the reason that if the asphaltum is melted at too high a temperature it will be turned or coked, or if the heating is prolonged at a low tempera- ture the result will be practically the same. In either case the petrolene is converted into asphaltene. 96. Asphaltic Cement. Asphaltum in a refined or pure state is valueless as a cementing medium, owing to its hardness, brittle- ness, and lack of cementitious properties; therefore it is necessary to add some substance which will impart to it the required plastic, adhesive, and tenacious qualities. This substance must be one that will partially dissolve the asphaltene and form a chemical union by solution instead of a mechanical mixture. The duty which it has to perform is an important and peculiar one : if it is a perfect sol- vent of the constituents of the bitumen, the adhesive qualities will be destroyed; if it is an imperfect one, the asphaltum will retain its brittleness. MATERIALS EMPLOYED IN THE CONSTRUCTION OF PAVEMENTS. 69 96a. The requirements of a suitable flux arc that it shall be a fluid containing no substances volatile under 300 F., and shall possess the power to dissolve the asphaltum without destroying or lessening its adhesive properties. 96b. The materials employed to give the required qualities to the hard asphaltum are called the "flux," and those in general use are crude or specially prepared residuum oil obtained from the distillation of petroleum, and crude or refined maltha. The process of adding the flux is called " oiling-" or " temper- ing," and is conducted as follows : The refined asphaltum is melted and the temperature raised to about 300 F. ; the oil previ- ously heated is then pumped or in other ways added to the asphaltum, in the proportion of 10 to 20 pounds of oil to 100 pounds of refined asphaltum the proportion of the oil is varied between the limits stated according to its quality, the hardness of the asphaltum, and the purpose for which the cement is to be em- ployed. The mixture of residuum oil and asphaltum is agitated either by mechanical means or by a blast of air for several hours or until the material has acquired the desired properties. The agitation must be performed with great thoroughness to secure a. uniform mixture, and must be continued whenever the material is in a melted condition, as a certain amount of separation takes place when the melted cement stands at rest. It is therefore customary to agitate it constantly when in use as well as during its preparation. 96c. The process of "tempering" when maltha is used as the flux is practically the same as outlined above, with the excep- tion that the mixing is performed at a lower temperature and entirely by mechanical means, and a separation of the ingredients seldom occurs when the cement is standing at rest. 96d. The maltha from many localities is to be had in the market; it is sold for fluxing purposes under various trade names,, among which may be named "Alcatraz" liquid asphaltum, " Standard " liquid asphalt, "Utah" liquid asphalt, etc.; also arti- ficial fluxing materials which are offered as substitutes for oil and maltha, such as the " Pittsburg asphaltic flux," etc. The analyses of some of these fluxing agents are as follows : 70 HIGHWAY CONSTRUCTION. " ALCATRAZ '' LIQUID ASPHALT. Specific gravity 1.05 Bitumen soluble in carbon disulphide 98.70 per cent, Bitumen soluble in petroleum naphtha 89.17 " " Mineral matter 1.30 " " Organic non-bituminous matter trace. "UTAH" LIQUID ASPHALT (CRUDE) Specific gravity 0.9068 Bitumen soluble in carbon disulphide. 76.15 per cent. Bitumen soluble in ether 64.90 " " Mineral matter 3. 40 " " Organic non-bituminous matter 20.45 " " LossatlOOC 24.72 " " "PlTTSBURG" ASPHALTIC FLUX. Moisture 0.05 per cent. Tola! ile oil 212 F. to 312 F 1.60 " " Tolatile oil about 312 F 89.19 " " Fixed carbon 8.48 " Ash 0.68 " " Bitumen soluble in carbon disulphide. 99.32 " " Bitumen soluble in ether 65.00 " " 97. The enduring qualities of an asphaltic cement depend upon (1) the character of the fluxing agent, (2) the temperature at which the asphaltum has been refined and the temperature at which the flux is added, (3) the degree of incorporation of the flux with the asphaltum, that is whether the union is a chemical or mechanical one. 97a. The diversity found in the durability of pavements made from cement in which the flux is residuum of petroleum is con- sidered by many authorities to be due primarily to the variable -character of the residuum. This material is a thick heavy oil varying considerably in composition, according to the source of the petroleum and method of distillation; its base is parqffine a sub- stance so different from asphaltum that when the two are brought together the result is a mixture partly mechanical and partly chemical, and, being of different specific gravities, they partly sepa- rate when allowed to stand for any considerable period without stirring. Regarding the use of petroleum residuum as a flux for asphaltum, Mr. A. W. Dow, Inspector of Asphalts and Cements, District of MATERIALS EMPLOYED IX THE CONSTRUCTION OF PAVEMENTS. 71 Columbia, in his report for 1897 says: "I have made a careful -study of this, and am thoroughly convinced that the use of all petroleum residuum is injurious, some much more so than others. That it is not adaptable, either chemically or physically, to this use, can be readily seen by looking into its properties. With a change of but a few degrees of temperature, it passes from a liquid to a solid state. On standing a month or two a hardening sets in, due either to polymerization or slow crystallization, which makes i,t even more susceptible to change in temperature. I am also led to believe, from various experiments, that many asphalts are not entirely soluble in petroleum residuum, and for that reason asphalt cement in which it is used is not a chemical, but merely a mechanical mix- ture or emulsion of the asphalt and the oil. From this it can readily be seen that the undesirable properties of the petroleum residuum are imparted to the asphalt cement to a degree propor- tional to the quantity of residuum used." 97b. During the early days of the manufacture of asphaltic -cement, for paving purposes, from Trinidad asphaltum and residuum oil, the oil as it came from the refineries was poured directly into the liquid asphaltum without any investigation as to its quality. The results produced by this method in cements nominally prepared in exactly the same way were very variable and oftentimes unsatisfactory. With the increased demand for asphaltic cement many improvements both in the method of add- ing the oil and in its quality have been made. The oil is now subjected to careful examination to ascertain : 1. Specific gravity. 2. Flash-point. 3. Percentage volatile in a given time at 400 F. 4. Susceptibility to changes in temperature as revealed by changes in viscosity. 5. Presence of crystals of paraffine. 97c. The demand for heavy petroleum oil or residuum for use in the manufacture of cement for paving purposes has become so extensive that the oil-refining companies find it profitable to pro- duce an oil that shall be nearly uniform in character. In pre- paring this oil the object aimed at is (1) the removal of the hard paraffines, which are very susceptible to changes of temperature, becoming soft under the summer sun and brittle at or below the HIGHWAY freezing-point ; their presence imparts similar properties to the asphalt cement ; (2) to remove the lighter and more volatile oils ; care in their removal must be exercised: if too large a percentage is removed, the oil becomes heavy and thick, and too large a pro- portion is required to make a cement of suitable consistency there- fore there is a limit to the amount that can be removed. 97d. Specifications for Petroleum Residuum. The petroleum residuum used in the manufacture of asphalt cement shall be a petroleum from which the lighter oils have been removed by distil- lation, without cracking, until the oil has the following character- istics : Specific, gravity ranging between 20 and 23 Baume. Flash-point (as taken in a New York State Board of Health oil-tester), between 300 and 425 F. Distillate at 400 F. for thirty hours, less than 10 per cent. The distillate shall be made with about 50 grams of oil in a small glass retort provided with a thermometer and packed entirely in asbestos. The residue in the retort after distillation must be fluid at 75 F., and not coarsely crystalline on cooling. The quantity of residuum necessary to soften the asphalt into a cement containing bitumen whose penetration is 80 on Bowen's scale shall not be over 33 per cent of the total quantity of bitumen in the asphalt. The flowing-point shall be determined by cooling 100 cc. of oil in a small bottle and noting the temperature at which it flows readily from one end of the bottle to the other. 98. Authorities differ as to the relative merits of residuum oil and maltha as fluxes for asphaltum. Some claim that they are unsuitable on account of the volatile oils they contain, which on evaporating leave the cement in a porous or spongelike condition, which readily absorbs water, and is thus subject to the destroying action of frost. Others hold that if the oil or maltha is heated sufficiently to drive off the volatile oils they are deprived of their solvent power and are converted into substances so similar to as- phaltum that their addition renders it more brittle. 98a. The writer, from his observations, considers that a more enduring cement can be obtained by adding asphaltum to maltha and allowing it to dissolve therein at a temperature of 212 to 220 a F., or by submitting maltha to a process of distillation in which MATERIALS EMPLOYED IN THE CONSTRUCTION OF PAVEMENTS. 73 the temperature is carefully regulated. Under such a process bitumen of any consistency from plastic to hard can be produced. Either of these methods would be more satisfactory and more under control than the present one of transforming a compara- tively hard and brittle substance into a soft and plastic one. 98b. An examination of the bituminous limestones and sand- stones shows them to be cemented together, not by hard bitumen, but by the softer varieties; and where these formations have been exposed to the destroying action of the elements they show no sign of disintegration, but are solid and impervious. 98c. Some of the most enduring constructions of antiquity, which have withstood the ravages of time for upwards of 3000 years, are cemented with bitumen. The bitumen which the an- cients used was not the hard brittle variety we employ, but the soft plastic maltha, used in its natural condition as it oozed out of the springs. 98d. Specification for Asphalt Cement. "The asphaltic cement must be practically free from water and must be within range of 40 and 70 penetration (on Dow's apparatus) when tested at 77 F., the amount of penetration to be fixed by the Engineer Commissioner. "Preference will be given to an asphaltic cement that is not readily affected by water, provided it is satisfactory in other re- spects. If an asphaltic cement is accepted that is affected by water, some provision satisfactory to the Engineer Commissioner must be made to guard against the results of such action, and such work must be included in the price bid." "The bitumen of the asphaltic cement must comply with the following tests: " 1. It must be of such a character that if when tested at 32 F. it shows a hardness of 10 penetration, it must not, when tested at 115F., be softer than 350 penetration. "2. When a briquette of pure bitumen having a minimum cross- section of one square centimeter is tested for ductility at 77 F. the bitumen must stretch to a distance of eight centimeters before breaking. . "3. When the bitumen is heated in an open tin at a temperature of 300 F. for eighteen hours in a hot-air oven it must not show 74 HIGHWAY CONSTRUCTION. a loss by volatilization of over 5 per cent., and it must not have hardened over 50 per cent, by this heating. "The asphaltic cement must never be heated to a temperature that will injure it. "When the asphaltic cement contains over 5 per cent, of ma- terial that will separate by subsidence while in a molten condition, it must be thoroughly agitated before drawing from storage and while in use in the supply kettles so as to insure a uniform cement. "If an asphalt has been proposed for use by the contractor and approved by the Engineer Commissioner, no change in the asphalt to be used shall be made unless with the approval of the Engineer Commissioner. If an asphalt is submitted for use which has not been successfully used for a period of at least two years for paving under conditions similar to those existing in the Dis- trict of Columbia, its use may be limited to such extent as may be deemed advisable, or it may be rejected entirely in the discre- tion of the Engineer Commissioner." (Washington, D. C., 1904.) 99. Asphaltic Paving Materials. All asphaltic or bituminous pavements are composed of two essential parts, namely, tho ce- menting material (matrix) and the resisting material (aggregate). .Each has a distinct function to perform: the first furnishes and preserves the coherency of the mass; the second resists the wear of the traffic. 99a. Two classes of asphaltic paving compounds are in use, namely, natural and artificial. The natural variety is composed of either limestone or sandstone naturally cemented by bitumen. To this class belong the bituminous limestones of Europe, Texas, Utah, etc., and the bituminous sandstones of California, Kentucky, Texas, Indian Territory, etc. The artificial consists of mixtures of asphaltic cement manufactured, as described in Art. 96, with sand and stone-dust. To this class belong the pavements made from Trinidad, Bermudez, Cuban, and similar asphaltums. For the artificial variety most of the hard bitumens are, when properly prepared, equally suitable. For the aggregate the most suitable materials are stone- dust from the harder rocks, such as granite, trap, etc., and sharp angular sand. These materials should be entirely free from loam and vegetable impurities. The strength and enduring qualities of the mixture will depend upon the MATERIALS EMPLOYED IN" THE CONSTRUCTION OF PAVEMENTS. 75 quality, strength, and proportion of each ingredient, as well as upon the cohesion of the matrix and its adhesion to the aggregate. 99b. Bituminous Limestone consists of carbonate of lime natu- rally cemented with bitumen in proportions varying from 80 to 93 per cent of carbonate of lime and from 7 to 20 per cent of bitumen.. Its color when freshly broken is a dark (almost black) chocolate- brown, the darker color being due to a larger percentage of bitu- men. At a temperature of from 55 to 70 F. the material is hard and sonorous and breaks easily with an irregular fracture; at tem- peratures between 70 and 140 F. it softens, passing with the rise in temperature through various degrees of plasticity, until,. at be- tween 140 and 160 F., it begins to crumble, at 212 F. it com- mences to melt, and at 280 F. it is completely disintegrated. Its specific gravity is about 2.235. 99c. Bituminous limestone is the material employed for paving purposes throughout Europe. It is obtained principally from de- posits at Vtil-de-Travers, canton of Neufchatel, Switzerland; at Seyssel, in the department of Ain, France; at Kagusa, Sicily; at Limmer, near Hanover; and at Vorwohle, Germany. 99d. The constituents of the more important of these deposits are given in Table XV. 99e. Bituminous limestone is found in several parts of the United States. Two of these deposits are at present being worked, one in Texas, the material from which is called " lithocarbon," and one on the Wasatch Indian Eeservation. These deposits con- tain from 10 to 30 per cent of bitumen. 99f. The bituminous limestones which contain about 10 per cent of bitumen are used for paving in their natural condition, being simply reduced to powder, heated until thoroughly softened, then spread while hot upon the foundation and tamped and rammed until compacted. For a detailed description of the asphalt and bituminous deposits in the United States, see report of George H. Eldridge in Twenty- second Annual Report U. S. Geological Survey. For a description of the processes and methods employed in the refining and manufacture of asphalt pavements, see "The Modern Asphalt Pavement/' by Clifford Richardson. John Wiley & Sons, New York City. 76 HIGHWAY CONSTRUCTION. TABLE XV. ANALYSIS OF EUROPEAN BITUMINOUS ROCKS/ Constituents. Val de Travers. Seyssel. Lobsan. Per cent. 3.40 11.90J 69.00 3.05 5.70 5.00 0.30 Sicil- ian. Mae- stu. Forens. Water and matter vol. at 212 F.f Bitumen Per cent. 0.50 10.10 87.95 Per cent. 1.90 8.00 89.55 Per cent. 0.80 8.85 87.50 0.60 0.90 Per cent. 0.40 8.80 9.15 57.40 4.35 Per cent. 0.25 2.25 97.00 Silicious sand , Aluminum and peroxide of iron Sulphur 0.25 0.15 0.15 Carbonate of magnesia 0.30 0.45 0.45 0.10 0.10 0.20 0.95 8.10 11.35 0.45 0.20 0.05 0.10 Different materials insol. in acids 1.65 0.40 100.00 100.00 100.00 100.00 100.00 100.00 * Laboratoire de 1'Ecole des Pouts et Chaussees. M. Leon Malo. f The water given above depends on the dryness of the sample at the time- of analysis, the figures not being of importance in the result. \ This quantity appeared to contain a certain proportion of oil, which wa mixed with the bitumen and was not exactly determined. This comprises 4.45 per cent of iron combined with sulphur. ANALYSIS OF LITHOCARBON, UVALDE COUNTY, TEXAS. Water 00.27 Asphalt 13.68 Sulphur trace. Iron pyrites trace. Alumina 0.60 Magnesia 0.31 Carbonate of lime 82.06 Silica.. 3.08 100.00 99g. Bituminous Sandstones are composed of sandstone rock impregnated with bitumen in amounts varying from a trace to 70 per cent. They are found both in Europe and America. In Europe they are chiefly used for the production of pure bitumen, which is extracted by boiling or macerating them with water. In the United States extensive deposits are found in the Western States,, MATERIALS EMPLOYED IN" THE CONSTRUCTION OF PAVEMENTS. 77 and since 1880 they have been gradually coming into use as a paving material, and now upwards of a hundred and fifty miles of streets in Western cities are paved with them. They are prepared for use as a paving material by crushing to powder, which is heated to about 250 F., or until it becomes plastic, then spread upon the street and compressed by rolling; sometimes sand or gravel is added, and it is stated that a mixture of about 80 per cent of gravel makes a durable pavement. Good results have been obtained by mixing from 10 to 50 per cent of bituminous limestone, such as that from Vorwhole, Germany. This rock contains from 7 to 10 per cent of hard asphaltum without any oils, and imparts to the more friable sandstones, having the asphaltum in a different condition, the tenacity and hardness which they lack in the natural condition. Kentucky Bituminous Sandstone. The bituminous sandstone found in Breckinridge County, Ky., has been used in several cities, including Louisville, Brooklyn, Buffalo, etc. It is composed of fine white sand and from 8 to 12 per cent of bitumen. An analysis of the sandstone showed that it contains 96.88 per cent of silica, 0.81 of sesquioxide of iron, 0.46 of alumina, 0.34 of lime, 0.2 of mag- nesia, 0.81 of soda, 0.2 of potash, and 0.25 of combined water and loss. Eecent specifications for the preparation of this material re- quire that the wearing surface of the pavement is to be composed of 80 to 70 per cent of the Kentucky rock and 20 to 30 per cent of Vorwhole (German) bituminous limestone. These rocks to be pulverized and the powder of each mixed in the mills and then screened. The mixture to be heated to a temperature of from 150 Q to 250 F., and to reach the street at not less than the former tem- perature, spread in one layer, compressed with hot rollers and tampers to a thickness of two inches. Utah Bituminous Calcareous Sandstone. This sandstone has been used for paving with varying results. It contains about 11 per cent of bitumen and 89 per cent mineral matter, which con- sists of Silica and insoluble silicates 68.00 Ferric oxide 1.16 Aluminum oxide 2.30 Calcium carbonate 26.63 Magnesium carbonate, alkali, and undetermined matter 1.91 100.00 78 HIGHWAY CONSTRUCTION. 100. Trinidad Asphaltum. The deposits of asphaltum in the island of Trinidad, W. L, have been the main source of supply for the asphaltum used in street-paving in the United States. Three kinds are found there, which have been named, according to the source, lake pitch, land or overflow pitch, and iron pitch, The first and most valuable kind is obtained from the so-called Pitch-lake; this lake or deposit is situated about 2 miles from the seashore of the island at an elevation of 138 feet, and has an area of about 115 acres and is of unknown depth. It is quite cir- cular in shape, and is supposed to occupy the crater of an extinct mud volcano. The surface is not flat and even, but is formed of irregular oval-shaped domes, resembling large mushrooms, separated by narrow and shallow channels and pools of water; with ihe- exception of a small space in the centre the surface is sufficiently hard to support the weight of animals and loaded carts. The small space in the centre is called the " boiling spring." Here soft pitch still wells up, but soon becomes hard. The asphaltum is easily excavated with picks, and in the early days of the industry was loaded into two-wheeled carts, hauled by mules to the shore, and there dumped into piles, from which it was carried in baskets by coolies wading through the surf to lighters and from the lighters loaded into sailing vessels. Recently the concessionaires of the lake have built a tramway and pier by which the material is easily con- veyed and quickly loaded into the vessels lying at the pier. lOOa. The term land or overflow) pitch is applied to the deposits of asphaltum found outside of the lake. These deposits form extensive beds of variable thickness, and are covered with from a few to several feet of earth; they are considered by some authorities to be formed from pitcli which has overflowed from the lake, by others to be of entirely different origin. The name cheese pitch is given to such portions of the land pitch as more nearly resemble that obtained from the lake. lOOb. The term iron pitch is used to designate large and isolated masses of extremely hard asphaltum found both within and with- out the borders of the lake. It is supposed to have been formed by the action of heat caused by forest fires which, sweeping over the softer pitch, removed its more volatile constituents. lOOc. The name epuree is given to asphaltum refined on th& MATERIALS EMPLOYED IN THE CONSTRUCTION OF PAVEMENTS. 79 island of Trinidad. The process is conducted in a very crude manner in large, open, cast iron sugar boilers. lOOd. The Characteristics of Crude Trinidad Asphaltum, both lake and land are as follows: It is composed of bitumen mixed with fine sand, clay, and vegetable matter. Its specific gravity varies according to the impurities present, but is usually about 1.28. Its color when freshly excavated is a brown, which changes to black on exposure to the atmosphere. When freshly broken, it emits the usual bituminous odor. It is porous, containing gas-cavities, and in consistency it resembles cheese. If left long enough in the sun, the surface will soften and melt and will finally flow into a more or less compact mass. The average composition of both the land and lake varieties is shown by the following analyses : TABLE XVI. AVERAGE COMPOSITION OP TRINIDAD ASPHALTUM. Constituents. La Land. Hard. Soft. AVater. Per cent. 27.85 Per cent. 34.10 Per cent. 26.62 Inorganic matter . . . 26 38 25 05 27 57 Organic non-bituminous matter. . . Bitumen 7.63 38.14 6.35 34 50 8.05 37.76 100.00 100.00 100.00 When tbe analyses are calculated to a basis of dry substances, the composition is inorganic matter 36 56 38 00 37 74 Organic matter not bitumen. . . . 10.57 9 64 10.68 52.87 52.36 51.58 100.00 100.00 100.00 The substances volatilize in 10 hours at 400 F. " soften at 3.66 190 F 12.24 170 F 0.86 to 1.37 200 to 250 F " ' flow at 200 F. 185 F 210 tc 328 F. lOOe. Refined Trinidad Asphatum. The crude asphaltum is refined or purified by melting it in iron kettles or stills by the ap- 80 HIGHWAY CONSTRUCTION". plication of indirect heat. In the earlier refineries upright cylin- drical kettles holding about ten tons were used; the heat was obtained from a coal fire, the kettles being protected from its direct action by a brick arch. In this form of still the refining process occupied from one hundred and twenty to one hundred and forty hours, and, as the plant became deteriorated, much longer; sediment collected on the bottom, causing much waste of fuel, coking of the asphaltum, and the burning out of the still itself. In consequence of these defects their use is practically abandoned and in their place horizontal boilers have been adopted. In their most approved form these boilers or stills consist of 3 toiler about twenty feet long and ten feet in diameter furnished with two longitudinal flues eighteen inches in diameter placed foui feet from the bottom and four feet between Centres. These stills are placed in brickwork surrounded with loam to prevent radia- tion, and are provided with flues so arranged that the direct heat from the fire passes first along one side, then back along the other, repeating this at a higher level, then through one flue in the still and back through the other, and finally under the bottom. In this way overheating on the bottom is prevented and better results are obtained in evaporating the water from the upper layers of crude material. These stills hold about thirty tons of crude ma- terial, and the time of refining is much reduced. After some years practice with the above-described method agitation of the asphal- tum with a current of air during the refining process was intro- duced, with the object of further reducing the time required and the possibility of injury to the asphaltum. Kecently a departure has been made from this last-described method ; it consists in the use of steam-heat in place of coal-fire heat. The objects aimed at are a reduction in time and prevention of the injury by coking or burning of the asphaltum, which fre- quently occurred when refining with direct heat. In this later process instead of large cylindrical boilers or stills smaller rectangu- lar kettles are used, holding about twenty-five tons ; these are fur. nished with gangs of pipe for the circulation of steam at a press- ure of about 100 pounds per square inch; agitation is produced by jets of dry steam or air. By this method a charge is refined in about twelve hours and the product is very uniform in quality. MATERIALS EMPLOYED IN THE CONSTRUCTION OF PAVEMENTS, 81 lOOf. Irrespective of the method adopted for heating, the proc- ess of refining proceeds as follows : During the heating the water and lighter oils are evaporated, the asphaltum is liquefied, the vegetable matter rises to thg surface and is skimmed off, the earthy and silicious matters settle to the bottom, and the liquid asphaltum is drawn off into old cement- or flour-barrels. lOOg. When the asphaltum is refined without agitation, the residue remaining in the still forms a considerable percentage of the crude material, frequently amounting to 12 per cent, and it was at one time considered that the greater the amount of this residue the better the quality of the refined asphaltum ; but since agitation has been adopted the greater part of the earthy and silicious matters are retained in suspension and it has come to be considered just as desirable for a part of the surface mixture .as the sand which is subsequently added. The refined asphaltum, if for local use, is generally converted into cement in the same still in which it was refined. lOOh. In the earlier part of the refining process the water con- tained in the crude material is liberated and forms in pools on the surface ; this water is of a distinct saline and thermal character, containing a large amount of salts in solution, which probably explains the efflorescence seen upon the crude asphaltum and which is frequently attributed to sea salt. 1001. The principal salts in solution are, in the order of their -amount, sodic chloride and sulphate, ammonic, potassic, and fer- rous sulphates, borates, iodides, etc. To the presence of these salts is due the rapid disintegration of the asphalt under the action of water and moisture, as seen in the gutters, etc. It is stated that the salts can be removed by washing the crude asphalt, which is accomplished in the following manner: The crude asphalt is ground in a disintegrator, then conveyed to a large vat, where it is mixed with water and agitated by revolv- ing paddles for about half an hour, after which the paddles are stopped, the asphalt allowed to subside, and the water drawn off. The operation is repeated, and upon completion the asphalt is run off to the stills and refined. It is claimed that the asphalt is more easily refined after having been washed. Test for the Action of Water. To determine if a cement is readily affected by water it is tested by flowing a thin film or coat on a 82 HIGHWAY CONSTRUCTION. piece of glass and immersing it in distilled water at a temperature between 70 F. and 90 F. If the surface of the asphalt cement remains bright and shows no corrosion or discoloration after seven days' immersion, it is considered as not being readily affected by water. lOOj. The distillate from the stills is strongly acid, and free hydrochloric, sulphuric, and hydrosulphuric acids and other sul- phur compounds have been determined in it. 100k. The steam which is formed in the refining of the crude asphaltumat first contains much hydrogen sulphide, which blackens all the white-lead paint in the vicinity of the refinery. This, under favorable conditions of heat and evaporation, at times changes to sulphurous anhydride, which again bleaches out the white paint. The condensed steam shows a strongly acid reaction. In the pres- ence of one another the hydrocarbons and the thermal water at high temperature evidently produce complicated reactions. 1001. The residue from the bottom of the still consists of some clay mixed with silica in the form of minute fragments of quartz and some of the salts contained in the water. An analysis showed it to consist of : Clay, silica, and silicates insoluble in acid 87.67 p.c. Soluble salts, alumina, iron, lime, etc 12.33 p.c. 100.00 P. c. Of the insoluble portion about 95 per cent is silica, and fre- quently the lime is absent. 100m. The organic matter not bituminous posseses no dis- tinctive characteristics; it occurs as an impalpable powder without any signs of organization. lOOn. The Characteristics of Refined Trinidad Asphaltum are; as follows : MATERIALS EMPLOYED IN THE CONSTRUCTION OF PAVEMENTS. 83 AVERAGE COMPOSITION OF REPINED TRINIDAD ASPHALTUM. Lake. Land. 1 38 1 42 Per cent. 56.29 Per cent. 53.75 8 05 8 01 Inorganic matter . . . . . . . 35 66 38.24 100.00 100.00 41 43 35.22 73.60 65.32 Softens fit . . . . . . . 190 F 210 F ' 205 F. ^30 F The color is black with a homogeneous appearance. At a tem- perature of about 70 F. it is very brittle and breaks with a con- choidal fracture; it burns with a yellowish-white flame, and in burning emits an empyreumatic odor, and possesses little cementi- tious quality; to give it the required plasticity and tenacity it is mixed while liquid with from 16 to 21 pounds of residuum oil to 100 pounds of asphaltum in the manner described in Art. 96. lOOo. The product resulting from the combination is called asphalt paving-cement; its consistency should be such that, at a temperature of from 70 to 80 F., it can be easily indented with the fingers and on slight warming be drawn out in strings or threads. lOOp. The relative quality of Trinidad lake and land asphaltum for paving has been the subject of much discussion and investiga- tion, but without any positive decision being reached. Laboratory examinations made at Washington, D. C., in 1902, indicate that paving cement made from lake asphalt is inferior to that made from land asphalt. The cement from the lake asphalt was found to be readily acted upon by water, while that from land asphalt was only slightly attacked. The lake asphalt was found to be more susceptible to changes of temperature; the cement made from the land asphalt was slightly inferior in ductility. 84 HIGHWAY CONSTRUCTION. lOOq. That there is no essential difference in the chemical composition will be seen by an examination of the analyses given in Table XVI and Art. lOOn. lOOr. The difference between the two varieties consists not in a material variation in the proportion of the constituents, but in a variation or change in the character of the bitumen. This change is due to evaporation, volatilization and oxidation of the light and volatile oils, thus hardening it and necessitating a larger amount of flux to soften the land asphaltum for use as a cement. This larger percentage of flux is by some authorities said to reduce the enduring qualities of the cement; others claim that no amount of flux will restore the lost qualities. Hence the object in selecting lake asphaltum, in which a large percentage of the natural oils still remains, and rejecting the land asphaltum which, has lost these oils in a large degree. 100s. In Europe crude Trinidad asphaltum is used for mixing -with the bituminous limestones in the manufacture of asphalt mastic; for this purpose it is refined as follows: The crude as- phaltum is melted in suitable vessels and to it is added the residue or by-products from the petroleum distilleries and paraffine factories in the proportion of about 2 parts of residue to 3 parts of asphaltum ; the mixture is boiled for 8 or 9 hours, during which time the earthy .and mineral substances in the asphaltum settle to the bottom ; the liquid asphaltum is then drawn off and is ready for use. This preparation is known in England as refined bitumen; in France as bitume rqfine, bitume compose, and goudron compose; in Germany as goudron. 101. Bermudez Asphalt. This is the name given to the asphaltum obtained from a lake or deposit situated in the state of Bermudez, Venezuela. This deposit is said to have an area of over 1000 acres. It is situated about 60 miles from the coast up the San Juan Eiver, and about 51 miles distant from it; a narrow-gauge stearn railroad connects the deposit with the shipping point, and vessels drawing 18 feet of water can be loaded directly from the cars. The crude asphaltum is of the same variety as the Trinidad, namely, bitumen mixed with sand, clay, and vegetable matter; its average specific gravity is 1.09, and its average composition is as follows: MATERIALS EMPLOYED IN THE CONSTRUCTION OF PAVEMENTS. $5 Per cent. Bitumen 93.54 Mineral matter 2.16 Organic matter not bituminous 1.15 Water 3.15 100.00 Petrolene ; 77. 9Q Asphaltene '. 21.08- Retiiie.. 1-02; 100.00- The refining process is practically similar to that desbribed under Trinidad asphaltum, but is much more rapid, owing to the small amount of water and mineral matter present. In manufac- turing the cement it requires much less petroleum residuum than the Trinidad on account of the large amount of oil that it contains;, it melts at a lower temperature than the Trinidad, and the follow- ing are some of its characteristics: At GO C F. compressible; at 70 F. viscous and malleable; at 100 F. flowing, and can be stretched in hairlike threads; at 189F. melts; at 400 F. gives no flash. (See also Art. 265a.) 102. California Asphaltum. Asphaltum is produced in Cali- fornia by refining the bitumen from the extensive sandstone and other deposits which are found in various parts of the State. The characteristics of both the crude and refined asphaltum from some- of the more important deposits are shown by the following an- alysis : ANALYSIS OF ASPHALTUM FROM BAKERSFIELD, CAL. Crude. RefinecL Specific gravity 1.132 1.240 Softens at 180 F. 150 F: Flows at 220 F. 180 F. Inorganic matter 9. 57 p. c. 9.77 p. c. Bitumen soluble in CS 2 85.49 p. c. 90.1ffp.c. Bitumen soluble in ether 69 . 98 p. c. 86 . 45 p. c. ' Percentage of total bitumen soluble in ether 81.85p.c. 95.88 p. c. -36 HIGHWAY CONSTRUCTION. ANALYSIS OP ASPHALTUM FROM ASPHALTO, CAL. Crude. Refined. Moisture 6.51 p. c. 0.42 p. c. Bitumen soluble in chloroform 84.79 p. c. 93.27 p. c. Organic matter (not bitumeu) trace 0.54 p. c. Inorganic mutter consisting of infuso- rial earth with traces of iron 8.70 p. c. 5.77 p. c. Petrolene soluble in acetone 67.50 p. c. 71.27 p. c. Asphalteue insoluble in acetone 32.50 p. c. 28.73 p. c. Combined sulphur (chemically held in the bitumen) 0.73 p. c. ANALYSIS OP ASPHALTUM FROM SANTA BARBARA Co., CAL. Crude. Refined. Specific gravity 1 .250 Organic non-bituminous matter 1.10 p. c. Inorganic matter consisting of finely divided quartz with oxide of iron and alumina 39. 75 p. c. Bitumen soluble in CS 2 59.15 p. c. Bitumen soluble in petroleum naphtha (petrolene) . . 42.50 p. c. Asphaltene 7.35 p. c. ANALYSIS OP ASPHALTUM FROM KERN Co., CAL. Bitumen soluble in CS 3 78. 90 p. c. Mineral substances sand, clay, and silica . . 9.40 p. c. Coky and volatile matter 4. 53 p. c. Water and loss 7.17 p. c. ANALYSIS OF BITUMINOUS SANDSTONE FROM VENTURA Co., CA.L. Bitumen... 24.00 p. c. Silica 64. 00 p. c. Oxide of iron i Calcium carbonate \ 13 ' 00 p ' c ' Cements for paving and other purposes are manufactured from the refined asphaltum described above by the admixture of maltha; the two substances are combined at a very low temperature, the heat being applied indirectly, and the mixing is performed mechan- ically; the degree of softness can be made to suit any requirement. 102a. Buena Vista Asphalt. The asphaltic paving cement sold under this name is prepared from a liquid asphaltum obtained from California and a hard asphaltum from Utah, and contains no residuum of petroleum. The following analysis shows its compo- sition : Bitumen soluble in carbon disulphide 99. 12 to 99.33 Earthy and insoluble organic matter 88 to .67 IdATERIALS EMPLOYED IK THE CONSTRUCTION OF PAVEMENTS. 87 102b. Analysis of asphalt produced from oil at Port Neches, Texas, by the Central Asphalt and Refining Company; Total bitumen 99. 16 per cent. Organic matter (not bitumen) 0.21 " " Mineral matter (ash) 0.07 " " Sulphur 0.56 " " 100.00 The total bitumen contains: Asphaltene 26 . 17 per cent. Petrolene 73.55 " " Physical tests show: Specific gravity 0.998 Softens at '. . . 154.4 F. Flows at 192 F. 102c. Cuban Asphalt. Analysis of asphalt from Bejucal, Cuba! Water and light oils volatile at 225 F 3 . 60 per cent. Bitumen soluble in CS 2 71.64 " Organic matter insoluble in CS 2 4 . 20 " " Mineral matter, clay, sand, and limestone 24 . 20 " " 100.04 The bitumen soluble in CS 2 showed 50% soluble in naphtha. Analysis of a cement made by fluxing 100 parts of crude asphalt with 65 parts of California maltha showed it to be practically similar to cement made with Bermudez asphalt and 13 parts of petroleum residuum. A comparison of these two cements is given in Table XVIa. TABLE XVIa. COMPARISON OF CUBAN AND BERMUDEZ ASPHALT CEMENTS. Cuban. Bermudez. Penetration at 77* F 53 51 Bitumen soluble in CS 2 , per cent 84 . 60 95 . 80 Heat test; Loss on heating for 18 hours at 325 F., percent. 5.20 3.20 Penetration at 77 F., after above heating, per cent 18 21 Hardened by heating, per cent 290 240 Penetration at 52 F., 200 gms., 1 minute, No. 2 needle 17.5 15 Penetrat'on at 100 F., 50 gms., 5 seconds, No. 2 needle 115 113 Ductility, inches to which drawn at 77 F . . 24 22 88 HIGHWAY CONST RUCTION. Neither of them showed the slightest signs of the action of water after two weeks' immersion in distilled water. About 5000 square yards of sheet asphalt pavement made from Cuban asphalt and California maltha was laid in Washington, D. C., during 1902. 103. Asphalt Mastic. In Europe mastic is made from a mixture of bituminous limestone and refined asphaltum (usually Trinidad). The bituminous limestone is reduced to powder and mixed with about 8 per cent of refined asphaltum, then melted and thoroughly mixed. The hot composition is run into moulds of various shapes, usually round or hexagonal, and of such dimensions as will give a cake or block weighing about 56 pounds ; these blocks usually have the name of the source or factory moulded on them. The mastic is prepared for use by breaking the cakes into small pieces, and heating it with the addition of about 5 per cent of re- fined asphaltum. The mass is constantly stirred and when soft, sand and fine gravel are added and thoroughly incorporated by stirring for about two hours at a temperature of about 300 F., when it is ready for use. Asphalt mastic is also prepared from bituminous sandstones and maltha or refined asphaltum, and from asphalt paving-cement. The principal use of mastic is for sidewalks and floors. In Europe it is called Asphalie couU in distinction from the compressed bituminous limestone, which is called Asplialte cow prime. (See- also Art. 266, et seq., and Art. 778, et seq.) 103a. Analysis and Tests of Asphaltum. The tests employed to determine the relative merits of asphaltum and asphaltic cements comprise both chemical and physical investigations. The chemical examination of the crude material involves the following determinations: Specific gravity. Percentage of moisture. " " matter soluble in turpentine. " " " " " carbon bisulphide. " " " " " alcohol. te e ther. " " " volatile in 10 hours at 400 F. ' " sulphuretted hydrogen evolved at 400 P. " " non-bituminous organic matter. " " mineral constituents. MATERIALS EMPLOYED 1JST THE COJS8TKUCT1ON OF PAVEMENTS. 89 Softening-point of the bitumen. Flowing-point " " " Stability of the bitumen at high temperature. Action of water and ammonia on the bitumen. Change in bitumen due to aging. Susceptibility of bitumen due to change with variations in temperature. The examination of the physical properties (mechanical tests) involve the following determinations: (1) The refining of the crude material and making of an asphaltic cement. (2) Determining the viscosity or softness of the cement. (This investigation is commonly called the " penetration " test; its purpose is to ascertain whether the cement is of the proper degree of softness to produce a good pavement. The degree of softness or viscosity depends partly upon the quality of the asphaltum and partly upon the character and proportion of the flux; it also increases and diminishes as the temperature is raised or lowered; hence great care is required when examining several samples of the same cement or comparing samples of different cements to have them all at the same temperature. .Experience shows that to secure the best results the viscosity or softness of the cement must differ in different localities according to the climate, and also according to the character of the sand and dust used.) (3) Making a paving mixture and testing it for tensile and crushing strength. Amount of Bitumen. The amount of bitumen contained in the crude material is ascertained by extracting it with a solvent (carbon disulphide is the most commonly used). This extraction may be made in numerous ways. The method requiring the least experience and giving the least trouble is by extracting in large test-tubes or cylinders, and decanting off the solvent containing the dissolved bitumen from the insoluble portions. The method of procedure is as follows: The sample of asphal- tum is spread in a thin layer in a suitable dish (nickel or iron), and kept at a temperature of 225 F., until it practically stops losing weight. The greater part, and in some cases all the water and some light oils are expelled in this way. From 2 to 10 grams HIGHWAY CONSTRUCTION. (depending on its richness in bitumen) of the sample is weighed in a large sized test- tube (8 inches long by 1 inch diameter), the tare of which has been previously ascertained. The tube containing the sample is then filled to within 1^ inches of the top with carbon disulphide and allowed to stand for a few minutes. Then the tube is tightly corked with a good sound cork. It is then shaken vigorously until no material can be seen adhering to the bottom. Care should be taken while shaking to keep one finger on the cork to prevent its being blown out. The tube should then be put away in an upright position and not disturbed in the slightest way for two days, after which the solvent is decanted off into a small bottle. As much of the solvent should be poured off as is possible without losing any of the residue. The tube is again filled and shaken as before, and put away for two more days. After the liquid has been carefully decanted the second time, the tube, with the residue, is dried at a low temperature. After cooling it is weighed. As there is always a small portion of the residue poured off in the solution with the bitumen, this solution must be evapo- rated and the bitumen burned off in a platinum dish and the weight of the residue added to that in the tube. The weight of the sample taken, less the sum of these two weights, is the weight of the bitumen extracted^ from which can be calculated the per- centage of bitumen contained. Stability of the Bitumen at High Temperature. The necessity of stability at high temperature for a length of time is owing to the length of time the bitumen must remain in a heated condition during the course of the manufacture of the asphalt mixture, which may cause it to lose valuable properties. The effect of this heat is rendered much more severe on the bitumen because of its great area exposed to evaporation when mixed with sand. The lack of stability resulting from the loss of light oils is manifest in different ways in different bitumens. Although generally so, it does not of necessity follow that the bitumen losing the most oil undergoes the greatest change in consistency. There are two methods of testing stability, and it is advisable to use both. The first consists in making the asphalt cement into a mixture with standard sand in such proportions that the mixture will con- tain 10 per cent of bitumen; the materials for the mixture are MATERIALS EMPLOYED IX THE CONSTRUCTION OF PAVEMENTS. 91 kept for fifteen minutes in an oven heated to 300 F., then incor- porated by stirring. One portion of the mixture is put aside to cool, while the other is kept at the temperature of 300 F. f cl- one-half hour longer. The bitumen is then extracted from both, and after reaching the same temperature their penetrations are compared. The second method consists in keeping a quantity of the sub- stance, equivalent to 20 grams of bitumen, at a temperature of .400 F. for thirty hours. The method of procedure is as follows: The substance is weighed in a short-necked, tabulated, 2-ounce retort, the tare of which has been previously taken. The retort is then hung in a copper cylinder so that the neck just protrudes. The copper cylinder is then jacketed with asbestos and provided with a thermometer. After being heated up to 400 F., at which temperature it is maintained for thirty hours, the retort is allowed to cool, then weighed and the per cent of loss ascertained. The retort is then broken and the character of its contents compared with that of the original substance. Action of Water and Ammonia on the Bitumen. The action of water and dilute ammonia is determined by moulding an inch cube of the mixture under a pressure of 1000 pounds, then breaking it into two pieces, one of which is immersed in water or dilute am- monia, while the other is kept in air. The two pieces are com- pared from time to time. If acted on by the liquid, the corners will be found to give away readily with a slight pressure of- the finger. After soaking some time it is well to evaporate the liquid to dryness and note if any bituminous residue remains. Changes in Bitumen due to Age. All bitumens undergo a more or less rapid change with aging, that appears to be due to two or, possibly, more causes. Two distinct changes manifest themselves. One is the surface hardening, which is likely due to indirect oxidation, and possibly to the volatilization of light oils. It begins at the surface and gradually extends into the bitumen. The other is" a hardening of the entire mass, evidently due to polymerization. Both these changes take place in all bitumens, but one or the other may predominate. The former is much the less objectionable, as it makes slow progress into *the mass. In making a test to ascertain the effect of aging, it is preferable to 92 HIGHWAY CONSTRUCTION. use the asphalt cement, as there is some danger in using extracted bitumen of the solvent not having been entirely removed, and its slow evaporation might be interpreted as a true change, due to the hardening of the bitumen. The test for aging is made as follows: The penetration of the sample is determined, after which it is put away for a week, when it is again ascertained. If the sample shows an appreciable hard- ening, a slanting cut is made into it with a sharp knife, laying over the upper piece, thus exposing a gradual descent from th'e surface into the interior. Penetrations are now taken down the side of this cut, beginning at the surface. In this way the increase in hardness of the surface and the interior over its original con- sistency is determined; also the hardening of the surface over the interior and the depth that the surface hardening has entered the sample. It is well to continue this test for as long a period as possible, making examinations at intervals of every few weeks. Susceptibility of Bitumen to Change wiih Variations in Tem- perature. This is determined by making penetration tests of the sample at several different degrees of temperature and noting the changes in its condition. Penetration Tests. The softness or viscosity of an asphalt cement was, in the early days of asphalt paving, determined by chewing a small piece and judging by the resistance it offered to the teeth; the rule was that if it chewed easily and yet was not soft enough to adhere to the teeth, it was of the proper consistency for paving. Bowen's Apparatus. In 1888 Prof. Bowen devised a machine for testing the viscosity of asphaltic cements which has been exten- sively employed. This machine consists of a lever about 17 inches long, having the fulcrum at one end and a cambric needle inserted in the other end, above which is placed a weight of 100 grams. The end near the needle is connected by a steel rod and waxed cord with a spindle having a long hand which moves about a dial divided into 360 degrees. Another cord and weight upon an enlarged part; of the spindle keeps the first-mentioned cord taut. By a suitably contrived spring clip the steel rod can be released for any length of time, and the needle, which has first been MATERIALS EMPLOYED IN THE CONSTRUCTION OF PAVEMENTS. 93 brought to coincide with the surface of the asphalt cement placed under it in a tin box, allowed to penetrate under the action of the weight into the cement. The number of degrees through which the hand moves on the dial records the penetration of the cement; the length of time for which the needle is released is one second. Originally Prof. Bowen selected 77 F. as the proper temperature at which the test should be made, and brought the cement and machine to this degree by keeping them in a room warmed to this point. But as it is sometimes inconvenient or impossible to have a room temperature of 77, other temperatures may be made avail- able by placing the tin sample-box of asphalt cement in water at 77 and allowing it to acquire that temperature, when the test can be made as before, certain allowance being made to reduce the result to the normal temperature of 77 F. Dow's Apparatus. Mr. A. W. Dow, Inspector of Asphalts and Cements at Washington, D. C., has devised a testing-machine in which he has endeavored to overcome the objections raised against Professor Bowen's. The tests are made in a water-jacketed copper box; any temperature can be obtained in this box by running through the jacket water cooled or heated as desired. The needle penetrates under a direct weight with practically no friction. The description of this apparatus in detail is as follows: The pene- trating needle, which is an ordinary No. 2 sewing needle, is rigidly fastened in the end of a small brass rod. This rod is inserted in the end of an aluminum tube, about 40 centimetres in length and 1 centimetre in diameter, where it is securely fastened by means of -a binding-screw. By filling or partially filling this. tube with mer- cury, it can 1 c made of any desired weight from 30 to 300 grams, after which it is closed by a cap which screws on to the end oppo- site the needle. When this cap is screwed into place, its surface, which is perfectly flat, is absolutely at right angles to the sides of the tube. The aluminum tube holding the needle passes down through a wooden framework in which it is held in a vertical posi- tion, with the needle-end down, by means of a jaw-clamp. When this clamp is released the tube can move freely up and down, while it is retained in its vertical position by two guides. These guides are each made of two metal plates a fraction of a centimetre in thickness. Each plate has a semicircular piece cut out of one P4 HIGHWAY CONSTRUCTION. side, so that when the two are placed together it leaves a circular opening through which the aluminum tube passes freely, but yet not so freely as to get out of the vertical. To facilitate the removal of the needle-tube from the framework, as it must be slightly inclined while withdrawing so as to clear the measuring device, the guides are constructed so that one plate in each can be pushed a short distance from the other, thus allowing the inclination of the tube. These plates are returned to their original position by springs. In the upper part of the framework directly over the tube is a spindle 3.17 millimetres in diameter, with a pointer on one end which turns on a dial. A small plumb-weight is suspended from the spindle by a fine platinum thread which winds on it. This weight is partly counterbalanced by a second weight suspended from the spindle by a linen thread. These weights are so that if they be allowed to move freely the former is just sufficiently heavy to cause it to fall gradually, and when the aluminum tube is in po- sition this weight will fall until it just touches the surface of the cap on the top of the tube. The fall of one centimetre of this weight causes the spindle to make one revolution, thus making one revolution of the pointer on the dial equivalent to one centi- metre. The above framework is fastened on to the cover of a copper chamber, the aluminum tube projecting through this cover into the chamber, needle-end down. This cover, which is of wood, is made in two thicknesses, with an air-chamber between^ thus more perfectly insulating the interior of the chamber from the outside air. It is supplied with two large windows on each side of where the needle-tube passes in, admitting light and allowing the operator to see the sample. The chamber to- hold the samples, which is of thin sheet copper, is constructed with a rounded bottom like a kettle, and is fitted with a flat false bottom or flooring of sheet iron. Raised above the flooring about an inch, resting on three rollers, is a circular disk, on which the samples to be tested are placed in a circle about half an inch from the edge. This disk can be rotated like a turntable by means of an iron rod which passes through its centre into a bearing on the floor and out through the cover of the chamber, where it is fitted with a wheel. By turning this wheel, thus revolving the disk,. MATERIALS EMPLOYED IN THE CONSTRUCTION OF PAVEMENTS. 95 each sample on it can be brought in turn under the penetrating needle. In this way twelve samples can be tested by this parties lar apparatus without opening the chamber. Two swinging mir- rors are fastened, one on each side of the copper chamber, one mirror being so adjusted as to throw light on the sample to be tested, while the other reflects the image of the sample so that it can be seen by looking; in through a window in the coyer. This copper chamber is fastened into a lead-lined tank, which is filled with water of any degree, or a freezing mixture, as the case may be, to produce the desired temperature in the chamber. To keep this temperature constant the tank is supplied with one inlet, in the centre of the bottom, and four outlet pipes, one on each side near the top. The temperature of the copper chamber is regulated by a simple electrical thermostat suspended in it, which will cut off or let on a supply of liquid or water entering the tank as the temperature requires. In making a test or tests the samples are placed in position on the disk in the copper chamber, the cover with the apparatus put in place, and the chamber secured in the lead-lined tank. The water or liquid of the desired temperature is run into the tank, which is allowed to fill and run off by the overflow pipes. The entire apparatus is then levelled by levelling-screws in the feet of the tank until the needle-tube is perfectly vertical. When asphalt is to be tested it is, for convenience, put into small round tins like small blacking boxes. By heating just sufficiently to rnelt it a smooth surface is obtained with quite a gloss. These boxes con- taining the samples are placed on the revolving disk, each sample resting on two raised points on the surface of the disk, this giving them a slight incline. The table is then revolved until the de- sired sample is directly under the needle-tube, when it is lowered until the needle is very nearly in contact with the surface. The surface of the sample being slightly inclined, it can be brought just in contact with the needle by a slight revolution of the disk. By arranging the mirror on top of the cover so that it will reflect the light from a window down upon one of the mirrors in the chamber, which in turn reflects it on the surface of the sample, and then having the other mirror in the chamber in such a position as to reflect the image of the sample up, the needle can be set accurately 96 HIGHWAY CONSTRUCTION". to the surface by watching its reflection in the surface of the sam- ple. To determine the penetration the reading of the dial is taken, the clamp is released, which allows the needle to sink in the asphalt under the weight of the tube. The apparatus is so constructed that when the clamp is released from the tube another clamp closes on the thread of the counterbalance weight, thus preventing the plumb-weight from falling and adding its. weight to that of the tube. On clamping the tube again at the expiration of the desired time the thread of the counterweight is released, which allows the plumb-weight to sink until it is checked by the top of the tube. The present reading of the dial, less that before taken, is the dis- tance the needle penetrated into the sample. Headings can be made with accuracy to one-fiftieth millimetre. 103c. Standard Tests. District of Columbia. The present standards employed for penetration tests by the Engineer Depart- ment of the District of Columbia is the distance (on Dow's apparatus) expressed in hundred ths of a centimeter that a No. 2 needle will sink or penetrate into the cement or bitumen in a given time and temperature as follows: At 32 F. needle weighted with 200 grams operating for one min. At 115 F. " " ". 50 " " " fivesec. At 77 F. " " " 100 " " " " " The tests are made in the following manner: The samples to be tested are immersed in a freezing mixture or water at the de- sired temperature and kept at such temperature for at least thirty minutes before testing. The sample is then placed in a glass dish and covered with the water or freezing mixture, then placed on a shelf in the machine and the penetration determined. The tem- perature of the watqr surrounding the samples is taken at the end of each test, and if it varies more than one half degree from the standard the test is rejected. 103d. Test for Effect of Heat. The effect of high temperatures and the loss by volatilization is determined in the following manner: Fifty grams of cement or bitumen, the consistency of which has been determined by penetration at 77 F., is placed in a tin box having a diameter of six centimeters and a depth of two centimeters. The box containing the sample is placed in a hot-air oven and the MATERIALS EMPLOYED IN THE CONSTRUCTION" OF PAVEMENTS. 97 temperature raised to, and maintained at, 300 F. for eighteen hours. During the last two hours the sample is stirred once each hour with an iron stirring-rod. At the end of the eighteen hours the sample is removed from the bath and allowed to cool to normal temperature; it is then weighed and the per cent, of loss calculated. When cooled to 77 F. the penetration test is repeated. The difference between the penetration before and after heating divided by the penetration before heating is considered as the percentage of hardening resulting from the heating at 300 for eighteen hours. Tensile Strength of Asplialtum. Tests of the tensile strength of asphalt are frequently made from the mixture prepared for lay- ing in the street, moulded into briquettes, and broken in a similar manner to Portland cement briquettes. This method is imperfect, -as it is quite impossible, without enormous pressure, to get the par- ticles of sand as firmly consolidated in briquette as they are by the kneading and rolling motion imparted to the surface mixture under a steam-roller, and whatever advantage is to be found in this method of examination it is complicated by any variation which may occur in the method of mixing. A method successfully employed to obtain the tensile strength of asphalt is by using the broken halves of Portland cement briquettes. These are united with the asphalt or asphaltic cement, and broken in a testing-machine in the following manner: The broken halves of a Portland cement briquette, which was broken clean and at right angles to the line of stress, are heated to drive off all moisture ; the two halves are then dipped in molten asphalt and pressure applied by hand until the thickness of the asphalt is reduced to less than T J of an inch. The briquettes are then al- lowed to cool slowly, and after standing 24 hours are broken in a cement testing-machine. Brass briquettes cast from the pattern of a Portland cement briquette are also used. The surfaces upon which the asphalt is to adhere are left rough. When using these briquettes they are heated to about 140 F. in water, taken out and dried, and the separate ends dipped in the molten asphalt. The two ends of the briquette are then stuck together and allowed to cool slowly in the same manner as the Portland cement briquettes. When testing asphaltic cement for tensile strength the penetra- 98 HIGHWAY CONSTRUCTION. tion of the cement must be taken into consideration as well as the temperature at which the test is made. Below 50 F. the results obtained will be very much more regular than with tests made above that temperature; the higher the temperature the greater will be the variation. An asphaltic cement made from well refined Trinidad Lake asphaltum should have with a penetration between 70 and 80 degrees (Bowen's scale) a tensile strength of over 450 Ibs. per sq. in. at a temperature of 35 degrees Fahr., and 300 Ibs. per sq. in. at 50 degrees Fahr., the strength being determined with a one-inch sec- tion, the strain to be applied at the rate of 1000 Ibs. per minute. The ductility or property of being drawn out in long threads or strings has been referred to in Art. 1000 as a measure of the proper consistency of a paving cement. Mr. W. H. Broadhurst, in Proc. A. S. M. I., describes the method employed by him to measure this property as follows: Twenty grams of pure bitumen were extracted from Trini- dad, Bermudez, and Alcatraz asphaltums with chloroform. To the pure Trinidad bitumen petroleum residuum was added to the amount of 33 per cent of its weight (this percentage being calcu- lated from the usual proportion of 18 Ibs. of residuum to 100 Ibs. of refined Trinidad asphalt, containing 55 per cent bitumen). The penetration was then taken with the Bowen apparatus, and found to be 40 at 80 F. The pure Bermudez was brought to the same degree of penetration, requiring approximately 13 per cent of its weight of petroleum residuum. The pure Alcatraz bitumen required approximately 24 per cent of Alcatraz maltha (2X grade) to give a penetration of 40. As a matter of technical interest, a separate portion of Trinidad bitumen was brought to 40 penetra- tion with Alcatraz maltha. These four cements were poured while hot into glass tubes 2 inches in length and T 5 inch in internal diameter, closed at one end with a cylindrical cork. These tubes had previously been cut in half, the edges ground true to plane, and cemented together with a thin film of plaster of Paris. This cement joint being easily broken by a slight side pressure, the tubes were kept at a temperature of 80 F. for one hour; they were then clamped in a vertical position and separated a distance of exactly of an inch. The lower half of the tube was then allowed MATERIALS EMPLOYED IN THE CONSTRUCTION OF PAVEMENTS. to draw apart from the upper by its own weight, thus pulling the cement out into 'a string, the cross-section decreasing as the length increased. The distance between the tubes at the time of rupture was noted, and the following results were obtained : RELATIVE DUCTILITY OF ASPHALT CEMENTS. Penetra- tion Ductility Ductility Composition of Cement. at 80 F. at 8 F. at IK) F. Bow-en's Length. Length. Scale Trinidad asphaltum and petroleum residuum. 40 Jin. fin. Bermudez asphaltum and petroleum residuum. 40 li 2* " Aleatraz asphaltum and Alcatraz maltha 40 2i 4 " Trinidad asphaltum and Alcatraz maltha 40 2-i 4A- " Pure Alcatraz asphaltum (soft) 50 8 44 ^4 Uvalde asphaltum (refined) and Alcatraz maltha 50 ^2 5* Trinidad asphaltum and petroleum residuum. . 55 1 Bermudez asphaltum and petroleum residuum . 55 3 Alcatraz asphaltum and Alcatraz maltha 55 4| Bakersfield asphaltum and Bakersfield maltha . 55 2* Test for Ductility. The ductility of an asphalt cement or bitu- men is determined by the distance in centimeters that a briquette > of the material will draw out cr stretch before breaking. The cement or bitumen is first brought to a consistency of 50 on Dow's apparatus at 77 F. by mixing with a flux similar to that proposed to be used in the practical work. The dimensions of the briquette; are: One centimeter in thickness throughout its entire length; dis- tance between clips, three centimeters; width at mouth of clips,, two centimeters; width at minimum cross-section half-way between clips, one centimeter. The briquette is molded as follows: The mold is placed on a, brass plate, the cement to be tested is poured into it while in a molten state, a slight excess being added to allow for shrinkage in cooling. Before the cement has hardened the excess is smoothed off by a trowel wet with water to prevent its sticking. When the briquette has cooled to the temperature at which it is desired to make the test, the sides of the mold are removed and the briquette 100 HIGHWAY CONSTRUCTION. tested by immersing it in water at 77 F. and pulling it apart at the rate of five centimeters a minute until the thread of cement separates. The distance between the ends are measured and re- corded as the measure of ductility of the particular cement tested. As asphalt cement possesses the same qualities and can be used for the same purposes as hydraulic and other cements, its physical qualities can be tested in a similar manner; but the tests which have been made and published have been conducted without any regard to uniformity and under widely different conditions; there- fore they are of little or no value in determining the relative merits of the cements. Uniformity in making the tests would accumulate much valu- able data which could be compared, and much definite information would thus be gradually collected from which definite conclusions could be ultimately drawn. A regular system of analysis and examination of both the crude and refined asphaltum, the oils or other agent used for fluxing, the method of refining the asphaltum, the method of manufactur- ing the asphaltic cement, the sand, stone-dust, etc., should be main- tained in all cities using asphalt pavements. The experience thus gained of the success or failure of pavements made of different asphalts will serve as a guide for similar work in the future. This experience, however, will not serve as a criterion for all cities, be- cause, owing to different climatic and local conditions, the propor- tions of the ingredients in the cement and paving mixture must be varied to suit the conditions of the place where used; therefore the mixtures which are successful in one locality may become failures in another. In comparing the relative qualities* of aspbaltums for paving purposes much stress is frequently laid upon the amount of bitumen tthey contain. As the amount of bitumen entering into the paving mixture is less than 20 per cent of the whole, the amount of bitumen contained in a crude asphaltum can in no way affect the quality of the pavement; but its quantity does affect the commercial value or price of the crude material in regard to the amount of refined asphaltum that it will yield. As far as the qualities of the paving mixture are concerned, it is the character and condition of the bitumen, and not its quantity, that affect the results. MATERIALS EMPLOYED IK THE CONSTKUCTIOX OF PAVEMENTS. 101 Essential Characteristics of a Bitumen. The necessary charac- teristics for a bitumen to possess to produce a satisfactory pave- ment are adhesiveness, cohesiveness, and elasticity to a certain degree. It must not show too rapid a change with aging, must be practically unaffected by water or dilute ammonia, and have a proper degree of consistency or softness. Its consistency should not be greatly altered by changes in temperature; and lastly, a certain degree of stability upon being kept at a high temperature for a length of time. 104. Prices, Production, and Imports of Asphaltum. The fol- lowing tables show the comparative prices of different varieties of asphaltum, the amount of the domestic production, and the im- ports to the United States during the year 1906: TABLE XVII. PRICES OF ASPHALTUM IN 1906. Trinidad, refined at New York $20 . 00 to $25 .00 per ton Cuban, crude " " " 25.00" 30.00" " Venezuela," " " " 25.00" 30.00" " Bermudez, " " " " 25.00" 30.00 " " California, refined, at New York 19.00 " 21.00 " '* " crude, at the mines 2.80" 15.00" *' " maltha, at the mines 10.50 " Kentucky (bituminous rock), at the mines 5.50 ' " 102 HIGHWAY CONSTRUCTION. TABLE XVIII PRODUCTION OF ASPHALTUM IN THE UNITED STATES. 18 17, 19( )4. State. Tons. Value. Tons. Value. Arkansas 1 700 $8 500 California. 68 650 $598 502 60279 639 429 Indian Territory 345* 3486 6 457 37 516 Kentucky 3 250 15 150 5 670 31 185 Missouri 2,735 21,171 Pennsylvania 1,200 10,800 Texas 3 60 Utah 3 700 47 500 3 528 155 080 Total 75,945 $664,632 81,572 $903,741 * Includes Texas. TABLE XVIIIa. VARIETIES OF ASPHALTUM PRODUCED IN THE UNITED STATES. 18 ( )7. 19( )4. Variety. Short Tons. Vdue. Short Tons. Value. Bituminous sandstone. . Bituminous limestone . . Mastic 48,801 2,100 483 $158,914 10,600 9,864 19,641 1,798 1,200 $71,465 4,495 10800 Hard and refined gum. . Liquid or maltha Elaterite 9,911 14,650 173,904 311,350 15,012 3,363 550 224,446 36,320 50,000 2978 105.080 Grahamite 1,000 25000 36,030 376,135 Total 75,945 $664,632 81,572 $903,741 MATEKIALS EMPLOYED IN THE CONSTRUCTION OF PAVEMENTS. 103 TABLE XIX. IMPORTS OF ASPHALTUM TO THE UNITED STATES. 18 97. IS 04. Long Tons. Value. Long Tons. Value. West Indies: British (Trinidad) Danish 85,034 400 $198,786 2,000 110,031 $368,623 Cuba 223 4,180 9,494 22230 Switzerland 414 3815 Italy 14,580 77,456 3 211 11 581 Venezuela (Bermudez). . . Germany 13,807 6896 75,943 25,986 50,194 1 528 217,017 11 755 France 861 3,327 Mexico 273 3992 382 2223 Turkey in Asia 31 3439 119 2763 Great Britain 11 309 63 932 British India L 49 312 United States of Colombia Austria-Hungary 3 130 23 2 1,456 46 Canada 2 6 130 1 032 Total 122 122 $395 554 175 640 $643 785 105. Uses of Asphaltum. Refined asphaltum and asphaltic -cement are extensively used in all branches of engineering. The paving industry absorbs about 60 per cent of the domestic produc- tion and about 80 per cent of the imported. Of the imports from Trinidad about 90 per cent is employed for street-paving. 106. Paving-pitch. This is the name given to the tar pro- duced in the manufacture of gas. It is also known as gas-tar, coal- 104 HIGHWAY CONSTRUCTION. * .. tar, etc. When the tar is redistilled, the product is called coal-far distillate, and is numbered Distillate No. 1, 2, 3, 4, etc., according* to the density or specific gravity. The character of the tar varies with the system of carbonization and temperature employed. There are several tars on the market which show to the analyst no material difference, although the grouping and character of the constituents are different. Some, when used for paving purposes, will become hard and brittle in a few months, and others will not harden or set. The pitch known as No. 4 is used mainly as a filler for granite and Belgian block. It is very soft, and frequently becomes semi- fluid under the heat of summer; for this reason it is put up in oil barrels which contain about 50 to 52 gallons. The No. 6 is generally used as a filler for brick pavement; it is termed medium hard, and is commonly put up in cement and lime barrels. The cement barrels contain about 28 gallons, and the lime barrels from 30 to 32 gallons. The pitch is sold by the ton, and the weight of the package is figured in. A square yard of brick paving requires from 1 to l gallons, according to the spacing and the manner in which the work is done. A square yard of stone-block paving will take from 2 to 4 gallons. Paving-pitch is frequently adulterated with wood-pitch, which serves to reduce its cost considerably, and also serves to make it very inferior for paving purposes. A paving-pitch suitable for stone pavements should be soft enough to almost stick to the fingers when worked in the hand at a temperature of about 70 F. For brick pavements it should be somewhat harder, so as to check* the tendency to flow during hot weather. Analysis of No. 4 pitch gives the following composition : Spe- cific gravity, 1.284 to 1.309; matter soluble in carbon bisulphide, 64.84 to 72.50; insoluble matter, 27.50 to 35.16. The price per gallon at the gas-works during 1898 varied from. 2.23 cents Tn Indiana to 10.17 in Montana and New Mexico. ,M \TERTALS EMPLOYED IX THE CONSTRUCTION OF PAVEMENTS. 10o Many persons consider that the enduring quality of the tar is increased by the addition of refined asphaltum, and specifications frequently call for the addition of from 10 to 20 per cent of as- pbalturn; but this clause is rarely complied with, and it is doubt- ful if the mixture would prove beneficial, because the materials,, although very similar in appearance and in some of their charac- teristics, are entirely different in composition. (See also Art. 160.) 107. Brick Clay. Pure clay consists of a hydrated silicate of alumina in combination more or less with other substances derived from the felspathic rocks, which by their disintegration and decomposition have formed the clay. The chemical formula of the most prominent varieties of clay according to Brogniart and others, may be expressed by 2Al 2 3 3Si0 2 4HO. 108. Pure clay is soft, more or less unctuous to the touctu white and opaque, and when breathed upon emits a characteristic odor. It is infusible, and insoluble either by water, nitric or hydrochloric acids. It may be converted by water into a doughy, tenacious, plastic paste. It absorbs water with avidity, but when burned at a -sufficiently high temperature it becomes hard and gritty and loses almost wholly or altogether this property of combining with water. When slowly dried and exposed to red heat, the particles of clay are augmented in volume and possess less density. At the same time, however, the interstitial spaces are diminished and they approach more closely together, giving an increase of density to the whole mass of burnt clay, which is prac- tically observed by a diminution of surface and technically called the shrinking of the clay. This shrinkage is very materially modi- fied and affected by the admixture and proportion of foreign matters possessing other properties. 109. In nature the greater number of clays is found inter- mingled with other substances foreign to them in their original localities. The usual constituents of clay are alumina, silica, iron, lime, magnesia, and alkalies, all of which modify the character of the clay and its applications, according as one or other of these in- gredients predominates. 110. The ingredients which most affect the character of the clay are the silica, iron, and lime, and its plasticity diminishes in proportion to the amount of any one of these substances which it contains, as they are not plastic. Sand exercises the most marked 106 HIGHWAY CONSTRUCTION. effect; it possesses no binding properties, and alone it is infusible except at the highest temperatures of the oxyhydrogen blowpipe. Bricks made of clay containing an excess of sand are rough and weak. Iron renders clay fusible, and its presence is objectionable in brick intended for furnace-lining; but in paving-brick it is advan- tageous, making the brick more homogeneous. Lime, although infusible, is at high temperatures changed into caustic lime, ren- ders the clay fusible, and when exposed to the action of the weather absorbs moisture and causes disintegration. Its presence is to be avoided in clay used for the manufacture of paving-brick. Magnesia exerts but little influence on the character of the clay; in small quantities it renders the clay fusible; at 60 degrees Fahr. its crystals lose their water of crystallization and cold water decom- poses them, forming an insoluble hydrate in the form of a white powder. In air-dried brick this action causes them to crack. The alkalies are found in small quantities in the best of clays; from 1 to 3 per cent renders the clay fusible. The greater the amount of quartz and silica that enters into the composition of the clay, the more difficult it will be of fusion. 111. Clay, to make a good paving-brick, must be rich in silica, free from lime, and able to withstand without fusing a red heat for a sufficient length of time to render the bricks hard, homoge- neous, and impervious to water. 112. Common hard-burned brick is not suitable for paving pur- poses, although such brick makes a smooth pavement under light traffic and lasts for a number of years ; still, under the influence of moisture and frost, disintegration is inevitable in the end. Noi will such brick sustain constant heavy traffic, aside from climatic influences. Brick made of suitable clay, however, will stand the severest frosts, and crushing tests show it to be equal to many granites. The shales or rock-like clays are now almost exclusively used in tin; manufacture of paving-brick. They usually contain a high percuiiL.ige of fluxing impurities, which enables them to be readily A very elaborate discussion of the chemical composition and the influence of impurities of clays is given by H. A. Wheeler, Assistant Geologist in Part I of the "Report on the Missouri Clays." MATERIALS EMPLOYED IK THE CONSTRUCTION OF PAVEMENTS. 10? vitrified. The average composition of the shales that have proved satisfactory for the manufacture of paving-brick is as follows: Silica(SiO a ) 56.00 Alumina (Al a O a ) 22.00 Water chemically combined and loss on ignition 7.00 Moisture (H a O) 2.00 Sesquioxide of iron (Fe 2 O 3 ) 7.00 Lime (CaO) 1.00 Magnesia (MgO) 1.00 Alkalies (K a ONa a O) 4.00 100.00 113. The color of clay is of no practical importance ; it is due to the presence of metallic oxides and organic substances. Clay containing iron produces bricks which are either red, yellow, or blue, according to the quantity of the oxide present and the de- gree of heat to which they have been subjected ; some organic sub- stances produce a blue, bluish-gray, or black color. The color of the brick is largely influenced by the burner in the manipulation of the fires, and cannot be relied upon as a guide to the quality of the brick; for a specific clay and a given burner it aids in estimating the degree to which the brick has been burned, and the care with which it has been handled. 114. The Manufacture of Paving-brick may be classified under the following heads: Excavation of the day either by hand labor or mechanical appliances. Preparation of the clay consists in (a) removing gravel, stones, or other im< hanical impurities; (b) pulverizing the clay. This is performed either by toothed rolls, centrifugal disintegrators, or crushing-rolls in the revolving dry or wet pan. The dry pan with a perforated grate bottom is generally employed for shales and fire clays. The pulverized clay is usually screened in either revolving trammels or fixed or shaking riddles, with 4 to 16 meshes to the linear inch. The degree of fineness of the screen is a very impor- tant matter, as the finer the clay the more plastic it is, and hence the more homogeneous and stronger the brick. The fineness of the screen, however, must be determined for each specifically, as ex- 108 HIGHWAY CONSTRUCTION. cessive fineness in some clays causes checking and cracking in drying or burning, and aggravates the trouble from laminations. In some works the clay is not screened any further than is accom- plished by the screen-plates of the dry pan, which are usually -J to inch in width. Tempering. The screened clay is mixed with water and worked to a more or less plastic mass in a pug-mill. The operation should be performed in such a way as to secure a thorough, uniform mix- ture of the clay and water; if this is not attained the clay leaves the machine with variable amounts of water. This causes check- ing and cracking in the drying, and sometimes in the burning, with marked variations in the strength of the brick. The more thoroughly a clay is pugged, the more plastic it is rendered, and the more uniform and reliable will be the quality of the brick. Moulding. The process most generally employed for moulding paving-brick is that called the " stiff-mud process." The clay is made into a stiff, plastic mud, which is forced through a die by a continuous-working auger or intermittent plunger as a bar of clay, which is then cut by wires into suitable lengths. For forming the bar of clay two types of dies are employed; in one the die is approximately 3" X 4" in section, and the bar of clay is cut into 9" lengths; this is known as the " end-cut system" : in the other the die is approximately 4" X 9" in section, and the bar of clay is cut into 3" lengths; this is called the "side-cut system." There is considerable difference of opinion as to the relative merits of these two methods of moulding. Drying. The moulded brick are packed in cars, in open checker work, direct from the brick- machine, which are run into chambers or tunnels heated by open fires, steam-coils, or a heated blast. The time required for drying depends upon the character of the clay; the finer and more plastic the clay the greater the time required, the coarser and leaner the clay the more rapidly it can be dried. Some clays can be safely dried in 24 hours, while others require from 60 to 72 hours. Burning. After being sufficiently dried the bricks are piled in the kilns, and the firing is conducted with the utmost care, as upon it the perfection of the brick largely depends. Two classes of kilns are in use for burning paving-brick, the down-draft and the MATERIALS EMPLOYED IN THE CONSTRUCTION OF PAVEMENTS. 109 continuous. The down-draft type seems to be the most pre- ferred, as with careful handling from 60 to 90 per cent of No. 1 brick can be obtained. The continuous type has greater economy of fuel, but the shrinkage and the difficulty of securing uniformity in burning is so great that they only yield from 40 to 70 per cent of No. 1 brick. After the brick are burned, the kiln is tightly closed to shut off the access of cold air, and the longer the time given the brick to cool and anneal the tougher the brick will be. Sorting. In emptying the kiln there are usually three grades of brick found : (1) Those which have received the highest heat, and, while hard, are not generally tough enough for paving pur- poses; (2) those which have not received sufficient heat to be prop- erly vitrified; and (3) those which have been properly burned, and which are designated as No. 1, or strictly first-class paving-brick. They are distinguished by the fracture, toughness, and the color from the other two grades of brick. They should be perfectly uni- form in the fracture, homogeneous, very dense, very hard, tough, and reasonably free from " kiln-marks/' or indentations made by the overlying brick. The depth of the kiln-mark is considered a gauge for the degree of the vitrification; the deeper the mark the more thorough the vitrification, but if too deep they make a rough uneven pavement; the allowable limit ranges from -J to inch. The absence of kiln-marks usually indicates underburning. Ex- cept in fire-clays, it is seldom that a properly vitrified brick is entirely free from slight indentations. 115. Repressed Brick are produced by subjecting the brick im- mediately after it leaves the brick-machine, and while still in a plastic condition, to a moderate vertical pressure in a metal mould- box. The operation fills out the edges and angles, and rounds them if desired. The appearance of the brick is much enhanced, but there is much difference of opinion as to whether the quality is improved; the tests by Professor Orton indicate that repressing an end-cut brick improves it, while repressing a side-cut brick injures it. 116. Analyses of Clay. Table XX shows the composition of some of the clays used in the manufacture of paving-brick. 110 HIGHWAY CONSTRUCTION. TABLE XX. ANALYSES OP CLAYS. 8 . A B &C o O Locality. 08 .3 1 . 1 1 ?*' HJJ j- 1 I 3 c a a be i 03 ^ 1 ll 11 c ^ "^ 1 02 q a s co 02 I * H E Woodbridge, N. J. 42.23 39.53 0.5 0.1 0.41 0.08 13.59 1.21 !1.40 0.50 bfc ii 42 05 35 83 77 f) 11 44 12 20 1 50 1 10 5 70 Phillipsburg, " 56.78 17.38 6.50 4,14 3,15 3 .42 89 7 ,60 13 Winchester, 111.. . . 23.15 17.08 3.47 0.28 1.10 6.30 1.20 0.90 46. 70 Bloomington, III 67.80 11.55 4.31 8.90 5.32 2 .42 trace .20 trace Cheltenham, Mo. . 61.22 25.64 1.70 1 31 4 9 68 38.10 31.53 2.32 tr. 0,40 11.30 2.50 1.50 12.70- Montgomery, Mo. . Woodlawn, Penn. . 43.93 42.15 40.09 31.43 0.88 1.57 0^32 0.20 2.01 .... 13.80 9.40 0.80 1.20 tr.* 1.00 0.60 10.25 Mt. Savage, Md... 39.90 30.08 1 67 2 30 7.00 6.90 1.15 16.90 Carter Co., Ky.... Marion Co., W. Va. 46.75 59 25 38.17 32 26 290.57 7 1fi 0.12 .07 14 03 1 33 San Fran., Cal 56.51 21.33 12 31 8 53 tr 6 30 Haydensville, O. . . 72 24 16.87 16 ^0 tr. 1 09 5 14 Burlington, la ... 77.40 11.74 3.29 1 60 1 91 ^ 76 47 Clinton, " ... 73 82 15.88 2 92 tr. tr 4 5 3 Morrison Colo .... 71 8 15 tr ^ 8 8 3 Golden " 52 41 32 21 66 20 61 61 14 05 Stourbridge, Eng. 67.34 23 03 2 03 38 8 24 64.05 23.15 1.85 .... .10 10 00 * With A1 2 O 3 . 117. The Characteristics of Brick suitable for Paving are: (1) Not to be acted upon by acids. (2) Not to absorb more than ^ F of its weight of water in 4& hours. (3) Not susceptible to polish. (4) Rough to the touch, resembling fine sandpaper. (5) To give a clear ringing sound when struck together. (6) When broken to show a compact, uniform, close-grained structure, free from air-holes and pebbles. (7) Not to scale, spall, or chip when quickly struck on the edges. (8) Hard but not brittle. 118. Tests of Paving-brick. To ascertain the quality of paving- brick they are now generally subjected to four tests, namely: (1) Abrasion by impact (commonly called the "Battler" test); (2) absorption; (3) transverse or cross-breaking; (4) crushing. With the view of securing uniformity in the methods of making MATERIALS EMPLOYED IN THE CONSTRUCTION OF PAVEMENTS. 1 1 1 the above tests the National Brick Manufacturers' Association have adopted and recommend the following: 118a. Standard Tests Adopted by the National Brick Manufac- turers' Association (Chicago, Jan. 27, 1900). RATTLER TEST. 1. Dimensions of the Machine. The standard machine shall be 28 inches in diameter and 20 inches in length, measured inside the chamber. Other machines may be used varying in diameter between 26 and 30 inches, and in length from 18 to 24 inches, but if this is done, a record of it must be attached to the official report. Long rattlers may be cut up into sections of suitable length by the inser- tion of an iron diaphragm at the proper point. 2. Construction of the Machine. The barrel shall be supported on trunnions at either end; in no case shall a shaft pass through the rattling chamber. The cross-section of the barrel shall be a regular polygon having fourteen sides. The heads shall be composed of gray cast iron, not chilled or case-hardened. The staves shall preferably be composed of steel plates, as cast-iron peans and ulti- mately breaks under the wearing action on the inside. There shall be a space of one-fourth of an inch between the staves for the escape of dust and small pieces of waste. Other machines may be used, having from twelve to sixteen staves, with openings from one- eighth to three-eighths of an inch between staves, but if this is done a record of it must be attached to the official report of the test. 3. Composition of the Charge. All tests must be executed on charges containing but one make of brick or block at a time. The charge shall consist of nine paving-blocks or twelve paving-bricks, together with 300 pounds of shot made of ordinary machinery cast iron. This shot shall be two sizes, as described below, and the shot charge shall be composed of one-fourth (75 pounds) of the larger size, and three-fourths (225 pounds) of the smaller size. 4. Size of the Shot. The larger size shall weigh about 1^ pounds and be about 2 inches square and 4 inches long, with slightly rounded edges. The smaller size shall be cubes of l inches on a side, with rounded edges. The individual shot shall HIGHWAY CONSTRUCTION". be replaced by new ones when they have lost one-tenth of their original weight. 5. Revolutions of the Charge. The number of revolutions of a standard test shall be 1800, and the speed of rotation shall not fall below 28 nor exceed 30 per minute. The belt-power shall be suffi- cient to rotate the latter at the same speed, whether charged or empty. 6. Condition of the Charge. The bricks composing a charge shall be thoroughly dried before making the test. 7. Calculation of the Results. The loss shall be calculated in per cents of the weight of the dry brick composing the charge, and no results shall be considered as official unless it is the average of two distinct and complete tests made on separate charges of brick. Tha rattler shown in Fig. G was designed at the Purdue Unh ersity. At the free end it permits easy access to the rattling chamber for the purpose cf inserting and removing the bricks, an operation which in the common form of rat- tler requires the removal of a stave of the drum. Thv3 rattler is enclosed in a dust- proof case made of sheet- iron. The dust and chips pass through a door in the bottom, and are caught in a pan as shown in the figure. FIG- G. RATTLER FOR TESTING BRICK- ABSORPTION TEST. 1. The number of bricks for a standard test shall be five. 2. The test must be con- ducted on rattled brick. If none such are available, the whole brick must be broken in halves before treatment. 3. Dry the bricks for forty-eight hours at a temperature ranging from 230 to 250 F. before weighing for the official dry weight. 4. Soak for forty-eight hours completely immersed in pure water. MATERIALS EMPLOYED IN THE CONSTRUCTION OF PAVEMENTS. 113 5. After soaking, and before weighing, the bricks must be wiped dry from surplus water. 6. The difference in the weight must be determined on scales sensitive to one gram. 7. The increase in weight due to water absorbed shall be calcu- lated in per cents of the initial dry weight. CROSS-BREAKING TEST. 9 1. Support th brick on edge, or as laid in the pavement, on hardened steel knife-edges, rounded longitudinally to a radius of twelve inches and transversely to a radius of one-eighth inch, and bolted in position so as to secure a span of six inches. 2. Apply the load to the middle of the top face through a har- dened steel knife-edge, straight longitudinally and rounded trans- versely to a radius of one-sixteenth inch. 3. Apply the load at a uniform rate of increase till fracture ensues. 4. Compute the modulus of rupture by the formula / = -rrj^, &OCI In which /= modulus of rupture in pounds per square inch; w = total breaking load in pounds;- I = length of span in inches = 6"; I breadth of brick in inches; d depth of brick in inches. 5. Samples for test must be free from all visible irregularities of surfaces or deformities of shape, and their upper and lower faces must be practically parallel. 6. Not less than ten brick shall be broken, and the average of all be taken for a standard test. CRUSHING TEST. 1. The crushing test should be made on half-bricks, loaded edge- wise, or as they are laid in the street. If the machine used is unable to crush a full half-brick, the area may be reduced by chip- ping off, keeping the form of the piece to be tested as nearly HIGHWAY CONSTRUCTION. prismatic as possible. A machine of at least one hundred thou- sand pounds capacity should be used, and the specimen should not be reduced below four square inches of area in cross-section at right angles to direction of load. 2. The upper and lower surfaces should preferably be ground to true and parallel planes. If this is not done, they should be bedded while in the testing-machine in plaster of Paris, which should be allowed to harden ten minutes under the weight of the crushing planes only, before the load is applied. 3. The load should be applied at a uniform rate of increase to the point of rupture. 4. Not less than an average obtained from five tests on five different bricks shall constitute a standard test. 119. Specific Gravity, Weight, Resistance to Crushing, and Ab- sorptive Power of Paving-brick. In regard to these qualities the paving-bricks made by different manufacturers and by the same manufacturer vary considerably, as will be seen from Table XXL In weight they vary from 5 to 7^ pounds; in specific gravity, from 1.91 to 2.70; in resistance to crashing, from 7000 to 18,000 pounds. per square inch; in absorption, from 0.15 to 5.00 per cent. Tests of Ohio Paving-brick. Table XXla contains the re- sults of a series of tests conducted by Prof. Edward Orton, Jr., at the solicitation of the Geological Survey of the State of Ohio. The tests were performed with the greatest care and absolutely without interest or bias of any kind, and the results are solely on the merits of the samples furnished. The tests are interesting and valuable in several ways. It is the first work of the kind under- taken by the State, and it is also probably the first large and gen- eral test in which the results could not be attacked as being ex pai'te. It is of great interest to those who compete for standing, of course, and it should be equally interesting to all clay-workers to see so large a list of factories, representing an annual capacity of three hundred millions of brick, showing so high an average quality of material. The samples were selected by the manufac- turers themselves, and therefore represent their best. II, was the intention to make this so; the public does not desire to know how poorly the brick-makers can do, but how well, and, having shown their ability to produce goods of this quality, it should be their constant endeavor to hold their average output up to the same high grade. MATERIALS EMPLOYED IN THE CONSTRUCTION OF PAVEMENTS. TABLE XXI. TESTS OF PAVING BRICKS MADE AT THE LABORATORY OP LATHBURY & SPACKMANN, IN PHILADELPHIA, IN ACCORDANCE WITH THE REQUIRE- MENTS OF THE SPECIFICATIONS OF THE NATIONAL BRICK MANUFAC- TURERS' ASSOCIATION. Catskill Shale Paving Bricks from Canal Street, July 26, 1897. Canton Shale 'Red Granite" Bricks from Jefferson Street, July 26, 1897. Corning Shale Paving Bricks from Second Street, Sept. 6, 1897. Average size, in inches Average weight, in pounds Average area of top surface, sq. in. ... Average volume of one brick, cu. in.. Average specific gravity .50X4.00X2.50 7.46 21.25 85.00 8.50X4.00X2.50 6.99 21 .25 85.00 2.45 8.06X3.91X2.4Z 20.0 78.0 Absorption of water, average of 5: Weight in Ibs. after drying 48 hours . . Weight in Ibs. after immersion 48 hrs. Weight in Ibs. of water absorbed Percentage of water absorbed 18.00 18.89 0.89 4.9 15.78 16.61 0.83 5.26 Cross-breaking strength, bricks on edge. Centre load between supports 6 inches apart : First Second Third Fourth Fifth Sixth.. Seventh Eighth Ninth Tenth 8,610 8,850 8,510 8.950 9,940 9,120 11,470 11,620 13,210 8,120 8,570 8,950 9,080 9,490 10,270 11,120 11,330 17.95 18.65 0.70 3.9 3,810' 6,380 6,390- 6,660- 6,720> 8,480 8,510 12,930 12,450 12,460 Average strength in Ibs.. Modulus of rupture Impact tests (two), 28-inch rattler, 20 inches long, making 30 revolutions per minute: Weight before test, Ibs Weight after 300 revolutions Weight after 1,800 revolutions Loss in Ibs. after 300 revolutions Loss in Ibs. after 1,800 revolutions Loss per cent after 300 revolutions . . . Loss per cent after 1,800 revolutions . . Average per cent after 1,800 revol. 9,712 1,778 2,185 400 10,155 1,486 2,285 334 8,112 2,605 1,934 621 (1) 156.65 128.36 17.9 (2) 161.09 (1) 146.87 123.20 120.98 25.89 23.5 17.6 20.7 (2) 146.84 118.98 27.86 18.9 (1) 153.37 146.96 123.34 6.41 30.03 4.17 19.57 18 (2) 153. 56- 141. 9* 125.75 11. ea 27.81 7.57 18.11 .84 116 HIGHWAY CONSTRUCTION. I S PQ d a M (2 W o d w qoui -no 'qiSuajqs SniqsruQ qoni -bg 'q^Suaa^s SuiqsnaQ icf ^ to t~ *a o" Tj" 1 <*' tn ~*f to j$ -*- ~ S . d t- of 18 S s '5 s ' N N 03 t v 5 : l : S3 ! O 0) ;^ = >. cs >, : 3 S : :i 8 : g ||I| IIli'K&HA ill ill 11 I II; > e'S ^ 5 a.2 B* ISBe*S 1 1 ?! iiil|jlli!l1|s o> . eS h S| : ill 03 PH fa IjEf 1 * cc fa .c^ *SW iJ.-_ U K- C- O 02 3ig igS .r 35 *S o &JC .*:M '3 I! d MATERIALS EMPLOYED IN THE CONSTRUCTION OF PAVEMENTS.il? no 3* o ~ o 5 *-! - >- 1-1 ~ CO f T 'uopdaosqy I . o> . -.a :: Jj _ g MO ' g . P ' :a :| : ;| ;j| il^ : 3 1,3 ; 3 ; gi*8 s l Pijijililili^M ^ 8 C ^ I J*"l fl pq O co c/2 E-I 120 HIGHWAY CONSTRUCTION. 120. Wood. Both the hard and scft varieties of wood have been employed for paving with varying results. In the United States the woods commonly used are cedar, cypress, pine, tamarack, and gum. In Europe nearly all varieties of native and fc reign woods have been tried, the most recent being pine from Florida and the Australian blue gums jarrah and karri. In England at the present time Florida pine and jarrah are considered the mcst suitable on account of their durability without the use cf a pre- servative, this being due to their closeness of grain and small absorp- tive power. The soft varieties of wood, owing to their high absorbing capac- ity, are liable to early decay. In order to diminish this tendency it is the custom to subject them to some preservative process; impregnating with creosote is at present considered the most re- liable process. The hard woods are generally used in their natural state, as, owing to their dense, close grain, preservative solutions can only penetrate to a very limited extent and do not materially affect their durability. The hard woods, like the hard varieties of stone, are very slippery when wet. 121. Whichever kind is used, it should be sound, close-grained, uniform in quality, free from knots and sap and from the blue tinge which is a sign of incipient decay. All sappy wood should be rejected. 122. Tests for Wood Paving-blocks. The tests commonly used for wood paving-blocks are : (1) Absorption. (2) Resistance to abrasion or wear. (3) Resistance to crushing (compression). (4) Resistance (o impact (toughness). (5) Expansion due to absorption of water. (6) Thrust exerted by expansion. 122a. Test for Absorption. This test is made in the usual manner by first drying the sample, weighing, and immersing in water for a given period and again weighing. Table XXII shows the percentage of water absorbed by various woods when dry and creosoted. MATERIALS EMPLOYED IN THE CONSTRUCTION" OF PAVEMENTS. 121 TABLE XXII. ABSORPTIVE POWER OF WOOD. (E. R. ANDREWS in '''Engineering News.") Percentage of Water absorbed. Dry Wood. Creosoted 1.0000 .7140 .2000 .1754to .8333 .1600 .4300 .47^2 .1250 .3470 .0625 .023610.0306 .0000 .1240 .0000 Oak " (Burnettized . 2500) Hard pine 122. The use of creosote or other preserving processes makes it difficult to discover defects in the wood, and on this account is- objectionable. It is doubtful if creosoting, etc., adds to the life of wood employed for paving. 122b. Resistance to Abrasion. The test for abrasion or wear is made with the Dorrey machine. The specimens consist of prisms of the same dimensions as those used for testing the abrasion of stones. The specimens are placed in the machine with the grain of the wood at right angles to the grinding disk; emery is used as the grinding agent. The loss in height of the specimen is recorded as the wear. 122c. Resistance to Crushing. The test is made with a hydraulic press upon prismatic specimens with a base 8 cm. square and a. height equal to that of a paving-block, the grain of the wood being parallel to the direction of the load. The test specimens are either dried at a temperature between 30 and 4C C. or they are saturated with an amount of water estimated to be equal to that absorbed by a paving-block in service. Table XXIII shows the resistance to crushing of various woods. T>2 HIGHWAY CONSTRUCTION. TABLE XXIII. SPECIFIC GRAVITY, WEIGHT, AND RESISTANCE TO CRUSHING OF VARIOUS WOODS. Specific Gravity. Average Weight, pounds per cubic foot. Resistance to Crushing, pounds per square inch. Acacia . 71 to . 79 44 16000 Ash American white dry 61 38 8 900 Beech 69 43 7 700 Cedar American white 36 22 45 4 400 Chestnut " 46 22 80 5 300 .60 38 .408 24 4 6 000 Deal Christiania 689 43 5 850 1 187 74 19 000 Elm 56 35 Fir, American (Pacific region). . .405 25.28 Fir European 512 32 6 500 Hemlock, Am. (Atlantic region) Hickory .... .409 85 25.5 53 5,300 L/iguum vit8B 1 33 83 10 000 .85 53 8 200 .56 35 8 000 Maple. ... 79 49 Mesquite. American (Texas) Oak " white (Atlantic) " chestnut " red " black English .756 .763 .711 .751 .687 .777 47 46.5 44 46.7 43.8 48 10,450 7,000 7,500 7,000 7,000 6 400 934 58 10 000 P ne, American white 35 to 45 21 to 25 5 400 ' " red .485 30 6 300 yellow (Pacific) pitch (Atlantic) ' *Dautzic .530 .632 649 33 39 40 12,000 5,000 5 400 Redwood, American (California) Spruce, " (Atlantic).. .473 .408 29.5 25.4 9,500 5,700 122d. Resistance to Impact is tested with the same machine described under Impact Test of Stone. The prisms used have a base of 6 cm. square and a height equal to that of a paving-block. The test-piece is placed in a cast-iron case 7 cm. square, open both at top and bottom, and is held in place by a resinous cement which completely surrounds it, the top of the prism projecting about 1 cm. abbve the case. The 20-kg. hammer is employed with a height of fall of 200 cm. The number of blows of the hammer which cause an appreciable breakage is noted. Failure in the test-piece is indicated by a smaller rebound of the Lammer and a diminution in the height of the specimen. Three dried and three wet specimens are subjected to this test. MATERIALS EMPLOYED IN THE CONSTRUCTION" OF PAVEMENTS. 123 122e. Thrust Exerted by Expansion. For determining the thrust caused by absorption when expansion is partially prevented, whole paving-blocks are used. The block, after thorough desicca- tion, is placed in a water-tight receptacle and held between two plates at top and bottom, so that the top face of the test-piece rests against a block of cast iron, which is stationary. The lower plate is supported on the small lever-arm of a cement-testing machine. Water at a temperature of 30 C. is poured around the paving-block, and as expansion takes place the lever-arm of the machine tends to rise. When it rises a valve is opened through which mercury pours into a vessel supported at the end of the arm till the arm comes back to mid-position, when the valve is closed. As the lower plate is fixed when the long lever is in its mid-position, and as this arm is always kept automatically in that place, the specimen is prevented from extending longitudinally. The weight of the mercury in the vessel at the end of the short arm is at any moment a measure of the force exerted by the test-piece, and as the vessel is supported by a spring balance, this can be read at any time. Observations are made at first at intervals of three hours, then at intervals of twelve hours, and finally at intervals of twenty-four hours till all increase ceases. It will be seen that while this test does not reproduce closely the conditions that exist in practice, the results are of value in giving some indication of the amount of thrust to be expected. After the test the specimens are weighed to ascertain how much water has been absorbed. 123. Sand, Sand is an aggregation of loose incoherent grains crystalline in structure and angular in shape, of silicious, argilla- ceous, calcareous, or other material, derived from the disintegration of rocks or other mineral matter, and unmixed with earth or organic matter. For road purposes the grains should not exceed one eighth of an inch in size. 124. The principal use of sand is as a foundation for broken stone, a cushion and bed for stone paving-blocks, and as a joint fill- ing. For these purposes it is eminently suitable, because when confined so that it cannot escape or spread it possesses the valuable properties of incompressibility, and mobility or the quality of as- siimirg a new position when any portion of it is disturbed. As a base or cushion for blocks it quickly adjusts itself to every irregularity of their inferior surfaces, and when the blocks finally 124 HIGHWAY CONSTRUCTION. settle in place it furnishes a solid incompressible medium to trans- fer the pressure to the foundation below. For this purpose it should be fine and dry; if coarse and damp, the blocks will adjust them- selves with difficulty and the fewer will be the points of support between them and the foundation, and the greater will be the pressure of contact and liability to unequal settlement. 125. Sharp sand, i.e., sand with angular grains, is much better than that with rounded grains, although it is often difficult to obtain. The sharpness of sand can be determined approximately by rubbing a few grains in the hand or by crushing it near the ear and noting if a grating sound is produced. 126. The sand for bedding blocks and jointing should be clean, i.e., free from loam or clay. The cleanness may be tested by rub- bing a little of the dry sand in the palm of the hand and, after throwing it out, noticing the amount of dust left on the hand. The cleanness of sand may also be judged by pressing it together be- tween the fingers while it is damp; if the sand is clean, it will not stick together, but immediately fall apart when the pressure is removed. 127. For concrete used for foundation it is not necessary that the sand should be free from clay; indeed a small amount of clay may be beneficial. Clay when dissolved or finely pulverized con- sists of an almost impalpable powder, and when mixed with sand its particles occupy the interstices between the particles of cement and sand, and are also completely enveloped by the cementing paste. Clay, dissolved or finely pulverized, mixed with cement up to the proportion of 1 to 1, appears to affect the strength essentially the same as an equal quantity of sand, and the mortar is much more dense, plastic, and water-tight. Such mortar is not affected by the presence of water. The voids of ordinary sand average from 0.3 to 0.5 of the volume; the more uneven the sizes the smaller the voids. 128. The quantity of sand required for bedding paving-blocks is about one cubic yard to twelve square yards of paving. 129. The price of sand varies from 40 cents to $1.60 per yard, according to locality. 130. Sand is sometimes sold by the ton. It weighs when dry MATERIALS EMPLOYED IN" THE CONSTRUCTION OF PAVEMENTS. 125 from 80 to 115 pounds per cubic foot, or about 1 to 1| tons per cubic yard. 131. Gravel is an accumulation of small stones which vary in size from a small pea to a walnut or something larger. It is often intermixed with other substances, such as sand, clay, loam, etc., from each of which it derives a distinctive name. In selecting gravel for road purposes the chief quality to be sought for is the property of binding (see Art. 424). Gravel in general is unserviceable for road-making. This is due mainly to the fact that the surface of the pebbles is smooth, .so that they will not bind together in the manner of broken stone. There is also an absence of dust or other material to serve as a binder, and even if such binding material is furnished it is diffi- cult to effectively hold the rounded and polished surfaces of the pebbles together. In certain deposits of gravel, particularly where the pebbly matter is to a greater or less extent composed of limestone, a con- siderable amount of iron oxide has been gathered in the mass. This effect is due to the tendency of water which contains iron to lay down that substance and to take lime in its place when the opportunity for so doing occurs. Such gravels are termed ferru- ginous. They are commonly found in a somewhat cemented state, and when broken up and placed upon roads they again cement, even more firmly than in the original state, often forming a road- way of very good quality. The gravel found in western Kentucky and known in com- merce as Paducah gravel is of this variety and is extensively used for road-ranking. "The so-called Tomkins Cove gravel, which is much used about New York, is a broken limestone, apparently of the cement series. It is usually spread over the road, and compacted by the traffic. The darker-colored stone is very pleasant to the eye, and it readily makes a smooth wheelway singularly free from either mud or dust even when subjected to rather heavy traffic, though it is too friable for economical use in such situations. Its performance is so differ- ent from that of the ordinary limestones that an analysis is ap- pended : 126 HIGHWAY CONSTRUCTION. Lime 60.20 per cent Alumina , 11.22 Silica 6.13 Magnesia 10.45 " Carbonic acid 8.00 Water... 4.00 100.00 per cent 132. Shingle is the gravel or accumulation of small stones- found on the shores of rivers or the sea. 132a. Chert is a silicious material approaching the character of flint; it is composed of lime, silica, iron and alumina, its ap- pearance varies from that of limestone to sand-stone; in color it ranges from pure white to milky blue, in texture from porous to flinty. It varies greatly in quality; it is usually brittle and deficient in binding quality. It is used to a large extent in the Southern States and gives fairly good service under light traffic. 132b. Artificial Sand. Artificial sand is obtained by (a) crush- ing and grinding sandstones of little coherence, (6) from the dust produced in crushing rock for the purpose of obtaining broken stone. The stone-dust sand differs from the natural sand in that it has not been subjected to weathering or attrition and conse- quently is sharp and has a rough surface. Artificial sand is em- ployed in the manufacture of concrete and for the aggregate in asphalt-paving mixtures. MATERIALS EMPLOYED IN THE CONSTRUCTION OF PAVEMENTS. 127 TABLE XXIV. SPECIFIC GRAVITY, WEIGHT, AND RESISTANCE TO CRUSHING OF VARIOUS SUBSTANCES. Substance. Specific Gravity. Weight, pounds per cubic foot. Resistance to Crushing, Ibs. persq. in. Asphaltum 905 to 1.65 1.277 2.9 2.95 .848 2.25 2.4 1.6 to 2 1.4 2.2 80 to 87.3 181 184 53 156 150 125 100 137 iTV-zoo"" 8,300 Basalt (greenstone) JSitumen liquid '"l4'.973"' 12,000 600 to 3,000 1.717 9,000 to 15,000 ""50i"" Urick best pressed . " common hard '' soft inferior " Stourbridge fire . work in cement-mortar masonry 1.8 2.5 1.8 to 2.1 112.5 156 119 63 155 56.60 81 to 102 76 to 88 100 119 137 72 to 80 82 " 92 90 " 100 70 " 76 66 " 68 75 " 90 90 " 100 104 " 112 110 " 120 126 166 186 168 96 175 100 56.25 62.5 450 485 Chalk Clay " dry, in lumps loose " with gravel 2.48 Cement hydraulic American Rosendale " English Portland 1.6 to 1.76 4k French " . ... " Roman 1.6 1.9 2.2 1.28to2 Concrete, ordinary . " cement (Portland) Earth common loam, dry, loose " common loam perfectly dry shaken Earth, common loam, perfectly dry, moderately rammed Earth, common loam, slightly moist, loose " " " more moist loose " " " ** " shaken " " " " " mod packed " as a soft flowing mud Earth, common loam as a soft flowing mud well pressed into a box Flint 2.6 2.5to2.8 2. 5 to 3. 45 2.69 Feldspar '27,'ood-30,bbb' Glass . . . Gneiss " in loose piles " hornblendic 2.8 '' quarried in loose piles Gun-powder loose .900 1.000 7 21 ' shaken 110,000 45,000 wrought 7.69 .917 to .92? 11. 30 to 11. 47 1.5 Ice Lead 709.6 95 53 64 75 165 154 138 144 140 125 100 183 106 80 to 110 110 " 130 104 " 120 52.9 6,944-7,780 Lime, quick, of ordinary limestones " quick, ground, loose " well shaken " " thoroughly shaken Masonry of granite or limestone dressed of dry rubble of sandstone dressed of brickwork, close joints " " medium quality . . . soft bricks... 2 '75 to 3.1 1.38 to 1.9 Mica Mortar . . Mud, dry, close '' wet. moderately pressed 1.63 wet, fluid Naphtha .848 128 HIGHWAY CONSTRUCTION. TABLE XXIV. Continued. SPECIFIC GRAVITY, WEIGHT, AND RESISTANCE TO CRUSHING OP VARIOUS SUBSTANCES. Substance. Specific Gravity. Weight, pounds per cubic foot. Resistance to Crushing, Ibs. per sq. in. Petroleum . . . 878 54 8 20 to 30 Pitch 1 15 69 2 66 to 2 8 170 Quartz pure .. 2 65 165 finely pulverized loose . . . 90 " shaken 105 v " packed 112 ' quarried loose 94 2.75 90 to 106 " " * k perfectly wet 118 " 129 1 88 117 pit coarse 1 61 100 ' fine . . 1 52 95 (Thames) England 1 64 102 2 5 to 2 6 162 Shales red or black 2.6 162 " quarried in piles . . . 92 Shingle 1 42 88 Slate 2.7 to 2. 9 175 10,000-21,000 1 73 170 Steel . . 7.85 490 336,000 Snow freshly fallen 5 to 12 15 " 20 Water, pure rain, or distilled at 32 Fan., barom. 62 417 Water, pure rain, or distilled at 62 Fah., barom. 30 inches 1 00 62 355 "Water, pure rain, or distilled at 212 Fah., barom. 30 inches 59.7 Water sea 1 026 to 1 030 1 028 64 08 CHAPTER III. STONE PAVEMENTS. 133. Stone Pavements. Stone in a variety of forms has been employed as a paving material for more than 2500 years. The Romans used it in the form of large, irregularly-shaped blocks laid on a massive foundation of concrete. In this form it is unsurpassed in regard to solidity and durability, but it is objectionable for modern traffic. The surface of the large blocks wears smooth, and hence affords but an uncertain foothold for horses. These large blocks were superseded by round pebbles or cobblestones, obtained from the beach and gravel-pits. This class of pavement has been used extensively in the United States. It is recorded that Boston, Mass., in 1663 had many streets paved with pebbles. In 1718 cobblestone pavements were introduced into Philadelphia, and this city is the only one to retain them on a large scale at the present day. 134. Cobblestone Pavement. Cobblestones bedded in sand possess the merit of cheapness and afford an excellent foothold for horses, but the roughness of such pavements requires the expenditure of a large amount of tractive energy to move a load over them. Aside from this, cobblestones are entirely wanting in the essential requisites of a good pavement. The stones being of irregular size, it is almost impossible to form a bond or hold them in place. Under the action of the traffic and frost the" roadway soon becomes a mass of loose stones. Moreover, cobblestone pave- ments are difficult to keep clean, and very unpleasant to travel over. 135. Specifications for Cobblestone Pavement. The following is the common form of specification for this class of pavement : Stone. The stones are to be the best selected water or bank paving-stones, of a durable and uniform quality. 129 130 HIGHWAY CONSTRUCTION. TYPES OF STONE PAVEMENTS FIG. 1. ROMAN. FIG, 2, COBBLESTONE, FIG, 3. BELGIAN BLOCK, FIG, 4. EARLY GRANITE BLOCK. STONE PAVEMENTS. 13 1 Size of Stone. No stone shall be less than four (4) inches nor more than eight (8) inches in any direction on the surface. No triangular or split stone will be allowed. All stones shall be set perpendicular and on their small ends, the large stones to be placed on the sides of the street, and the small ones in the center. Foundation and Laying. The pavement shall be laid on a bed of good sharp sand or fine gravel, at least ten (10) inches ir depth, except where clay or a similar substance is met with, wher the sand must be eighteen (18) inches deep. The bed of sand o; gravel shall be laid ready for the pavement at least thirty (30) feel in advance of the pavement. The stones after being set in position must be rammed with a heavy rammer until they are firmly settled in their beds. After the pavement is rammed a layer of sand 01 gravel two (2) inches thick is spread over it and left to work it, 4 way in between the stones. In consequence of the many defects of this class of paving its construction has been practically abandoned, but large areas still, remain, which are being gradually removed. 136. Belgian Block Pavement. Cobblestones were displaced by pavements formed of small cubical blocks of stone. This type of pavement was first laid in Brussels, thence imported to Paris, aud : from there to the United States, where it has been widely known as the " Belgian block" pavement. It has been largely used in New York City, Brooklyn, and neighboring towns, the material being trap-rock obtained from the Palisades on the Hudson River. 137. The stones being of regular shape remain in place better than the cobblestones, but the cubical form (usually five inches) is a mistake. The foothold is bad, the stones wear round, and the number of joints is so great that ruts and hollows are quickly formed. This pavement offers less resistance to traction than cobblestones, but it is rough and noisy. 138. Specification for Belgian Block Pavement. The following is the common form of specifications for the Belgian block : Stone. The stones are to be obtained from the trap or other durable rocks. Size of Stones. Each block shall measure not less than five (5) inches nor more than seven (7) inches in length; nor less than five (5) inches nor more than six (6) inches in width; in depth not less than six (6) inches nor more than seven (7) inches; nor shall 132 HIGHWAY CONSTRUCTION. the difference between the base and the top surface of any block exceed one inch in either direction. 139. The blocks are laid upon a foundation of sand six inches thick, in parallel courses, perpendicular to the axis of the street. When so laid, the blocks are thoroughly rammed to the required grade and cross-section. No ramming should be done within twenty-five feet of the work that is being laid. After ramming the surface is covered with a coat of clean sand which is broomed into the joints. 140. Granite Block Pavement. The Belgian block has been gradually displaced by the introduction of rectangular blocks of granite. Blocks of comparatively large dimensions were at first employed. They were from 6 to 8 inches in width on the surface, by from 10 to 20 inches in length, with a depth of 9 inches. They were merely placed in rows on the subsoil, perfunctorily rammed, the joints filled with sand, and the street thrown open to traffic. The unequal settlement of the blocks, the insufficiency of the foothold, and the difficulty of cleansing them led to the gradual development of the latest type of stone-block pavements, which consists of narrow rectangular blocks of granite, properly proportioned, laid on an unyielding and impervious foundation, with the joints between the blocks filled with an impermeable cement. This type is practically a return to the system of the Romans, but with blocks of lesser dimensions than they used. 141. Experience has proved beyond doubt that this latter type of pavement is the most enduring and economical for roadways subjected to heavy and constant traffic. Its advantages are many, while its defects are few. 142. Advantages. (!) Adaptability to all grades. (2) Suits all classes of traffic. (3) Exceedingly durable. (4) Foothold, fair. (5) Requires but little repair. (6) Yields but little dust or mud. (7) Facility for cleansing, fair. 143. Defects. (1) Under certain conditions of the atmosphere its surface becomes greasy and slippery. (2) The incessant din and clatter occasioned by the movement STONE PAVEMENTS. 133 IMPROVED GRANITE-BLOCK PAVEMENT. GUTTER FORMED OF 3 ROWS OF BLOCKS LONGITUDINALLY. ////////) }////'//}f///}//Jj//ri Vjxtw#w*s#0yfa 'f l %'&i $ -CURB 5" WIDE I AND 18" DEER is.5. CROSS SECTION. s 10 ro "~l - r i " I i " MM -< i i i i i i FLAGGING i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i I i I 1 I I 1 1 1 1 1 1 1 ! 1 1 1 1 J -J_ L- L U X Fig. 6. PLAN. FIG. 7. LONGITUDINAL SECTION. 134 HIGHWAY CONSTRUCTION". of traffic over it is an intolerable nuisance, and it is claimed by many physicians that the noise injuriously affects the nerves and health of persons who are obliged to live or do business in the vicinity of streets so paved. (3) Horses constantly employed upon it soon suffer from the continual jarring produced in their legs and hoofs, and quickly wear out. (4) The discomfort to persons riding over it is very great because of the continual jolting to which they are subjected. (5) If stones of an unsuitable quality are used, i.e., those that polish, the surface quickly becomes slippery and exceedingly unsafe for travel. 144. Quality of the Stone. The harder and more durable rocks like basalt and true granite are unsuitable; they have the fault of wearing smooth and more or less spherical when subjected to heavy traffic, and under certain conditions of the weather they become greasy and slippery. 145. The less durable rocks, such as syenite, the granites in which hornblende predominates, and the harder sandstones, are the most suitable; they do not polish and afford a good foothold for the horses. Where the harder and more durable rocks have been used, they have caused dissatisfaction, and have been removed before they had been down many years. 146. Size and Shape of the Blocks. The proper size of the blocks for paving purposes has been a subject of much discussion, and a great variety of forms and dimensions are to be found in all cities. For stability a certain proportion must exist between the depth, the length, and the breadth. The depth must be such that when the wheel of a loaded vehicle passes over one edge of its upper surface it will not tend to tip up. The resultant direction of the pressure of the load and adjoining blocks should always tend to depress the whole block vertically; where this does not happen the maintenance of a uniform surface is impossible. To fulfil this requirement it is not necessary to make the block more than seven (7) inches deep. 147. Width of the Blocks. The maximum width of the blocks is controlled by the size of horses' hoofs. To afford good foothold to horses drawing heavy loads, it is necessary that the width of each block measured along the street shall be the least possible consistent with stability; if it is large, a horse drawing a heavy load attempt- STONE PAVEMENTS. 1:33 ing to find a joint slips back, and requires an exceptionally wide joint to pull him up. It is therefore desirable that the width of a block should not exceed three (3) inches, or that four taken at random and placed side by side will not measure more than fourteen (14) inches. 148. Length of the Blocks. The length measured across the street must be sufficient to break joints properly, for two or more joints in a line lead to the formation of grooves. For this purpose the length of the block should be not less than nine (9) inches nor more than twelve (12) inches. 149. Form of the Blocks. The blocks should be well squared and must not taper in any direction; sides and ends should be free from irregular projections. Blocks that taper from the surface downwards (wedge-shaped) should not be permitted in the work; but if any are allowed, they should be set with the widest side down. 150. Mannsr of Laying the Blocks. The blocks should be laid in parallel courses, with their longest side at right angles to the axis of the street, and the longitudinal joints broken by a lap of at least two inches (see Fig. 6). The reason for this is to prevent the formation of longitudinal ruts, which would happen if the blocks were laid lengthwise. Laying the blocks obliquely and t{ herring-bone " fashion has been tried in several cities with the idea that the wear and formation of ruts would be reduced by having the vehicles cross the blocks diagonally. The method has failed to give satisfactory results; the wear was irregular and the foothold defective, the difficulty of construction was increased by reason of the labor required to form the triangular joints, and the method was wasteful of material. 151. The gutters should be formed by three or more courses of block, laid with their length parallel to the curb. 152. At junctions or intersections of streets the blocks should be laid diagonally from the centre, or " herring-bone " fashion, as shown in Fig. 7. The reason for this is (1) to prevent the traffic crossing the intersection from following the longitudinal joints and thus forming depressions and ruts; (2) laid in this manner they afford more secure foothold for horses turning the corners. The ends of the diagonal blocks where they abut against the straight blocks must be cut to the required bevel. 136 HIGHWAY CONSTRUCTION. STONE PAVEMENTS. 137 TABLE XXIVa. SIZES OF STONE PAVING-BLOCKS USED IN DIFFERENT CITIES. American Cities. Length, Inches. Width, Inches. ,-1 I European Cities. i i -1 3 8 "1 g. Albany N Y 8-14 7-12 9-12 3 -44 3 -4| 3 -4 34-4* 3*-4A 3~-44 31-i 3 -5 3 T ,-4^ 3Mi 3H4 3*-4^ 3Mi 3 -5 S3* 7 -8 64-7 6 -7 7^8 6 6 -7 6 -6| 6 -7 7 -8 7 -8 7 -8 6 -6* 6 -7 64-7 74-84 5f-6 Antwerp 5*-6* 7 -7j 7|-7 6 -12 7 6 -9 27J 6 8 -14 31 5-7 9 61-7| 24-60 w 5J 34-4 74-7* 34^*4 31 3 m 6 3 -4| 31 3 -3i 61-9 41-54 12-18 6f 71 $4 61-7 74-7* 6J-7 &4 5 -7 7| 6 6 61 6 -64 9 41-7 6-10 6 71 Buffalo' N Y Barcelona Baltimore, Md. . . . Boston Mass Berlin Copenhagen Dublin Chicago, 111. . . Cincinnati, Ohio. . . Cleveland, Ohio. . . Columbus, Ohio. . . New Haven, Conn. Newark, N. J New York, N. Y. .. Philadelphia, Pa. . . Pittsburg, Pa Rochester, N. Y.. . St. Louis, Mo Washington, D. C. . 8-10 8-12 6-^12 8-14 8-12 8-12 8-12 6-10 7-12 9-12 6-^8 Glasgow Genoa Leeds London Liverpool Manchester Paris i ( Trieste Valencia . . . Vienna 153. The blocks forming each course must be of the same depth, and no deviation greater than one quarter (^) of an inch should be permitted. The blocks should be assorted as they are delivered, and only those of corresponding depth and width should be used in the same course. The better method would be to accurately gauge the blocks at the quarry: the cost would be considerably less; it would also avoid the inconvenience to the public by the stopping of travel resulting from the rejection of defective material on the ground. This method would undoubtedly be preferable to the contractor, who would be saved the expense of handling unsatisfactory material, and it would also leave the inspectors free to pay more attention to the manner in which the work of paving is performed. 138 HIGHWAY CONSTRUCTION". The accurate gauging of the blocks is a matter of much im- portance. If good work is to be executed, the blocks when laid must be in parallel and even courses; and if the blocks be not ac- curately gauged to one uniform size, the result will be a badly paved street with the courses running unevenly. The cost of assorting the blocks into lots of uniform width, after delivery on the street, is far in excess of any additional price which would have to be paid for the accurate gauging at the quarry. 154. Foundation. The foundation of the blocks must be solid and unyielding, a bed of hydraulic cement concrete is the most suitable, the thickness of which must be regulated according to the traffic; the thickness, however, should not be less than four (4) inches and need not be more than nine (9) inches. A thickness of six (6) inches will sustain a traffic of 600 tons per foot of width. 155. Cushion-coat. Between the surface of the concrete and the base of the blocks there must be placed a cushion-coat formed of an incompressible but mobile material, the particles of which will readily adjust themselves to the irregularities of the base of the blocks and transfer the pressure of the traffic uniformly to the con- crete below. A layer of dry, clean sand f of an inch thick forms an excellent cushion-coat. Its particles must be of such fineness as will pass through a No. 8 screen ; if coarse and containing pebbles, they will not adapt themselves to the irregularities of the base of the blocks, hence the blocks will be supported only at a few points and unequal settlement will take place when the pavement is subjected to the action of traffic. The sand must also be perfectly free from moisture, artificial heat must be used to dry it if necessary. This requirement is an absolute necessity. There should be no moisture below the blocks when laid, nor should water be allowed to penetrate below the blocks; if such happens, the effect of frost will be to up- heave the pavement and crack the concrete. Where the best is desired without regard to cost, a layer half an inch thick of asphaltic cement may be substituted for the sand with superior and very satisfactory results. 156. Laying the Blocks. The blocks should be laid stone to stone, so that the joint may be of the least possible width; wide joints cause increased wear and noise and do not increase the foot- hold. The courses should be commenced on each side and worked toward the middle, and the last stone should fit tightly. STONE PAVEMENTS. 139 157. Ramming. After the blocks have been set they should be well rammed down, and the stones which sink below the general level should be taken up and replaced with a deeper stone or brought to level by increasing the sand-bedding. 158. The practice of workmen is invariably to use the rammer so as to secure a fair surface. This is not the result intended to be secured, but to bring each block to an unyielding bearing. The result of such a surfacing process is to produce an unsightly and uneven roadway when the pressure of traffic is brought upon it. The rammer used should not weigh less than fifty pounds and have a diameter of not less than three inches. 159. Joint - filling. All stone -block pavements depend for their water-proof qualities upon the character of the joint-filling. Joints filled with sand and gravel are of course pervious. A grout of lime or cement mortar does not make a permanently water-tight joint ; it becomes disintegated under the vibration of the traffic. An impervious joint can only be made by employing a filling made from bituminous Or asphaltic material; this renders the pavement more impervious to moisture, makes it less noisy, and adds con- siderably to its strength. 160. Bituminous Cement for Joint-filling. The bituminous ma- terials employed are (1) the tar produced in the manufacture of gas, which, when redistilled, is called distillate, and is numbered 1. 2, 3, 4, etc., according to its density; this material under the name of paving-pitch is extensively used both alone and in com- bination with other bituminous substances; (2) combinations of gas- or coal-tnr with refined asphaltum; (3) mixtures of refined &sphaltum, ' : osote, and coal-tar. The formula for the bituminous joint-filling used in New York City is: Refined Trinidad asphaltum 20 parts No. 4 coal-tar distillate 100 " Residuum of petroleum 3 " In Washington, D, C., coal-tar distillate No. 6 is used alone. In Europe a bituminous cement much used is composed of coal- tar, asphaltum, gas-tar, and creosote oii, in the proportion of 100 pounds of asphaltum to 4 gallons of tar and 1 gallon of creosote. These proportions are varied somewhat, according to the quality of the asphaltum employed. The mixture is melted, and boiled from 14:0 HIGHWAY CONSTRUCTION. one to two hours in a suitable boiler, then poured into the joints in a boiling state. This mixture is impervious to moisture, and possesses a degree of elasticity sufficient to prevent it from cracking. 161. The mode of applying the bituminous cement is as follows: After the blocks are rammed the joints are filled to a depth of about two inches with clean gravel heated to a temperature of about 250 a F., then the hot cement is poured in until it forms a layer of about one inch on top of the gravel, then more gravel is filled in to a depth of about two inches, then cement is poured in until it appears on top of the gravel, then more gravel is added until it reaches to within half an inch of the top of the blocks; this remaining half inch is filled with the cement, and then fine gravel or sand is sprinkled over the joints. In some cases the joints are first filled with the heated gravel,, then the cement poured in until the sand beneath and the gravel between the blocks will absorb no more and the joints are filled flush with the top of the pavement. This method is open to ob- jection, for if the gravel is not sufficiently hot the cement will be chilled, and will not flow to the bottom of the joint, but instead will form a thin layer near the surface, which, under the action of frost and the vibration of traffic, will be quickly cracked and broken up, the gravel will settle and the blocks will be jarred loose, and the surface of the pavement will become a series of ridges and hol- lows. The quantity of cement required per square yard of pavement will vary according to the shape of the blocks, width of the joints,, and depth of the sand-bed ; with well-shaped blocks, close joints,, and one half inch sand-bed the quantity will vary from 3^ to 5 gallons; with ill-shaped blocks, wide joints, and heavy sand-bed 10 to 12 gallons would not be an excessive amount to use to secure the result obtained by employing well-shaped blocks and close joints. The cost of paving-pitch is variable; it ranges from six to ten cents per gallon. A joint-filling known as " Murphy's Grout Filling " has been and is extensively used in the Central States. This filling is com- posed of Portland cement, iron-slag, and sand. It is said to be waterproof, durable, and cheap. It can be used with equal advan- tage for block, brick, cobblestone, and macadam pavements. STO^E PAVEMENTS. 141 In manner of application it differs but little from that of ths bituminous cement. It is mixed in a portable box, and when of a good flowing (but not liquid) consistency it is thrown upon the pavement with shovels and swept into the joints with steel brooms, and after forty-eight hours it is set and the pavement is ready for traffic. In a granite-block pavement laid at Cleckheaton, Eng., a thin strip of steel was inserted between the courses of blocks with the object of protecting the edges of the blocks from abrasion. The method has been patented under the name of the " Standard System." 162. Sandstone-block Pavements. Block pavements formed of Medina and Berea sandstones are used in several of the Lake cities, While not as lasting as granite, the sandstone is very durable, is less noisy, and does not become polished or slippery under traffic, wears evenly, and is adapted to all classes of traffic. 163. The best examples of this kind of pavement are found in Buffalo, N. Y., where two classes are used. For first class the specifications call for a foundation of six inches of concrete with a three-inch cushion of aand. The blocks are of dressed stone, four inches wide, seven inches deep, and not less than eight inches long. The joints are filled with bituminous cement. For the second class the blocks are of irregular size laid on a foundation of ten to eighteen inches of sand, depending upon the character of the sub- soil, the joints are filled with sand." 164. The cost of first-class Medina in Buffalo is $4 per square yard; Cleveland, $3.50; Columbus, with a 10-inch broken-stone foundation, $3.25. Second-class average $1.75, and with asphalt filling cost 36 cents per yard more. In New York, with Portland-cement joints, from $2.80 to $2.90. The number of square yards laid by a paver per day ranges from 45 to 50. In grouting the joints one barrel of cement will be sufficient for about 12 square yards. 164a. Specifications for Medina Sandstone Pavements (NEW YORK). " Paving-blocks shall consist of the best quality of Medina sandstone, free from quarry check or cracks, and shall be quarried 14.2 HIGHWAY CONSTRUCTION. from fine-grain live rock, showing a straight and even fracture. The material shall be of uniform quality and texture, free from seams or lines of clay or other substances which, in the opinion of the Chief Engineer, would be injurious to its use as paving material. " Blocks shall measure not less than 3J nor more than 5| inches thick, and not less than 6 nor more than 6^ inches deep, and from 7 to 12 inches in length. Stones to have parallel sides and ends and right-angle joints. All roughness in joints or stones to be broken off so that when set in place they shall have tight joints for a distance of at least 3J inches from the top down, the top to have a smooth, even surface, with no projection or depression exceeding J inch. "Upon the bed of sand the stone blocks and crosswalks must be laid. The stone blocks are to be laid in straight courses, at right angles with the line of the street, except in intersection of streets (including the space within the railroad tracks), when the courses shall be laid diagonally, except in special cases, when they shall be laid at such angle, with such crown and at such grades as the Chief Engineer may direct. Each course of blocks shall be of uni- form width and depth, and shall be gauged and selected fcr the pavers, on the sidewalks, and so laid that all longitudinal joints or end joints shall be close joints and shall be broken by a lap of at least 3 inches, and that joints between courses shall be not more than J inch in width top and bottom. As the blocks are laid they shall be covered immediately with clean, hard, hot, dry gravel, artificially dried, which shall be brushed into the joints to a depth of 3 inches. The blocks shall then be thoroughly rammed by courses at least three times by a rammer weighing not less than 80 pounds no iron of any kind being allowed on its lower face to come in contact with the paving, and until brought to an un- yielding bearing, with a uniform surface, true to the roadway or the established grade. "The joints shall then be filled with clean, dry, hot gravel of proper size as herein specified, heated in pans especially provided for that purpose and poured from cans having small spouts, and thoroughly settled in place with wire picks, until the level of the gravel is at least 2 inches below the .top of the pavement. STONE PAVEMENTS. 143 "The gravel used between the blocks shall be of such size as will pass through a sieve having four meshes per square inch, and be retained on a sieve having sixty-four meshes per square inch, and must be screened dry. "There shall then be immediately poured into the joints, while the gravel is still hot, paving cement, heated to a temperature of 300 Fahrenheit, until the joints and all interstices of gravel filling are full and will take no more and are filled flush with the top of the blocks. Dry hot gravel must then be poured along the joints, filled with paving cement, as above described. "When Portland cement is used in the joints, the blocks shall be laid as closely as possible, and after having been rammed till they are brought to a firm bearing and an even surface, a grout made of equal parts of Portland cement and clean, 'sharp sand shall be poured upon the surface of the pavement and swept into joints, and this process repeated until all the joints are completely filled and remain full." 165. Limestone-block Pavements. Limestone block was tried in Kansas City on a concrete foundation, but being set on edge it wore unevenly, and in a year or two was shivered and split by the frost. This is the universal experience of all cities using limestone blocks. 166. Pavements on Steep Grades. Stone blocks may be em- ployed on all practicable grades, but on grades exceeding 10$ cobblestones afford a better foothold than blocks. The cobble- stones should be of a uniform length, the length being at least twice the breadth, say stones 6 inches long and 2i to 3 inches in diameter. These should be set on a concrete foundation, laid stone to stone, and the interstices filled with cement grout or bituminous cement; or a bituminous concrete foundation may be employed and the interstices between the stones filled with 344 HIGHWAY CONSTRUCTION. STONE PAVEMENTS ON GRADES. ;\ - / . - N, . - FIG. 8. COBBLE ON CONCRETE. FIG, 9, GRANITE BLOCKS STEPPED. FIG, 10. GRANITE BLOCKS-WIDE JOINTS, PAVEMENTC. asphaltic paving-cement. Should stone blocks be preferred, they must be laid, when the grade exceeds 5$, with a serrated surface by either of the methods shown in Figs. 9 and 10. The method shown in Fig. 9 consists in slightly tilting the blocks on their bed so as to form a series of ledges or steps, against which the horses' feet being planted, a secure foothold is obtained. The method shown in Fig. 10 consist in placing between the rows of stones a course of slate, or strips of creosoted wood, rather less than one inch in thickness and about an inch less in depth than the blocks; or the blocks may be spaced about one inch apart, and the joints filled with a grout composed of gravel and cement. The pebbles of the gravel should vary in size between one quarter and three quarters of an inch. 167. Durability of Granite Blocks. The average life or dura- bility of granite blocks under heavy traffic may be taken at fifteen years; but since the nature of the traffic, the state of cleanliness and other conditions must be taken into account when inquiring into the durability, it follows that in no two streets is the endur- ance or the cost the same, and the difference between the highest and the lowest period of endurance and amount of cost is very considerable. The practice followed almost uniformly in the English cities is to remove the worn blocks, re-dress them and relay them in other and secondary thoroughfares. Thus the duration or life of the blocks may be doubled or more than doubled. Indeed, with the exception of the portion worn off by the friction of the traffic, not a fragment of granite paving may be said to be lost. After passing its first years in a leading thorough- fare it goes into a secondary thoroughfare until completely worn down and rounded, and will even then command a price of from 30 to 60 cents per square yard. Not even a fragment that is knocked off the component stones when undergoing the operation of being dressed into shape is lost, as it is made available either for macadamizing or for concrete to form the foundation of other pavements. " In truth granite can only be said to be worn out when it has been broken up for macadamization and then crushed into powder by the vehicles." 168. Wear of Granite Blocks. Stones from different quarries and even from the same quarry will show considerable variation in the amount worn away in a given time under exactly similar conditions. Therefore no statement of wear can be given which 146 HIGHWAY CONSTKUCTION. will be applicable to all varieties of stones. On London bridge,. which has a traffic of over 15,000 vehicles in 12 hours, the wear of granite blocks has been found to be at the rate of .222 inch per year, or the number of years required to wear ^way one inch is four and one half. TABLE XXV. WEAR AND DURATION OF ABERDEEN GRANITE PAVEMENTS IN THE CITY OF LONDON. BLOCKS 3 INCHES WIDE, 9 INCHES DEEP. Aberdeen Granite Pavements. Vertical wear per 100 vehicles in 12 hours, per foot of width per year .............. ^ 1 Total vertical wear in principal streets ...... 2 15 Total additional wear in minor streets ....... 2 20 Total vertical wear when laid aside ......... 4 35 Remaining depth when laid aside ........... 5 Depth of new blocks ....................... 9 ID Liverpool, under a traffic of 216,570 tons per yard of width pei annum, the wear was not measurable. 169, Cost of Maintaining Granite-block Pavements. As to the durability and cost of maintaining granite-block pavements in America no satisfactory statistics can be obtained. The annual cost of maintenance in London varies from six to nineteen cents per square yard, depending upon the traffic. In Liverpool repairing costs four cents per annum, and cleaning and sprinkling fourteen cents. In London the cost of maintenance, including interest, etc., on first cost is from 25 to 69 cents per square yard per annum. In St. Louis, Mo., maintenance costs from to 2 cents per annum. The average cost of maintaining granite-block pavements in the United States, irrespective of traffic tonnage, and exclusive of cleaning and sprinkling, appears to be about 1^ cents per square yard per annum. 170. Method of Paying for Granite-block Pavements. The present system of paying for granite-block paving is erroneous. The contractor buys his blocks at so much a thousand, and sells them at so much a square yard laid; thus it is his interest to have as few blocks to the square yard as possible and joints as large as he can. Or he may purchase them from the stone man at so much a square yard : in this case the stone man is interested in having as- STONE PAVEMENTS. 147 few blocks as possible; as is also the contractor, for the fewer blocks to be laid to the yard the more yards of paving will the pavior lay in a day, thus increasing the profits of the contractor. In some cases the pavior is paid by the square yard of paving; then it becomes his interest to have as few blocks to handle as possible and as wide joints as he may, thus increasing the number of square yards of paving he can lay in a day, and thereby increasing his wages. No matter how looked at, all parties concerned in furnishing and laying the blocks are deeply interested in having as few blocks and as wide joints as possible to the square yard. As both of these are serious defects, the temptation to adopt them should be removed. The number of blocks to be laid per square yard should be clearly stated in the specifications; a sum should also be designated to be deducted from the estimate, by way of a penalty or forfeit, for every block less that is used than the number called for. As the labor expended in ascertaining the number of blocks laid to each square yard would be very great, it would be better to specify, as is the custom in Liverpool, that four courses of block shall not measure more than fourteen (14) inches. Under this rule the number of blocks laid can be very quickly determined by measuring any four courses at random over the length of the street, City Engineer Horace Andrews of Albany has introduced with considerable success a reform in the manner of paying for granite block pavements. The following unusual clauses are taken from his specifications, under which a large area of granite-block pavement has been laid : " It is expressly understood and agreed, by and between the parties hereto, that the sum paid per square yard for granite block pavement shall be ascertained and fixed as follows namely: The number of granite blocks per square yard, upon which the bid of the proposer is based, shall be 24. The actual average number of blocks laid per square yard by the contractor on the whole street shall be determined as follows : The City Engineer shall, from time to time, during the progress of the work, measure the width of the blocks as laid (by measuring the aggregate width of 50 to 100 courses, from this deducing the average width), which he shall combine with the average length of block as laid (hereby fixed and determined as 12 inches), for the purpose of computing the number of blocks laid per square yard. 148 HIGHWAY CONSTRUCTION'. "For each block, or fractional part thereof, that the average number laid per square yard shall exceed 24 there shall be added to the contractor's bid per square yard an amount computed at the rate of 9| cents per block. For each block, or fractional part thereof, that the average number laid per square yard shall fall short of 24, there shall be deducted from the contractor's bid per square yard an amount computed at the rate of 9| cents per block. " In order to lay 24 to the square yard, the width of five courses, including the joints between the stones, should not exceed 22 inches." The number of blocks specified per square yard differed on the individual streets; otherwise there were few changes in the above clauses. The results obtained by the use of these clauses in the specifica- tions d iring the last two jears are indicated in the following TABLE SHOWING OPERATION OF SPECIFICATIONS REGARDING JOINTS IN GRANITF PAVEMENT IN 1890 AND 1891. Width of Number of Area in Five Courses blocks laid Excess or Contractor's Contractor's Square Yards. as laid. Inches. per Square Yard. Deficiency. Gain. Loss. 1 3,624 23.38 22.62 4 0.12 $43.40 2 1,588 23.13 22.87 4-0.37 55.56 3 879 23.50 22.50 0.00 4 11 202 23.28 22.72 + 0.22 238.61 5 3.918 22.99 23.01 - 1.99 $740.09 6 15,218 23.86 22.17 -0.33 471.75 7 1.641 24.57 21.53 -0.93 150.93 8 2,363 21.69 24.39 + 0.39 87.44 9 2,146 22.06 23.98 -0.02 4.29 10 2,679 24.18 21.88 -0.62 158.08 11 5,120 24.91 21.23 -1.27 614.38 12 2,846 23.31 22.70 - 1.30 350.01 1 NOTE. The specified number of blocks per square yard varied on different streets. It can be easily found from columns 4 and 5. From an inspection of this table it is evident that close paving can be secured. Mr. Andrews believes that it might be more beneficial if the amount of deduction for non-fulfilment were increased, to guard against the contingency of wide blocks being STOXE PAVEMENTS. obtainable at so low a rate as to make it profitable for a contractor to use them notwithstanding the deduction from his contract price per square yard. 171. Number of Granite Blocks per Square Yard.- Tible XXVI shows the average number of granite blocks of different sizes Width. Length. Average Number of Blocks per sq. yd. Exclusive of Joints. Number of Square Yards 1 ton will cover at a depth of 7 inches. 9 inches. 3 inches 7 inches 62 2.50 2,00 3 9 48 3 10 4? tt 3 12 G6 8i 7 53 < : 3^ 9 41 ti 3^ 10 37 tt 8* 12 30 tt per square yard, and the average number of square yards that one ton of granite will cover, but these quantities will vary with the specific gravity of the stone employed. 172. Cost of Construction. The cost of granite-block pavements varies greatly; it is materially affected by the weight of the blocks; when their transportation for any considerable distance has to be taken into account, by the character of the foundation and kind of joint-filling, and frequently by the condition of the labor market,, demand, etc. With blocks costing five cents each delivered on the street, the cost per square yard laid on sand foundation and sand joints ranges from about $1.35 to $1.80. Laid on concrete foundation 6 inches thick, with 2-inch sand cushion and joints filled with tar and gravel, the range is from about $2.40 to $4.25. Tables XXVII, XXVIII, XXIX, and XXX show the extent Q f granite-block, trap-block, sandstone-block, and cobble-stone pave- ments in the principal cities of the United States in 1903. 150 HIGHWAY CONSTRUCTION. TABLE XXVII. EXTENT OF STOi^E-rLOCK LAVEMENTS IN THE PRINCIPAL CITIES OF THE UNITED STATES IN 1903. City. Area, Sq. Yds. ^ength, Miles. City. Area, Sq. Yds. Length, Miles. Albany N. Y. . . 554,508 31.5 Milwaukee, Wis . 267 055 9 o Auburn N. Y 15,000 0.5 Minneapolis, Minn. 346 184 21 9 Allegheny, Pa Altoona Pa. . . . 580,254 14,214 32.9 0.9 Montgomery, Ala . . Nashua, N. H 78,156 57928 2 2 3 Akron Ohio. . . . 13,227 0.8 Newark, N. J. . . 59 5 Augusta, Ga Baltimore, Md .... Bayonnc N J 40,492 816,190 45,400 2.0 43.1 2.5 New Haven, Conn. Newburg, N. Y. .. . New York N. Y 0,432 10,629 9 610 188 4.2 0.8 430 Bingha-iiton, N. Y. Birmingham, Ala. . Boston, Mass Brockton Mass 2,622 61,025 2,042,384 159 617 0.1 2.0 92.8 8.4 New Bediord, Mass. North Adams, Mass Nashville, Tenn. . . Norfolk Va. 60,743 3,366 98,032 218 219 4.7 0.2 5.6 13 2 Buffalo N Y 186 029 9.6 Omaha Neb 594 880 25 2 Butte, Mon" Bridgeport, Conn. . Cambridge, Mass. . Chelsea, Mass Camden, N. J 80,837 27,717 168,:33 89,227 426,965 2.5 1.6 6.9 3.6 29.1 Pawtucket, R. I. Providence, R. I.. . Philadelphia, Fa. . . Pittsburg, Pa Passaic, N. J 97,155 538,214 6,169,984 1,673,762 8,905 5.7 30.6 367.8 109.5 1-7 Chattanooga, Tenn. Chester, Pa 57,298 128,480 2.2 7.3 Paterson, N. J Portland, Me. . 74,800 218,402 4.3 11.2 Charleston, S. C. Cincinnati, Ohio . 351,325 1,060,000 17.1 48.5 Portland, Ore Quincy, Mass. 127,800 33 557 4.5 2.2 Cleveland, Ohio. . 2,065,290 87.9 Racine, Wis. 26687 1.1 Columbus, Ohio 209,818 9.6 Reading Pa. 9 974 0.5 Council Bluffs, la. . Dayton, Ohio. 73,153 35,120 2.4 1.6 Rochester, N. Y. . . Sacramento Cal 618,C06 9 660 31.1 1 Denver, Colo Duluth, Minn Detroit, Mich Elizabeth, N. J. ... Elmira, N. Y. . 69,313 34,599 88,532 385,076 30 507 2.7 1.5 4.1 17.1 1 3 San Francisco Savannah, Ga Schcnectady, N. Y. Syracuse, N. Y. . . . Scranton Pa 1,515,800 71,017 20,963 75,851 30 4C5 94.7 2.1 1.0 1.7 1 5 Erie, Pa 1C N 5 639 4 8 Springfield Ohio 14 855 6 Everett, Mass 4,927 0.3 Salem, Mass. . . . 205*333 14.0 Fall River, Mass. . . Fitchburg, Mass. . . Gloucester, Mass. . , Haverhill, Mass. . . Holyoke, Mass. . . . 144,623 93,476 27,867 84,040 65,590 9.5 4.7 1.9 3.8 2.6 Somerville, Mass. . . Springfield, Mass. . So. Omaha, Neb . . . St. Joseph, Mo St. Louis, Mo. . 48,400 48,560 80,928 18,045 2,041,080 2.8 2.4 2.4 1.1 141.0 Hartford, Conn. . . . Hoboken, N. J. . . 12,810 315,083 0.6 16 2 St. Paul, Minn Superior, Wis. 172,346 614 6.4 0.1 Jersey City, N. Ji 78 Taunton, Mass 63360 4.0 Kansas City, Kan. 2,974 1 Topeka, Kan. 102 315 3.5 Kansas City, Mo. . . Kingston, N. Y. . 125,013 20,530 2.2 1 Trenton, N. J Troy, N. Y. 125,869 458 384 6.1 26.2 Lancaster, Pa. . . 29,354 1 5 Toledo Ohio 488 731 25.1 Lawrence, Mass. . . Lowell, Mass Lynn, Mass Lincoln, Neb Little Rock, Ark. . . Los Angeles, Cal. . . Louisville, Ky Maiden, Mass Manchester, N. H. . McKeesport, Pa. . . Memphis, Tenn. . . . 79,269 302,300 92,225 12,310 28,440 30,037 660,785 15,856 80,439 145,760 297.000 3.1 15.4 3.8 1.4 0.8 1.3 41.0 0.7 2.9 5.7 11.3 Utica, N. Y Washington, D. C. . Waterbury, Conn . . Wilmington, Del.. . Worcester, Mass. . . Wilkesbarre, Pa. . . Woonsocket, R. I. . W. Hoboken, N.J.. Youn" stown, Ohio . Yonkers,N.Y 107,736 615,924 48,083 172,218 232,709 23,850 12,320 139,920 34,720 45,03 1 5.3 26.7 2.4 11.5 11.4 1.7 7 4.8 0.9 2.5 STONE PAVEMENTS. 151 TABLE XXVIII. EXTENT AND COST OF BELGIAN BLOCK (TRAP) PAVEMENTS IN SOME OP THE PRINCIPAL CITIES OF THE UNITED STATES IN 1890. Cities. Extent. Miles. Cost of Construction per square yard. New York N. Y. . . . 199.07 $2.50 Philadelphia Pa 119.60 2.37 Brooklyn N Y 22.41 2.75 1.80 to $2. 14 2.08 2.00 Albany NY 1 42 2.60 Kingston. N. Y. . 1.90 TABLE XXIX. EXTENT AND COST OF SANDSTONE-BLOCK PAVEMENTS IN SOME OF THE PRINCIPAL CITIES OF THE UNITED STATES IN 1890. Cities. Extent. Miles. Cost of Construction per square yard. Buffalo N Y 138 00 $2.00 Toledo Ohio 17.48 1.34 16 50 2 25 11 00 1 98 6 81 2 78 Elmira NY . 5 00 Utica NY 4 63 Lockport N Y 4 00 3 40 1 80 to $3 69 * 2 98 " 3 94* * Concrete foundation. 152 HIGHWAY CONSTRUCTION. TABLE XXX. EXTENT OF COBBLESTONE PAVEMENT IN THE PRINCIPAL CITIES OF THE UNITED STATES IN 1903. Cities. Area, Sq. Yds. Length,! Miles. Cities. Area, Sq. Yds. Length, Miles. Albany, N.Y Altoona, Pa Allegheny Pa 324,332 1,576 210 960 18.4 0.1 12 New Haven, Conn.. New York, N.Y... Newburg, N. Y . . . . 3,816 2,783,180 13,914 0.1 155.1 6 Baltimore Md 5 240 960 373 1 Norfolk Va 41 049 3 2 Bay City, Mich Boston, Mass Buffalo N Y 6,738 6,830 1 840 972 0.7 0.5 87 4 Paterson, N. J Portland, Me Peoria, 111 24,640 16,294 11,772 1.4 0.8 0.6 Camden, N. J 67,509 4.6 Philadelphia, Pa. . . 2,049,183 73.1 Council Bluffs, la. . Cincinnati, Ohio. . . Columbus, Ohio. . . Chester, Pa 1,724 580,460 101,380 26,400 0.2 64.3 8.9 1.5 Pittsburg, Pa Reading, Pa Rochester, N.Y. Sacramento, Cal. . . 642,196 124,668 23,585 14,240 42.2 6.3 1.0 1.5 Charleston, S. C. . . Dayton, Ohio Detroit Mich . 76,795 882,350 19813 3.7 94.0 1.0 San Francisco, Cal.. Savannah, Ga Schenectady, N. Y. 308,400 177,712 36,390 12.5 7.8 2.4 18 538 8 Scranton, Pa. . 33,814 3 2 Elizabeth, N. J Evansville, Ind. . . . Fall River, Mass . . . Fitchburg, Mass. . . Fort Wayne Ind 2,388 5,280 9,152 , 7,821 1 014 0.1 0.2 0.6 0.5 1 So th Bend, Ind. . . Saginaw, Mich. . . . Taunton, Mass. . . . Trenton, N. J Utica, N.Y. 3,050 77,394 1,584 11,292 36390 0.1 4.7 o.i 0.6 2.1 Gra'd Rapids, Mich. Jackson, Mich Johnstown, Pa. . . . Kingston, N.Y Louisville, Ky Manchester, N. H. . Milwaukee, Wis. . . Meriden, Conn New Bedford, Mass 13,200 2,640 159,176 7,000 231,879 4,400 760,000 1,563 173,568 0.8 0.3 8.5 0.3 12.7 0.3 74.5 0.1 13.7 Washington, D. C. . Waterbury, Conn. . Wheeling, W. Va. . Wilkesbarre, Pa. . . Williamsport, Pa. . Wilmington, Del. . . Worcester, Mass . . . Yonkers,N.Y 223,529 2,666 120,305 133,584 1,846 160,275 452 1,333 10.3 0.1 7.0 7.6 0.3 10.7 0.1 0.1 173. Heads of Specifications for Granite-blocli .faveiiieiiG. (1) Preparation of Roadbed. (2) Foundation. (3) Quality of the Blocks. The paving-blocks shall be of syenite or granite from or other approved quarries. All the blocks shall be of the same quality as to hardness, color, and grain ; no outcrop, soft, brittle, or laminated stone will be accepted. When stone is obtained from more than one quarry, that from each quarry shall be piled and laid in separate sections of the work. In no case shall the stones from different quarries be mixed. (4) Dressing. The blocks are to be split and dressed so as to present regular and true surfaces on all sides, with straight edges on top, bottom, and sides. All sides of the block must be free from depressions or projections, and all blocks whose faces vary more than one half inch from rectangular shape will be rejected. STONE PAVEMENTS. 153 * (5) Size of the Blocks. The blocks shall measure 3^ inches, wide, 7 inches deep, and may vary between 9 and 12 inches in length. In no case will any variation in the width be permitted. In some cases, as paving around man-hole heads, etc., blocks of lesser depth may be required, and will be used as directed by the engineer. (6) Inspection and Culling. The blocks will be inspected after they are brought on the line of the work, and all blocks which in quality and dimensions do not conform strictly to these specifica- tions will be rejected, and must be immediately removed from the line of the work. The contractor must furnish such laborers as may be necessary to aid the inspector in the examination and the culling of the blocks: and in case the contractor neglect or refuse to furnish said laborers, such laborers as in the opinion of the may be necessary will be employed by said , and the expense thus incurred by will be deducted and paid out of any money then due or which may thereafter become due to said contractor under the contract to which these specifica- tions refer. (7) Cushion-coat. On the concrete foundation a layer of clean sharp sand free from moisture will be evenly spread to a depth of one half inch. The sand if not dry must be made so by the appli- cation of artificial heat, in such apparatus as may be suitable for the purpose and approved of by the engineer. (8) Laying the Blocks. The blocks will be bedded in the sand, laid stone to stone in parallel courses at right angles to the axis of the street (except at intersecting streets, where they will be laid on the diagonal as shown on the plans). Each course shall consist of blocks of uniform width and depth. The blocks shall be so laid that the longitudinal joints shall be broken by a lap of at least two inches. (9) Jointing. After the blocks are so laid, the joints between them shall be filled to a depth of two inches with clean, dry gravel, then rammed to an unyielding bearing with a hand rammer weigh- ing not less than fifty pounds. All blocks which sink below the general level must be removed and replaced with blocks of greater depth. After the blocks are rammed the paving cement will be poured into the joints, to a depth of two inches; the joints will then be filled flush with gravel and the cement poured in until the 154 HIGHWAY CONSTRUCTION. joints are filled and will absorb no more. Dry sand will then be poured along the joints and spread over the entire pavement. The quantity of paving cement required per square yard of pavement will not be less than four gallons. This quantity must be brought upon the ground, and whatever may remain after the completion of the work will be the property of the city. Any wastage of paving coment by pouring over the surface instead of between the blocks must be covered with a sufficient quantity of fine dry gravel to absorb it. The amount so wasted will be estimated, and the quan- tity so estimated must be replaced by the contractor at his expense. (10) Composition of Paving Cement. The paving cement will be composed of the residuum obtained from the direct distillation of coal-tar and creosote oil, in the proportion of fifty gallons of oil to one ton of residuum; the two ingredients will be melted together in suitable iron boilers having a capacity of not less than one ton. It shall be poured into the joints while in a boiling state. (11) Quality of the Gravel. The gravel used for filling the joints shall be free from sand, clay, or other objectionable substances; it shall be of such size as will pass entirely through a sieve of three quarters of an inch mesh and be retained by a quarter-inch mesh. (12) Materials to be Kept Dry. The stone for the pavement, the sand for the bed, and the gravel for the joints shall each and severally be laid only when dry and free from moisture. After being laid the contractor shall protect them from the weather until the joints have been filled with the paving cement; should they become moist from any cause previous to filling the joints with the said cement, the contractor shall at his own expense remove that portion of the work so moistened and replace and complete the same with dry materials. (13) Laying Granite Blocks adjacent to Railway Tracks, etc. Between, and one foot outside of railroad tracks, over vaults, around sewer-manhole frames, and in such other places as the engineer may designate, the contractor shall furnish and use for the pavement blocks of such lesser depths as the engineer may direct. The general dimensions of such blocks on the top surface shall be the same as for the main pavement. (14) The number of blocks laid per square yard shall be thirty, so laid that ten courses measured lengthwise of the street shall measure not more than 35 inches. The actual average number of STONE PAVEMENTS. granite blocks laid per square yard shall be ascertained by the city engineer; and for each block, or fractional part thereof, that the average number of blocks laid per square yard shall fall short of thirty there shall be deducted from the contractor's bid price an amount computed at cents for each block less than thirty. (15) Interpretation of specifications. (16) Omissions in specifications. (17) Engineer defined. (18) Contractor defined. (19) Notice to contractors, how served. (20) Preservation of engineer's marks, etc. (21) Dismissal of incompetent persons. (22) Quality of materials. (23) Samples. (24) Inspectors. (25) Defective work, responsibility for. (26) Measurements. (27) Partial payments. (28) Commencement of work. (29) Time of completion. ^30) Forfeiture of contract. {31) Damages for non-completion. (32) Evidence of the payment of claims. (33) Protection of persons and property. (34) Bond for faithful performance of work. (35) Power to suspend work. (36) Right to construct sewers, etc. (37) Loss and damage. (38) Old materials, disposal of. (39) Cleaning up. (40) Personal attention of contractor. (41) Payment of workmen. (42) Prices. (43) Security retained for repairs. (44) Payment, when made. Final acceptance. CHAPTER IV. WOOD PAVEMENTS. 174. Wood Pavements.* Pavements formed of wood have been extensively employed both, in Europe and the United States, but with widely differing results in the two countries. The experience in the United States has been, with but few exceptions, unsatisfactory, while in Europe, especially in the city of London, wood pavements have proved very successful and are quite popular. 175. The success of wood pavements in Europe is due to the fact that more care is exercised in their construction and mainte- nance. There, a solid concrete foundation, well-seasoned wood, and water-proof cement filling for the joints are employed, with constant and careful attention to keep them in repair. 176. The unsatisfactory results obtained in the United States are attributable, first, to the methods of construction; second, to the employment of green wood ; and third, to the lack of careful maintenance. 177. The advantages of wood pavement may be stated as. follows : (1) It aifords good foothold for horses. (2) It offers less resistance to. traction than stone and slightly more than asphalt. (3) It suits all classes of traffic. (4) It may be used on grades up to five per cent. (5) It is moderately durable. (6) It yields no mud when laid upon an impervious foundation. (7) It yields but little dust. (8) It is moderate in first cost. (9) It is not disagreeably noisy. 178. The principal objections to wood pavement are: (1) It is difficult to cleanse. (2) Under certain conditions of the atmosphere it becomes greasy and very unsafe for horses. * Wood as a paving material appears to have been first employed in Russia, where, according to the testimony of Baron de Bode, it has been, though rudely fashioned, used for some hundreds of years. Wood pavement was first laid in New York during the year 1835-36, and in London, Eng., in 1839. 156 WOOD PAVEMENTS. 157 (3) It is not easy to open for the purpose of gaining access to underground pipes, and rather a large surface has to be removed for this purpose, and it has to be left a little time after being repaired before traffic is again allowed upon it. (4) It is absorbent of moisture. (5) It is claimed by many that wood pavements are unhealthy. 179, Objections to Wooden Pavements on Hygienic Grounds. Dr. 0. W. Wight, Health Officer of Detroit, in a report to the City Council, says : " On sanitary grounds, therefore, I must earnestly protest against the use of wooden-block pavements. Such blocks, laid endwise, not only absorb water which dissolves out the albuminoid matter that acts as a putrefactive leaven, but also absorbs an infusion of horse-manure and a great quantity of horse-urine dropped in the street. The lower end of the blocks, resting on boards, clay, or sand, soon becomes covered with an abundant fungoid growth, thor- oughly saturated with albuminous extract and the excreta of ani- mals in a liquid putrescible form. These wooden pavements undergo a decomposition in the warm season, and add to the unwholesome- ness of the city. The street, in fact, might as well be covered a foot deep with rotting barnyard manure, so far as unwholesomeness is concerned. Moreover, the interstices between the blocks and the perforation of decay allow the foul liquids of the surface to flow- through, supersaturating the earth beneath, and constantly adding to the putrefying mass." M. Fonssagrivs, Professor of Hygiene at Montpellier, France, objects to wooden pavements because they " consist of a porous substance capable of absorbing organic matter and by its own de- composition giving rise to noxious miasma, which, proceeding from so large a surface, cannot be regarded as insignificant. I am con- vinced that a city with a damp climate, paved entirely with wood, would become a city of marsh-fever/' Professor Brewer, of Yale College, says that " even in the free air and full sunlight, along with the putrescence a white fungous growth begins on the surface of the wood, which rapidly becomes slimy. This forms much more rapidly on the ends of the grain of the wood than on the radial or tangential sides. The fungous growth goes on, modified, of course, by the temperature and the degree of concentration, and it continues for an unknown period, or until the 158 HIGHWAY CONSTRUCTION. decay has become complete. Heartwood and sapwood act essen- tially alike in this matter; the difference is one of degree rather than character." The following comments are from the report of a Board appointed by the Legislature of New South Wales to inquire into the alleged deleterious effects of wood pavement supon the public health. " The Board examined specimens of wood pavement as laid in the city of Sydney, taking up blocks at different points. In all cases the concrete bed underneath was moist; in three cases a large amount of slimy mud was found giving off an ammoniacal odor. In all these the joints and blocks appeared to be uninjured. The blocks were chemically examined to determine whether they had absorbed organic matter, with the result that some were found impregnated with filth to the very centre, while others were com- paratively free from it. " The Board comes to the conclusion that wood is a material which cannot safely be used for paving unless it can be rendered absolutely impermeable to moisture, and so laid that while the entrance of water between the blocks is rendered impossible, the separation of the fibres at the surface by the concussion of traffic is also effectually prevented. These conditions have nowhere, to the knowledge of your Board, been fulfilled. " So far as the careful researches of your Board go, the porous, absorbent, and destructible nature of wood must, in its opinion, be declared to be irremediable by any process at present known; nor,, were any such process discovered, would it be effectual unless it were supplemented by another which should prevent fraying of the fibres. Still less can the defects of wood be considered to be of less consequence than the defects of other kinds of material. " In this city it may perhaps be considered that an amount of wood has not yet been laid sufficient to affect the public health whatever its condition within reasonable limits may be; and upon this ground your Board does not recommend that the present pav- ing should be removed, but that the Board of Health should be empowered to examine it, and to report upon it, from time to time, with a view of ascertaining its behavior under longer exposure to weather and traffic than it has yet had, and that it should be no longer watered, but cleansed by sweeping at least twice a day (the sweeping to be done at right angles to the direction of the street, or WOOD PAVEMENTS. 159 parallel to the courses, so that the latter may be cleared out by the broom), in order that destructive dampness and penetration of dis- solved organic matter may be reduced as much as possible. But the presumption is, upon the evidence here adduced, that in this climate the results alluded to would ensue if the extent of surface were sufficiently enlarged or fouling and decay sufficiently extensive. Your Board therefore recommends that the paving of the streets. o1 this city with wood should be discontinued, and desires to add that this recommendation is extended to apply not to the particular mod> -1 Situation. a 1 "o ^*S-5 I to P, S lit If . 3 1 Hi n 111! ^ i. tl It Q fc w* E 51 E- SB < King William St. Feb. 1873 I Improved ) { Wood. V 1 Pav. Co. j 16 $4.32 ( 1 yr. free, 15 yrs. | "( at 36cts. = $5.40f $9.72 $0.61 Ludgate Hill. Nov. 1873 Ditto 16 4.32 ( 1 yr. free, 15 yrs. "( at 36 cts. = $5 40 f 9.72 0.61 Portions of Great ) Tower St. and > Seething Lane. ) Sept. 1873 Ditto 16 3.84 j 1 yr. free, 15 yrs. | 1 at30cts.=$4.50f 8 34 0.52 207. Assuming the life to be 7 years, Mr. Stayton estimates the annual cost of wood paving in Chelsea, England, with a traffic of 500 to 750 tons per square yard of width per day, to be 42 cents per square yard, which includes the cost of original construction, repairing, renewals, and interest spread over 15 years. Cleansing .-and sanding are estimated to cost 10 cents per square yard in ad- dition. 208, Description of Various Systems of Wood Paving. Cedar- olock Pavement, Detroit, Mich. The cedar-block pavements used here are made of sound blocks, stripped of bark, cylindrical in WOOD PAVEMENTS. 175 shape and not more than 9 inches nor less than 5 inches in diame- ter and 7 inches deep. These blocks rest on a bed of bank sand and gravel 6 inches deep, well compacted with a roller weighing 2400 pounds. After the blocks are set they are rammed to a solid bearing with a rammer weighing 80 pounds; the spaces between them are filled with screened gravel rammed in with steel bars. The surface of the finished pavement is finally covered with gravel and sand to a depth of f of an inch. 209. Mesquite-block Paving in San Antonio, Tex. The blocks are hexagonal in shape, the minimum diameter being 4 inches and the maximum 8 inches, with a depth of 5 inches. The blocks are sawed with a slight batter, making the top about J of an inch smaller than the bottom. The roadbed is excavated to the required depth and rolled with a steam-roller. The foundation is 6 inches of cement concrete. A cushion- coat of sand 1 inch in depth is spread over the concrete and the blocks bedded thereon. The joints are sand-filled, The cost per square yard, including foundation, is about $2.80. 210. Asphalt Wood Pavement. This is one of the more recently adopted pavements in England. It consists of a concrete founda- tion, on which is placed a coating of asphalt mastic one-half inch thick; the blocks are creosoted and are placed on the asphalt with spaces of half an inch between rows, and the joints are broken by a lap of at least two inches. The lower portion of the spaces for 2 to 2 j- inches up is filled with melted asphalt and the remainder with cement-grout and gravel. In London this costs $4.00 per square yard. 211. Henson Pavement. The Henson system, which has been largely used in London, is as follows: The blocks are bedded and jointed with ordinary roofing-felt, a strip of which, cut to a width equal to the depth of the blocks, is placed between every two courses. The joint is made as close as possible by driving up the blocks, as every eight or ten courses are laid, with heavy mallets, a plank being laid along the face of the work ; a perfectly close and slightly elastic joint is thus formed. A continuous layer of felt is likewise laid over the concrete foundation to give a slightly elastic bed to the blocks. The surface of the pavement is dressed over with a hot bituminous compound, and covered with fine clean grit. The 176 HIGHWAY CONSTRUCTION". blocks are laid in courses at right angles to the curb, any change in the latter being accommodated by shorter courses ending with wedge-shaped blocks. At street-intersections the courses are laid diagonally or meeting at right angles. Two or three courses are laid parallel with the curb to form the gutter. 212. Improved Wood-pavement Company. The method em- ployed by this company in constructing the wood pavements in Paris is as follows : (1) Foundation. This consists of a bed of Portland-cement beton 0.15 m. (6 inches) thick, with a top coat of cement mortar about 0.01 m. (f inch) thick. The beton is thus proportioned : A mixture of about one third sand and two thirds gravel is put in a bottomless box containing half a cubic meter (0.65 cubic yard), and after the removal of the box 100 kilograms (220 pounds) of cement are emptied on the heap. This is in the proportion, by volume, of about one seventh as much cement as there is sand and gravel, since 1400 kilos 'is the mean weight of a cubic meter of good Portland cement heaped loosely. The sand was dredged from the bed of the Seine, and the gravel taken from pits on the seashore. The cement was furnished by the manufactory of Demarle & Lonquety, of Boulogne-sur-Mer. The paving-blocks have a uniform thickness and are not laid on the bed of beton until after it has set, in order to exactly preserve the curvature of the surface of the beton required for the convexity of the roadway. In the Avenue des Champs Elysees the convexity was 0.42 m. (16| inches) in a width of 27 m. (87 feet 7 inches), which represents a mean transverse slope of a little more than 3 in 100. This convexity, though less than first proposed by the company, appears to be a little excessive, and it seems that for roads under satisfactory drainage conditions the convexity might be diminished: 0.42m. is only a mean convexity, for, on account of the small longitudinal slope of the avenue, the grade of the gutters is not parallel to the grade of the street, but presents a series of short slopes from the hydrants to the sewer-openings; consequently the convexity varies from 0.39 m. (15J inches) at the hydrants to 0.45 m. (17f inches) at the sewers. To exactly regulate the surface of the beton a series of trans- verse profiles were defined by stakes levelled to the grade of the top of the bed. Along each profile a strip of stiff beton was laid. The WOOD PAVEMENTS. 177 top of this beton was carefully levelled and smoothed and received a guide-rule, laid flat, whose thickness exactly corresponded with that of the beton coating. This series of rules thus formed a set of guides close together, between which it was easy with large straight-edges to level the beton to the required surface. The first levelling could never be more than approximate, the surface of the beton naturally remaining somewhat rough. The exact level re- quired, as fixed by the tops of the rules, was secured by the top coat of cement mortar which filled the spaces between the pebbles and made an exact surface. This mortar was first composed of 200 kilos of cement to a cubic meter of sand (336 pounds to the cubic yard), but this proportion proving too small it was increased to 300 kilos. It was always mixed with a great excess of water, so as to penetrate the interstices of the gravel. (2) Paving. The covering is formed of small uniform blocks of red Northern fir, 0.15 in. (6 inches) high, 0.22 m. (8| inches) long, and 0.08 m. (3^ inches) wide. These are set close lengthwise, with joints, transverse to the street, of about 1 centimeter (f inch). The blocks are sent, ready for use, from England, where they were cut from planks of the ordinary size, 0.08 m. thick by 0.22 m. wide. The third dimension, taken in the length of the plank, forms the height of the block, so that in position the fibres of the wood are placed upright. The blocks are superficially creosoted after being cut. When the foundation has set, two or three days after being laid, the blocks are set by the pavers. Owing to the light weight of the blocks the work of paving is very rapid. Between crossings the blocks are set in rows perpendicular to the axis of the street, with their longitudinal joints staggered exactly half the length of a block. The methods used at crossings to avoid a continuous joint parallel to the traffic are analogous to those used in stone-paving. Special precautions are taken to insure exact spacing and regu- larity of the rows. Before commencing a new row, a strip of wood whose thickness is exactly that of the required joint is set edgewise in contact with the last row, and the paver has onlv to set the ad- jacent blocks in contact with it. The blocks do not at first adhere to the foundation and are easily displaced after the removal of the strips; to maintain them in place, as soon as the strips are taken out a small quantity 178 HIGHWAY CONSTRUCTION. of bitumen is poured into the joints. This liquid material fills the small spaces that may exist under the blocks and partially fills the joints, and in solidifying effectually seals the blocks. The joints are then filled by a thin grouting of neat Portland cement, distributed by the aid of a broom. This is done at least twice to insure perfect filling and the essential impermeability. The pavement cannot be opened for traffic until after the ce- ment in the joints has completely set, for which a delay of four or five days is considered necessary. During this interval the last operation is performed, viz., spreading a thin layer of dry sharp sand over the surface. The company claims that this dressing, crushed under the action of the wheels, incrusts itself in the wood and lends resistance to the wearing surface. It seems more prob- able that this coating is simply to protect the fresh mortar from the direct action of the wheels, for it can be maintained but a very short time on a travelled road, and is soon transformed into a dis- agreeable greasy mud. 213. Heads of Specifications for Wood-block Pavement. (1) Preparation of Roadbed. (2) Foundation. (3) Cushion-coat. The cushion-coat shall consist of a layer of dry, clean, sharp sand evenly spread on the concrete to a depth of one-half inch. NOTE. Asphaltlic paving-cement may also be used for the cushion-coat; or the blocks may be laid directly upon the concrete. (4) Qualify of the Blocks. The blocks shall be of timber, sound and thoroughly well seasoned, free from all sap, shakes, large and loose knots or other defects. NOTE. If the blocks are to be creosoted, the number of pounds of creosote that should be absorbed in a cubic foot of the wood should be specified; this is generally about 10 Ibs. of creosote to 1 cubic foot of wood. (5) Size of the Blocks. (Rectangular:) The blocks must not be less than 6 inches nor more than 12 inches in length by 3 inches in width and 6 inches in depth. (Eound Blocks :) The blocks shall not be less than 4 inches nor more than 8 inches in diameter, with a uniform length of 6 inches. Each block to be of uniform cross-section from end to end, the ends to be sawn off at right angles to the axis. The diameter of the block preferred i, 4 inches, WOOD PAVEMENTS. and 70 per cent of the whole number of blocks furnished must be of this size. (6) Inspection and Culling. The blocks will be inspected aftei they are brought on the line of the work, and all blocks which in quality and dimensions do not conform strictly to these specifica- tions will be rejected and must be immediately removed from the line of the work. The contractor must furnish such laborers as may be necessary to aid the inspector in the examination and culling of the blocks ; and in case the contractor neglect or refuse to fur- nish said laborers, such laborers as in the opinion of the may be necessary will be employed by said , and the expense thus incurred by will be deducted and paid out of any money then due or which may thereafter become due to said contractor under the contract to which these specifications refer. (7) Cushion-coat. On the concrete foundation a layer of clean sharp sand, free from moisture, will be evenly spread to a depth of one-half inch. The sand, if not dry, must be made so by the appli- cation of artificial heat in such apparatus as may be suitable for the purpose and approved of by the engineer. (8) Laying the Blocks. The blocks (rectangular) shall be set on the cushion-coat with the fibre vertical, in parallel courses, with the length of the blocks at right angles to the axis of the street; any change in the direction of the latter being acconrnodated by shorter courses ending in wedge-shaped blocks. No joints shall exceed f of an inch in width. The blocks shall be so laid that all longitudinal joints will be broken by a lap of at least 2 inches. At street-intersections the courses are to be laid diagonally as shown in Fig. 13. The gutters will be formed by three courses of blocks laid par- allel to the curb ; the course adjoining the curb will be left out until expansion has ceased. The space so left unpaved will be filled with sand. (9) Laying the Blocks (round blocks). The blocks will be laid on the cushion-coat, in parallel rows across the street and in close contact with each other. Split blocks shall be used adjoining the curbs, around sewer-manhole heads, and at such other places as the engineer may direct but no split blocks shall be laid in the main pavement. 180 HIGHWAY CONSTRUCTION. (10) Ramming. After the blocks are so laid they shall be rammed to a solid bearing with a hand rammer weighing not less than 50 pounds. All blocks which sink below the general level shall be taken out and sufficient sand poured in to bring them to the required level. (11) Jointing (rectangular blocks). The joints shall be care- fully filled with a grout composed of two parts of fine, sharp, clean sand and one part of Portland cement of an approved brand. (12) Jointing (round blocks). The interstices between the blocks shall be filled for a depth of 2 inches from the bottom with clean, screened gravel, the pebbles of which shall not be less than J inch nor more than inch in diameter, then hot paving-cement shall be poured in to a depth of 2 inches and sufficient gravel poured in to fill the joints flush with the top of the pavement, then more paving cement poured in until the joints are full and will absorb no more. After which a layer half an inch deep of dry, sharp sand will be spread uniformly over the surface of the pave- ment. The quantity of paving-cement required per square yard will not be less than 3-J gallons. This quantity must be brought upon the grou id, and whatever may remain after the completion of th& work will be the property of the city. Any wastage of paving- cement by pouring over the surface instead of between the blocks must be covered with a sufficient quantity of fine dry gravel to absorb it. The amount so wasted will be estimated, and the quan- tity so estimated must be replaced by the contractor at his own expense. (13) Composition of Paving -cement. The paving-cement will be composed of the residuum obtained from the direct distillation of coal-tar and creosote oil, in the proportion of 50 gallons of oil to 1 ton of residuum. The two ingredients will be melted together in suitable iron boilers having a capacity of not less than 1 ton. The cement shall be poured into the joints when in a boiling state. (14) Quality of the Gravel. The gravel used for filling the joints shall be free from sand, clay, or other objectionable SUD- stances. (15) Interpretation of specifications. (16) Omissions in specifications. (17) Engineer defined. WOOD PAVEMENTS. 181 (18) Contractor defined. (19) Notice to contractors, how served. (20) Preservation of engineer's marks, etc. (21) Dismissal of incompetent persons. (22) Quality of materials. (23) Samples. (24) Inspectors. (25) Defective work. (26) Measurements. (27) Partial payments. (28) Commencement of work. (29) Time of completion. (30) Forfeiture of contract. (31) Damages for non-completion. (32) Evidence of the payment of claims. (33) Protection of persons and property. (34) Indemnification for patent claims. (35) Indemnity bond. (36) Bond for fait'hful performance of work. (37) Power to suspend work. (38) Right to construct sewers, etc. (39) Loss and damage. (40) Old materials, disposal of. (41) Cleaning up. (42) Personal attention of contractor. (43) Payment of workmen. (44) Prices. (45) Security retained for repairs. (46) Payment, when made. Final acceptance. 214. Maintenance of Wood Pavements by Contract. The con- tractor will undertake the maintenance of the pavement for years (usually eighteen) from day of 189 . This maintenance will consist in preserving the surface and regularity of the profile, and in making all general or ' partial repairs neces- sary to keep the roadway in a perfect state, even if the dilapida- tions are the result of accidental causes, as fires, sinking of the subsoil, etc., excepting only defects caused by the digging of trenches. The contractor will be required to make general repairs on alj 182 HIGHWAY CONSTRUCTION. portions of the road where there is: (1) A reduction of the curve diminishing the original pitch by at least one fourth. (2) Where the thickness of the paving-blocks has been worn away f of an inch or more. (3) Depressions or partial defects of the road numerous enough to make it rough, the engineer being judge of the time when it shall be required for this reason. The concrete foundation will generally be preserved by simply adding Portland-cement mortar on top if there is room for it; the removal of the foundation is not obligatory except in case of its bad condition. Besides the general repairs the contractor must insure the con- stant good state of the pavement by partial repairs that may be necessary. He must immediately replace paving-blocks that are decayed, crushed, broken, or depressed by any cause whatever, also those which have become impregnated with urine or other offen- sive liquids and emit a bad odor. He must repair holes whose depth reaches f of an inch for a length of 3 feet in any direction. At the junction-lines of the wooden pavement with the stone or asphalt pavement, paving-blocks will be replaced when they ^hall have been worn away T \ of an inch. In all partial repairs the new pavement must have the same level as the adjacent pavement; no projections will t>e permitted. If any of the defects enumerated in this article are not repaired within three days after notification, a charge of dollars per day will be deducted from the contract price for each day's delay. Eenewals of the pavement over trenches opened for any cause must be executed in the same time and under the same restriction as above. The renewed portions will immediately pass into tLe maintenance of the contractor, who must preserve them in accord- ance with the foregoing conditions. No claims will be allowed for repairs required by sinking of the earth. The contractor will only be paid for the area of the trenches measured when filled up. The old material -and rubbish from repairs must be entirely removed from the street on completion of the work, in default of which the contractor will be subjected to a penalty of dollars per day for each deposit not removed. At the expiration of the maintenance period the pavement must be delivered in perfect condition. Three months before the WOOD PAVEMENTS. 183 expiration of the contract term the engineer will make a statement showing the condition of the pavement. The pavement shall not be received unless it satisfies the following requirements: (1) There must be no holes having a depth of f of an inch in any square yard of the pavement. (2) The transverse contour of the surface must not at any point be reduced so that the rise is less than four fifths of its original value. (3) The thickness of the blocks must at no place be less than 2 inches. After the engin- eer's inspection and report the contractor will be allowed three months to place the work in the required condition. The contract price fixed for the renewal of the pavement will be paid for the repairs over trenches, the demolition of the pave- ment being at the expense of the person or companies opening the trench. The contractor must, if necessary, relay the pavement with entirely new materials, and can make no claim for damages to the work or its maintenance. The price to be paid for maintaining the pavement in the above- described condition is cents per square yard, and will be payable quarterly during the contract period. Ten percentum of the amount payable quarterly will be retained and shall not be due or payable until the expiration of the contract period. The price to be paid per square yard for the renewal of the pavement over trenches is dollars. 215. Specifications for Laying Cedar Pavement in Chicago. Before paving the street shall be graded to conform to stakes or profiles to be given by the engineer in charge, and thoroughly flooded, rammed, and rolled to give it a solid bed. Paving. 1st. The pavement shall not be laid on any street until the material thereof shall have been made firm and unyield- ing, and the contractor shall assume all the responsibility therefor. 2d. A bed of clean lake-shore sand, not less than three (3) inches in depth, shall be smoothly and evenly spread over the surface of the street, and compactly rammed and rolled down. 3d. A foundation of two- (2-) inch sound common hemlock plank, to be laid lengthwise of the street, close together upon one- (1-) inch by eight- (8-) inch pine stringers under the ends and centres. Stringers to be firmly bedded in the sand. 4th. Upon said foundation live cedar blocks, free from bark and perfectly sound, not less than four (4) inches nor more than eight 184 HIGHWAY CONSTRUCTION. (8) inches in diameter, and six (6) inches in length, shall be placed on end, close-laid, resting properly on their bases and well driven together. All blocks more than eight (8) inches in diameter shall be split and the corners cut sufficiently to make good joints with adjacent blocks. No split blocks of less than three (3) inches in thickness will be allowed. All knots or excrescences must be cut off: to make the blocks practically uniform in diameter throughout their length. No interstice between the blocks to be more than one and one- half (1|) inches nor less than three quarters (f) of an inch. No square holes will be allowed, nor must two split sides come together. The surface of the pavement must be true and uniform'. In case any loose or defective blocks shall be found in the pave- ment, they shall be removed and replaced by perfect blocks of proper size, and so much of the pavement as may be necessary to make the work perfect shall be taken up and relaid at the expense of the contractor. The blocks will be carefully inspected after they are brought on the line of the work, and all blocks or other material which, in quality or dimensions, do not strictly conform with these specifica- tions, or which may be otherwise defective, shall be rejected, and must be immediately removed from the line of the work by the contractor. The contractor will be required to furnish such labor- ers as may be necessary to aid the inspector in the examination and culling of the blocks and other material ; and in case the contractor shall neglect or refuse so to do, such laborers as in the opinion of the Commissioner of Public Works maybe necessary will be em- ployed, and the expense incurred shall be deducted from any money then due or which thereafter may become due the contractor. 5th. The spaces between the blocks to be filled with clean, dry lake-shore gravel, of one fourth () to one (1) inch in size, the pro- portion of said gravel to be such as to completely fill the interstices, and shall be thoroughly rammed with proper tools and by compe- tent and experienced help, and again filled with the same kind of gravel and again thoroughly rammed. In the above-described ramming the filling in each interstice must be struck three full blows and driven down well. Two com- WOOD PAVEMENTS. 185 petent rammers must be constantly employed after each paver. No teams will be allowed on the pavement before it is properly rammed. After ramming the pavement will be flooded with hot composition, not less than one and one half (1-J) gallons per square yard being used. The tar will be distributed with a three- (3-) gallon kettle, the work to be done in sections as the Commissioner of Public Works, or his representative, may direct. 6th. After which clean, dry lake-shore gravel, about one fourth (J) inch in size, shall be spread over the street in such quantity that when swept all the interstices between the blocks will be thoroughly filled. When the gravel is put on the second and third time there must be enough space left between the portions rammed once and twice for the other portions to enable the inspector to see that every part of the street is thoroughly rammed. 7th. The whole surface will be swept over and covered with hot composition not less than one half (^) gallon per square yard, and immediately covered with dry roofing-gravel, or ^gravel screened from that used to fill the spaces between the blocks, said covering to be not less than one (1) inch thick. All gravel used here must be lake-shore gravel, entirely free from sand or pebbles, over one half (^) inch in size, and dried and heated enough to prevent the chilling of the composition. The gravelling and tarring must be completed each day to within fifteen (15) feet of the end of the paving, and the top dressing to within fifty (50) feet. If the gravel and pavement becomes wet before the tarring is completed, the same may be ordered taken by the Commissioner of Public Works. The composition used will be furnished by the city in the ordi- nary portable tanks at some point within the city limits ; the same to be transferred by the contractor from the receiving point to the work, and the empty tanks returned to the place of reception; the contractor to furnish the necessary fuel and labor to keep the com- position at a temperature of not less than 300 degrees Fahrenheit, and be at all times responsible for the tanks and their contents while in his care. The Department reserves the right to increase or diminish the quantity of the composition used. 216. Extracts from the Specifications for Laying Cedar-block Pavements in Minneapolis. Street Railway. Upon such streets as the street-railway company has tracks, it shall be the duty of the street-railway company to lower its tracks to the grade of the pave- ment to be laid. The said street-railway company in lowering its 186 HIGHWAY CONSTRUCTION. tracks shall deposit the material excavated on the outside of its tracks, and the contractor will be required to remove the same at the same price per cubic yard as for extra excavation. It is, how- ever, expressly understood that when the street-railway company has double tracks the contractor will be required to excavate and pave the spaces between said double tracks in the same manner as the remainder of the roadway, and shall receive the same price per square yard for said paving as he shall receive per square yard for the remainder of the paving of said roadway. Blocks. The blocks must be of the best quality of cedar, live and perfectly sound, and when in place be free from projecting knots and bark. They must be of a uniform length of six (6) inches, and have a diameter of not less than four (4) inches nor more than (10) ten inches. No blocks exceeding ten (10) inches in diameter will be allowed in the work either whole or split, and it is hereby expressly understood that the contractor will not be allowed to deposit upon the line of the work any blocks having the diameter greater than ten (10) inches, or any blocks turned from, a post of a greater diameter than ten (10) inches. It is expressly understood that the contractor will be required to repair in a satisfactory manner any paving that may settle or become defective on account of improper workmanship or material, or on account of the laying or construction of water-mains, sewers, gas-pipes, or making sewer, water, or gas connections, or conduit- laying, or any excavations allowed to be made in the street by the city council, which may have been done previous to the laying of said pavements, without cost to the city of Minneapolis. Flooring. Upon the finished sub-grade must be laid a floor of sound white-pine plank, of the quality equal to the grade known as first common lumber, as the city engineer and the city council may determine. These plank must be laid lengthwise of the street with close joints, and be two (2) inches thick, from eight (8) to twelve (12) inches wide, and from fourteen (14) to sixteen (16) feet long. They must have a bearing at each end and in the centre upon a one- (1-) inch by eight- (8-) inch stringer firmly bedded in the sand. Planks not less than six (6) inches wide may, however, be used in order to form the crown of crossings. Laying. The blocks must be placed upon their ends in close contact with each other, on a clean floor. The joints between the WOOD PAVEMENTS. 187 blocks must not exceed two inches in their longest direction. Blocks of less diameter than six inches must not be split, nor must a piece of less size than half the block be used. The corners of split blocks must be trimmed so as to make proper joints. Un- necessary splitting of blocks will not be allowed. Joints to be Filled. The joints or spaces between the blocks must be filled in the following manner : First, fill the joints by sweeping clean, screened gravel, the pebbles of which shall be of a size not exceeding one inch in their largest diameter, into them. After sweeping, the surface of the pavement must be clean and free from gravel, then the gravel must be thoroughly tamped. This process must be repeated asecond time. Gravel of the same kind as before used must be spread over the surface to a depth of not less than one inch above the top of the blocks. Gutters and Corners of Crossings must be made as follows : The outside plank shall be 3 inches thick, 16 inches high, and 20 feet long on 80-foot streets, and 3 inches by 16 inches by 16 feet on 60- foot streets, and held in place by not less than six posts of 3 by 6 by 30 inches, driven to a depth of three inches below the top and equidistant along the length of the plank. There shall be a plank 2 inches thick, 10 feet long, for 80-foot streets, and 2 inches by 8 feet on 60-foot streets, and of a width of 3 inches less than the depth of the gutter, placed against the curb to support the gutter- cover, which shall be made of two pieces of 3 by 12 inches by 10 feet on 80-foot streets, and of 3 by 12 inches by 8 feet on 60-foot streets, fastened together with four pieces, 2 by 19 inches, well nailed with six 30d. spikes to each piece. The top of the outside gutter-plank on the slope of the crossing shall be trimmed to con- form to the top of the paving. In making proposals the contractor will state a price which shall include cost of excavating eight (8) inches below the top of the finished paving; also the furnishing and putting in place complete of all lumber required in the gutter crossings and covers. The contractor will state a price per cubic yard for extra excavation. 216a. Microbes in Wood Pavements. Kecent investigations made in Europe regarding the sanitary qualities of wood pave- ments are reported in " Le Lyon Medical " as follows : In the superficial layers of a wood pavement, after it had been thoroughly swept and washed with water, there were found in one 188 HIGHWAY CONSTRUCTION". case 50,000,000 and in another 79,360,000 microbes to the gram; at a depth of five centimeters in one case 51,000, at a depth of six centimeters in another case 423,600 to the gram. Only a few of the microbes found were liquefying organisms, and in no case did they seem noxious when introduced by inoculation into the circulation of guinea-pigs. 216b. Cedar-block Pavements. INDIANAPOLIS, IND. Wash- ington red cedar untreated; rectangular blocks; sand foundation unsatisfactory; concrete foundation, 1-inch sand cushion coat; blocks laid close together. After five years shows considerable wear, while here and there rotted blocks are visible. Red cedar treated with 3 pounds - of creosote per cubic foot; rectangular blocks 4 inches wide and 5 inches with the grain of the wood; concrete foundation, 1-inch sand cushion; blocks laid at an angle of 45 with the axis of the street; no provision for expan- sion; blocks driven close together with a sledge; joints filled as far as possible with paving-pitch. Extent of wood-block pavement in 1899, 209,094 square yards. TORONTO, CAN. In 1898,41.1 per cent of all the pavements in the city was cedar block. Mr. Rust, City Engineer, explains the preference for this pavement as follows : "A cedar-block pavement is cheap, easily laid and repaired, noiseless, and dependent upon the extent of the traffic will remain in good repair for from six to eight years, and at the end of that period it can be renewed at a cost of from 45 to 50 cents per square yard, making it the cheapest pavement that can be laid." 21 6c. Karri (Australian) Block Pavement. NEW YORK, N. Y. The experimental block of Karri or Australian redwood pavement laid in 1895 on Twentieth Street is not considered a success, on account of its excessive slipperiness in wet weather. LONDON, ENG. The Australian hard-wood blocks laid in 1896 or earlier are reported as either in " fair condition " or " showing signs of wear." " Outside the city proper hard-wood blocks laid in Tottenham Court Road in December, 1892, .had worn very unevenly by June, 1899, besides which the noise caused by the traffic was very great, and the pavement was being extensively repaired." (Mr. J. D. Ross, Engineer to the City of London.) WOOD PAVEMENTS. 189 216d. Creosoted Pine Blocks. INDIANAPOLIS, IND. Material: Long-leaf Southern pine treated with 10 pounds of creosote per cubic foot. Size of Hocks : 4 inches by 4 inches, and from 6 to 10 inches long. Foundation : Concrete. Cushion coat : 1 inch of sand. Width of joints : Blocks laid close. Joint-filling : Fine sand or paving-pitch. Ramming : Blocks compacted by rolling. Expansion-joint : 1 to 2 inches at curb (according to width of street), filled with sand and covered with paving-pitch. Surface of blocks covered with J inch of clean coarse sand or granite screenings. Composition of paving-pitch: 10$ of refined Trinidad asphalt and 90$ of coal-tar distillate. Cost of construction : $2.10 to $2.50, with guaranty for five to nine years. GALVESTON, TEX. Material : Yellow pine impregnated by the vacuum process with 12 pounds creosote per cubic foot. Size of blocks : 5 inches wide, 5 inches deep, 10 inches long. Foundation : The natural sandy soil, compacted by saturating with water and shaped to the required form. Joint-filling : Sand. Width of joints : Close. Ramming : By hand-rammers. Surface is flooded with coal-tar sufficiently fluid to permeate the joints, followed by a coating composed of asphaltic paving- cement or asphaltum and dead-oil, after which the surface is cov- ered with a thin layer of sand. 21 6e. Cottonwood and Gum Blocks. ST. Louis, Mo. Gum and cottonwood blocks impregnated with chloride of zinc; concrete foundation 6 inches thick; joints filled with bituminous paving- cement. Burnettized cottonwood used on Broadway developed decay in the third year. 216f. Redwood Block Pavement. OAKLAND, CAL. Rectangu- lar blocks 4 inches by G inches by 6 inches cut from seasoned butt- cut redwood and boiled in asphalt; foundation 6 inches concrete, 190 HIGHWAY CONSTRUCTION. surface of which is painted with hot asphalt; blocks laid close in rows at right angles to axis of street; joints filled with asphalt, and surface covered with a coat of asphalt T ^ inch thick. The asphalt coat is designed to be the wearing surface and to be renewed as often as necessary. It is said that this pavement has given satisfaction during three years' service in San Francisco. 216g. Jetley's Patent.* The wood blocks are compressed to- gether by machinery in slabs 4 feet 6 inches long and 12 inches wide. These slabs are laid directly upon the compacted earth sur- face, and when the surface exposed to traffic becomes worn they can be turned over, presenting a new surface to the traffic. The Jetley system is the most recent contribution to the numerous inventions for the improvement of wood pavements; it has been tried in London with, it is said, satisfactory results; but it seems strange, in view of past experiences, to hear any one advo- cating the laying of a pavement directly upon the earth. 216h. Creo-resinate Wood Paving-blocks. This is the name given to wood blocks impregnated with a compound composed of Crersote, 60 to 80 per cent. Rosin, 38 to 18 per cent. Formaldehyde, 2 per cent. The wood used is either long-leaf yellow pine or black gum; the dimensions of the blocks are 3 to 4 inches wide, 3J to 4 inches deep, and range from 6 to 12 inches in length. The specifications under which this pavement was laid in Boston, Mass., are as follows: (1) All lumber is to be of long-leaf Georgia or Florida yellc w pine, free from sap, loose or rotten knots or other defects which would be detrimental to the life of the wood. No second-growth timber is to be used. (2) Blocks, except as otherwise ordered, are to be not less than 4 inches deep, 4 inches wide, and 8 inches long, uniform in depth, width, and length, with grain vertical. (3) Blocks are to be treated as follows: The blocks are to be placed iii an air- tight cylinder, and when the doors are closed the dry heat is to be * Engineering News, vol. xliii. p. 409. WOOD PAVEMENTS. 191 raised to 215 degrees Fahrenheit, without pressure, for one hour, for the purpose of getting rid of the moisture. Then the heat is to be increased, pressure is to be applied, and both are to be raised gradually, to avoid injury to the fibre, for two hours, until the heat has reached about 285 degrees and the pressure about 90 pounds, and both are to be held there for one hour. The heat is then to be shut off and the tanks are to be allowed to cool gradually for one hour. At the end of this time the heat is to be reduced to 250 degrees and the pressure to about 40 pounds. The pressure is then to be blown off and the heat still further reduced. Vacuum is then to be applied until about 26 inches is reached, and while under vacuum the creo-resinate mixture (creosote and rosin) is to be run into the cylinders at a temperature of 175 to 200 degrees, and hydraulic pressure is to be applied, reaching 200 pounds per square inch, and kept at this point until 21 to 22 pounds of mixture per cubic foot has been absorbed. The liquid is then to be run off and the wood is to be placed in another cylinder, and milk of lime at a temperature of about 150 degrees is to be run in, and hydraulic pressure of about 200 pounds is to be applied for from one-half to one hour. (4) The blocks are to be laid close on a cement concrete foundation six inches in depth, as hereinbefore provided, and at such an angle to the curb as directed by the superintendent on a 1-inch cushion of clean-screened sand, and are to be driven as tightly together as possible at every sixth row. (5) The joints are to be filled with dry-screened sand and the pavement rolled with a steam roller weighing not less than five tons, until the blocks present a firm, uniform and unyielding surface. The joints are then to be filled with paving pitch, creo-resinate mixture heated to 300 degrees Fahrenheit, or Portland cement grout, as required. (6) The sur- face of the paving when completed is to be covered with ^-inch deep dressing of clean-screened, sharp sand or crushed-stone screenings. Experience in Boston. The experience with the above-de- scribed pavement is stated by Mr. B. T. Wheeler, Superintendent of Streets, as follows: "It is apparent, after a year's experience with this pavement, that it is satisfactory as so laid in every respect except with regard to slipperiness, and that, as so laid, an almost absolutely noiseless pavement was obtained, the surface of which, under use, became 192 HIGHWAY CONSTRUCTION. so unified that the joints were indistinguishable and the pavement consequently slippery. No wear has yet been apparent. The surface remains perfect, and in comparison with the asphalt ad- joining it, it is preferable in all respects except that of slipperiness, in which practically it does not differ; and upon the grade of 4 per cent, at which it was laid it has nothing to recommend it in this respect." As a remedy for the slipperiness mentioned above Mr. Wheeler has laid on a 3 per cent, grade 2000 square yards of pavement in which the shape of the block and the jointing is changed as follows (Fig. 13B): From each block, 4x4x8 inches, there was removed FIG. 13B. RECTANGULAR BLOCK WITH WIDE JOINTS, from one side at the top a section one-quarter inch in thickness for the length of the block and one and one-half inches in depth. When these blocks were laid as above described and driven closely, there was between each course of blocks an opening, or joint, extending across the street, one-quarter of an inch wide and one and one-half inches in depth. These joints were filled with Portland-cement grout. It is expected that the cement joints extending across the street every 4 inches will tend to relieve the slipperiness by afford- ing a better foothold for the horses. . The creo-resinate blocks are in use in Baltimore, Boston, WOOD PAVEMENTS. 193 Chicago, Cleveland, Duluth, Indianapolis, Minneapolis, New York, Springfield, St. Louis, and Toledo. The blocks cost at the factory from $2 to $3 per square yard, according to the depth. 2161. Kreodone Blocks. The name "Kreodone" is employed to designate a wood preservative prepared from creosote-oil. It is claimed for this material that the tar acids are fixed and will not volatilize at a temperature under 130 F.; that the preservative qualities of the creosote are enhanced, thus giving longer endurance; that the material forms a varnish-like film or coating on the sur- face of the wood, thus protecting it from the action of the elements and preventing the washing out of the preservative. In treating the wood with the kreodone the same methods are followed as in the case of ordinary creosoting : the blocks are sub- jected to a temperature of 240 F. for eight hours; the kreodone- oil is then forced in under a pressure of 70 pounds per square inch, maintained for from two to three hours or until about 12 pounds cf the oil has been absorbed by each cubic foot of the wood. Samples]were laid itfChicago, 111., and Indianapolis, Ind., in 1901. 216j. Experiment with Different Woods. In 1895 several samples of untreated wood block were laid on the same street in Toronto, Can.; all the blocks were rectangular 4x7x8 to 12 inches, with the exception of the cedar, which was round. In June, 1901, these different woods were examined by City Engineer C. H. Rusk with the following results: Beach. Nearly all the blocks were decayed. Maple. A few of the blocks were in good condition; decay caused by dry-rot. Soft Elm. All blocks decayed. Hemlock. The majority of the blocks were sound. Norway Pine. Fairly good condition; depth reduced by traffic about one-half inch; dry-rot appeared in a few blocks. White Pine. Fairly good condition, dry-rot appearing. Cedar. The blocks were in better condition than any of the other woods. 216k. Cracking of Wood Pavement. In Municipal Engineering, Vol. XXII, p. 154, there is recorded an account of the cracking of wood pavements in Indianapolis. During a period of zero weather 194 HIGHWAY COXSTKUCTION. there occurred in a pavement of Washington red cedar transverse cracks extending from curb to curb. These cracks appeared' quite regularly at intervals of 25 to 30 feet, with occasional spaces greater or less. The width of the cracks indicated a shrinkage of about one inch in 30 to 35 feet of length of pavement. The blocks were laid in rows perpendicular to the curb and the cracks generally fol- lowed a single joint. On a street paved with creosoted yellow-pine blocks laid diag- onally, a similar cracking was observed along the long joints. These cracks were much closer together, and consequently nar- rower, and there was more tendency to scatter, cracks frequently passing from one joint to another, usually in the joint between blocks in a row, but sometimes through a block. " Wagons passing over the pavements produced, when in or near the cracks, a rumbling sound similar to that over a hollow pavement. "Ten days or more after the first cracks were observed, on a night when the temperature was 20 F., after a day near freezing- point, rather loud reports, similar to those heard in expanses of ice, were heard, indicating that the cracks already opened were not sufficient to allow for all the contraction occurring. . . ." CHAPTEK V. ASPHALTUM AND COAL-TAR PAVEMENTS. 217. Asphalt was first employed for street-paving in Paris in 1838, but it was not employed to any great extent until 1854. In 1869 it was introduced into London, and since then has been ex- tensively used throughout Europe. The success which attended this pavement led to its introduc- tion into America. The great cost of importing the materials from Europe made the pavement so expensive as to induce American inventors to seek to manufacture a material which should havo similar qualities. The result was the introduction of many sub- stitutes and imitations, the majority of which proved defective. The great cost of the imported material and the failure of the substitutes directed attention to the deposits of natural bitumen on the island of Trinidad, which could be brought here very cheaply. Experiments were made which demonstrated the possibility of mak- ing a mastic with Trinidad bitumen as its cementing material, as strong, elastic, and durable as that imported from Europe; but it was only after some years that this process was introduced and made a commercial success. 218. The difference between the asphalt pavements of Europe and those of America is due to the character of the materials. The former are composed of limestone rock naturally impregnated with bitumen, while the latter are composed of an artificial mixture :i bitumen, limestone, and sand. The limestone in the European pavements becomes hard, smooth, and slippery under traffic, and is thus objectionable for general use in frosty latitudes. The 195 196 HIGHWAY CONSTRUCTION. granular nature of the sand used in preparing the Trinidad asphal- tum diminishes the tendency to wear smooth and materially lessens the slipping of horsss. 219. Although many deposits of bituminous rock are found in the United States, they have been used only to a limited extent. The principal sources of supply at present are the island of Trinidad, Bermudez, Venezuela, and California. 220. The cost of preparing the different varieties of asphaltum for street pavement is nearly the same; and as all appear to be about equally durable, the exclusive use of any oxie of them is due merely to the advantage in freights. TYPE-SECTIONS OF ASPHALT PAVEMENTS. % ASPHALT 2" BINDER /%- COMCftCTES FIG, 14. HEAVY-TRAFFIC PAVEMENT. ASPHALTS* CONCRETE +' FIG, 15, LIGHT-TRAFFIC PAVEMENT, ASPHALTUM AND COAL-TAB PAVEMENTS. 197 ASPHALT ^" B//VDEft /&' STONE BLOCK FIG. 15A. ASPHALT ON STONE BLOCKS. % ASPHALT 2* BINDER I/& MflC/WflM FIG, 15B, ASPHALT ON MACADAM. 221. The Advantages of Asphalt may be summed up as follows: (1) Ease of traction. (2) It is comparatively noiseless under traffic. (3) It is impervious. (4) It is easily cleansed. (5) It produces neither mud nor dust. (6) It is pleasing to the eye. (7) It suits all classes of traffic. (8) There, is neither vibration nor concussion in travelling over it. (9) It is expeditiously laid, thereby causing little inconvenience o traffic. (10) Openings to gain access to underground pipes are easily made. (11) It is durable. (12) It is easily rapaired. 222. Defects of Asphalt Pavement. (1) It is slippery under certain conditions of the atmosphere. 198 HIGHWAY CONSTRUCTION. The American asphalts are much less so than the European on account of their granular texture, derived from the sand. The difference is very noticeable : the European are as smooth as glass, while the American resemble fine sand-paper. (2) It will not stand constant moisture, and will disintegrate if excessively sprinkled. (3) Under extreme heat it is liable to become so soft that it will roll or creep under traffic and present a wavy surface, and under extreme cold there is a danger that the surface will crack and become friable. (In Washington, D. C., with a range of tem- perature from 5 to 150 degrees Fahr., no serious trouble has been experienced with the Trinidad asphalts.) (4) It is not adapted to grades steeper than 2| percent. In the city of New York there are streets paved with asphalt on which the grade varies from 2 to 6 per cent, and Mr. North, C.E., states that the traffic has deserted Ninety-third Street, which is paved with granite on a grade of 5.15 per cent, for Ninety-fourth Street, which is paved with asphalt on a 6 per cent grade. (See also Art. 261.)* (5) Repairs must be quickly made, for the material has little coherence, and if, from irregular settlement of the foundation or local violence, a break occurs, the passing wheels rapidly shear off the sides of the hole, and it soon assumes formidable dimensions. In London this is prevented by constant watchfulness. Workmen are employed to traverse the street with a light repairing outfit, and whenever a defect is observed it is patched at once, and so effectually that the spot cannot be distinguished. 223. The strewing of sand upon asphalt renders it less slippery; but in addition to the interference of the traffic whilst this is being done, there are further objections, viz., the possible injury by the sand cutting into the asphalt, the expense of labor and materials, and the mud caused thereby which has afterwards to be removed. 224. Although pure asphaltum is absolutely impervious and insoluble in either fresh or salt water, yet asphalt pavements in the continued presence of water are quickly disintegrated. Ordinary- rain or daily sprinkling does not injure them when they are allowei * James Street, Syracuse, N. Y., is paved with asphalt on a 7.30 per cent grade. ASPHALTUM AND COAL-TAR PAVEMENTS. 199 to become perfectly dry again. The damage is most apparent in the gutters and adjacent to overflowing drinking-fountains. This defect has long been recognized, and various measures have been taken to overcome it, or at least to reduce it to the minimum. In some cities ordinances have been passed seeking to regulate the sprinkling of the streets, and in many places the gutters are laid with stone, while in others the asphalt is laid to the curb and a space of 12 to 15 inches along the curb is covered with a thin coat- ing of asphalt cement. Vitrified brick has been used for the gutters of streets paved with sheet asphalt. Eegarding the use of this material in Washington, D. C., the Eeport of the Engineers' Department for 1899 says: " The use of brick gutters for sheet-asphalt pavements has been continued, and the experience of the office leads to the conclusion that this form of construction is decidedly better than laying asphalt to the curb. The first gutters of this material were laid with the brick toothed into the asphalt. This practice, however, was discontinued, and the gutters have been laid since with con- tinuous joints. The latter construction has been found to be much better than the toothed method, as it has been demonstrated by several years' experience that it is impossible to sufficiently compact the asphalt between the teeth to prevent water entering, thus producing early decay or breaking up of the asphalt. With continuous joints it is possible to run the roller up to and along the very edge of the brick, producing as much compaction at this point as on other portions of the street. It has been observed in the cases of gutters of the two classes laid about the same time that in the toothed gutter the asphalt between the teeth and immediately adjacent thereto is, in a number of cases, already beginning to show signs of breaking up, while the asphalt adjacent to the con- tinuous-joint gutter is apparently as good as ever." It is said that the pavements formed of asphalt cement in which "maltha," or liquid asphalt, is used, instead of the residuum of petroleum, as the fluxing agent, are not affected by moisture. Investigations * made to ascertain the action of water on asphalts * By Messrs. G. C. Whipple and D. D. Jackson at Mt. Prospect Labora- tory, Brooklyn, N. Y. Paper read before Brooklyn Engineers' Club, March 8, 1900. 200 HIGHWAY CONSTRUCTION. show that some asphalts are acted upon to a considerable extent, while others are apparently unaffected; that the action varies with the character of the water. Distilled water and waters containing the smallest amounts of mineral matter produced the greatest action. Sea-water gave but little action, and a concentrated solu- tion of brine showed no action. The action of the water was exhibited by a change in color from black to brown, and in condition from hard to soft and punky, with the surface covered with cracks and pits. The softening action penetrated to depths ranging from 00 to 1.3 millimeters with distilled water and 00 to 1.1 millimeters with surface and ground water. The amount of soluble matter extracted from the asphalt corre- sponded with the intensity of the action of the water; distilled water showed the greatest action and took up the largest amount of soluble matter. The amount ranged from 2.83 to 21.42 per cent. The mineral constituents given up were sodium chloride,- carbon- ates and sulphates of calcium and magnesium, and oxide of iron. Some of the samples yielded both mineral and organic soluble matter. All the samples showed an increase in weight which varied with the condition of exposure. The greatest increase was observed in the case of Trinidad asphalt. The sample exposed in Mt. Prospect reservoir gained 3.92 grams per square metre in one day; after two months it had gained 31.24 grams; in the conduit at Freeport the gain during two months was 84.41 grams; in Mt. Prospect stand-pipe, where the pressure was great, the gain was 137.09 grams, equivalent to 4028 per square yard of exposed surface. The gain in weight of the other samples was less, but corresponded in a general way with the amount of action observed. " The cause of the action of water upon asphalt appears to be in part chemical and in part physical. " The action of water upon asphalt is due to the unsaturated na- ture of the hydrocarbons present, and is attended by a partial solu- tion of the asphalt in the water. There is also a loss of sulphur as hydrogen sulphide, and an increase in weight of the asphalt itself, due to oxidation and to the mechanical admixture of water. By ASPHALTUM AND COAL-TAR PAVEMENTS. 201 far the most important action which occurs is that produced by this oxidation of the asphalt by means of the dissolved oxygen in the water." " The following asphalts and fluxes are arranged in the order of least to greatest action by water: Petroleum residuum; Assyrian asphalt; Asphaltina; Cuban asphalt; Alcatraz maltha No. 2; Alca-. traz maltha No. 1 ; Alcatraz asphalt D ; Alcatraz asphalt XX ; Ber- muda asphalt; Trinidad asphalt. FIG. 15c, ASPHALT 1 BRICK GUTTER FIG. 15D. -ASPHALT WITH BRICK GUTTER. 225. Asphalt laid adjoining centre-bearing street-car rails is quickly broken down and destroyed. This defect is not peculiar to asphalt. All other materials when placed in similar positions are quickly worn. Granite blocks laid along such tracks have been cut into at a rate of more than half an inch a year. The frequent entering and turning off of vehicles from car-tracks is one of the severest tests that can be applied to any paving material; moreover, the gauge of trucks and vehicles is frequently greater than that of 202 HIGHWAY CONSTRUCTION. the rails, so one wheel runs on the rail and the other outside. The number of wheels thus travelling in one line must quickly wear a rut in any material adjoining the centre-bearing rail. To obviate the destruction of asphalt in such situations it is usual to lay a strip of granite block or brick paving alongside the rail. This pavement should be of sufficient width to support the wheels of the widest gauge using the street. The burning of leaves or making of fires on asphalt pavements should not be permitted, as it injures the asphalt, and the paving companies cannot be compelled to repair the damaged places with- out compensation. 226. Asphalt Pavement Injured by Illuminating-gas. The asphalt pavements on some of the streets of Frankfort, Germany, became friable and porous. City Engineer Dehnhardt attributed this to the escape of illuminating-gas. This view was ridiculed by several German authorities on this material. The pavements were taken up, and it was found that the gas-pipes had several leaks under the worst parts of the street. Some of the injured pavement and pieces of sound pavement were tested. The sound fragments were placed in a tube through which gas was allowed to flow. After a week the samples were reduced to the same friable condition in which parts of the pavement had been found. The samples after several weeks' exposure to the atmosphere regained their original good condition. The explanation offered is that a portion of the carburetted hydrogen of the gas is absorbed by the asphalt, thus destroying its cohesion. Regarding the destruction of asphalt pavements by illuminating- gas, Mr. A. W. Dow, Inspector of Asphalts and Cements, District of Columbia, in his report for 1898, says: " As it has been doubted by some that this disintegration is really due to illuminating-gas, I have made a most thorough investi- gation of the subject, and believe have positively proven that gas is the cause. Samples of pavements were obtained from several affected spots, and in all cases I have been able to obtain from them a gas that exploded by passing an electric spark after mixing with air. The method employed to obtain the gas from samples of the surface mixture was by heating them under boiling water and collecting the gas given off in an inverted funnel. . . . Two sam- ASPHALTUM AND COAL-TAR PAVEMENTS. 203 pies of a pavement were taken, one from an affected spot, and the other from a good portion of the pavement about ten feet away. These samples were treated under boiling w^ter until they ceased to evolve gas. The affected sample gave several times more gas than did the other. On testing, the gas from the good sample was found to consist of oxygen and nitrogen, which was evidently just the air from the voids in the pavement. The gas from the affected piece gave on analysis the results shown in column I of the follow- ing table." For comparison the composition of illuminating-gas is given in column II. i. ii. Gas from Pavement. Ilium inating-gas. Per Cent. Per Cent. Carbon dioxide 8.4 0.2 Oxygen 10.8 0.0 Heavy hydrocarbons 13.4 12.1 Carbon monoxide 0.7 25.5 Hydrogen 6.6 39.2 Methane 2.0 23.0 Nitrogen 58.1 0.0 The composition of the gas obtained from the disintegrating pavement does not correspond to that of a natural or marsh gas, sewer-gas, or air; hence the only gas it can be compared with is illuminating-gas, the analysis of which is given in column II of the preceding table. " On comparing the composition of the gas given off from the disintegrating pavement with the illuminating-gas, it is seen that they are not at all similar in composition. At first glance it would not seem possible that the former gas could originate from the latter, but when the properties of asphalt are considered it is easily explained. "Heavy hydrocarbons, to which class asphalts belong, are known to absorb other gaseous hydrocarbons: the heavier the gas the more affinity between it and tfre heavy hydrocarbons. Knowing this, the ingredients of the illuminating-gas that asphalt would have the greatest affinity for would be the heavy hydrocarbon gases, a slight affinity for the marsh-gas or methane, and no affinity for any of the other ingredients. If we examine the ingredients of the gas from the affected pavement, it will be found to consist of some carbon 204 HIGHWAY CONSTRUCTION. dioxide, air that was in the voids and cracks of the pavement, and the constituents of illuminating-gas with the heavy hydrocarbon gases very much in excess, which is what we would expect. To practically demonstrate that the above takes place when asphalt is in contact with illuminating-gas, I took two samples of gas from a tap in the laboratory. One was analyzed, while the other was kept for several weeks in a tube the interior of which was coated with asphalt cement, such as is used in pavements, after which it was analyzed. The results of the two analyses are given in the follow- ing table : Original Gas. Gas after Asphalt Per Cent. Absorption. Per Cent. Carbon dioxide 0.2 0.1 Oxygen 0.0 0.0 Heavy hydrocarbons 12.1 7.2 Carbon monoxide 25.5 27.3 Hydrogen 39.2 42.2 Methane 23.0 23.2 Nitrogen 0.0 0.0 " It is evident from this that the asphalt cement has absorbed over 5 per cent of the heavy hydrocarbon gases, a little methane, and practically nothing else. " I have ascertained by experiment that one part by volume of asphalt cement will absorb forty-two parts of illuminating-gas in somewhat over a month. I have also practically shown that asphalt is much softened by absorbing gas, the ordinary asphalt cement becoming as soft as a thick maltha after being in an atmos- phere of illuminating- gas for several months. As to the quantity of gas contained in the affected pavements, this of course varies, but in one instance 1000 c.c. of pavement gave off 500 c.c. of gas." There is but one remedy for the disintegration caused by gas and that is to stop the leak of gas. 227. Durability. The systems adopted for the maintenance of asphalt pavements render it difficult to ascertain their actual life under traffic. They are repaired immediately they need it, and as each repair is so much new material laid, the whole surface is really relaid in the course of years. Col. Haywood states that in his opinion asphalt will last without extensive repairs from four ASPHALTUM A.ND COAL-TAR PAVEMENTS. 205 to six years, and that in the course of ten years the entire surface will have been renewed. 228. That asphalt successfully sustains an enormous traffic is shown by the following figures : From London, Cheapside has a traffic of 13,772 vehicles in 24 hours; Mansion House Street, 23,332 vehicles in 24 hours. Cornhill, Holborn Viaduct, and many others have a daily traffic of upwards of 12,000 vehicles. These streets are paved with asphalt. 229. There are no streets in America or elsewhere in the world that have so much traffic as the above-mentioned London streets. Among the vehicles that travel on them are omnibuses loaded with passengers inside and out, light vehicles of all descriptions, carts, carriages, and brewery trucks loaded with tons of ale and porter. The first asphalt pavement was laid in the city of London in 1860, on Threadneedle Street, adjacent to the Bank of England, and was renewed at the end of 17 years. Asphalt has lasted on Holborn Viaduct 17 years, on London Wall 20 years, in Loth- bury 23 years, and in Princess Street 22 years; in many of the minor streets it has lasted 30 years. Cheapside was paved in 1870, and the pavement remained in constant use for 19 years, with of course extensive repairs; but up to 1889 the carriageway was never closed entirely for a general relaying of the pavement. In 1889, the contract for maintenance of the asphalt having expired, a new contract was made and a new surface of asphalt was laid. Most of the main thoroughfares of the old city of London are paved with asphalt, under 17-year maintenance contracts. 230. St. Louis, Mo." The asphalt laid on Pine Street in 1883 is now in good condition after a test of eight years under a mixed traffic of 3000 vehicles in 12 hours from 7 A.M. to 7 P.M. The work was carefully executed, and consists of a 6-inch hydraulic-cement concrete base, -^-inch cushion-coat and 2-inch surface or wear- ing coat; cross-section camber 0.50; width between curbs 36 feet. Traffic is what may be termed building materials, residence supplies, and suburban. While it has been subjected to the heavi- est loads hauled in the city with fair results, it must stand below granite for wear." (Report of Mr. T. H. Macklind, District En- gineer.) 206 HIGHWAY CONSTRUCTION. 231. Wear. Asphalt is to a certain extent elastic and does not begin to wear until this elasticity is overcome by thorough com- pression. This is the case with no other paving material. Stone and wood begin wearing from the day traffic commences. Under ordinary traffic it may be estimated that it will take two years to complete the compression of asphalt, and the weight of a square foot of this pavement will at the expiration of that time be nearly the same as on the day it was laid, though the thickness is reduced daring the first two years as much as it will be in the following eight. The extent to which the thickness has been reduced is said to be as much as one fourth the original thickness. A pavement in Paris which had lost more than one fourth of its thickness was found to have Lost only 5$ of its weight after 16 years' use. The pavement in Cheapside, London, after fourteen years' use, shows a reduction, where not repaired, from its original thickness of 2^ to If inches. 232. Cost of Construction. The cost of construction varies with the locality, thickness of wearing surface, and kind of founda- tion. Table XXXV shows the extent and cost in several cities in America. In London the first cost is from $3.75 to $4.50 per square yard, including maintenance. The total annual expense varies from 33 to 57 cents per square yard. In Omaha, Neb., the first cost per square yard, including main- tenance for five years, is about $2.98. The prices per square yard given in Table XXXV for American cities includes in nearly all cases the maintenance of the pavement for a period of five years. The extent of the asphalt pavement in use in 1890 was: United States, 6,803,054 square yards, equal to 446 miles of roadway 26 feet wide; Europe, 1,698,846, equal to 111.3 miles. 233. Cost of Maintenance. Asphalt pavements are generally maintained by the companies that construct them. The systems adopted are as follows : The company constructing the pavement undertake to maintain ASPHALTUM AKD COAL-TAR PAVEMENTS. 207 TABLE XXXV. EXTENT OF ASPHALT PAVEMENTS IN THE PRINCIPAL CITIES OF THE UNITED STATES IN 1903. Cities. Area, Sq. Yds. Length, Miles. Cost of Con- struction per Sq. Yd. Guarantee Period, Years. Akron Ohio 61 860 2 4 Albany N. Y 167,757 9.5 $3.08 5-7 Allegheny Pa 601 500 35 1 1 67-2 75 Allentown Pa 65 664 2 7 Altoona Pa 106 383 6 5 2 58 35,728 5.7 2.08 10 Auburn N Y 57 736 2 Augusta Ga 51 398 9 2 58-2 63 Auro r a 111 176 800 9 5 499,450 20.9 2.25-2.70 Bayonne N J 44 900 1 6 Binghamton N Y 117 290 5 1 69-2 69 5 Boston Mass 329 003 20 3 3 5-10 Bridgeport Conn 36 146 1 8 2 18 5 Buffalo N ' Y 4 354 874 232 8 2 18-2 67 5-10 Cambridge Mass . 4 445 2 3 Oamden N J 315 376 19 7 1 95 Cedar Rapids Iowa . . . 67 892 2 9 Charleston S. G . . 14 989 7 2 56 5 Chattanooga Tenn . . . 81 335 3 6 Chester Pa 128 480 7 3 Chicago 111 3 815 000 197 2 Cincinnati Ohio 592 000 30 2 39-2 78 Cleveland Ohio 298 096 17 4 1.66-2 95 Columbus Ohio 357 970 18 2 2 25 Covington Ky 72617 3 3 3 09 Dallas Texas 115 239 3 3 Dayton Ohio 391 647 17 8 2 07-2 30 5 Denver Colo 493 925 19 1 2 30-2.62 Des Moines Iowa 81 653 3 3 Detroit Mich 736 108 33 9 1 90-2 48 5-10 Duluth Minn 22997 7 Elizabeth N. J 41 243 1 9 Elmira N Y 66411 2 8 2 29-2 69 10 Erie Pa 207 087 14 2 1.80-2 45 East St Louis, 111 3,432 2 71,856 3.5 1,930 1 Fort \Vayne Ind 268 955 14 1 1 40-1 60 10 Fort Worth Texas 8 693 0.1 122,496 7.0 1 . 77-2 . 40 77997 2.7 Hartford Conn 209 530 8 7 2 55-2 70 5 133,909 6.5 2 . 35-2 . 65 5 Hoboken N J ... . . 94408 4 8 1 51 Holyoke Mass 20510 8 2 75 (Block) Houston Texas 6 3 208 HIGHWAY CONSTRUCTION. TABLE XXXV (Continued). EXTENT OF ASPHALT PAVEMENTS IN THE PRINCIPAL CITIES OF THE UNITED STATES IN 1903. Cities, Area, Sq. Yds. Length, Miles. Cost of Con- struction per Sq. Yd. Guarantee Period, Years. Indianapolis, Ind 1,012,332 7,700 48.3 0.4 16.2 5.8 0.1 0.5 13.8 122.7 1.0 0.3 6.1 3.3 0.7 13.7 24.2 5.1 0.1 2.4 6.1 0.3 20.3 12.4 3.3 0.2 0.5 0.7 1.0 0.1 7.5 3.3 0.2 26.3 51.1 436.7 18.4 35.7 2.0 1.7 3.5 0.1 12.6 357.0 104.9 4.6 4.9 6.4 50.2 2.0 1.75-3.00 Jackson Mich. Jersey City N J 1.65-2.73 Joliet 111 134,215 3,251 9,400 243,583 2,546,682 21,341 6,707 127,380 81,749 16,000 320,963 615,847 95,347 350 46,079 129,046 7,219 561,733 196,900 53,919 1,200 4,959 16,397 20,820 2,500 131,120 69,349 3,030 Joplin Mo Kalamazoo Mich . . .... Kansas City, Kan Kansas City, Mo 2.06-2.54 2.50 10 2 Lancaster, Pa Lawrence, Mass Lima Ohio Lincoln Neb Little Rock Ark Los Angeles Cal 1.80 2.00 2.65 "s^-io" Louisville Ky Lowell Mass . . Lynn Mass . .... Manchester N H Memphis Tenn. . Meriden, Conn Milwaukee, Wis 2.12-2.30 2.18-2.49 Minneapolis, Minn Mobile Ala Nashua N H Nashville Tenn Newburg N Y New Bedford Mass New Britain Conn New Castle Pa New Haven, Conn 3.36^3.80 10 Newport Ky New Orleans La 2.85 2.35-2.68 2.72-2.95 2.00 1.45-2.17 Newark N J New York N Y 8,675,516 320,049 848,261 36,040 8,905 61,773 919 249,883 5,347,165 1,609,911 126,314 86,415 122,873 811,344 58,608 Norfolk Va Omaha Neb 5 Oshkosh Wis Passaic N J Paterson N J Pawtucket R I 3.15 1.85-1.97 2.05-2.30 Peoria 111 5 Philadelphia Pa Pittsburg Pa Portland Ore Providence R I 2.25 Reading Pa Rochester N Y 2.33-2.77 1.65 Rockford 111 ASPHALTUM A^D COAL-TAR PAVEMENTS. 209 TABLE XXXV (Contin ued}. EXTENT OF ASPHALT PAVEMENTS IN THE PRINCIPAL CITIES OF THE UNITED STATES IN 1903. Cities. Area, Sq. Yds. Length, Miles. Cost of Con- struction per Sq. Yd. Guarantee Period, Years. Sacramento, Cal 7,360 0.3 Saginaw Mich 179 64'? 9 1 1 54-2 39 Salem, Mass 37,201 2.5 Salt Lake City, Utah 4.7 2 74 San Antonio, Texas 155,632 6.5 San Francisco, Cal 2,929,810 104.9 Savannah, Ga 140,813 5.7 Schenectady N Y 291 678 17 5 Scranton Pa 248 824 12 5 2 26-2 47 Seattle Wash 198 740 13 3 Sioux City Iowa . ... 195,688 6 8 2 38 Somerville Mass 11 616 7 South Bend ind . . 100 340 3 9 South Omaha Neb. . . . 41 203 1 4 Spokane Wash 242 134 8 8 Springfield Mass 8005 4 2 50-3 07 Springfield Ohio 11 440 5 St Joseph Mo. 197,189 7.8 2 15 St. Louis, Mo 703,224 28 3 2 25 St. Paul, Minn 603,299 25 4 2 08-2 46 10 Syracuse, N. Y 630,889 32 3 2 00-2 20 5-10 Tacoma, Wash 57,040 2 2 2 00 Terre Haute, Ind Toledo, Ohio 85,418 566 448 3.6 29 9 1.95-2.14 5 Topeka, Kan 193 810 7 1 Trenton, N. J 171 659 8 4 Troy, N.Y 87 931 4 9 2 50 Utica, N.Y 702 472 41 1 2 26 Washington, D. C 3 427 534 157 3 1 78-2 19 Waterbury, Conn 6 917 3 West Hoboken, N. J 62 339 1 5 Wichita, Kan 141 046 4 6 Wilkesbarre, Pa 133 043 8 4 Williamsport, Pa 67 439 2 9 Wilmington. Del 3 945 3 Worcester Mass 12 698 7 2 ^0 K Yonkers,N.Y 144 590 7 3 2 89 York, Pa 17 600 1 Youngstown, Ohio 220 300 12 7 2 48 210 HIGHWAY CONSTRUCTION. it in good condition for a fixed number of years. In America the cost of maintenance is included in the price paid for the construc- tion, and the period varies from five to fifteen years. In Europe a fixed price is paid for construction, and the com- pany maintain the surface free for two years, after which period they are paid a certain amount annually per square yard, depending upon the amount of the traffic over the pavement, for maintaining it in good condition (usually fifteen years) ; in case of any disturb- ance of the pavement by a corporation or by a private citizen, the company replaces the pavement at the expense of such corporation or citizen, and is responsible for the maintenance thereafter. A force of men is kept constantly at work making repairs, and any defect, however slight, is repaired immediately. It is not considered that the necessity for continual repairs is an evidence of poor workmanship in the original construction or of defective materials used, but rather that an earnest endeavor is being made to keep the pavement, even under heavy traffic, at all times in perfect order. This prompt and constant repairing explains the superior condition of the pavements in the cities of Europe. 234. In Table XXXVa is given the cost of maintaining asphalt pavements per square yard per annum in several American cities and London, Paris, and Berlin. ASPHALTUM AND COAL-TAR PAVEMENTS. 211 TABLE XXXVa. COST OF MAINTAINING ASPHALT PAVEMENTS. Locality. Cost per Square Yard per Annum. Remarks. St Louis Mo . . Cents. 4^ to 9 10-year contract Buffalo, N. Y.: Residence streets $0 047 With railroad tracks 1 1 (i 048 Without " " Business " 148 With " " ( ( t ( 112 Without" " Resurfacing 1 05 1898. Skimming. . 64 Painting gutters 02 Per lineal foot. Cleaning and pouring cracks. Omaha, Neb 0.01 08 i ( 1 1 1 1 10-year contract. Baltimore Md 1897. Highest 7620 Lowest 0017 Average 1297 Cincinnati 0.075 By contract for the second 5 0.01-0.23 years, the first 5 years being 0. Irrespective of age of pavement it ii 0.063 Average for total area of Trini- t( it 0.10-0.30 dad asphalt, 1881 to 1895. Sicilian rock irrespective of age (f (C 027 Average for total area Columbus Ohio. 0425 Trinidad 1 to 8 years out of e e ic 0218 guaranty. Kentucky rock 6 years out of (t it 1714 guaranty. Average for total area includ- Rochester, N. Y 0283 ing 5.17 c. for superintend- ence. 10 years 1 1 1 1 0530 15 " (i ec 0864 20 " St. Paul, Minn 0945 10 Toronto, Can 043 10 K a 044 15 Washington, D. C. . 003 11 ft ( ( 016 15 it 1 1 042 20 New York, Bor. of Brooklyn. . . 1 1 (i ( e < : f { 0.043 0.026 10 15 London: Val de Travers 0.074 24 20 Average of 15 years Limner. . 19 it (i t( Societe Franchise. . . 22 ft fktt 1 1 Paris 40 Including renewal of -r^ part of Berlin 1 50 the surface every year. For 20 years by contract 21 2 HIGHWAY CONSTRUCTION. 238. Mr. Elliot C. Clarke gives the following as the cost per square yard per annum of Val de Travers compressed asphalt under an annual traffic tonnage of 100,000 tons per yard of width: Interest on original cost 19.4 cents Maintenance per square yard 7.2 " Scavenging per square yard 0.8 " Total 27.4 cents Nothing is charged for renewal, as the annual sum for mainte- nance provides for the asphalt in perpetuity. 239. The items composing the cost of an asphalt pavement are: Cost per sq. yd. Removal of old pavement and grading $0.10 6" concrete foundation (1:2:5) 48 400 Ibs. asphalt cement $8.00 200 Ibs. stone-dust. 20 1 cubic yard sand 1.25 $9.45 This will lay 13 yards = 73 Labor mixing 04 Hauling 10 Labor laying 06 Superintendence 025 .225 $1.535 To which are to be added profits, risks, etc. 240. Foundation. A solid unyielding foundation is indispen- sable with all asphaltic pavements, because asphalt of itself has no power of offering resistance to traffic; consequently, if the founda- tion is not thoroughly solid and unyielding the weight of the traffic will crush it, and the asphalt will give way in all directions and go to pieces. Two classes of foundation are used : (1) Hydraulic- cement concrete; (2) Bituminous concrete. Eecently, with the object of reducing the cost of construction, the asphaltic paving composition has been laid upon the surface of old macadam, cobble, and stone-block pavements, and the results seem to be equally as satisfactory as with the concrete foundations. Old brick pavements have been used at Youngstown, Ohio, as a foundation for asphalt. The brick pavement is thoroughly swept and washed clean, and, after it is dry, it is heated with sur- face heaters, which destroys all combustible matter and completely ASPHALTUM AND COAL-TAR PAVEMENTS. 213 dries the brick. While they are still warm the surface of the bricks is painted with a thin coat of asphalt applied with brushes; If the holes and depressions are deep, they are filled with broken stone mixed with asphaltic cement; and if shallow, they are filled with the same material as the surface coat and thoroughly tarn pod. On this the surface coat is placed in the usual manner. 241. Each class of concrete has its advantages and disadvan- tages: with cement concrete, the bond between the foundation ami the wearing surface is not very great, hence it is very easy to strip off the surface in case repairs are necessary; but, on the other hand, the surface sometimes slips on the foundation, and under traffic rolls into waves and irregular surfaces, and sometimes cracks with sudden and great changes of temperature. A cement concrete foundation must be set and thoroughly dry before the asphalt is laid ; the best asphalt laid in the most skilful manner on first-class but damp concrete will rapidly go to pieces. When the hot asphalt is applied to a damp surface the water is immediately sucked up and turned into steam, which tries to escape through the heated material; the result is that coherence is prevented, and, although the surface of the asphalt is smooth, the mass is really disintegrated from underneath by its bitter enemy, "water." As soon as the pavement is subjected to the action of traffic, the fissures formed by the steam appear on the surface, and the whole pavement quickly falls to pieces. For the same reason asphalt should be laid only in dry weather. 242. With bituminous concrete the foundation and wearing surface are united into one mass and cannot be easily separated. Repairs are difficult, but waving and cracking are less frequent, and the bituminous concrete is less expensive. 243. Asphalt Cement Pavements are composed of two essential parts, the matrix and the aggregate, and the success or failure of the pavement will depend upon the care exercised in selecting the materials and the skill displayed in combining them and laying the pavement. 244. The matrix consists of cement prepared from some selected asphaltum in the manner described in Art. 96. Its propor- tion-varies from 10 to 15 per cent, according to the character of the aggregate, climate of the locality where used, amount and char- acter of the traffic, In cold climates more cement is required than in warm ones; pavements subject to constant and heavy traffic re- quire less cement than those used by light traffic. 214 HIGHWAY CONSTRUCTION. 245. The aggregate consists of sand and stone-dust. 246. In quality the sand should be equal to that used for the best quality of hydraulic cement mortar; it must be free from loam and vegetable impurities; its character should be angular grains ranging from coarse to fine. (See also Art. 252.) All of it should pass a 10-rnesh screen ; 20 per cent an 80-mesh screen; and 10 per cent, a 100-rnesh screen. 247. The stone-dust is used to aid in filling the voids in the sand and thus reduce the amount of cement required for this pur- pose (the voids in sand range from 0.30 to 0.50 per cent). The amount used will vary with the coarseness of the sand and quality of the cement. The proportion used ranges from 5 to 15 per cent. All of it should pass through a 30-mesh screen, and 75 per cent should pass a 100-mesh screen. Portland cement is being substituted for the stone-dust; recent specifications require that not less than 5 per cent be used. Its employment permits the us^ of more asphalt cement, thus produc- ing a dense mixture with a minimum of voids; the increased amount of asphalt tends to prolong the life of the pavement. 248. As to the quality of the stone-dust; that from any durable stone is equally suitable. Limestone-dust was originally used and has never been entirely discarded, although it may be one of the weak elements in the composition; for carbonate of lime, though practically insoluble in pure water, is decidedly soluble in water containing carbonic acid gas. As rain-water contains this gas in absorption, its action upon the lime in the pavement is to slowly dissolve it, and thus expose the cement to the oxidizing action of the atmosphere. Organic and weak acids such as are found on streets also decompose the lime. 249. The paving composition is prepared by heating the mixed sand and stone-dust and the asphalt cement separately to a tem- perature of about 300 F. The heated ingredients are measured into a pug-mill and thoroughly incorporated ; when this is accom- plished, the mixture is ready for use. It is hauled to the street in iron carts, the interior surface of which is previously painted with petroleum oil to prevent it from sticking; it is spread with iron- rakes to such depth as will give the required thickness when com- pacted (the finished thickness varies from 1| to 2-j- inches ; the re- duction of thickness by compression is generally about 40 per cent). ASPHALTUM AND COAL-TAR PAVEMENTS. 215 250. The compression is accomplished by means of rollers and tamping-irons, the latter being heated in a fire contained in an iron basket mounted on wheels ; these irons are used for tamping such portions as are inaccessible to the roller, viz., gutters and around manhole heads, etc. Two rollers are generally employed one a hand-roller weighing about 800 pounds, the other a steam-roller of the form shown in Chap. XXIII, ranging in weight from 5 to 10 tons. The surface of the hand-roller is painted with kerosene to prevent the mixture from sticking to it, and is generally propelled by four or more men walking on the surface of the heated paving mixture. The hand-roller is being super- seded by heating the front roll of the steam-roller ; the heating is effected either by fire carried in an iron basket suspended from the axle inside the roller, or by an attachment for using steam from the boiler. Two steam-rollers are sometimes employed, one weighing from 5 to 6 tons and of narrow tread this is used to give the first com- pression; and the other, weighing about 10 tons and of broad tread, is used for finishing. The amount of rolling varies ; the average ap- pears to be about one hour per one thousand square yards of pave- ment. After the primary compression by either the hand or heated roller natural hydraulic cement or any impalpable mineral matter is sprinkled over the surface to prevent the adhesion of the material to the cold roller and to give the surface a more pleasing color. To prevent rotting of the paving material in the gutters they are formed of either hydraulic cement, granite blocks, vitri- fied brick, etc., or when the asphaltic material is laid up to the curb the surface of the portion forming the gutter is painted with a coat of hot asphaltic cement. 251. The paving composition is usually spread upon the foun- dation in two layers; the first is called the " binder" or "cushion coat"; it contains from 2 to 5 per cent more cement than the sur- face layer; its finished thickness varies from one half to one and one- half inches. The object of the binder is to unite the surface mixture with the foundation, which it does through the larger percentage of cement that it contains, and which if put in the surface mixture would render it too soft. When the " binder " has been compressed, it is ready to receive the surface coat, which is laid and compressed as above described. When bituminous concrete is used as the foun- dation, the " binder " is omitted. When the pavement is to be laid 216 HIGHWAY CONSTRUCTION. upon the surface of an old pavement, the binder or cushion coat is used to fill up the inequalities and bring its' surf ace to the uniform grade and contour. 252. Failure of Asphaltic Cement Pavements. The failure of this class of pavement may be attributed to any one or all of the following causes: (1) Unsuitable asplialtum. (That is, asphaltum which has been so changed by natural causes as to possess little or no cementing power.) (2) Too high temperature in refining the crude asphaltum. (That is, a temperature which converts the petroleue or cementing me- dium of the asphaltum into asphaltene and thus reduces or entirely destroys its cementing qualities.) (3) Too low a temperature continued for a considerable length of time. (This has the same effect as a high temperature for a short time, and is analogous to the action of solar heat, which through ages has been changing the liquid bitumen wherever exposed into asphaltum.) (4) Unsuitable fluxing agents, (Such as those which are not solvents of the asphaltene and thus form a mechanical instead of a chemical union, or fluxes which contain volatile oils, which under the action of solar heat evaporate from the pavement and leave it porous and in a condition to absorb rain-water, the oxidizing action of which is to gradually convert the petrolene or cementing agent of the bitumen into asphaltene, thus rendering the pavement brittle, in which condition it is easily broken up under the action of the traffic.) (5) Unsuitable temperature employed during the process of flux- ing. (That is, either a high temperature for a short time or a low one for a long time, the effects of which are similar to those stated under 2 and 3.) (6) Unsuitable sand. (That is, sand either too coarse or too fine, or a sand of suitable fineness, but containing loam, vegetable matter or clay. The sand should be clean, sharp, large-grained, and not too uniform in size, well screened and if necessary washed. The presence of clay prevents that intimate contact between the cement and the grains of sand so essential to a homogeneous body, because the particles of clay adhere to the grains of sand and form diaphragms between it and the cement. The sand imparts crushing strength ASPHALTUM AND COAL-TAR PAVEMENTS. 217 and fulfils practically the same offices as in hydraulic cement mor- tar, therefore its quality should be in all respects equal to that used in the best mortar for important structures.) (7) Use of limestone-dust. (This material is speedily dissolved by rain-water and some of the organic acids found in streets ; its dissolution leaves the pavement in the same condition and exposed to the same agent of destruction as described under cause 4.)* (8) Insufficient mixing of the ingredients. (Whereby the ce- ment and the particles of sand are not brought into intimate contact ; to secure a strong mortar or concrete it is essential that each piece of the aggregate shall be entirely surrounded by the cementing material, so that no two pieces are in actual contact.) (9) Insufficient quantity of cement. (The quantity of cement required to coat each particle of the sand will vary with the char- acter of the sand ; if the grains in a given volume are small, the magnitude of the total surface to be covered is greater than when the grains are large; hence a fine sand requires more cement than a coarse one ; therefore the proportion of the cement must be varied to suit the character of the sand to be used, or else the quality of the pavement will be impaired.) (10) Laying the paving composition on a wet foundation. (When hydraulic concrete is used as the foundation, it must be set and thoroughly dry before the asphalt is laid upon it; if not, the contained water will be sucked up and converted into steam, which tries to escape through the heated material ; the result is that co- herence of the asphaltic mixture is prevented, and, although its surface may be smooth, the mass is really honeycombed, and as soon as the pavement is subjected to the action of traffic the voids or fissures formed by the steam appear on the surface, and the whole pavement is quickly broken up.) f * The results obtained from several experiments indicate that the presence of finely divided amorphous calcium carbonate, calcium oxide, silicic oxide, or free or fixed carbon is detrimental to asphaltum. The action of these sub- stances is to take up the oily constituent and pass it from one particle to another until the surface of the mass is reached, where it is expelled in such a metamorphosed condition that the oil is changed from a partial non-volatile to a slowly or even a rapidly volatile state at ordinary temperatures, and in some cases a portion at least in gaseous form. The effect of this action is to produce a porous mass easily disintegrated. f The length of time which should elapse before the asphalt is laid upo'n 218 HIGHWAY CONSTRUCTTOX. (11) Weak or insufficient foundation. (A weak or improperly prepared foundation will, by unequal settlement and settlement in spots, cause cracks and depressions in the asphalt surface which under traffic will be speedily enlarged, and the pavement will there- fore be broken up.) (12) Use of paving mixture which has become chilled. (Al- though asphaltum is a bad conductor of heat, and the cement re- tains its plasticity for several hours, occasions may and do arise through which the composition before it is spread or rolled has cooled; its condition when this happens is analogous to hydraulic cement which has taken a " set," and the same rules which apply to hydraulic cement in this condition should be respected in regard to asphaltic cement.) (13) Insufficient compression. (To prevent the admission of the rain and other water falling upon the surface of the pavement, and its destroying effects, it is necessary that the paving composition be compacted into a solid homogeneous mass; if not, the oxygen con- tained in the water will have the effect described under cause 4.) (14) Lack of water-tight connection with street furniture, curbs, and crossings, which permits the entrance of water under the as- phaltic surface. (15) Destruction by natural causes. (All materials in nature are undergoing changes due to the action of the elements, and asphal- tum is no exception. Under the action of solar heat and water all the bitumens undergo a change ; this change is due to evaporation, volatilization, and oxidation, and tends at first to greater solidifi- cation or hardness. When the maximum degree of hardness is at- tained, natural decay apparently commences, and under the com- bined action of organic acids, rain-water, and frost the material seems, so to speak, to rot and finally disintegrate. At any stage of the change the substance is still asphaltum and the process is termed "ageing," and a great deal of the controversy regarding the relative qualities of different asphaltums is due to ignoring the changes wrought by nature. While these changes are slow in the concrete depeuds upon two conditions ; the character of the cement and atmospheric conditions. It is desirable that ten days at least should elapse before surfacing, accompanied in warm weather by frequent sprinkling. There is no objection to lay surface in cold weather if proper attention is paid to the temperature of the mixture. ASPHALTUM AND COAL-TAR PAVEMENTS. 219 nature, some or all of them may be hastened by the unskilful application of artificial heat in preparing the material, and by the action of the organic acids and rain-water falling upon the pave- ment. The failure or disintegration of an asphalt pavement manifests itself in different ways according to the cause and character of the pavement. Disintegration caused by water entering the pavement either from the surface or through the base manifests itself differently, depending upon the character of the pavement. If the asphalt sur- face is soft, or the surface of the concrete" smooth, the first defect noticed will be the tendency of the pavement to become wavy in warm weather. This is due to the under portion of the surface mixture rotting, so to speak, thus destroying the cementing properties of the asphalt. The upper portion, although good, being deprived of the support of the affected mixture under it, will be crowded out by the traffic. This crowding is assisted by the surface of the base being smooth, and also by the bond between the base and binder being destroyed by the moisture* In cases where the surface of the base is rough and the surface mixture hard the principal disintegration will take place in cold weather, nothing abnormal being noticed until the pavement begins a rapid crumbling away in the affected spot under traffic. On examining a section of asphalt surface disintegrating from t'his cause, especially where it has not been going on for too long a time, there will be found a layer of perfectly sound and good material at the surface of the pavement, while underneath the mix- ture will show evidence of being disintegrated by water; that is, the sand will appear clean and white in spots, as though there had been a deficiency of asphalt cement to cover it. The base under the affected pavement will generally be found damp or even wet. In Washington, D. C., the destruction of several pavements from this cause has been prevented by the use of blind drains put in under the gutter next to the lawn or terrace, and in some cases having bone drains placed under the pavement. Disintegration caused by unsuitable oils or coal-tar in the binder is manifested by a slight depression over the affected spots. In time numbers of small cracks appear, running parallel with the 220 HIGHWAY CONSTRUCTION. street; these gradually increase in importance, accompanied with transverse cracks, until the pavement has the appearance of an alli- gator-skin. On examining a section of the surface mixture cut from the affected spot it will be found to be quite soft near the binder, if the disintegration has not proceeded for a length of time; if older, the soft zone will be nearer the surface, while the bottom of the mixture will show the disintegrating effect of the water that has likely entered the pavement through the crack. The affected piece of mixture will smell strongly of coal-tar (if coal-tar was used in the binder), and will, in all cases, give a greenish fluorescence to a solution in carbon disulphide. The portion of the pavement thus acted on will be crowded or worn out by the traffic until nothing is left of it. If the surface mixture is soft, the pavement will roll at this place, the soft affected material crowding before the traffic. Binder made with asphalt cement, in some few cases, affects the surface mixture in the same way, due probably to the presence of some free oil, which may not have been properly incorporated with the asphalt in making the binder cement. Disintegration caused by the absorption of illuminating-gas be- comes apparent in very much the same way as when coal-tar is the cause, except that the fine cracks, running parallel with the street, make their appearance some time before the pavement begins to roll. Pieces of the surface mixture taken up smell very strongly of illuminating-gas, and in some cases the gas can be ignited by apply- ing a match to the under surface when it has just been taken up. In nearly every case enough gas will be given off by heating a small piece of the affected pavement in a tube to have it flash by ignit- ing. (See Art. 226.) Disintegration caused by a deficiency of asphalt cement will be made apparent by cracking and crumbling during cold weather. Defective bond between base and binder, or between binder and wearing surface, is shown by rolls and waves. (See also Art. 3036.) 253. Trinidad Asphalt Pavements. The source of the asphal- tum used in this class of pavement is described in Art. 100. The characteristics of the crude asphaltum are given in Art. lOQd. The method of refining is described in Art. lOOe. The characteristics of the refined asphaltum are given in Art. ASPHALTUM A1STD COAL-TAR PAVEMENTS. 221 100^, and the relative qualities of "lake" and "land" asphaltum are discussed in Art. WOp. The paving material consists of silicious sand and stone-dust (usually limestone) cemented together with asphaltic cement, man- ufactured as described in Art. 96. The proportions of the ingre- dients are not constant, but vary with the climate of the place where the pavement is to be used, the character of the sand, and the amount and character of the traffic that will use the pave- ment; the range in the proportions is as follows : Asphalt cement 12 to 15 per cent. Sand . 83to70 " " Stone-dust '. 5 to 15 " " 100100 The sand and asphaltic cement are heated separately to about 300 F. The stone-dust (pulverized carbonate of lime) is added to the hot sand in the required proportions, and is then mixed with the hot asphaltic cement in a suitable mixing machine and thor- oughly incorporated; when this is accomplished, the mixture is ready to be laid on the street. Specifications for Trinidad asphalt pavements are given in Ar- ticles 262, 263, and 264. 254. The proportions of the materials for the Trinidad asphalt pavements at Washington, D. 0., average as follows : Weight of Cranford. Barber. Pounds. Per cent. Pounds. Per cent. Sand 584 54 30 111 75.0 6.9 3.8 14.3 637 60 35 125 74.3 7.0 4.1 14.6 Limestone d ust Asphalt cement COMPOSITION OF PAVING MIXTURES. 255. The following table shows the maximum, minimum, and average per cent of the bitumen, and the mesh composition of the sand, in the paving mixtures used at Washington, D. C., during 1899: 222 HIGHWAY CONSTRUCTION. Eastern Cranford Bermudez Paving Co. Paving Co. Number of samples 29 62 Average per cent bitumen 10.7 10.7 Lowest " " " 9.1 9.3 Highest " " " 12.0 12.3 Sand Per cent retained on sieve having 20 mesh per inch 2.5 3.0 40 " " " 20.0 25.5 60 " " " 31.9 38.3 80 " " " 8.3 7.0 100 " " " 10.8 6.5 Passed 100 mesh 26.0 18.5 256. Memoranda. One ton of refined asphaltum mixed with the flux makes about 2300 pounds of asphaltic cement, equal to about 3.4 cubic yards of paving material. One cubic yard of paving mixture contains one cubic yard of sand, 675 Ibs. of asphaltic cement, and 490 Ibs. stone-dust; weighs about 4500 Ibs., depending upon the character of the sand; and will lay the following amount of surface : 2 inches thick 12 square yards 2 " " 18 " 1 " " 27 " 257. Temperatures. Refining, not over 400 F. Fluxing, " " 325F. Sand Lowest 250 F. Highest 300 F. In cold weather not lower than 280 F. Mixing ingredients 275 F. When spreading not lower than 250 in summer or 275 F. in winter. Never over 300 F. Cold or chilled mixture should not be used. No compaction can be secured with such material. It is doubtful if surface mixture can be successfully reheated. 258. Extracts from the Reports of City Civil Engineers. Washington, D. C. (Capt. Greene, 1885). The Trinidad asphalt has been the standard pavement for the last seven years, about 600,000 square yards having been laid on a foundation of hydraulic concrete, and about 160,000 yards more on the stone foundations of the worn-out tar pavements. Its cost for the last three years has been about $2.25 per square yard. When made with skilled ASPHALTUM AND COAL-TAR PAVEMENTS. 223 labor and laid under proper supervision it seems to answer all the requirements of a first-class pavement in this city. It is almost noiseless, not slippery, under ordinary conditions offers little resist- ance to traction, is easily repaired and cleaned, and is very dur- able. Large numbers of streets have been laid five, six, and seven years, and are in perfect order, although not a cent has been ex- pended on them for repairs. On other streets mistakes have occasionally been made in the mixture, and defects have appeared which needed repairs. Nearly all these repairs have been made at the contractor's expense during his guarantee period; but as nearly as it can be ascertained the total expense both to contractors and the District for repairing asphalt pavements during the eight years since they were first laid has been about $30,000, or $3750 per year, so that the average annual expense for maintenance up to date has been T 9 of one cent per yard per year. This is certainly a small expense for the luxury of smooth pavements, and much less than for any other pavement having the combined durability and smooth- ness of the asphalt. 259. The French Asphalt Pavement, made from the natural bituminous limestone of Switzerland, and similar in every respect to the asphalt pavements as laid in Paris, was tried here in 1873 and 1876, 31,388 yards having been laid on the following streets, viz. : Pennsylvania Avenue, between First and Sixth streets ; I Street, betwen Thirteenth and Fifteenth streets ; and Grant Place, between Ninth and Tenth streets. Experience has shown that this pavement is more slippery than the pavement of sand and Trinidad asphalt, and that it is not quite as durable. Its cost is nearly fifty per cent greater; for these reasons no more of it has been laid. 260. Buffalo, N. Y. The streets paved with asphalt have stood the extreme changes of this climate without any serious defect, are giving satisfaction to our people, being healthful, easily kept clean, smooth, yet not slippery. 261. Omaha, Neb. " Our temperature varies as much as 150 degrees Fahr., between the extremes of summer and winter. We are subject to rapid changes of temperature, which in the winter season occasionally are as high as 60 degrees in twenty-four hours. Doug- lass Street, which was paved in the fall of 1882 and spring of 1883, has experienced a range of temperature of from 120 degrees in the summer to 34 degrees below zero in the winter. . . . Our experience 224 HIGHWAY CONSTRUCTION. is very favorable to asphalt pavements on all grades ranging from 6 inches to 4 feet rise per 100 feet, and I am not sure but that as high as 5 or 6 feet per 100 feet may be favorably overcome. The asphalt pavement is not as cheap as wood, but, in my opinion, a preferable pavement upon permanently established and well-im- proved streets. It is not quite as easy for horses as wood, but more comfortable for those who ride, is more cleanly, and from a sanitary standpoint far superior." 262. Heads of Specifications for Standard Trinidad Asphaltum Pavements. (1) Preparation of Roadbed. (2) Foundation. (Hydraulic-cement or bituminous concrete.) (3) The Wearing Surface will be composed of (a) Refined Trinidad asphaltum. (b) Heavy petroleum oil. (c) Find sand containing not more than one per centum of hydrosilicate of alumina. (d) Fine stone-dust. (e) Fine powder of carbonate of lime. (4) Preparation of the Asphalt. The Trinidad asphaltum shall be refined, and as far as possible freed from foreign organic and animal matter and volatile oil, and brought to uniform standard of purity and gravity, containing not less than 60 per cent of bitumi- nous matter soluble in bisulphide of carbon. The asphaltum must be refined under the direction and to the satisfaction of the engineer, and kettles will not be drawn lower than may be ordered by him. The heavy petroleum oil shall be freed from all impurities and brought to a specific gravity of from 18 to 22 degrees Beaume and a fire test of 250 degrees Fahrenheit. From these two hydro carbons shall be manufactured an asphalt cement which shall have a fire test of 250 degrees Fahr., and at a temperature of 60 degrees Fahr. shall have a specific gravity of 1.19, said cement to be composed of 100 parts of pure asphalt and from 15 to 20 parts of heavy petroleum oil. (5) Manufacture of the Paving Material The asphalt being prepared in the manner above described, the pavement mixture will be formed of the following materials, and in the proportions stated. ASPHALTUM AND COAL-TAR PAVEMENTS. 225 Asphaltic cement from 12 to 15 Sand " 83 " 70 Pulverized carbonate of lime " 5 " 15 or Asphaltic cement from 13 to 16 Sand " 63 " 58 Stone-dust " 28 " 23 Pulverized carbonate of lime " 3 " 5 The proportion of the materials will depend upon their char- acter and the traffic on the street, and will be determined by the engineer. If the proportions of the mixture are varied in any manner from those directed to be used, the mixture will be con- demned ; and if already placed on the street, it will be removed and replaced by proper material, at the expense of the contractor. The sand, stone-dust and asphaltic cement are to be heated sep- arately to about 300 degrees Fahr. The pulverized carbonate of lime while cold shall be mixed with the hot sand and stone-dust in the required proportions, and then mixed with the asphaltic cement at the required temperature, and in the proper proportion, in a suitable apparatus, which will effect a perfect mixture. The pro- portions will be gauged daily in the presence of the inspectors. (6) Quality of the Materials. All the materials used, as well as the plant and method of manufacture, will be subject to the inspec- tion and approval of the engineer. The degree of fineness, both of the sand, stone-dust, and powdered limestone, will be determined by testing with screens, as follows: The powdered carbonate of lime will be of such degree of fineness that 15 per cent by weight shall be an impalpable powder of limestone, and the whole of it shall pass a No. 26 screen. The sand will be of such size that more than 50 per cent of it will pass a No. 80 screen, and the whole of it shall pass a No. 20 screen. The stone-dust shall be the residue of granite or other approved stone, and shall pass a sieve of not more than 6 meshes to the inch. (7) Laying the Asphalt. (Two-coat Pavements.) The pave- ment mixture, prepared in the manner thus indicated, shall be laid on the foundation in two coats. The first coat, called cushion-coat, shall contain from 2 to 4 per cent more asphaltic cement than given above; it will be laid to such depth as will give a thickness of inch after being consolidated by a roller. The second coat, 226 -HIGHWAY CONSTRUCTION. called surface-coat, prepared as above specified, shall be laid on the cushion-coat; it shall be brought to the ground in carts at a tem- perature of about 250 degrees Fahr., and if the temperature of the air is less than 50 degrees iron carts with heating apparatus shall be used in order to maintain the proper temperature of the mix- ture; it shall then be carefully spread by means of hot iron rakes, in such manner as to give a uniform and regular grade, and to such depth that after having received its ultimate compression it- will have a thickness of 2 inches. The surface then shall be com- pressed by hand rollers, after which a small amount of hydraulic cement shall be swept over it, and it then shall be thoroughly com- pressed by a steam roller weighing not less than 250 pounds to the inch run ; the rolling to be continued for not less than five hours for every 1000 yards of surface. (8) Laying the Asplialt. (One-coat Pavement.) The pavement mixture, prepared in a manner thus indicated, will be laid on the foundation ; it will be laid to such depth as will give a thickness of 2|- inches after being consolidated by rollers. It will be brought to the ground in carts, at a temperature of not less than 250 de- grees Fahr. nor more than 310 degrees Fahr., and if the tempera- ture of the air is less than 50 degrees the contractor must provide Ctmvas covers for use in transit. It will then be carefully spread by means of hot iron rakes, in such manner as to give uniform and regular grade and to such depth that, after having received its ultimate compression of two fifths, it will have a net thickness of 2J inches. This depth will be constantly tested by means of gauges furnished by the engineer. The surface will then be com- pressed by hand rollers, after which a small amount of hydraulic cement will be swept over it, and it will then be compressed by a steam roller weighing not less than 5 tons, to be followed by another steam roller weighing not less .than 10 tons, the rolling being con- tinued for not less than 10 hours for every 1000 yards of surface. (9) In order to make the gutters entirely impervious to water, a width of 12 inches next the curb will be coated with hot pure asphalt and smoothed with hot smoothing-irons in order to saturate the pavement to a certain depth with an excess of asphalt; or if so directed by the engineer, the gutters will be formed with gutter- stones, granite blocks, or bricks, in accordance with the specifica- tions for such work. ASPHALTUM AND COAL-TAR PAVEMENTS. 2*27' (13) Laying Granite Blocks adjoining Railway Tracks. When asphalt pavement is laid in a street containing the tracks of a street railroad one row of selected granite paving-blocks will be laid next to the track. The foundation will extend to the depth of the bottom of the cross-ties, and will be similar in all respects to the foundation of the carriageway pavement, except as to the thickness of the base. If the foundation consists of bituminous concrete, the blocks will be laid directly upon and embedded in the binder while it is still in a hot and plastic condition. If the foun- dation consists of hydraulic-cement concrete, the base will be cov- ered with a layer of fine sharp sand, washed and dried, 2 inches in. thickness, and the blocks will be laid directly upon and embedded, in the sand with close joints. The top of the blocks will be even with the surface of the tread of the rail, which shall conform with the grade of the street. The: blocks will be laid before the asphaltic wearing surface is laid upon the carriageway, and carefully rammed to a firm bed. Care will be taken to fit them well up against the stringers or web of the rail of the railroad. The space back of the blocks will be filled to the surface of the base for the carriageway pavement with the same material as is used for said base, well rammed. Immediately after the wearing surface shall have been laid,, clean, fine, hot gravel, not larger than one-half inch in any direction, will be poured into the joints of the blocks until they; become nearly filled. There will then be poured into the joints, at a temperature of 300 degrees Fahr., paving cement made of No. (>' coal-tar distillate, until the joints are completely filled flush with; the surface of the pavement. Additional fine hot gravel will thenr be poured along the joints, and will be consolidated by tapping; with a light rammer. If found necessary additional paving cement will be poured between the blocks until the joints are thoroughly filled. In measuring this work for payment, when standard size gran- ite blocks are used, the area included between the outer edge of the rail and a line parallel to and six inches from rail will be taken as the area of granite-block pavement laid. Bids will be based on this rule. When so ordered, the block pavements will be extended to cover the entire area included between the rail and parallel to. 223 HIGHWAY CONSTRUCTION. and 2 feet distant from said rail. In case the tracks are laid with a grooved girder rail, these blocks may be omitted if so ordered by the engineer, and the asphalt pavement laid close to the rail. (11) The work of laying the asphalt shall not begin until the curbstones, crosswalks, catch-basins, manhole heads, etc., have been properly adjusted to the finished grade of the street, and permis- sion to proceed has been received from the engineer. (12) Interpretation of specifications. (13) Omissions in specifications. (14) Engineer defined. (15) Contractor defined. (16) Notice to contractors, how served. (17) Preservation of engineer's marks, etc. (18) Dismissal of incompetent persons. (19) Quality of materials. (20) Samples. {21) Inspectors.* (22) Defective work, responsibility for. (23) Measurements. {24) Partial payments. (25) Commencement of work. (26) Time of completion. (27) Forfeiture of contract. (28) Damages for non-completion. {29) Evidence of the payment of claims. (30) Protection of persons and property. {31) Indemnification for patent claims. (32) Indemnity bond. {33) Bond for faithful performance of work. (34) Power to suspend work. (35) Right to construct sewers, etc. (36) Loss and damage. (37) Old materials, disposal of. (38) Cleaning up. (39) Personal attention of contractor. (40) Payment of workmen. * An inspector should be placed at the plant of the contractor, to know what course is pursued ; otherwise the municipality has no data for studying the various mixtures nor does it know that the contractor is carrying out the specifications. ASPHALTUM AND COAL-TAR PAVEMENTS. 229 (41) Prices. (42) Security retained for repairs. (43) Payment when made, final acceptance. 263. Specifications for Asphalt Pavement on Bituminous Base. Combination asphalt pavement on bituminous base will consist of a base 4 inches, a binder of 1| inches, and a wearing surface of H inches in thickness, when compacted. The space over which the pavement is to be laid will be ex- cavated to the depth of 7 inches below the top of the surface of the pavement when completed. Any objectionable or unsuitable ma- terial below the bed must be removed, and the space filled exactly parallel to the surface of the new pavement when completed ; and the entire roadbed will be thoroughly rolled with a heavy steam- roller weighing not less than 5 tons. Upon the foundation will be laid the base and binder, 5 J inches in thickness, in the following manner : Base. The base will be composed of clean broken stone that will pass through a 3-inch ring, well rammed and rolled with a. steam-roller weighing not less than 5 tons, to a depth of 4 inches. The rolling will be continued until the stone ceases to creep before the roller, and until it is evident that the final compression has been reached. It will be thoroughly coated with No. 4J coal-tar paving cement in the proportion of about one gallon to the square yard of base. Binder. The second or binder course will be composed of clean broken stone, thoroughly screened, not exceeding 1 inch in the largest dimension, and No. 4 coal-tar paving-cement. The stone will be heated to a temperature between 230 and 250 degrees Fahr., by passing through revolving heaters, and thoroughly mixed by machinery with the paving-cement in about the proportion of one gallon of No. 4 tar to one, cubic foot of stone. It will be hauled upon the work, spread upon the base course to such thick- ness that when compacted it will be 1J inches thick, and immedi- ately rammed and rolled with hand and steam rollers while in a, hot plastic condition. Wearing Surface. The wearing surface will be 1J inches thick when compacted, and will conform in all other respects to the wearing surfaces as prescribed for the standard asphalt pavement, as described in these specifications. 230 HIGHWAY CONSTRUCTION. The pavement so constructed must be a solid mass, 7 inches thick, and must be thoroughly rolled and cross-rolled until it has become hard and solid. Gutters, wherever directed, will be formed of granite-block or l>rick, of such width as may be directed, laid upon a hydraulic base of not less than 4 inches in thickness, in accordance with the speci- fications for granite-block pavement and for brick gutters. 264. Specifications for Asphalt Pavement on Hydraulic Base. The asphalt pavement on hydraulic base will be 7 inches in thick- ness, consisting of a base composed of 4 inches of hydraulic con- crete and 2 inches of binder, 1J inches when compacted, and a wearing surface of standard asphalt, 2J inches in thickness, or 1| inches when compacted. Binder Course. The binder course will conform in all respects to the binder course for the asphalt pavement on bituminious base, .and will be 1J inches in thickness when compacted. Wearing Surface. The wearing surface will be 1J inches thick ~when compacted, and will conform in all other respects to the wear- ing surfaces as prescribed for the standard asphalt-pavement. 264a. Specifications for Asphalt Pavement on the Surface of an Old Pavement. The surface of the old pavement shall be thor- oughly cleansed by sweeping with stiff brooms until all the dirt, etc., lias been removed from the surface and from the joints to a depth of about one inch. The surface shall then be brought to a uniform grade and cross- section by excavating where necessary, and by filling and repairing all depressions with bituminous concrete or binder, this binder to be composed of clean broken stone, the fragments of which shall not exceed one and one quarter inches in their largest dimensions, and asphaltic pavement cement (or coal-tar paving-pitch). The stone shall be heated in suitable heating apparatus, and -shall be thoroughly mixed with the paving cement in the propor- tion of 12 to 15 per cent of asphalt paving cement (or one gallon of paving-pitch) to one cubic foot of stone. This binder shall be spread to such thickness that, after being thoroughly compacted by tamping and rolling, its thickness shall be not less than one inch, and its surface shall be exactly parallel with the surface of the pavement to be laid upon it. Upon this foundation the wearing surface or pavement proper of asphaltic cement shall be laid. (See also Articles 262, 263, 264.) ASPHALTUM AND COAL-TAR PAVEMENTS. 231 264b*. Specifications for Asphalt Pavement, Washington, "0. C., 1899 Binder. The binder course shall be composeu of clean., sound stone broken into fragments of such size that 85 per cent of the whole amount will pass through a screen haviog 1^-inch meshes, and of the remaining 15 per cent no piece shall have a larger dimension than 2 inches, and the stone after passing the heating-drums shall not contain less than 5 nor more than 10 per cent of material passing a No. 10 screen. The stone shall be heated not higher than 350 F. in suitable apparatus. It shall then be mixed thoroughly by machinery with the asphaltic cement, which shall be of the same quality as that used for the wearing surface, and having a penetration on Bowen's scale of 100 to 200, in such proportions that the mixture will have life and gloss without an excess of cement. Should it appear dull from overheating or lack of cement, it will be rejected. While hot it will be hauled upon the work, spread upon the base to such depth that when compacted it will be at least 1^ inches in thickness, and immediately rammed and rolled until it is cold. Should the resulting course not show a proper bond, it shall be immediately removed and replaced by the contractor. Asphaltum. The crude asphaltum shall be refined to the satis- faction of the engineer. Flux. Petroleum residuum, Pittsburg flux, maltha, or any other softening agent complying with the required tests may be used. (See Art. Q7d for specifications of petroleum residuum.) Asphaltic Cement. When the refined asphaltum is not already of the proper consistency the cement shall be prepared by temper- ing refined asphaltum with petroleum residuum or other approved softening agent, at a temperature between 250 and 350 F. The asphalt cement must not be inferior in quality to a cement made of the best quality Trinidad asphalt and petroleum re- siduum. Its penetration must be within the range of 60 and 120 on Bowen's scale, and will be fixed by the engineer. A variation of 10 from the degree decided upon willbe sufficient for rejecting the mixture. Samples of the asphalt, flux, and asphaltic cement must be furnished the engineer as required. Sand. The sand used shall be hard and moderately sharp. 232 HIGHWAY CONSTRUCTION. On sifting, at least 15 per cent should be retained in a 40-mesh-per- inch sieve, 25 per cent that will pass 80-mesh-to-the-inch sieve, 10 per cent of which at least must pass a 100-mesh-to-the-inch sieve. If the sand does not contain the desired fine material, limestone dust or other suitable material can be added to make up the deficiency. Inorganic Dust. This shall be any inorganic dust not acted upon by water, the whole of which shall pass a 30-mesh screen and at least 75 per cent pass a 100-mesh screen. Manufacture of the Paving Mixture. The materials comply- ing with the above specifications shall be mixed in proportions by weight, depending upon their character and the traffic on the street and upon the character of the asphalt, determined by the engineer, but the percentage of bitumen in any mixture soluble in carbon bisulphide shall not exceed the limits, 9 to 13 per cent. If the proportions of the mixtures are varied in any manner from those decided upon, the mixture will be condemned, its use will not be permitted, and if already placed on the street it will be removed and replaced by proper materials at the expense of the contractor. The sand or the mixture of sand and stone dust and the asphaltic cement will be heated separately to about 300 F. The dust, while cold, will be mixed with the hot sand in the required proportion and then mixed with the asphaltic cement at the required temperature and in the proper proportion, in a suitable apparatus, so as to effect a thoroughly homogeneous mixture. Sand-boxes and asphalt-gauges will be weighed in presence of inspectors as often as may be desired. Samples as desired shall be furnished the inspector in suitable boxes, and he shall have access to all branches of the works at all times. 265. Maintenance of Asphalt Pavements under Contract. The contractors will furnish all the labor and materials necessary to make repairs and renewals required to preserve the surface in a perfect state, true to the profile, without humps or depressions, even if the dilapidations are the result of accidental causes, as sink- ing of the subsoil, etc., except only the digging of trenches. The contractor must renew all places where the surface is cracked, split, ASPHALTUM AND COAL-TAR PAVEMENTS. 233 depressed, swelled, or in any way perforated, where it matches un- evenly with manhole heads and other street fixtures, etc., and especially where sunken near trenches. Where the foundation is defective, it shall be removed and re- placed with good material. Defective spots must be carefully cut out with a sharp tool, and at least 2 feet larger in every direction than the defective place; the sides must be cut on straight lines ; there must be a perfect union of the old and new material, and the surface must show no irregularities. On September 1st, or sooner in case of bad weather, a general examination will be made with the contractor, who must immedi- ately begin repairs on doubtful surfaces, not likely to endure through the winter. In rainy weather the bottoms of patches must be sponged and dried as carefully as possible with fine hot ashes, and then be well brushed. Special care must be taken to clean all sand, powder, etc., from the bottom of patches. During bad weather no repairs shall be made to the asphalt, unless expressly authorized by the engineer. Patches made during winter are to be considered as only temporary, and must be replaced by the 15th of May. The contractor is absolutely forbidden to use pebbles for filling holes in the asphalt. When the contractor fails to make the neces- sary repairs, and the administration, exceptionally and in default of other available means, fills the holes with broken stone or other material, the contractor must pay for the work and materials, and cannot claim damages for injury to the pavement caused by such materials. In winter, holes in the foundation may be filled with a mixture of 3 parts by volume of pebbles to 1 part of hot asphalt; but this, provisional filling must be removed as soon as possible and replaced in the standard manner. The contractor will be paid for repairs to all trenches opened in the street. He can, however, make no claim for settlement or any other injury at these places, and must maintain the pavement there in the same condition as elsewhere. To secure a perfect welding at the edges of the asphalt, a width of 2 inches greater in every direction than the trench will be paid for. To provide for settlement of the earth in the trenches, the con- tractor may maintain the area occupied by the trench, during a 234 HIGHWAY CONSTRUCTION. period of eight days, with broken stone or gravel, well rammed, sprinkled, swept, and maintained, so as to prevent injury to horses. If after eight days final repairs are still impossible, the contractor must at his own expense make a provisional surface of bituminous concrete, which will be removed for final repairs. If for any reason it becomes necessary to tear up asphalt pave- ments, it shall be done as follows : It will be cut in as straight lines as possible with sharp chisels, and when torn up must on no ac- count pull up with it any of the adjacent material. Then the concrete is to be cut by sharp chisels in lines about 3 inches from the edge of the asphalt, which may be broken into pieces and laid aside. In removing the earth from the excavation, care must be taken that no portion of the concrete is undermined. 265a. The " Bermudez " Asphalt, recently introduced for paving purposes, is obtained from a lake or deposit which covers an area of several hundred acres in the state of Bermudez, Venezuela, 8. A. (See also Art. 101.) The purity and quality are said to be exceedingly high ; the fol- lowing analysis is given by Prof. E. J. De Smedt : Bitumen soluble in CS 2 .. 97.86 percent Organic and inorganic matter (impurities) 2. 14 " 100.00 per cent The following are some of the characteristics of this asphalt : At 60 F. compressible; at 70 F. viscous and malleable; at 100 F. flowing, and can be stretched in hair-like threads; at 189 F. melts; at 400 F. gives no flash. The paving-cement is manufactured by adding 15 Ibs. of re- siduum oil, 20 Baume at 60 F., to each 100 Ibs. of refined asphalt. This 100 Ibs. of refined asphalt yields 97. 06 Ibs. of pure bitumen; consequently 13^ per cent of oil is added to the pure bitumen. The asphalt is melted at from 250 to 300 F. The oil is then added and thoroughly mixed with the melted asphalt. The pavement mixture is composed of the following materials and in the proportions stated: Aspbaltic cement 9 to 10 parts Pulverized carbonate of lime 20" 30 ' Fine clean sand 71" 60 " [ 100 100 ASPHALTUM AND COAL-TAR PAVEMENTS. 235 The sand and carbonate of lime are mixed and heated to from 250 to 300 F. The asphaltic cement is heated separately to from 225 to 250 F. The materials so heated are mixed in a suitable mixing apparatus, and the mixture while at a temperature not below 200 F. is spread upon the foundation in two coats, the lower or cushion coat being one-half inch thick after compression, and the second or wearing coat being two inches thick after final compression with a roller weighing not less than 250 Ibs. per inch run. A small amount of hydraulic cement is swept over the surface before the application of the roller. It is claimed that pavements made from this asphalt do not rot in contact with water. One square yard of pavement 2J inches thick weighs 250 Ibs. 266. European Asphalt Pavements. In Paris two kinds of as phalt pavement are employed. First, asphalt coule, made from natural rock asphalt to which is added sufficient bitumen to make the total 15 to 18 per cent of bitumen. The mass is heated for about six hours so as to make a thorough mixture. The ground having been graded, sprinkled and thoroughly rammed or rolled, a bed of hydraulic-cement concrete from 4 to 6 inches thick is laid, and after this is set and well dried the asphalt mixture is spread and surfaced by a wooden float. The thickness of the asphalt is about 1 inches, and it is usually applied in two layers. This covering will not soften at a temperature of 140 degrees Fahr. 267. The second kind of asphalt covering is asphalt comprime, or compressed asphalt. In this the natural rock alone is used. It comes from Yal de Travers in Switzerland, Seyssel in France, and other localities, and consists of carbonate of lime impregnated with bitumen. The color is a dark (almost black) chocolate-brown. When cold the rock breaks easily, with an irregular fracture and without definite cleavage. Its grain should be regular and homo- geneous; the finer the grain the better. When exposed to the atmos- phere the bituminous rock gradually assumes a gray tint, by reason of the bitumen evaporating from the surface, leaving a thin film of limestone behind. 268. The following is a test for bituminous rock given by Mr. Delano in a paper he read before the Institution of Civil En- gineers in the year 1880. " A specimen of the rock, freed from all 236 HIGHWAY CONSTRUCTION. extraneous matter, having been pulverized as finely as possible, should be dissolved in sulphurate of carbon, turpentine, ether, or benzine, placed in a glass vessel and stirred with a glass rod. A dark solution will result from which will be precipitated the limestone. The solution of bitumen should then be poured off. The dissolvent speedily evaporates, leaving the constituent parts of the bitumen, each of which should be weighed so as to determine the exact proportion. The bitumen should be heated in a lead bath and tested with a porcelain or Baume thermometer to 428 degrees Fahr. There will be little loss by evaporation if the bitumen is good, but if bituminous oil is present the loss will be considerable. Gritted mastic should be heated to 450 degrees Fahr. The limestone should be next examined. If the powder is white and soft to the touch, it is a good component part of asphalt; but if rough and dirty, on being tested with reagents it will be found to contain iron pyrites, silicates, clay, etc. Some bituminous rocks are of a spongy or hygro- metriral nature; thus, as an analysis which merely gives so much bituir.en and so much limestone may mislead, it is necessary to know the quality of the limestone and of the bitumen/' The European bituminous limestone appears like a fine-grained rock, friable in summer, hard in winter. When heated to 50 or 60 degrees (centigrade) it can be crushed between the fingers, and if exposed for several hours to a fierce sun it crumbles into unctuous brown powder. Examined under the microscope it is found to consist of minute calcareous grains, each covered with a thin film of bitumen which causes them to adhere together. If a small por- tion is heated, the cementing bitumen is melted and releases the solid particles from a loose heap of a deep chocolate color. If this powder is raised to 175 or 212 degrees Fahr. and rapidly com- pressed in a mould, it will regain, in cooling, its original consistency in the new form. And the process may be indefinitely repeated, no change being produced by melting, followed by compression and cooling. 269. The best material used by the " Compagnie Generale des Asphaltes de France " comes from the Pyrimont mines of the Seyssel region in the Department of Haute Savoie and Litin, France. The workings are in great part subterranean and the deposit lies in eight superimposed beds separated by beds of white limestone. One of these bituminous beds lies about 100 feet above ASPHALTUM AND COAL-TAR PAVEMENTS. 237 the level of the Rhone and has a thickness of 23 feet; it is the largest of all known beds of this material. The galleries nor* driven aggregate about seven miles in length. - 270. The rock is extracted in a temperature ranging from 53 to 55 degrees Fahr., and it is relatively hard. This desirable quality can be increased by taking it outside during the winter, but it should not even then be exposed to the sun. Dynamite or gunpowder is used in extracting it, the latter being used when the mass is com- pact, dry, and without fissures. As the rock is to a certain degree plastic, it compresses easily and does not work well with the more violent and quick explosives. On the other hand, dynamite is effectively used in the wetter parts of the mine and in places where fissures would permit the slower-acting gases from gunpow- der to escape without efficient work. The blocks of bituminous rock are removed outside by rail and as few blocks as possible are piled upon one car, to avoid crushing under the effect of the heat of the sun. This crushing is undesir- able for two reasons: first, there is more waste in the transport and handling; and secondly, if rain falls upon a pulverized mass, it ab- sorbs water rapidly and becomes exceedingly difficult to treat. 271. The operations preliminary to the application of the bitu- minous rock to the street surface are : (1) The extraction and (3) the crushing of the rock. (3) The heating of the powder. (4) Transporting the heated powder to the street. (5) Spreading if while warm. (6) Ramming. (7) Rolling. 272. The quarried blocks of mineral are crushed betweer toothed cylinders, revolving at unequal speeds, which reduce it to pieces of the average size of eggs. These are pulverized in " Carr " machines, which run about 600 revolutions per minute, and delivei it as powder, which is sifted to uniform extreme fineness. Thi& powder is heated in an apparatus resembling a "coffee-roaster;" the revolving cylinder is about 6^ feet in diameter and the same in length; the exterior envelope carries a chimney, disposed in such fashion that the heated air from the furnace passes all around the cylinder. The furnace itself is movable and placed immediately below the cylinder, and rests on a railway so that it may be run out of the way. The moving cylinder is mounted upon an axle and supported on journals in the enveloping cylinder, which rests upon four stout legs. HIGHWAY CONSTRUCTION. 273. The powder is put into the roaster by means of a hopper placed opposite a central hole forming an annular space around the axle. The powder falls into the cylinder, which is moving very slowly; the cylinder is provided with interior blades arranged in a spiral, by which the contents are lifted up to the top and fall in a shower through the hot air in the cylinder, until it is thoroughly warmed both by this action and by contact with the hot sides of the cylinder. As the movement of the cylinder is perfectly regular, the powder remains on the blades only a determinable time, and the entire mass has imparted to it a uniform temperature. The apparatus used on the work of the city of Paris heat, to a tempera- ture of about 300 degrees Fahr., about 3960 pounds of powder- in 15 minutes. When the powder is sufficiently heated the furnace is run out from under it, and is replaced by the special vagon used for trans- porting the warm powder to the place of use, into which the powder falls after opening a gate in the side of the cylinder. 274. Asphaltum is a bad conductor of heat, and this negative quality much simplifies the difficulties of its preparation, and per- mits the material to be heated at central stations and conveyed a considerable distance before it will fall appreciably in temperature ; in fact, the powder loaded into sheet-iron carts with double sides and cover may be carried from 1^ to 9| miles from the place of heating to the place of use without losing on the way more than 35 or 40 degrees Fahr. of its mean temperature. 275. The hot material is emptied out on the concrete founda- tion, spread by hot rakes in a layer of sufficient thickness to allow for compression to the exact finished surface and required thick- ness, viz., about 3 inches for a 2-inch coat. The surface, and consequently the thickness, is regulated by a wooden straight-edge bearing on parallel guides set at the required height in the surface of the concrete. 276. The ramming is done by round cast-iron rams, 6 to 8- inches in diameter,, which are used by fifteen or twenty men, marching side by side and vigorously ramming the asphalt while it is yet hot. After a few minutes a roller drawn by two men and heated by an internal furnace gives what is called the " primary compression," the normal compression being effected under the traffic by the carriage-wheels. During the rolling a small quantity ASPHALTUM AND COAL-TAR PAVEMENTS. 239 of hydraulic cement is strewn over the surface. The rolling is con- tinued until the asphalt is cold. The bituminous limestone to form a good roadway pavement should contain from 9 to 10 per cent of bitumen, and be non-evap- orative at 428 Fahr. Limestones containing much more than 10 per cent of bitumen become soft and wavy in summer; those con- taining much less have not sufficient binding power to sustain heavy traffic. 277. Bituminous Limestone Pavements in the United States. About 55,000 square yards of bituminous limestone pavement were laid in Washington, D. C., during 1876 and 1887, and about 3000 square yards in New York in 1883 or 1884; nearly all of this was subsequently taken up and replaced by Trinidad asphalt. In 1887 about 10,000 square yards were laid in Rochester, N. Y. ; in 1888 about 20,000 square yards in St. Augustine, Florida; and in 1890 40,000 square yards in New York City. The total amount of bituminous limestone pavements now in use in the United States is estimated at 75,000 square yards. These pavements are composed of c, mixture of about three parts of bituminous limestone rock from Ragusa, Sicily, and one part of a similar rock from Vorwohle, Germany; the latter is a harder rock and contains less bitumen than the Sicilian. The paving mixture contains from 10 to 12 per cent of bi- tumen, and is prepared by pulverizing the mixed rock and heating it to a temperature of about 160 Fahr. The heated powder is laid and compressed in the manner described under European Asphalt Pavements. 278. Coal-tar Pavements.* The wearing surface of the earlier pavements was made in various ways, according to the patent, but consisted essentially of small gravel, sand, and stone-dust, cemented by a product of coal-tar. In the later pavements of this variety a certain proportion of bitumen is mixed with the tar, and with beneficial results. *The Report of the Engineer Department of the District of Columbia for 1898 says regarding tar pavements: "This pavement answers the 'purpose well during hot weather, but as soon as the temperature becomes low enough to cause the tar to become brittle, it goes to pieces with but little more cohe- sion than so much loose gravel or broken stone." 240 HIGHWAY CONSTRUCTION. Wherever laid in the United States, coal-tar pavements, as a rule, have given little satisfaction, their failure being due to the pres- ence of volatile oils in the tar, which on exposure to atmospheric influence slowly oxidize and become inert, thus destroying the cementing qualities of the tar. If these oils are removed before the tar is used the resulting material is brittle, and soon crumbles to pieces after being laid. Coal-tar is also very sensitive to heat : in summer it is soft, in winter brittle. On account of these defects, the use of coal-tar alone, as a cementing material for pavements, has been almost entirely abandoned. 279. Coal-tar and Asphalt. To overcome the defects of coal-tar when used alone, the practice has arisen of mixing the gas tars with bitumen, and this has been successful in proportion to the amount of the bitumen used. The most successful pavement of this char- acter is that known as the " Vulcanite." This pavement is prepared as follows : 280. Filbert Vulcanite Asphalt Pavement as laid by the National Vulcanite Company of New Jersey. The pavement is 8-J inches in thickness, formed as follows: The wearing surface 1^ inches when compacted, and a bituminous base and binder 7 inches in depth. The base is composed of stone broken to pass through a 3-inch ring. It is spread on the earth surface, previously graded to receive it, to a depth of 5 inches, these consolidated with a steam roller, after which it is covered with a hot paving-cement composed of No. 4 tar distillate in the proportion of about one gallon to the square yard of pavement. The second or binder course is composed of stone broken to pass through a IJ-inch ring, the stone being thoroughly cleansed and screened, and No. 4 tar distillate. The stone is heated by passing through revolving heaters, and is thoroughly mixed by machinery with the distillate in the proportion of one gallon of distillate to one cubic foot of stone. The binder is spread upon the base to a depth of two inches, and is immediately rammed and rolled with hand and steam rollers while hot and in a plastic condition. The wearing surface, 1 \ inches thick, is made of paving-cement, composed of 25 per cent of asphalt and 75 per cent of tar distillate, ASPHALTUM AND COAL-TAR PAVEMENTS. 241 and clean sharp sand and stone pulverized to pass through a ^-inch ring in the proportion of two parts of sand to one part of stone. To 21 cubic feet of the above ingredients are added one peck of hydraulic cement, one quart of flour of sulphur, and two quarts of air-slaked lime. To this mixture is added 320 pounds of paving- cement. The materials above described are heated to about 250 degrees Fahr. the paving cement in kettles, the sand, stone, etc., in revolv- ing heaters then thoroughly mixed by machinery, carried to the gtrc'jt, and spread on the binder course to a depth of two inches. While hot and plastic it is rolled with a steam roller, hydraulic cement being dusted over the surface. The rolling is continued until the roller ceases to leave an impression on the surface. 281. Advantages of Coal-tar and Asphalt or Distillate Pavement. (1) It is chearp. (2) Its surface is more granular and less slippery than asphalt. (3) The binder binds the base and wearing surface firmly together and eliminates to a great extent the faults of weather cracks and wave-surfaces. (4) It can be laid from curb to curb, as it will not "rot" in the gutters as does the asphalt. (5) Pavements constructed of carefully selected and combined materials and properly laid will cost but little, if any, more than the asphalt for maintenance. 282. Defects of Coal-tar and Asphalt Pavement. (1) The wearing surface consists of 75 per cent of coal-tar, which material can rarely be obtained of uniform quality. (2) The wearing surface, being only 1^- inches thick, requires renewal at frequent intervals. (3) The pavement is not so pleasing to the eye as asphalt in color. (4) The use of the bituminous base gives rise to many per- plexing problems in the grade of the streets on which it is used, due to the fact that the base, the binder, and the wearing surface co- alesce so as to form a solid mass. The wear on the surface is never quite uniform; and when the binder or base becomes exposed on the most travelled part of the street, the pavement near the gutter may be worn but slightly. To resurface properly, the remnants of the old surface should be removed, and the new surface laid directly 242 HIGHWAY CONSTRUCTION. upon the binder. It is, however, impracticable to strip a coal-tar surface. It may be broken by the pick and bar, but it breaks as readily in the base or binder as at the original line of demarcation. In fact, there is no such line. The practice is to cut out what may be necessary near the curb and put a new surface on the roadway as it stands. The result is to raise the level of the roadway at every resurfacing, or, if the original level at the curb be maintained by the method of cutting out as stated, to increase the crown of the street; but as such pavements will not, as a rule, require resurfacing at more frequent intervals than every fifteen years, and as the surfac- ing should not raise the level more than one-half inch, the upward growth will not exceed 3i inches per century. If the surface is tarred over every year with a brush and sprinkled with sand, the life is lengthened. 283. Asphalt and Coal-tar or Distillate Pavements in Washing- ton, D. C. (Extract from the Report of Capt. E. Griffin, United States Engineers, Assistant to the Engineer Commissioners, for the year ending June 30, 1887.) During the year 1886-1887 six per cent of the new pavements laid was sheet coal-tar distillate. As this is the first year since the organization of the present form of District government that coal-tar distillate pavements have been laid in the streets of Washington, a few words in this connection will not be inappropriate. Previous to 1878, 745,305 square yards of coal-tar pavements of various kinds were laid at prices ranging from $1.74 to $3.70 per square yard. Many of these pavements proved unreliable, either through inherent defects in the materials used or faulty methods of mixing and laying. Some went to pieces in a few years, and others deteriorated so rapidly as to soon place the annual cost of maintenance at excessively high figures. Of the so-called Evans pavement 190,663 square yards were laid, mostly in 1873. When only two years old nearly all these pavements were resurfaced at an average cost of $1.09 per square yard. 284. As late as 1877 Lieutenant Hoxie estimated twenty cents per yard per annum as the cost of maintaining coal-tar pavements. 285. The average annual expenditure for maintenance of coal- tar pavements for the fifteen years ending June 1, 1886, has -been 7^ cents per square yard. Of the Evans pavement, 157,324 square yards were resurfaced by Scharf within two years after being laid, and virtually became Scharf pavements. Considering them as such,. ASPHALTUM AND COAL-TAR PAVEMENTS. 243 the mean average annual expenditure for maintenance was 5-J cents per square yard. For the first five years the annual average was 3 T iL cents; for the second five years, 6 cents; for the last five years, 6 T 6 o- cents. 286. " That a durable coal-tar pavement can be laid is proven by the fact that the 158,595 square yards of vulcanite pavements have only averaged 2^ cents per square yard per annum for four- teen years' maintenance, the average being 3%- cents per yard for the first five years, 4 T 2 ir cents for the second five years, and 4 cents for the last four years. 287. The return to the coal-tar distillate pavements was virtu- ally forced upon the commissioners by the clause in the appropria- tion act for 1886-7 which "provided" that under this act no- contract shall be made for making or repairing concrete or asphalt pavements at a higher price than $2.00 per square yard for a quality equal to the best laid in the District prior to July 1, 1886, and with same depth of base. . 288. No bids were received for asphalt pavements in response to proposals advertised for under this act, so a return to distillate* pavements was made. 289. In 1888 bids for a modified asphalt pavement were received* and contracts have been made to lay a large proportion of the streets with it during the present year. This modified asphalt pavement consists of a 4-inch bituminous base, l inch binder course, with a wearing surface of 1^ inches of Trinidad asphalt instead of 1^ inches of coal-tar distillate composition. 290. "Another modification of the standard asphalt pavement; was laid in Washington last year. This consists of a base of 4 inches of hydraulic concrete, 1 inches of bituminous binder, and 1J inches of asphalt wearing surface-coat. This is in every respect a most excellent pavement, and more o-f it would be laid, only the contractors refuse to lay it for less than $2.10 per square yaj'l, and as the law prohibits the payment of more than $2.00 its use had to be discontinued." (Report of Capt. T. W. Symons, United States Engineers, Assistant to the Engineer Commissioners of the District of Columbia in 1889.) 291. Specifications for Coal-tar Distillate Pavement. Coal-tar distillate pavement will consist of a base and binder of 4| inches in depth when compacted, and a wearing surface of 1 inches in 244 HIGHWAY CONSTRUCTION. thickness when compacted. The space over which the pavement is to be laid will be excavated to the depth of 6 inches below the top of the surface of the pavement when completed. Any objec- tionable or unsuitable material below the bed must be removed arid the spaces filled with clean gravel or sand well rammed. The bed will then be trimmed so as to be exactly parallel to the surface of the new pavement when completed, and the entire roadbed will be thoroughly rolled with a heavy steam roller. Upon this foundation will be laid the base and binder, 4^ inches in thickness, in the following manner : Base. The base will be composed of clean broken stone that will pass through a 3-inch ring, well rammed and rolled with a steam roller to a depth of 4 inches, and thoroughly coated with No. 1-J coal-tar paving-cement in the proportion of about 1 gallon to the square yard of base. Binder. The second or binder course will be composed of clean broken stone, thoroughly screened, not exceeding 1| inches in the largest dimension, and No. 4 coal-tar paving-cement. The stone will be heated to a temperature between 230 and 250 degrees Fahr., by passing through revolving heaters and thoroughly mixed by machinery, with the paving-cement in about the proportion of 1 gallon of No. 4 tar to 1 cubic foot of stone. It will be hauled upon the work, spread upon the base course at least 2 inches thick, and im- mediately rammed and rolled with hand and steam rollers while in a hot plastic condition. Wearing Surface. The wearing surface will be composed of the following materials in the given proportions : Per cent. Clean sharp sand 63 to 58 Broken stone or rock-dust 28 to 23 Paving-cement , 13 to 15 Hydraulic cement 0.9 Slaked lime 0.15 Flour of sulphur 0.1 The sand shall be clean, sharp river sand, free from clay, and of such size that not more than 20 per cent shall be retained upon a sieve of twenty meshes to the inch and not more than five per cent shall pass through a sieve of 70 meshes to the inch, about 60 per cent to be coarser than 40 meshes to the inch. The broken ASPHALTUM AND COAL-TAK PAVEMENTS. 245 stone or stone-dust shall be the residue from the crushing of stone from the base and binder which passes a sieve of not more than 6 meshes to the inch. The paving-cement shall be composed of fine Trinidad asphalt, twenty-five to thirty parts; No. 4 coal-tar paving-cement, seventy- five to seventy parts. The refined asphalt must contain at least GO per cent of pure bituminous matter, soluble in carbon bisulphide. The No. 4 coal-tar paving-cement must correspond to a standard to be furnished by the engineer, and be free from excess of sooty mat- ter, naphthaline and creosote oils. The hydraulic cement, lime, and sulphur must be cf the best commercial quality. The materials for the wearing surface will be heated to not over 26 degrees Fahr., the paving-cement in kettles, the sand and stone- dust in revolving heaters. To the latter the hydraulic cement, lime,, and sulphur will be added cold in the sand-box before going to the mixer. They will be thoroughly mixed by approved machinery,, and the mixture carried upon the work, where it will be spread upon the binder course 2 inches thick with hot iron rakes and other suitable appliances, and immediately compacted with hot tamping- irons and hand and steam rollers, while in a hot and plastic state. In spreading the material the joints are to be diagonal to the line of the street. The surface will be finished with a d Listing of dry hydraulic cement rolled in. In cool weather or when ordered the carts carrying the mixture are td be protected with canvas covers. The pavement so constructed must be a solid mass 6 inches, thick, and must be thoroughly rolled and cross-rolled until it has become hard and solid. The relative proportions of the component materials will be changed upon the order of the engineer, as occa- sion shall require. All materials, as well as the plant and methods of manufacture, will be subject to the inspection and approval of the engineer. The degree of fineness, both of sand, stone-dust, and powdered limestone, will be determined by testing with screens as follows: The powdered carbonate of lime will be of such degree of fineness that 16 per cent of weight shall be an impalpable powder of limestone, and the whole of it shall pass a No. 26 screen. The sand will be of such size that no more than 50 per cent of it will pass a No. 80 screen, and the whole of it shall pass a No. 20 screen. The broken stone or stone-dust shall be the residue from the erushiri > of stone- HIGHWAY CONSTRUCTION". from the base and binder which passes a sieve of not more than 6 meshes to the inch. Gutters, wherever directed, will be granite-block or brick, of such width as may be directed, laid upon a hydraulic base of not less than 4 inches in thickness, in accordance with the specifications for granite-block pavement or brick gutters. 292. Asphalt Block Pavements. The manufacture of paving- blocks from crushed stone and asphaltic cement was begun in San Francisco in 1869, but, in consequence of imperfectly prepared materials and crude appliances, the blocks were weak and friable and the results were unsatisfactory ; since that time to the present improvements have been made in the processes and machinery, resulting in the production of a tougher and more enduring block, A large amount of which has been laid, particularly in Washington arid Baltimore. Composition. The blocks are composed of crushed stone and asphaltic cement in the proportion of 87 to 90 per cent of stone and 13 to 10 per cent of cement. The stone employed is trap, gneiss, limestone, etc.; the stone is broken and partially pulverized under crushers and rollers ; the asphaltic cement is prepared from any selected asphaltum (usually Trinidad and California) in the manner described in Art. 96. The composition of the blocks now used in Washington, D. C., is: Asphaltic cement ........................ 13 per cent. Limestone-dust..., ...................... 10 " " Crushed gneiss ........................... 77 " " 100 per cent. (Sand is not used, because it has been found to cut the moulds.) Manufacture. The materials are heated to a temperature of "300 P., then thoroughly combined in mechanical mixers. As the mixture leaves the mixing apparatus it passes into a pressing machine very similar to that used for pressing bricks, and is moulded and compressed while hot into blocks measuring 4 X 5 X 12 inches; the blocks are then cooled under water and are ready for use. The blocks weigh from twenty-two and a half to twenty-four pounds each, according to the specific gravity of the ASPHALTUM AND COAL-TAR PAVEMENTS. 247 stone employed, and about twenty-six blocks are required per square yard. The dimensions of blocks from different factories vary slightly. The blocks are laid on the street in close contact, in the same manner as stone paving-blocks, either with or without an artificial foundation; the foundation usually employed is gravel or gravel and sand or sand alone. 293. Advantages and Defects. The advantages and defects stated under Asphalt Pavement in Articles 221 and 222 are equally applicable to asphalt block pavements. The special advantage which they possess over "Sheet" asphalt is that they can be made at a factory located near the materials, whence they can be trans- ported to the place where they are to be used, and laid by ordinary pavers without the aid of* skilled labor ; whereas sheet pavements require special machinery and skilled labor in each city where they are laid. Compared with stone blocks they are much smoother and less noisy, and they form a practically impervious pavement, because under the action of the sun and traffic the asphalt cements the blocks together. For narrow well-travelled streets they do not make a suitable pavement, but where the traffic is of such a character (such as resi- dence streets where the traffic is light) to warrant their use they make when laid upon a concrete foundation an excellent pavement, smooth, durable, and easily cleaned, healthy and pleasant to the eye. 294. Cost. The blocks cost abouc $60.00 per 1000 or $1.56 per square yard f. o. b. at the factory. The cost of construction will vary with the locality, cost of transportation, character of foundation, etc. Table XXXVI shows the extent and cost of construction in some of the principal cities ia 1890. In Washington, D. C., the contract price for 1900 was $1.77 per square yard. 248 HIGHWAY CONSTRUCTION. TABLE XXXVI. EXTENT AND COST OF ASPHALT-BLOCK PAVEMENTS IN SOME OF THE PRINCIPAL CITIES OF THE UNITED STATES IN 1890. Cities. Extent. Miles. Cost of Construction per square yard. Philadelphia Pa 18.80 10.10 $2 00 Ciimden NJ 586 2 00 Chicago 111 4.11 200 Treuton N J . . V 50 2 50 Schenectady NY 75 295. Cost of Maintenance. No statistics are available as to the cost of maintenance. Some of the cities using them report that no repairs have been made in five years, and that, as the traffic is very light, it does not appear likely that repairs will have to be made; others report that' no repairs have been made and that the blocks are badly worn. (See also Art. 782, el seq.)* 296. Specifications for Laying Compressed-asphalt Blocks. Upon the soil-bed, previously compacted by roiling and ramming, a layer of bank gravel, screened from all pebbles measuring more than one and one-half (14) inches in their largest dimensions, will be laid of such depth as to give five (5) inches in thickness when compacted by rolling and ramming. Upon the gravel will be spread a layer of fine sharp sand two (2) inches in thickness, to serve as a bed for the blocks, which will be laid directly upon and embedded in it with close joints. Special care will be observed to make the surface of the sand exactly parallel to the surface of the pavement when completed. The blocks shall be laid by the pavers standing or kneeling upon the blocks already laid, and not upon the bed of sand. The blocks shall be laid with their length at right angles to the axis of the street; each course will be formed with blocks of a uni- form width and depth. The blocks shall be so laid that all longi- tudinal joints shall be broken by a lap of at least four (4) inches. * Cost of maintaining asphalt-block pavements, Baltimore, Md., 1897 : Cost per square yard : Highest $0. 1633 Lowest 0.0013 Average 0. 071 1 ASPHALTUM AND COAL-TAR PAVEMENTS. 249 Each course of blocks will be driven against the course preceding it by a heavy wooden maul, in order to make the lateral joints as tight as possible. The longitudinal joints will be closed by pressing on a lever inserted at the end of the course adjoining the curb, and keying with a block cut to the required size. When laid, the blocks will be immediately cevered with clean, fine sand entirety free from loam or earthy matter, perfectly dry, and screened through a screen having 20 meshes to the inch. The blocks will then be rammed by placing an jron plate, 24 inches by 8 inches, and f inch thick, over four blocks, and striking on the plate with a rammer weighing not less than 45 Ibs. The ramming will be con- tinued until the blocks reach a firm, unyielding bed and present a uniform surface, with the required grade and crown. Any lack of uniformity in the surface must be corrected by taking up the blocks, increasing the sand bedding, and relaying them. When the ramming is completed, a sufficient amount of fine, dry sand, as above described, will be spread over the surface and swept into the joints. 297. American Bituminous-rock Pavements. Beds of sand- stone rock impregnated with bitumen are found in many places in the United States, but it is only within the last few years that it has come into use as a paving material. San Francisco, Los Angeles, and other cities now have several miles of this pave- ment. 298. The rock is quarried, broken into fragments, heated, and while hot taken to the street and compressed by rolling and tamping. 299. The reports concerning the durability of these pavements are confiictiDg. A claim is made that pavements made of this material 15 years ago and used under heavy traffic have recently been removed and found to have lost very little either in weight or thickness. On the other hand, it is claimed that these pave- ments are soft; that wheels and horses sink into them quite deeply, but these marks appear to be more or less obliterated by the next passing vehicle. The granular nature of these pavements renders them less slippery than the ordinary asphalt pavements. They also possess the quality of resisting disintegration by moisture. It is also claimed that these pavements stand equally well the high tern- 250 HIGHWAY CONSTRUCTION. perature of the interior cities and the cold, damp atmosphere of the coast. 300. Cost of Construction. The cost of construction in the West is less than that of the standard asphalt, the average being about $2.50 per square yard, including a 6-inch concrete base, In le Eastern cities there is bit little difference in their cost. L31. Cost of Maintenance. As none of these pavements has been laid on a large scale for a sufficient length of time, nothing can be said as to the cost of maintaining them. 302. One ton of the bituminous rock will form 10 square yards of pavement 2 inches thick. 303. Specifications for Bituminous-rock Pavements. The man- ner of laying the bituminous rock is left to the contractor, except in the following particulars : The bituminous rock used for the paving must contain not less than 7 nor more than 13 per cent of its weight of bitumen. The powdered rock shall be prepared at a uniform temperature in suitable boilers. Ten days before the award of contracts bidders must deposit in the office of the engineer samples of the bituminous rock which they propose to use. Each sample shall bear the bidder's name and the name of the place where obtained, All materials used must conform to the samples so deposited. If other material is wished to be used, samples of them must be deposited and accepted by the engineer. The asphalt covering, when completed, is to have a thickness of at least 2 inches, everywhere equally firm and compact, and jointing closely to the curb of the sidewalks, gutter-covers, etc., and the surface must in every place conform to the prescribed longitudinal transverse profiles. Laying the Asphalt. The asphalt is to be laid in dry weather. Work must not be carried on during rains or snowstorms. Only on the special permission of the engineer may the asphalt be laid on the concrete, which is to be thoroughly cleaned of earth, dirt, and. loose substances of all kinds. If the cleaning reveals any soft or injured places in the concrete, they are to be chiselled out and filled with new concrete containing a greater proportion of cement. This is not to be covered over until it has set. All possible measures must bo taken to prevent the cooling 1 of the asphalt powder while being carried to ttie place where it is ASPHALTUM AND COAL-TAR PAVEMENTS. to be laid. While the hot powder is being spread out and before the commencement of the tamping and rolling,, the greatest care must be exercised in removing all, even the smallest, foreign bodies, such as stones, paper, wood, straw, leaves, cigar-stumps, etc., and no one shall be allowed to throw such bodies on the work. Moreover, the carts in which the asphalt is to be moved must be carefully cleaned after each use. The engineer has the right to require proofs of their cleanliness, and to require a second cleaning under supervision. 303a. Expansion of Asphalt. The coefficient of expansion of asphalt paving material has not been definitely determined, but ^ie investigations made so far indicate that it has about the same coefficient as steel, which, according to Kent, is .0000063811. 303b. Repairs to Asphalt Pavements. The damages which have usually to be repaired in the surface of an asphalt pavement are : cracks, rolls or waves, and disintegration, breaking down or wearing away in patches. Irregular Cracks. These are generally attributed to contrac- tion of the asphalt from cold; in some cases they are due to the settlement and cracking of the foundation. They usually start near the gutter, and gradually extend in an irregular course across the street. They are also found radiating from manhole-heads and other street furniture set in the pavement, and sometimes at the junction of a new with an old pavement, and at the joint between one day's work and another. They appear sooner and increase more rapidly on a street with little traffic. (With respect to this peculiarity, Mr. A. W. Dow, Inspector of Asphalts and Cements, Washington, D. C., says : "This appears on first thought para- doxical, but it is simply explained. When the pavement is sub- jected to a continuous traffic, the asphalt surface, which is more or less plastic at all temperatures, is kept from cracking by the constant kneading, so to speak, produced by the traffic. And again, when an asphalt surface has but little or no traffic, it be- comes more porous, owing to the fact that, expanding and contract- ing from heat and cold without the compression due to traffic, it becomes spongy and, as a consequence, materially weakened. If such cracking occurs at all on a street with a fair amount of traffic, it is evident that the paving mixture used is at fault, either 252 HIGHWAY CONSTRUCTION. in not being rich enough in bitumen, or the asphalt cement used was too hard/ 7 ) In order to lessen the tendency to crack, and, if possible, con- fine it within certain limits, expansion-joints have been used in several places. City Engineer Thompson of Peoria, 111., has pro- vided expansion spaces at intervals of 50 feet. These were made by cutting the asphalt surface (after it had been compacted with a hand-roller), with an ordinary trowel, down to the concrete ; the crevice thus formed was filled with dry cement, and the compac- tion continued with a steam-roller. The employment of expansion- joints seems to be of doubtful utility. The asphalt mixture being more or less plastic, the space^ will be closed under the action of the traffic. If the mixture be sufficiently hard to resist the spreading action of the traffic, and thus keep the joint open, its edges will be broken down and the pavement will be speedily disintegrated; they also afford an en- trance to water, which, finding its way under the surface material, will quickly rot it; hence they are equally objectionable as the cracks which they are intended to avoid. The tendency to crack may be lessened, and in many cases eliminated, by the use of a ce- ment as soft as is practicable to put into the mixture without having it mark too badly in the hottest weather to which the pavement will be subjected. Cracks are repaired by first cleaning thoroughly, then filling, by pouring in asphaltic cement. Rolls or Waves. This condition may be produced by (a) un- equal thickness ; (b) sliding towards the gutter under the action of the traffic ; (c) creeping in the direction of the heaviest traffic; (d) expansion of the asphalt or the concrete or both ; (e) too soft a ce- ment; (f) a defective bond between the base and binder (this occurs when the surface of the concrete is made smooth by bring- ing an excess of mortar to the surface through too much ramming, or by the use of an inappropriate aggregate) ; (g) a defective bond between the binder and the wearing surface (a proper union is~ prevented between binder and wearing surface when the binder contains an excess of cement, or its surface is dirty when the wear- ing coat is put on); (h) a combination of two or more of the fore- going. ASPHALTUM AND COAL-TAR PAVEMENTS. 253 The above causes are due to errors in the preparation of the different parts of the pavement, or defects in its laying, and their occurrence may be prevented by the exercise of proper care. Disintegration. This usually occurs in spots, and may be pro- duced by any one or a combination of the following causes: (a) ex- cessive traffic; () action of water; (c) unsuitable asphalt; (d) un- suitable flux; (e) Imperfect mixture and improper manipulation,; (f) deficiency of asphalt cement; (g) soft spots due to an excess of cement; (h) improper binder; (i) action of illuminating-gas. The damage due to disintegration is repaired by cutting out the surface material down to the base and replacing with new material. The repairing of an asphalt surface is now generally effected by the "skimming process," in which is used either a heater, such as the " Perkins " (Fig. 267), having a tank for fuel-oil and hooded burners, or an open grate on low wheels, in which coke is burned. Either of these appliances is placed immediately over that part of the pavement to be repaired, and sufficient heat is produced to soften the asphalt so that it can be scraped off to the required depth. To protect the adjoining pavement from injury, the por- tion to be removed is surrounded with asbestos boards. It is claimed that by the "skimming process" a perfect union can be secured between the new material and the old pavement. It is not advisable to take this statement as an established fact. In many cases the patches have scaled or peeled off. This may have been due to careless manipulation, presence of moisture, or de- fective material. The injury to gutters is usually repaired by cutting out and replacing' t 1 " surface material and by painting with liquid cement. 303c. f Specifications for the Repairs of Asphalt Pavements. Extent of Repairs. The repair of wearing surface, binder, and concrete base shall be made to such an extent as is directed by the city engineer. In every case the defects, such as ruts, cracks, depressions, holes, etc., are to be remedied and repaired. Pavement taken up to give access to sewer-, water-, gas-, or other underground pipes or structures will be included under the head of repairs. Concrete Base. When it is necessary to replace the concrete "base, the base thus replaced shall be six (6) inches in thickness, 254 HIGHWAY CONSTRUCTION. and composed of one part of freshly burned hydraulic ( cement and two parts of clean, sharp, coarse sand, and five parts of clean broken stone, all by measure. The material from the old concrete shall not be used in restor- ing the base. Earth Foundation. Should the earth under the concrete to- be replaced be soft, spongy, or otherwise deficient in affording a firm foundation, it shall be dug out and replaced with sand,, gravel, or broken stone well compacted by ramming. Binder. The binder course will be placed on the concrete base, and shall consist of a concrete made of clean broken stone not ex- ceeding one and one-half (1^) inches in the largest dimension, and asphalt paving-cement (or coal-tar paving composition No. 4). The stone will be heated to the required temperature in revolving heat- ers, and shall be thoroughly mixed by machinery with the cement in the proportion of one gallon of cement to one cubic foot of stone. The binder will be hauled to the work while hot, carefully spread on the base with hot iron rakes to such a depth that the least thickness for the wearing surface will be 1^ inches when the sum of the wearing surface and binder is not over 2 inches. As ihis sum increases the thickness of the wearing surface will be increased until it attains a. depth of 2 inches. Beyond this the thickness of the binder may be increased when the wearing surface has slid on the concrete. The surface of the latter must be roughened by picks. Wearing Surface. Upon the binder the wearing surface shall be laid. This shall consist of the same kind of composition or kind of asphalt as the existing pavement, and laid so as to bring the surface even with the adjoining pavement, making a close, smooth joint therewith, without any cracks, depressions, or eleva- tions. The edges of the old pavement shall be cut so as to form a bevelled joint, and will be painted with hot asphaltum before the new material is laid. The repairs are to be so made that at the completion of each day's work no holes cut out for repair shall be left unfilled or un- finished. The holes must be perfectly dry before the material is laid, and no material shall be laid during a rain. Old Material. All old material, dirt, asphalt, concrete, etc.. ASPHALTUM AND COAL-TAR PAVEMENTS. 355 broken np is to be the property of the contractor, and must be removed promptly from the street by him. 303d. Specifications for the Condition of Asphalt Pavements at End of Guarantee Period. 1. The pavement shall not be reduced more than one-fourth (^) inch from the original thickness at the end of the first five years, nor more than one-half (-J) inch from the original thickness at the end of the first ten years. (This re- quirement shall not apply to pavements constructed of rock as- phalt, as this material does not receive its ultimate compression for a considerable period after being laid.) 2. Places which show a disintegration of the material shall be removed to the binder or concrete foundation, as found necessary, and replaced with new material having the same thickness and conforming to the adjacent pavement. 3. All elevations or depressions three-eighths (f) of an inch or more above or below the general surface of the street shall be brought to the same elevation as the general surface, these eleva- tions and depressions to be determined by measuring from a straight-edge four (4) feet in length, placed on the surface of the pavement parallel to the line of curbing. (In making such repairs the process known as "skimming" may be employed.) 4. AVhere elevations or depressions are due to the failure of the concrete foundation from any cause, the asphalt and concrete shall both be removed a length and width to include the entire defect. If the failure is due to buckling of the concrete, the new founda- tion shall consist of broken stone thoroughly compacted, and of the same thickness as the original concrete. In all other cases a new foundation of concrete shall be placed of the same quality and thickness as the original construction. Upon the foundation shall be placed the pavement, of the same thickness as the adjacent sur- faces. 5. Cracks which show any indication of disintegration, or which are three-eighths (f) of an inch or more in width, shall be cut out to the binder or concrete foundation, as found necessary, a length and width sufficient to include the entire portion affected : this portion to be replaced with new material of the same quality and thickness as shown in the pavement adjacent thereto. 6. Should it be found necessary to replace twenty-five per cent 256 HIGHWAY CONSTRUCTION. or more of any section of the street with new material, the entire section shall be resurfaced. The above specifications are recommended by the Committee on Street Paving of the American Society of Municipal Improve- ments, with the following comment : " Your committee does not consider it possible to give definite specifications for this work that will be applicable to all localities, but after a careful consideration of all the facts obtainable, and after due consideration of the opinions presented, we would recom- mend that the following [above] clauses, modified as found neces- sary for each locality, be included in the guarantee contracts of the cities belonging to the association." 303e. Diagram for Showing Location of Asphalt Repairs. Fig. 15e illustrates the method employed in Columbus, Ohio, fcr re- FIG. 15E. DIAGRAM FOR SHOWING LOCATION OF ASPHALT REPAIRS. cording the location of repairs to asphalt pavements. The street surface is divided into 10-foot squares by means of chalk-lines, and the patches are then sketched in a field-book with properly ruled pages, the notes are platted to a scale of 10 feet to 1 inch and traced on 20X30 mch sheets. The contractor is given a set of blue-prints of each street. As it is the intention to make repairs annually under similar contracts, the patches of different years will be dis- ASPHALTUM AND COAL-TAR PAVEMENTS. 257 tinguished by various methods of cross-hatching. Should the patches of different years overlap at any time, this will be consid- ered evidence that the first work had disintegrated; the contractor for that year will have to make good the defect, 303f. Asphalt Pavement Reinforced with Steel. A method recently patented for improving sheet-asphalt pavement and ren- dering it less slippery and more durable consists in imbedding in the asphalt before it is rolled a network or grillage formed of steel bands one inch wide and one-eighth inch thick. The bands are heated, placed two inches apart, the asphalt is raked over them, and the rolling proceeded with in the usual way. CHAPTER VI. BRICK PAVEMENTS. 304. BKICK, although one of the oldest materials used for paving, was not employed for this purpose in the United States until about twenty years ago. The first brick pavement laid in the United States was in Charleston, W. Va., in 1872. Since then the use of brick as a paving material has extended over a wide section of country; and in localities with moderate traffic such pavements appear to give satisfaction. 305. The advantages of brick pavements may be stated as fol- lows: (1) Ease of traction. (2) Good foothold for horses. (3) Not disagreeably noisy. (4) Yields but little dust and mud. (5) Adapted to all grades. (6) Easily repaired. (7) Easily cleaned. (8) But slightly absorbent. (9) Pleasing to the eye. (10) Expeditiously laid. (11) Durable under moderate traffic. Brick pavements will be found in many localities to be superior to wood or broken stone, and in many cities and towns will be found superior to stone blocks. 306. The Defects of Brick Pavements. The principal defects of brick pavements arise from lack of uniformity in the quality of the bricks and the liability of incorporating in the pavement bricks of too soft or porous structure, which crumble under the action of traffic or frost. The employment of unsuitable brick is liable to be fostered by a popular desire to help a local industry without due regard to the- 258 BRICK PAVEMENTS. 259 TYPES OF BRICK PAVEMENTS. ^>X:;:x^rw:->V SAND tt&yftk&^i:. \y FIG. 1 6. SECTION OF HALE PAVEMENT. FIG, 17. PLAN OF HALE PAVEMENT, m FIG. 18.-SECTION OF BRICK PAVEMENT ON CONCRETE, FIG. 19. PLAN SHOWING ARRANGEMENT OF JUNCTION. 260 HIGHWAY CONSTRUCTION. quality of the local clays for the manufacture of good paving brick. This circumstance, together with the comparative ease with which contractors who have little experience can bid on this class of work, and the difficulty of rejecting the lowest bid by local authorities, will in many places result in the failure of the brick pavements. If cities, however, in making contracts for brick pavements, will keep these contingencies in mind, and as far as possible exercise discrimination in selecting bricks made especially for this purpose and contractors interested in making these pavements popular, then the development of a great industry may be anticipated. 307. Durability. Brick has been used for upwards of a hun- dred years in the Netherlands, and pavements laid half a century ago are still in good condition. There are several brick pavements in the United States from ten to eighteen years old which are still in good condition. 308. The general experience with pavements formed of suitable brick, laid on an unyielding foundation, with the joints filled with bituminous or Portland-cement grout, is that they furnish a smooth and durable surface, well adapted to moderate traffic. 309. Failures of the earlier pavements are frequently reported. These pavements were generally constructed on defective founda- tions, and with the ordinary building bricks of the locality. Such failures are the result of overhaste in the selection of the material, .and poor foundations. 310. The durability of the bricks seems to depend (1) on the olay from which they are made being practically free from lime; (2) on the thorough grinding and mixing of the clay, so as to have no lumps in the bricks; (3) upon the bricks being thoroughly an- nealed. 311. The brick pavements at The Hague, Holland, are made of a hard-burned brick 8.668 inches by 4.33 inches wide and 2.16 inches thick. They are laid on a sand foundation 7.88 inches deep, with very little clay. Joints are laid as close as possible. The Hague is a city of residences, and street traffic is very light. Amsterdam is paved almost entirely with brick. The road from Utrecht to Connighem, twenty-seven miles, is paved with brick. 312. Bricks are successfully used in Rotterdam, which is a com- mercial city. Two classes of brick are used one made from local clays, and the other a scoria brick, manufactured by the Tees Scoria BEICK PAVEMENTS. 261 Brick Company, of England* The local bricks are preferred for light traffic, and for medium traffic the scoria bricks. 313. Size and Shape of Bricks. Bricks have passed through an ordeal similar to that through which wood for paving passed many years ago, with practically the same results, viz., that with a proper foundation neither odd shapes, grooves, lugs, nor other devices are necessary or beneficial. Experience shows that the most economi- cal and desirable size for paving bricks is that of the standard building brick. Bricks of this size can be made more cheaply, burned more uniformly, and those which are unsuitable for paving^ can be utilized for building purposes, which would be impracticable with odd shapes. The imperfect ones of said shapes or peculiar form are so much waste material, and the cost of their manufacture must be added to the price of the good ones in order to protect the* manufacturer from loss. Moreover, with irregular sizes and odd. shapes it would be necessary for the towns employing brick pave- ments to keep a large stock of the different bricks on hand to make repairs, which would be expensive and troublesome. The sizes in common use at the present time are (1) the brick measuring 8JX2JX4 inches, weighing about 7 pounds each and requiring fifty-eight to a square yard; (2) the blocks measuring 3X4X9 inches, weighing about 9J pounds each and requiring forty- five to the square yard. Both bricks and blocks are made with cither flat sides and square edges or flat sides and rounded edges. Each fcrm of edge has its advocates, one set claiming that the rounded edge wears better than the square edge. A variation from the flat sides is made by grooves and projections formed during the repressing, the object of which is to facilitate the introduction of the joint filling and to increase its holding power. The grooves are formed either by having the name of the maker in sunken letters or one or more horizontal grooves on sides and ends. Some makers form both horizontal and vertical grooves; horizontal grooves are by some considered objectionable, for the reason that the brick is liable to spall or fracture down to the groove. The projections are formed by having the name of the maker in raised letters or by either round or square buttons. The depth of the grooves and height of the projections vary with the maker from one-eighth ta three-sixteenth inch. 262 HIGHWAY CONSTRUCTION". 314. duality of Bricks. The qualities essential to a good paving brick are the same as for any other paving material, viz., hardness, toughness, and ability to resist the disintegrating effects of water and frost. As with other materials, porous brick are unfit for paving. These qualities are not obtained, as is commonly supposed, by vitrifying the bricks : in fact the application of the term vitrified to paving bricks is a misnomer. The process of vitrification is to con- vert into glass by fusion or the action of heat. Glass is a smooth, impermeable, brittle substance, easily fractured ; therefore the edges of bricks that are vitrified or turned into glass will be quickly broken off, and their surface will be slippery. Vitrification adds nothing to the strength ; in fact it defeats the object for which the bricks are made. 315. The required qualities are imparted to the brick by a pro- cess of annealing. The bricks should be burned just to the point of fusion, then the heat gradually reduced until the kiln is cold. This process will produce a brick thoroughly compact, hard, and tough. If the cooling off is done quickly, it will produce a brittle brick, that will speedily go to pieces under traffic. 316. Foundation. A solid unyielding foundation is as indis- pensable with bricks as with any other paving material : the fail- ure of the earlier pavements was due, in many cases, more to de- fective foundations than to defective material. The use of plank laid on sand is objectionable for the same reasons stated under wood pavements, Articles 185, 186. 317. The foundation in all cases should be formed of cement concrete, the aggregate of which, in localities where stone or gravel are unobtainable, may be of broken bricks. The usual proportions for the concrete are : hydraulic cement 1 part, clean, sharp sand 2 parts, broken stone 5 parts. 317a. Sand Cushion. The sand cushion is a layer of sand placed on top of the concrete to form a bed for the brick. Prac- tice regarding the depth of this layer of sand varies considerably. In some cases it is only half an inch deep, varying from this up to three inches. The sand cushion is very desirable, as it not only forms a perfectly true and even surface upon which to place the brick, but it also makes the pavement less hard and rigid than, would be the case were the brick laid directly on the concrete. BRICK PAVEMENTS. 2G3 The sand is spread evenly, sprinkled with water, smoothed and brought to the proper contour by screeds or wooden templets, prop- erly trussed, mounted on wheels or shoes which bear upon the upper surface of the curb. Moving the templet forward levels and forms the sand to a uniform surface and proper shape. The sand used for the cushion-coat should be clean and free from loam, moderately coarse, and free from pebbles exceeding one-quarter inch in size. 318. Manner of Laying. The bricks should be laid on edge, as closely and compactly as possible, in straight courses across the street, with the length of the bricks at right angles to the axis of the street. Joints should be broken by at least 3 inches. None but whole bricks should be used except in starting a course or making a closure. To provide for the expansion of the pavement, both longitudinal and transverse expansion-joints are used; the first are formed by placing a board templet seven-eighths of an inch thick against the curb and abutting the brick thereto. The transverse joints are formed at intervals varying between 25 and 50 feet, by placing a templet or building-lath three-eighths of an inch thick between two or three rows of brick. After the bricks are rammed and ready for grouting, these templets are removed, and the spaces so left are filled with coal-tar pitch or asphaltic paving-cement. The amount of pitch or cement required will vary between one and one and a half pounds per square yard of pavement, depending upon the width of the joints. After 25 or 30 feet of the pavement is laid, every part of it should be rammed with a rammer weighing not less than 50 pounds, a plank being laid on the surface parallel to the curb to receive the blows of the rarr- mer, and the bricks which sink below the general level should bo removed and replaced by a brick of greater depth. In placo < f ramming by hand, a steam-roller weighing not to exceed 5 tons may be used; the rolling should be continued until the brick are brought to an even surface. Soft brick may be detected after the rolling by wetting the pavement; they retain moisture longer than the harder ones, and thus can be readily detected. After the ram- ming and rectification Portland-cement grout should be poured into the joints until it appears on the surface, then the whole surface should be covered with a layer of dry sand one-half inch deep. At 264 HIGHWAY COXSTKUCTIOX. street intersections the courses should be laid meeting at an angle, as shown in Fig. 19 or 19a, so that the courses may not run parallel to the traffic. FIG. 19A. PLAN OF BRICK PAVING AT STREET INTERSECTIONS, Baying the brick in courses running diagonally with the length of the street has been advocated and tried in some cities. (Tried in Toronto, Canada, and abandoned.) The reasons advanced in favor of this method are: Less noise, increased bearing surface fcr. wheels on each brick along the line of travel, and consequently less, wear. The reasons in favor of laying the bricks at right angles to the length of the street are: Saving in cost both in labor and material BRICK PAVEMENTS. 265 (diagonal courses cause considerable waste in cutting the brick to fit at the curb) ; better foothold and no appreciable increase in wear or noise. The laying of bricks lengthwise adjoining the curb to form a gutter is detrimental and productive of a rut. 319. Joint-filling. The character of the material used in filling the joints between the brick has considerable influence on the suc- cess and durability of the pavement. Various materials have been used, as sand, coal-tar pitch, asphalt, mixtures of coal-tar and asphalt, Portland cement, and various patented fillers, as " Murphy's grout," made from ground slag and cement; each material has its advocates, and there is much difference of opinion as to which gives the best results. The office of a filler is to prevent water from reaching the foundation, and to protect the edges of the brick from spalling under traffic. In order to meet both of these requirements every joint must be filled to the top and remain so, wearing down with the brick. Sand does not meet these requirements, although at first making a good filler, being inexpensive, and reducing the liability of the pavement to be noisy; it soon washes out and leaves the edges of the brick unprotected and consequently much more liable to be chipped. Coal-tar and the mixtures of coal-tar and asphalt have an advantage in rendering the pavement less noisy and in cementing together any breaks that may occur by upheavals from frost or other causes; but unless made very hard they have the disadvantage of becoming very soft in hot weather and flowing to the gutters and low places in the pavement, there forming a black and unsightly scale, leaving the high parts unpro- tected. The joints thus deprived of their filling become the recep- tacle of water, mud, and ice in turn, and the edges of the brick are quickly broken down. Some of these mixtures become so brittle in winter that they crack and fly out of the joints under the action of the traffic. The Murphy grout works well in places, being fairly hard and elastic, but is said to be uneven in its results. The best results seem to be obtained by using a high grade of Portland cement containing the smallest amount of lime in its composition, the presence of the lime increasing the tendency of 266 HIGHWAY CONSTRUCTION". the filler to swell with age and the absorption of moisture, causing the pavement to rise or lift away from the foundation, and so pro- ducing the roaring or rumbling noise so frequently complained of. The Portland-cement grout, when uniformly mixed and carefully placed,, resists the impact of traffic and wears well with the brick. When a failure occurs the repairs can be quickly made; and if made early, the pavement will be restored to a good condition; but if neg- lected, the brick soon loosens and the pavement fails. The Portland-cement filler is prepared by mixing two parts of cement and one part of fine sand with sufficient water to make a thin grout. The most convenient arrangement for preparing and distributing the grout is a water-tight wooden box carried on four wooden wheels about 12 inches in diameter. The box may be about 4 feet wide, 7 feet long, and 12 inches deep, furnished with, a gate about 8 inches wide in the rear end. The box should be mounted on the wheels with an inclination, so that the rear end is about 4 inches lower than the front end. The operation of placing the filler is as follows: The cement and sand are placed in the box and sufficient water is added to make a thin grout. The box is located about 12 feet from the gutter, the end gate opened and about 2 cubic feet of the grout allowed to flow out and run over the top of the brick (care being taken to stir the grout while it is discharging). If the brick are very dry, the entire surface of the pavement should be thoroughly wet with a hose before applying the grout; if not, the absorption of the water from the grout by the bricks will prevent adhesion between the bricks and the cement grout. The grout is swept into the joints by ordinary bass brooms. After about 100 feet in length of the pave- ment has been covered, the box is returned to the starting-point and the operation is repeated with a grout somewhat thicker than the first. If this second application is not sufficient to fill the joints, the operation is repeated as often as may be necessary to fill them. If the grout has been made too thin or the grade of the street is so great that the grout will not remain long enough in place to set, dry cement may be sprinkled over the joints and swept in. After the joints are completely filled and inspected, allowing three or four hours to intervene, the completed pavement should be covered with sand to a depth of about inch and the roadway barricaded and no traffic allowed on it for at least ten days. BRICK PAVEMENTS. 2G' If coarse sand is employed in the grout, it will separate from the cement during the operation of filling the joints, with the result that many joints will be filled with sand and very little cement, while others will be filled with cement and little or no sand; thus there will be many spots in the pavement in which no bond is formed between the bricks, and under the action of traffic these portions will quickly become defective. The object of covering *the pavement with sand is to prevent the grout from drying or setting too rapidly; hence in dry and windy weather it should be sprinkled from time to time. The coal-tar filler is best applied by pouring the material from buckets and brooming it into the joints with wire brooms. To . effectually fill the joints it must be used only when very hot. To secure this condition a heating-tank on wheels is necessary. It should have a capacity of at least five barrels, and be kept at a uni- form temperature all day. One man is necessary to feed the fire and draw the material into the buckets, another to carry the buck- ets from the heating-tank to a third, who pours the material over the street. The latter starts to pour in the centre of the street, working backward toward the curb, and pouring a strip about two feet in width. A fourth man with a wire broom follows immedi- ately after him, sweeping the surplus material toward the pourer and in the direction of the curb. This method leaves the entire surface of the pavement covered with a thin coating of the pitch, which should be immediately covered with a light coating of sand; the sand becomes imbedded in the pitch. Under the action of the traffic this thin coating is quickly worn away, leaving the surface of the brinks '-lean and smooth. Sever 1 : sphaltic fillers have been recently placed on the market, the makers of which claim that they are unaffected by the weather; the most notable of these are: "Hydrolene," made by the Sun Co. of Philadelphia; "Cimmerian," made by Callahan & Co., Chicago, is said to contain 99.4 per cent, bitumen; " Pioneer," made by the American Asphaltum & Rubber Co., Chicago, and which is very favorably reported on, is said to be composed of approximately 99 per cent, bitumen containing 68 per cent, petrolene and 31 per cent, asphaltene, its specific gravity is about 0.99 and its melting- point is about 210 F. The quantity required per square yard of 268 HIGHWAY CONSTRUCTION. paving is approximately one gallon. The cost is said to be about 16 cents per square yard. The advantages claimed for the asphaltic fillers are: They do not run in summer or become brittle in winter. They always remain flush with the surface of the brick, thus protecting the edges from injury .and preventing the wheels of passing vehicles from jolting and rattling over the joints. They suppress and reduce noise. They are impervious and sanitary. They can neither be washed nor swept out of the joints. They take care of the expansion of the brick and thus prevent rumbling sounds. Openings in the pave- ment can be made and repaired with greater facility than with a cement filler. They may be removed from the brick, heated, and used again in making the repairs. Their use permits the pave- ment to be used by traffic immediately after the joints are filled. The cost of filling the joints with the various fillers is variable , depending upon the width of the joints and the locality. The range, including material and labor, is about as follows: Sand 2 to 3 cents per sq. yd. Portland- cement grout 10 " 12 " " " " Coal-tar 10 " 14 " " " " Asphaltum 15 " 17 " 320. Cost of Brick Pavements. The cost of brick pavements varies with the locality and the method of construction. The range appears to be from about $1.30 per square yard in the vicinity of the manufacturers to $2.60 in places remote from the factories, in which places the freight on the bricks forms an important item of the cost. The items composing the cost are as follows: Excavating and preparing sub-grade $ \ cubic yard concrete 1" sand cushion, -fa cubic yard Forming cushion 60 brick Hauling to street Laying brick Rolling brick Removing and replacing defective brick Ramming Asphaltic filler in place Sanding and sweeping Superintendence Profit and use of tools $. BRICK PAVEMENTS. 269 321. Table XXXVII shows the extent of brick paving in the principal cities of the United States. TABLE XXXVII. EXTENT OF BRICK PAVING IN THE PRINCIPAL CITIES OF THE UNITED STATES IN 1903. Cities. Area, Sq. Yds. L,ength, Miles. City. Area, Sq. Yds. Length, Miles. Akron Ohio .... 450,692 24.8 Galveston, Tex. . . . 54,592 2.1 Albany NY.. 351,240 20.0 Grand Rapids, M'h. 152,416 8.7 Allegheny, Pa Al lent own Pa 270,000 11,267 15.4 0.4 Hamilton, Ohio. . . . Harrisburg, Pa. ... 2,463 9,061 0.1 0.5 Altoona Pa 14,323 1.1 Holyoke, Mass. . . . 41,301 1.8 Atlanta Ga 2.0 Houston Tex. . . . 9.8 Atlantic City, N. J.. Auburn NY 17,254 23 930 1.9 9 Indianapolis, Ind. . Jackson Mich 490,060 30.4 2 1 Augusta Ga . . 3 361 1 Jacksonville Fla 233,912 11 2 Aurora 111 . . . . . 68 500 3 1 Jersey City N J 1 Baltimore, Md Bay City, Mich. . . . Binghamton, N. Y. Birmingham, Ala. . Boston, Mass Bridgeport, Conn. . Buffalo iN i 84,449 177,154 107,3^0 55,882 3,670 43,652 203,915 4.9 7.8 5.2 2.0 0.4 2.3 12.7 Johnstown, Pa. . . . Joliet, 111 Joplin, MJ Kalamazoo, Mich. . Kansas City, Kan. . Kansas City, Mo. . . Kingston, N. Y. . . . 179,128 83,374 54,000 85,251 582,560 818,315 1,774 10.2 3.8 1.8 3.0 33.1 39.9 4 Cambridge, Mass. . Camden, N. J Canton Ohio 49,689 37,222 297 097 2.7 2.5 18.4 Knoxville,Tenn. . . La Crosse, Wis. . . . Lancaster Pa 60,000 82,745 83 826 3.0 3.8 3 5 Cedar Rapids, Mich Charleston S C. . . 396,877 7,803 15.2 0.4 Lexington, Ky. . . . Lima, Ohio . . 178,200 177,120 7.0 8 4 Chattanooga, Tenn. Chelsea, Mass Chester Pa . . . . 86,195 11,800 47,520 4.0 0.7 2.7 Lincoln, Neb Little Rock, Ark. . . Los Angeles, Cal . . 421,349 36,960 10,793 14.8 2.1 5 Chicago 111 1,432,000 75.5 Louisville, Ky. . 1,090,826 63 5 Cincinnati, Ohio. . . Cleveland, Ohio. . 670,000 2,016,349 55.0 117.6 Lowell, Mass Lynn, Mass 3,843 2,740 0.2 2 Columbus, Ohio. . . Council Bluffs, la. . Covington Ky 1,587,584 280,305 49364 78.5 14.5 3 5 Maiden, Mass Memphis, Tenn. . . . Meriden Conn. 1,665 121,089 10 630 0.1 5.2 4 Dallas, Tex Davenport, la Dayton, Ohio Denver, Colo Des Moines, la. ... Detroit, Mich Dubuque, la 18,302 739,981 355,510 4,154 1,189,642 828,873 117,624 0.8 30.4 13.9 0.4 63.6 36.9 5.1 Milwaukee, Wis. . . Minneapolis, Minn. Mobile, Ala Montgomery, Ala . . McKeesport, Pa. . . Nashville, Tenn. . . Newburg,N.Y 180,686 209,550 19,579 157,251 289,813 41,887 9,530 6.9 13.2 1.2 4.7 16.2 2.4 0.6 Duluth, Minn Easton, Pa Elizabeth, N. J. . . . Elmira,N.Y . 48,910 77,400 10,202 95 509 1.5 2.2 0.5 4 1 New Bedford, Mass New Castle, Pa. ... New Haven, Conn. Newport Ky. . . . 9,276 94,800 143,160 85460 0.3 5.5 6.5 3 8 Erie, Pa . 113 303 12 9 New Orleans La 6 E. St. Louis 111 444 329 19 4 Newark N J 9 8 Evansville, Ind.. . Fort Wayne, Ind. Fort Worth, Tex.. 598,400 277,753 25.5 16.3 1.0 New York, N.Y... Norfolk, Va No. Adams, Mass. . 257,716 36,609 32,249 12.1 2.5 1.7 270 HIGHWAY CONSTRUCTION. TABLE XXXVII (Continued}. EXTENT OF BRICK PAVING IN THE PRINCIPAL CITIES or THE UNITED STATES IN 1903. Cities. Area, Sq. Yds. Length, Miles. Cities. Area, Sq. Yds. Length, Miles. Omaha, Neb 278,124 13.5 Springfield, Mass. . 84,688 3.7 Oshkosh, Wis 22,900 0.8 Springfield, Ohio. . . 166,450 7.0 Paterson, N. J 103,840 5.9 St. Joseph, Mo. . . . 256,658 15 7 Pawtucket, R. I. 1,965 0.1 St. Louis, Mo 1,634,639 89.5 Peoria, ill 625,495 30.2 St. Paul, Minn 208,075 9.4 Philadelphia, Pa. . . 2,239,789 141.7 Syracuse, N. Y. . . . 304,574 13.7 Portland, Ore 16,368 0.6 Tacoma, Wash. . . . 15,500 .6 Providence, R. I.. . 7,395 0.4 Terr Haute, Ind. . 128,085 f . o Quincy, 111 508,084 23.1 Toledo, Ohio 1,289,322 ( Racine, Wis 96,321 4.5 Topeka, Kan 437,705 21. i Rochester, N. Y. 191,975 10.0 Trenton, N. J 177,202 8.6 Rockford, 111 44,073 1.9 i Troy,N.Y 240,483 12.8 Saginaw, Mich 206,348 9.8 i Utica,N.Y 44,833 0.4 San Antonio, Tex . . 1,905 0.1 Washington, D. C. . 177,459 0.9 Savannah, Ga 172,647 8.2 Waterbury, Conn. . 29,635 1.7 Schenectady, N. Y . 84,939 5.0 Wheeling, W. Va. . 405,141 27.0 Scranton, Pa 100,101 5.0 Wichita, Kan 11,582 0.4 Seattle, Wash 64,530 4.8 Wilkesbarre, Pa. . . 146,666 8.3 Sioux City, la 147,113 7.5 Williamsport, Pa. . 87,912 3.7 Somerville, Mass.. . 2,464 0.1 Wilmington, Del. . . 210,023 14.1 So. Bend, Ind 581,891 26.5 Woonsocket, Mass. 4,051 0.2 So. Omaha, Neb . . . 24,743 0.9 Yonkers,N.Y 4,666 0.2 Spokane, Wash. . . . 14,200 0.5 York, Pa 53,000 3.0 Springfield, 111 594,300 28.1 Youngstown, Ohio . 38,700 2.5 321a. Maintenance. The amount of maintenance required by a brick pavement will depend upon the quality of the brick and the character of the foundation. With good bricks and concrete foundation the amount will be small, with a weak foundation and inferior bricks it will be large. 321b. Guarantee. The custom of requiring the contractor to guarantee the pavement for a fixed period is not general; only a few cities require it. Where it is required, the period ranges from one to ten years. Albany, N. Y., requires periods of five and ten years, and the contract provides the following method for determining if the pavement requires replacing: "During the progress of the work the City Engineer shall weigh not less than fifty of the bricks of apparent average quality and appearance, and file a certificate # of the result. During the ten-year guarantee period the proper officer shall take up and re- BRICK PAVEMENTS. 271 weigh fifty brick from time to time, and whenever a 15 per cent, loss of weight is found in any bricks on the street they must be re- placed with bricks as nearly as possible of the size and quality of the original." The stipulations of the contract employed by the city of Buffalo, N. Y., are as follows: " During the period of maintenance, whenever the surface be- comes uneven, holding water more than J inch in depth, or when the pavement has settled over trenches, or heaved, showing a varia- tion of more than f inch from the line of a 4-foot straight-edge, the brick shall be taken up and be relaid at proper crown and grade. If in any continuous 300 lineal feet of the pavement it is found necessary to repair more than one-third of the area, or if the cracks in the brick exceed the proportion of 3 linear feet of cracks to 1 linear foot of pavement, all the brick shall then be taken up in the area included in the 300-foot lines and the curb lines and shall be relaid. During the last year of maintenance, any brick in the pavement shall show not less than one-half the original width or thickness of such brick, and the wear or abrasion at the end of any brick shall not exceed three-fourths of an inch." 322. Variety of Systems. Many patented systems of forming brick pavements have been introduced, differing either in the shape and size of the bricks or in the method of laying them. The fol- lowing are representative systems : The Hayden Paving-block. The shape and manner of laying these blocks is patented. The blocks are square in plan, with deep hollows underneath to facilitate burning and save material; the top surface is flat, broken by indentations, and the edges of the top are bevelled. The blocks are made in two sizes, the smaller ones 5 inches deep and 5f inches square. The hollows in the bottom of the blocks are filled with moist sand, then laid in posi- tion on the foundation, rammed to grade, and the joints filled with hot pitch. 323. The Halwood Block. These blocks are composed of a mixture of mica shale, clay, and sand. The blocks measure 3x4x9 inches, taking 48 to a square yard. They are laid on a foundation of either 6 inches of concrete or 8 inches of broken stone, joints filled with coal-tar. The cost per square yard, includ- ing foundation, is from $2.50 to $2.10. 272 HIGHWAY CONSTRUCTION. 324. The McReynolds Patent Brick. The patent, consists in the bricks having lugs, and in one end of each brick a recess. The claim is that this arrangement permits the joint-filling to flow around the brick, and that these projections act as an obstruction to the cement running during hot weather to the gutter. 325. The Hale Pavement, Introduced in 1873 is a patent pro- cess foi laying any brick for paving purposes, the novelty being in the foundation, which consists of 3 inches of sand, on which are laid 1-inch oak boards dipped in coal-tar. The boards are laid either lengthwise or crosswise of the street. On the boards a layer of clean sand from an inch to an inch and a half thick spread, and the bricks laid on edge, " herring-bone " fashion, with the joints filled with tar or sand as may be desired. This costs in West Virginia $1.35 per square yard, varying of course with the cost of the brick used. A royalty of 10 cents per square yard is charged by the Hale Com- pany for the use of this method (see Figs. 16 and 17). 326. " Charleston Plan." On the graded surface of the street spread 3 inches of clean coarse sand; on this place 1-inch oak boards dipped in hot coal-tar; on the boards spread a cushion-coat of clean sand 1^ inches deep; on this lay the bricks (common red) on edge, " Herring-bone" fashion; cover the bricks with dry clean sand, and broom well to fill the joints. 327. " Wheeling Plan." The roadbed is first graded and com- pacted by rolling with a 5-ton roller, then 3 to 7 inches of coarse gravel and sand is spread and rolled ; on this the bricks are laid with their length at right angles to the axis of the street and then brought to a solid bearing by rolling; the joints are filled with sand and coal-tar, and the surface covered with dry sand. Both the common red and special bricks are used. 328. Paving-bricks are made at Kakos near Buda Pesth from carefully selected clay mixed with a little lime. The bricks when moulded are subjected to a pressure of about 3500 pounds per square inch, and then burned nearly to vitrification. The product is regular in form, homogeneous, of uniform density, and of great resistance to wear. According to the experiments of Prof. Ignaez, they have supported without deformation or fissuring a maximum load of over 45,000 pounds per square inch and a mean load of 31,426 pounds per square inch. A square meter(1.196 square yards) of this pavement costs $3.80. In forming the paving, the soil is BRICK PAVEMENTS. 273 first consolidated and a bed of ordinary brick masonry is laid upon it; the paving-bricks are set in mortar, leaving a joint of T 4 5 of an inch between them to be filled with cement. The dimensions of the bricks are 7.87 X 7.87 X 3.9 inches and they weigh 24 pounds each. It takes 22 bricks to lay 1 square yard of paving. The brick foundation is 6 inches deep. The pavement made with these bricks is easy to clean, does not become slippery, and is pleasant to drive over. The only objection is that it is somewhat noisy in the nar- row streets. 329. Iron Bricks, so called, are said to be used satisfactorily for paving in Germany. These bricks are made by mixing equal parts of finely ground red argillaceous slate and finely ground clay, with the addition of 95 per cent iron-ore. The ingredients thus mixed together are then moistened with a solution of 25 per cent of sulphate of iron to which fine iron-ore is added ; after this the com- pound is shaped in a press, dried, dipped once more in a concen- trated solution of finely ground iron-ore, and then baked in an oven for about 48 hours in a reducing-flame. 330. Bricks made from blast-furnace slag and scoria have been tried ; they are durable, but soon wear slippery and afford little foot- hold for horses. Ordinary building-bricks saturated with gas-tar have been experimented with in Nashville, Tenn. The results were not satisfactory, and the pieces of experimental paving have been removed. 331. Heads of Specifications for Brick Pavement. (1) Preparation of roadbed. (2) Foundation. (Concrete.) (3) Quality of the Bricks. The bricks shall be manufactured from suitable clay containing not more than one per centum of lime. They must be burned especially for paving purposes. They shall have a resistance to crushing of not less than 8000 pounds, per square inch on the flat, and must not absorb more than -%%-$ of their weight of water after 48 hours' immersion. They must possess such a degree of toughness that when struck a quick blow with a 4-lb. hand hammer on the edges, the edges shall not spall or chip. (4) Size and Shape. They shall be of a uniform size of 8-J X 4 X 2^- inches, shall be square on the edges, straight, and free from fire- cracks or checks ; when broken, the fracture shall be smooth and 274 HIGHWAY CONSTRUCTION. straight, not conchoidal; and the texture shall be uniform through- out and not granular. (5) Samples. Not less than three bricks of the quality, size, and shape proposed to be used shall be furnished with ^ach pro- posal, each brick to be labelled with both the bidder's and maker's name and address; these samples shall be deposited in the office of three days before the time of opening the bids. They will be subjected to the required tests, and the characteristics of those deposited by the successful bidder will become the standard by which will be tested all the bricks to be furnished by him, and no deviation from this standard greater than one per cent in any particular will be permitted in the bricks placed in the work. (6) Inspection and Culling. The bricks will be inspected after they are brought upon the ground, and all bricks which are soft, cracked, checked, overburned, or otherwise defective in quality or dimensions will be rejected and must be immediately removed from the line of the work. The contractor must furnish such laborers as may be necessary to aid the inspector in the examination and the culling of the bricks ; and in case the contractor neglect or refuse to furnish said laborers, such laborers as in the opinion of the may be necessary will be employed by said , and the expense thus incurred by will be de- ducted and paid out of any money then due or which may there- after become due to said contractor under the contract to which these specifications refer. (7) Cushion-coat. On the concrete foundation a layer of clean, sharp sand, free from loam and pebbles exceeding J inch in size, will be evenly spread to the depth of inches. A template shall be used for striking the sand cushion to the exact shape of the crown of the street. This template shall be made in accordance with the plans and directions of the engineer; it shall be kept whole, true to shape, and in good condition; it shall rest on the curbs, and be drawn forward immediately before the bricks are laid. Particular care must be taken that the sand be wet at the time the bricks are laid. (8) Laying the Bricks. The bricks shall be set on the cushion- coat in close contact with each other, both on sides and ends; they will be laid in parallel courses across the street, with the length of the bricks at right angles to the axis of the street. The bricks of BRICK PAVEMENTS. 275 adjoining courses shall break joints by at least 3 inches. At street- intersections the bricks will be laid on the diagonal, as shown on the plans. . . . Whole bricks only shall be used, except in starting a course or making a closure and in paving around manhole- heads, etc. The bricks shall be laid by skilled workmen, who shall stand on the bricks already laid, and in no case shall the sand bed in front of the pavement be disturbed or walked on after having been smoothed over and brought to the required crown. (9) Ramming. The bricks shall be rammed to a solid bearing, with hand-rammers weighing not less than 50 pounds, and all bricks which sink below the general level must be removed and the sand bedding increased until the level is uniform. As soon as practicable after the ramming and rectification, and not to exceed three days after the bricks are laid, they are to be rolled with a roller weighing not less than three and not more than five tons, the surface of the bricks to be swept clean before the. rolling. (10) Jointing. After the bricks have been satisfactorily rolled,, the joints will be filled with (Portland-cement grout made front two parts cement and one part fine, sharp sand) or (paving-cement of straight-run coal-tar pitch of standard quality, such as is ordi- narily numbered 6 at the factory). After the jointing is completed and inspected, the entire sur- face of the pavement shall be covered with a layer of clean, sharp sand to a depth of about -J inch and the roadway barricaded and no traffic allowed on it for ten days. At the end of this period the contractor shall thoroughly sweep the street and remove the sweepings. (11) Interpretation of specifications. (12) Omissions in specifications. (13) Engineer defined. (14) Contractor defined. (15) Notice to contractors, how served. (16) Preservation of engineer's marks, etc. (17) Dismissal of incompetent persons. (18) Quality of materials. (19) Samples. (20) Inspectors. 276 HIGHWAY CONSTRUCTION. (21) Defective work, responsibility for. (22) Measurements. (23) Partial payments. {24) Commencement of work. (25) Time of completion. (26) Forfeiture of contract. {27) Damages for non-completion. (28) Evidence of the payment of claims. (29) Protection of persons and property. (30) Indemnification for patent claims. (31) Indemnity bond. (32) Bond for faithful performance of work. (33) Power to suspend work. -{34) Right to construct sewers, etc. (35) Loss and damage. . (36) Old materials, disposal of. (37) Cleaning up. (38) Personal attention of contractor. (39) Payment of workmen. <(40) Prices. (41) Security retained for repairs. '(42) Payment, when made. Final acceptance. 332, Specifications for Brick Pavements in Memphis, Tenn. The roadway between curb lines shall be taken down to sub-grade, care being taken not to plough within three inches (3) of the sub-grade stakes, which last shall be carefully removed wijh pick and shovel, in such manner as to leave a true and perfect surface, which shall be rolled down with a 5-ton roller three times before the concrete foundation is laid. Before the sub-grade foundation is finally fixed, all water and gas pipes must be put in and adjusted; water- pipes must be of lead, double strength, and the gas of the best gal- vanized pipe; the trenches shall be filled in layers of three inches, and carefully rammed to within six inches of sub-grade and the balance of trench concreted. Concrete. Upon the sub-grade thus formed shall be spread the concrete foundation, composed of hard limestone, broken or crusb.ftd to pass a two-inch ring, the same to be free of all dirt, trash , etc., clean, sharp sand mixed with fine gravel, and the best fresh Louisville cement, in the following proportions, viz., one BRICK PAVEMENTS. measure of cement and two of sand, thoroughly mixed, and then made into mortar, with the least possible amount of water; into this will be put the macadam,, which shall first be well wet, and the whole worked into a concrete in such quantities as will produce a surplus of free mortar when well rammed. This pro- portion, when ascertained, will be regulated by measure. Each total of concrete will be thoroughly mixed, in suitable boxes, with hoes and shovels, the mortar always to be mixed fresh before being; applied to the broken stone. It will then be spread and at once thoroughly compacted by ramming with heavy cast-iron rammers,, until free mortar appears on the surface: the whole operation shall be done as expeditiously as possible. The upper surface will be made exactly parallel with the surface of the pavement to be- laid, by floating over the surface with cement and the straight edge. The depth of concrete consolidated shall not be less than nine (9) inches. No walking or driving shall be permitted on the concrete when it is setting, and it shall be allowed to set for three (3) days before any pavement is laid on it. Pavement. On the concrete foundation thus prepared a bed" of clean, sharp sand, free from moisture, two (2) inches deep, shall be laid. The paving bricks to be used shall be such as shall be satisfactory and acceptable to the Engineer, and shall conform 1 strictly to the samples offered by the contractor, and accepted by the Engineer and the Council. The sand must be brought to a true and perfect surface, and made to conform strictly to the grade pegs set by the Engineer, by means of a drag straight-edge, severt (7) feet long, drawn over the surface, and resting on two pieces of scantling 2x4x16 feet long, having planed surfaces, the top of the sand bed being flush with the grade pegs. Upon this bed of sand the paving bricks are to be laid on edge, at right angles to the line of curbs, in parallel lines, in as close contact as possible on sides and ends; the joints broken one with another, by starting at curb-lines with half-bricks, in alternate rows, so as to break the joints. No half or broken brick shall be laid except at the curb- lines, in order to make closures, but the brick must be laid whole throughout, except as above named. As the pavement is laid over thirty or more feet at a time, it shall be thoroughly rammed over three times with a flat iron ram- mer, about one foot in diameter, weighing thirty or forty pounds,, 278 HIGHWAY CONSTRUCTION. which must be done by lifting and dropping the rammer verti- cally. When the bricks have been rammed to a solid bearing and brought to a perfect surface, the interstices shall then be thor- oughly and completely filled, from bottom to top, with distilled coal-tar pitch (known as No. 6) heated up to 300 degrees. All crevices must be filled, and the entire top surface covered to a depth of not less than one fourth inch, and upon this must be spread one fourth inch of clean, sharp sand, which must be com- paratively dry and free from moisture. This sand must be thrown evenly over the boiling pitch as rapidly as the pavement is filled In, and the pitch spread over the surface of pavement, the aim and object being to make the pavement one solid mass, which, when completed, shall be practically a fixture and water-tight. The bricks shall be rigidly inspected before being laid in the pavement, .and all objectionable ones removed. The sand and pitch shall be ^acceptable, and shall also be applied as directed by the Engineer, or his assistant, and to his entire satisfaction and acceptance. The pavement, when completed, must be smooth, and conform to the grades given by the Engineer. Dimensions of Brick. Square-edged, to wit: Length, 8| inches; thickness, 2f inches; width, 4 inches. Halwood block, patent length, 9 inches; width, 4 inches; thickness, 3 inches. Bricks thoroughly burned throughout to vitrification. 333. Extracts from Specifications for Laying Brick Pavements in the City of Bloomington, 111. Roadbed. The roadbed shall be carefully graded and shaped to an elevation of at least eleven inches below the established grade line given by the City Engineer, and intended for the surface of the pavement when completed. The City Engineer, or his assist- ant, shall set all grade stakes, and thereafter the same must be protected and maintained by the contractor and his employees un- til the services of the same are no longer needed. The contractor shall do all necessary grading and shall provide all earth necessary for filling, and dispose of all surplus excavation by removing the .same to the lawns or other dirt streets as the City Engineer may direct. In order to bring the roadbed to the proper shape and .grade, a pattern made under the direction of the City Engineer, giving the street proper convexity, shall be continuously used as a guide to the graders. After said roadbed is properly graded and BRICK PAVEMENTS. 279 shaped it shall be thoroughly rolled and compacted by the steam roller, wherever it is practicable to use said roller; and wherever the use of the steam roller is impracticable the foundation shall be com- pacted either by the use of the smaller roller or by tamping. The roadbed, being properly rolled, shall then be covered with cinders of a uniform depth of at least three inches, and the same shall be rolled and compacted as before; and there shall then be spread a covering of sand of sufficient thickness to grade the surface of said roadbed to a uniform shape, regular and smooth surface for receiv- ing the bottom course of brick. Should any depressions appear during the process of rolling, such as the settlement of sewer branches or otherwise, the same must at once be filled up and again rolled, so that, when the process of rolling shall cease, the entire roadbed shall be uniform and complete in its settlement. Brick Work. There shall then be placed a course of brick upon their flat surface, long dimensions parallel with the street, laid as closely together as practicable and all joints broken. Dry sand, screened, will then be spread over the entire course of brick, and well brushed in so as to completely fill all crevices. Sufficient screened sand will then be placed on the bottom course of brick to make a bed of one inch depth upon which to place the top course of brick. The top course of brick will then be laid on their longest two-inch surface across the screet, breaking joints and laying the brick as closely together as possible. Nothing less than whole bricks to be used in the top course except were necessary to break joints. The courses of brick in the top course must be kept straight across the street, at right angles to the curbing as near as practicable. Brick that are badly swelled and irregular will not be permitted in the top course. They must constitute a good quality of " paving-brick," maintaining uniformity and regularity in shape to such a degree as will be consistent with a first-class pavement, and render satisfac- tion to the Engineer in charge. The bottom course of brick must be composed of a good quality of such as are known as "sidewalk brick." The top course of brick, having been laid as above provid- ed, must then be covered with screened sand and rolled with a roller weighing at least two tons. During this final process of rolling the sand must continually be brushed into the pavement so as to effectually fill all crevices. All such work shall be under the supervision and subject to the approval of the Engineer. 280 HIGHWAY CONSTRUCTION. 334. Extract from Specifications for Paving-brick Wheeling, W. Va. Quality. The brick must be thoroughly hard, -well and uniformly burned, and free from warps and fire-cracks. They must be free from all loose lumps of uncrushed clay or laminations, and all particles completely fused and coalesced or vitrified. By " vitrified " is here meant a perfect blending of the constituents in burning. The quality requirements compactness, uniformity of texture, hardness, toughness, vitrification must extend uniformly through the whole interior, and when broken, bricks shall show no variation in structure. Slight kiln marks or indentations will be no bar, but overburned or checked bricks will not be accepted. Dimensions. The dimensions must be the same throughout the entire contract, and the size shall be approximately 8|X4X2^ inches. This shall not be considered to shut out any brick of ordinary size. They shall be true in form and rectangular in shape. Test. The bricks shall be subjected to such tests and inspection as the City Engineer shall direct, but the governing test shall be the "rattler " test. For this test five entire bricks of each sample shall be placed in a tumbler or rattler of cylindrical form, 30 inches in diameter, 4J feet in length, along with ten cast-iron weights of cylin- drical form, weighing 6 pounds each. These materials shall not be accompanied by any kind of cushioning material or any other material whatever. The rattler shall then be revolved for thirty minutes at a speed of 24 revolutions per minute. The bricks are weighed before they are placed in the rattler and after they have been tested, and the loss in weight found. This last, divided by the original weight, gives the percentage of loss. The average per- centage of loss of the five bricks shall not exceed 10 per cent. In weighing the result of the rattler test, pieces of brick less than one- half pound in weight shall be considered a normal loss; but in case of a single piece of brick weighing more than one-half pound, the brick sustaining such loss may be discarded and the percentage determined by using the remaining four bricks. This shall not be construed as permitting the rejection of an inferior brick, but as an assumption that the brick had a large fire-crack, overlooked at the start. A second test of the brick may be required at the discretion of the engineer. Inspection. The brick will be inspected at the kiln by a repre- sentative of the board of public works. If the board so elects, the BRICK PAVEMENTS. 281 contractor must give two days' notice to the clerk of the board cf public works when bricks are to be loaded or shipped. The brick shall again be subject to inspection and rejection during the laying of the pavement or any handling of the brick, and all brick rejected will not be paid for. Sample Brick. Bidder must submit not less than ten samples of brick proposed to be furnished; five of these bricks to be subject to the rattler test, and the remaining five, supplied by the successful bidder, being retained as samples for comparison until the expira- tion of the contract, and all shipments shall be equal to samples. 334a. Extract from Paving-brick Specifications. ST. Louis, Mo. " The bricks shall not be less than eight inches nor more than nine inches long, not less than two and one-half inches nor more than three and one-half inches wide, not less than four inches nor more than four and one-half inches deep, with rounded edges with a radius of three-eighths of an inch. Said brick shall be of the kind known as ' repressed ' brick, and shall be repressed to pro- duce a mass free from internal flaws, cracks, or laminations. " The bricks shall be uniform in size and quality, and thoroughly burned and annealed. "All bricks so distorted in burning or with such prominent kiln-marks as to produce an uneven pavement shall be rejected. "Each bidder shall submit one hundred bricks, which shall be subjected to such physical tests as may, in the opinion of the Street Commissioner, be necessary to determine their quality and suitability for the work. "To secure uniformity in bricks of approved manufacture, de- livered for use, the following tests shall be made: " 1. They shall show a modulus of rupture in cross-breaking of not less than twenty-five hundred pounds per square inch. " 2. Specimen bricks shall be placed in the machine known as the "rattler," twenty-eight inches in diameter, making thirty revolutions per minute. The number of revolutions for a standard test shall be eighteen hundred, and if the loss of weight by abrasion or impact during such test shall exceed thirty per cent of the orig- inal weight of the bricks tested, then the bricks shall be rejected. An official test to be the average of two of the above tests. " No bid contemplating the use of rejected brick shall be enter- tained. 282 HIGHWAY CONSTRUCTION. "Samples maybe submitted by manufacturers, in which case the bidders proposing to use brick of such manufacture will not be required to submit samples. The quality of the brick furnished must conform to the samples presented by the manufacturers and kept in the office of the Street Commissioner. " The Street Commissioner reserves the right to reject any and all bricks which, in his opinion, do not conform to the above speci- fications." The specifications for vitrified block differ from the above only in the following particulars: Dimensions. The blocks shall not be less than nine inches nor more than twelve inches long, not less than three and one-half inches nor more than four and one-half inches wide, not less than five inches nor more than six inches deep. Rattler Test. When tested in the rattler, under the above con- ditions, if the loss exceeds twenty-five per cent of the original weight, then the blocks shall be rejected. 334b. Rumbling in Brick Pavements. The rumbling is caused by vacant spaces between the brick and the foundation. These spaces may be formed in a number of ways. If the sand bed is carelessly made or not properly compacted, the settlement will leave a space between the bed and the brick; if the rows of brick are keyed up too tightly, they are forced off the sand bed a slight distance, which is sufficient to transmit a rumbling sound; or the same result is obtained if the brick are not rolled sufficiently to force them solidly into the sand bed. Lime in the material used for joint-filler will, by swelling, cause the brick to rise from the foun- dation. It is now thought that the tendency to lift may be remedied by introducing at intervals of 25 or 30 feet across the street, and on both sides of the street at the curb, an expansion-joint of pitch, so that any movement of the pavement due to swelling of the filler or to change in temperature will be taken up by the elasticity of the pitch-joints. BRICK PAVEMENTS. 283 334c. Number of Brick and Block Required per Square Yard. , Number Weight of Trade Name. per Yd l br k) lbg Mack repressed brick 60 6.88 Mack (Lug) repressed brick 58 7.06 Corning repressed brick 60 6.40 Johnsouburg repressed brick 63 6.81 Preston repressed brick 62 6.04 McMahon-Porter repressed brick 56 7.07 Park repressed brick 59 6 31 Park (wire-cut) brick 58 6.35 Metropolitan (repressed) block 43 9.98 Nelson ville repressed block 42 9.50 Mack (Lug) repressed block 44 9.11 Townsend repressed block. 46 8.60 Athens repressed block 42 9.50 Harris repressed block 43 9.00 Bolivar repressed block 44 8.25 Guise repressed block , 46 9.25 Park repressed block 40 9.30 Eastern repressed block. ... 46 9.25 McMahon-Porter repressed block 43 9.14 Clearfield repressed block 48 8.20 Clearfield (wire-cut) block 47 8.56 334d. Brick Paving for Country Roads. Brick is being success- fully used for paving country roads, both as a substitute for broken stone and in localities where good stone is not obtainable, and also in combination with broken stone. The first experiment with brick for this purpose was made at Monmouth, 111., where a strip of pavement 3000 feet long and 7 feet wide was constructed, at a cost of $2650. The method of construction was as follows : The earth road-bed was graded and formed to the proper contour. The curbing to hold the brick in place was made of 2 X 6-inch oak plank set 7 feet apart, and held in place by oak stakes 18 inches long, driven 4 feet apart ; in the space inclosed by the curbs a sand bed 5 inches thick was formed and shaped to the required contour; on this was placed a single course of No. 1 paving-brick set on edge, and the joints were filled with sand. Outside the curbing broken stone was placed for a width of 2 feet, thus making the width of 284 HIGHWAY CONSTRUCTION. the improvement 11 feet. The earth road on each side of the paved strip was graded and formed to afford trackways for use in dry weather. The total width of the road being 40 feet. The use of brick for the construction of trackways has been suggested by Engineering News. The advantages of such track- ways would be the same as stated in Art. 439 under Stone Track- ways. The details of construction, such as the foundation, under the bricks, the construction of the broken-stone pavement at their sides and between them, the material for filling the joints between the bricks, drainage, etc., will have to vary with local circum- stances. The method of construction adopted must make provi- sion against the tilting of the brick under loads crossing them, and also against their displacement by frost. To provide against the first, a rough stone curb may be used, as shown in Fig. 196. If FIG. 1 98. CROSS-SECTION MACADAM ROAD WITH BRICK TRACK- WAY. stone is not available, brick set on edge, artificial stone, or fire-clay curbing may be used. Where provision has to be made for drainage, the construction may be as shown in Fig. 19c. FIG. 1 9c.~ CROSS-SECTION BRICK TRACKWAY UNDERDRAINED. BRICK PAVEMENTS. 285 The ditch above the drain-tile may be filled with any coarse materials field-stone or quarry-spalls too soft or gravel too large for road-covering or with lumps of burnt clay. The filling to be thoroughly compacted by ramming. The space between the brick .strips and outside them to be covered with gravel, and the joints between the bricks filled with sand. 334c. Average price of paving-brick per thousand in 1904: State. Price. State. Price. Alabama $13 87 Missouri . $10 17 California 18 08 Montana . ... 16 00 Colorado 9 67 Nebraska . .... 8 15 Connecticut and Rhode Isl 14 00 New Jersey 13 49 Georgia 12 00 New Mexico 10 00 Idaho 25 00 New York 13 06 Illinois 10 20 North Carolina 8 95 Indiana 9 90 Ohio 10 16 Indian Territory 7 44 Oklahoma 7 00 Iowa 10 38 Pennsylvania 10 72 Kansas 7 63 Tennessee 11 80 Kentucky . 14 91 Texas 8 81 Louisiana 10 07 Utah 9 00 Maine 15 02 Virginia 10 46 Maryland 10 08 Washington 16 20 Massachusetts 14 00 West Virginia 11 87 Michigan 13 28 Minnesota . 10 00 Average for the U. S 10 28 i The total number of brick made was 735,489,000, valued at $7,557,425. 334f. Expansion of Brick Pavements. The coefficient of ex- pansion of paving-brick has been determined by experiments at the Watertown Arsenal to be about 0.0000032 for one degree Fahr. The increase in width of a street 34 feet wide, if unconfined, would be 0.013 inch for a rise in temperature of 10 F. CHAPTER VII. BROKEN-STONE PAVEMENTS. 335. As near as can be ascertained, the first broken-stone pave- ments were constructed in France in 1764 by one M. Tresaguet, who built many miles of such pavements in the latter part of the 18th century. In the early part of the 19th century two systems were introduced into England, the first by Telford, the second by Macadam. 336. The name of Telford is associated with a rough stone foun- dation, which he did not always use, but which closely resembled that which had been previously used in France. Macadam disre- garded this foundation, contending that the subsoil, however bad, would carry any weight if made dry by drainage and kept dry by an impervious covering. The names of both have ever since been associated with the class of 'road which each favored, as well as with roads on which all their precepts have been disregarded. 337. The following specifications show the difference in the methods of the inventors. 338. Tresaguet's Method, 1764 (Fig. 21). "The bottom of the foundation is to be parallel to the surface of the road. The first bed or foundation is to be placed on edge and not on the flat, in the form of a rough pavement, and consolidated by beat- ing with a large hammer; but it is unnecessary that the stones should be even one with the other. The second bed is to be equally placed by hand, layer by layer, and beaten and broken coarsely with a large hammer, so that the stones may wedge together and no empty spaces remain. The last bed, three inches in thickness, is to be broken to about the size of a nut with a small hammer, on a sort of anvil, and thrown upon the road without a shovel to form the curved surface. Great attention must be given to choose the .hardest stone for the last bed, even if one is obliged to go to more 286 BROKEN-STONE PAVEMENTS. 287 distant quarries than those which furnish the stone for the body of the road. The solidity of the road depending on this latter bed, one cannot be too scrupulous as to the quality of the materials which are to be used for it." Fig.20. FRENCH. PREVIOUS TO 1775 Fig.21. TRESAGUET, Fig.22. TELFORD. Fig.23. MACADAM- 339. Telibrd's Method, 1824 (Fig. 22)." Upon the level bed prepared for the road materials a bottom course or layer of stones is to be set by hand in the form of a close firm pavement. The stones set in the middle of the road are to be sever inches in depth; at nine feet from the centre, five inches; at twelve feet 288 HIGHWAY CONSTRUCTION". from the centre, four inches ; and at fifteen feet from the centre, three inches. They are to be set on their broadest edges lengthwise across the road, and the breadth of the upper edge is not to ex- ceed four inches in any case. All the irregularities of the upper part of the said pavement are to be broken off by the hammer, and all the interstices to be filled with stone chips firmly wedged or packed by hand with a light hammer, so that when the whole pavement is finished there shall be a convexity of four inches in the breadth of fifteen feet from the centre. " The middle eighteen feet of pavement is to be coated with hard stones to the depth of six inches. Four of these six inches to be first put on and worked in by carriages and horses; care being taken to rake in the ruts until the surface becomes firm and con- solidated, after which the remaining two inches are to be put on. " The whole of this stone is to be broken into pieces, as nearly cubical as possible, so that the largest piece in its largest dimen- sions may pass through a ring of two and one half inches inside diameter. " The paved spaces on each side of the middle eighteen feet are to be coated with broken stones or well-cleaned gravel up to the footpath or other boundary of the road, so as to make the whole convexity of the road six inches from the centre to the sides of it, and the whole of the materials are to be covered with a binding of an inch and a half of good gravel free from clay or earth." 340. Macadam's Method (Fig. 23). Macadam omitted the foun- dation of large stones, claiming that it was not only useless but injurious; he placed on the natural soil a layer of stone broken equally into cubes of about one and a half inches in their greatest dimensions, and spread equally over the surface of the road to a depth of ten or twelve inches. Binding material was not used, the stone being left to work in and unite by its own angles under the traffic. Macadam preferred the test of weight to that of measure- ment, and insisted that no stone should weigh more than six ounces, which is the weight of a cube of one and a half inches of hard compact limestone; his overseers were provided with small scales and a six-ounce weight to test the larger stones. Although Macadam was the pioneer of good road construction in England, and from whose name the word macadamized is de- rived, it may be observed that he had been anticipated in the pro- BROKEN-STONE PAVEMENTS. 289 mulgation of the system of a regularly-broken stone covering by Mr. Edgeworth, an Irish proprietor, whose treatise on roads, of which the second edition was published in 1817, contains the re- sults of his experiments on the construction of roads, with some useful rules. He advocated the breaking of the stones to a small size, and their equal distribution over the surface. He also recom- mended that the interstices should be filled with small gravel or sharp sand a practice which, though condemned by Macadam, is now adopted by the best road makers.* 341. Since Telford and Macadam's time the practice of road- making has been greatly improved by the introduction of rollers and stone-crushing machinery. 342. Modern Telford. On the natural-soil bed, properly graded, a layer of stones eight inches thick is set by hand, arranged and wedged as described by Telford. On the stone foundation so prepared a layer of broken stone of a size not exceeding three inches is evenly spread and rolled; the surface so rolled is covered with a layer of sand one-half inch thick, and the rolling continued ; then a layer of stones not larger in any dimension than two inches is spread to a depth of four inches and rolled, followed as before with a layer of sand and also rolled. Finally a coating of clean sharp sand is applied, well watered, and the rolling continued until the surface becomes smooth. The surplus sand is then swept off and removed. 343. Modern Macadam pavements are constructed in the man- ner above described, only omitting the stone foundation, and the depth of the stone varies from four to twelve inches. 344. Defects of the Telford System. (1) No matter how care- fully the interstices between the foundation-stones are filled with chips, a large percentage of voids is left giving free access to water, thus defeating the object of the covering, which is to pre- serve the natural soil from contact with water. The pavement acts as a drain; the natural soil becomes saturated with water, and a slow but constant sinking of the bottom stone into the sub- soil and a slow but gradual rising of the natural soil takes place, * Renuie also brought into use, eight or ten years before Macadam, the system of broken-stone road construction in connection with the formation of the road-surface upon many of the bridges built by him, notably the bridge commenced in 1809, afterwards known as Waterloo Bridge, where upon a compacted clay foundation a layer of fine gravel was rolled in to receive a coating of flints broken to the size of an egg. 290 HIGHWAY CONSTRUCTION. the cohesion of the superstructure is destroyed, and it finally becomes a mass of mud and stones. (2) If the foundation be of a harder rock than the covering, it- becomes an anvil on which the softer stones are pounded to pieces by the passing loads. (3) The stone foundation unnecessarily increases the cost of construction. The roads of Central Park, N. Y., are excellent examples of the Telford system. They are of indefinite thickness, reposing on a bed of thoroughly drained earth; they were con- structed and are maintained at a cost that is prohibitory to an exten- sive use of such pavements. 345. Defects of the Macadam System. The broken stone laid as directed by Macadam cannot be impervious, because the inter- stices compose one half of the bulk of loosely spread stones, and no amount of rolling will reduce the voids more than one fourth; and as nature abhors a vacuum, the subsoil when moistened will rise up and fill the vacant space, and the weight of the traffic will force the lower stones down until the whole becomes a mass of mud and stones, as shown by the following analysis of a portion of the crust of the macadamized roads in the Mall, St. James Park, London : ANALYSIS OF MACADAMIZED KOAD CRUST. Mud ll.OOcu. ft. or 41.00 percent Sand with pebbles not exceeding -^ of an inch. . . 2.40 " " 9 Stones from ^ to $ inch 6.56 " "24 " itolinch 4.48 " " 16 " Ito2iinches 2.56 " " 9| Total volume 27. 00 cu. ft. or 100.00 percent From this analysis it appears that less than 9-|- per cent, say one tenth of the original stone, escaped underground, whilst 40 per cent of it was reduced to the state of mud. 346. Advantages of Broken-stone Pavements. (1) Good foothold. (2) Reasonably easy traction when in good condition. (3) Moderate first cost. (4) Comparatively noiseless. 347. Defects Common to all Broken-stone Pavements. (1) Mud when wet. BROKEN-STOITE PAVEMENTS. 291 (2) I) nst when dry. (3) Excessive cost of maintenance under heavy traffic. (4) Impossibility of keeping them clean. 348. The foregoing defects condemn the use of broken stone for city streets, yet when properly built and maintained broken stone forms the pleasantest, safest, and most economical road- surface known for city suburbs and country highways. Owing to diversity of climate and tramc it is manifest that no single material is adapted to all cases; therefore to secure the best results the materials must be selected and the method of con- struction must be adapted to the conditions under which the road is to be used and maintained. The standard methods introduced by Telford and Macadam were devised for a country with a humid climate, in which water lent its aid in binding the road material together, and its removal by drainage of the roadbed and sur- face was the most important item in the maintenance of a good surface. With the construction of roads in localities having little or no rain, drainage becomes unimportant, and the preservation- of a well- bonded surface is of more consequence. This bonding may be secured with a bituminous binder, as is so successfully practised in California. Ideally perfect broken-stone road construction has never been' attained, owing to (1) the diversity in the quality of the materials which must necessarily be employed; (2) the conflicting proper- ties which the materials must possess; and (3) the too close adherence to precedents established under entirely different con- ditions of climate and traffic. However, with methods of con- struction adapted to the locality and the requirements of the traffic, together with a thorough knowledge of the behavior of the available materials under the given conditions, it will in time be possible to construct roads with the same accuracy as bridges and with the same certainty of success. 349. Essentials Requisite to Successful Construction. The essen- tials requisite to the successful construction of broken-stone pave- ments may be summed up as follows: (1) The entire removal from the roadbed of all vegetable or perishable matter. (2) The removal of the natural soil to such depth as may be 292 HIGHWAY CONSTRUCTION. determined by its character, and by the thickness of the intended covering. (3) Sub-surface drainage wherever required. (4) The thorough compacting of the natural-soil bed. (5) The employment of sand or gravel for the foundation. (6) The employment of the best materials afforded by the locality, and, if the traffic warrants it, the importation of suitable materials from other places. (7) The reducing of the voids in the mass of broken stone to the least possible amount by properly proportioning the different sizes of stone from chips up to the maximum size to be used. (8) The complete exclusion cf clay cr loam from the broken stone. (9) The employment of sand or stone-dust and screenings in quantity sufficient to fill the voids. (10) The thorough compacting of the broken stone with a roller of competent weight and suitable form. 350. Erroneous Methods of Construction. Broken-stone pave- ments can be made very unsatisfactory and defective by: (1) A permeable foundation in humid climates. (2) By the use of excessively hard stones which no amount of rolling will consolidate. (3) By the use of improper binding material, such as loam and clay. (4) By an undue proportion of soft among hard stones. A small quantity (about one fourth) of soft stones judiciously mixed with the harder will be an undoubted advantage. (5) By employing stones of too large a size. (6) By using stone from which the smaller fragments have been excluded by screening. Unscreened stones may be used for the lower course, provided no " tailings" or long flaky pieces are present. Experience with unscreened or " crusher-run " stone has shown that when used for the surface it wears unevenly and produces a generally unsatisfactory road, owing to the irregularity in the size of the fragments, and the variation in the proportion of the several sizes and their unequal distribution in the mass, which makes it impossible to decrease the amount of voids. BROKEN-STONE PAVEMENTS. 293 (7) By assorting the stone and laying it in layers according to the size of the stone. The practice of forming a road with strata of screened stone assorted in different sizes and growing smaller and smaller towards the top is erroneous ; the smaller stone will find its way to the bottom, and the larger stone will work to the surface and ruts will be quickly formed. It will be porous, and no matter how heavily rolled it will be continually crumbling. The stone should be assorted by screening into the several sizes, then re- mixed in such proportions (determined by a test) as will produce a mixture containing the least possible amount of voids or a density as nearly equal to that of the rock from which the broken stone was obtained as it is possible to attain. This may be ascertained by determining and comparing the specific gravity of the original rock and that of the mixture. (8) By covering the surface of the compacted stone with a layer of stone-dust. (9) By the use of an excessive quantity of binding material. (10) By the use of an excessive quantity of water when rolling. 351. duality of the Stones. The materials used for broken-stone- pavements must of necessity vary very much according to the locality. Owing to the cost of haulage, local stone must generally be used especially if the traffic be only moderate. If, however, the traffic is heavy, it will sometimes be found better and more economical to obtain a superior material, even at a higher cost, than the local stone ; and in cases where the traffic is very great, the best material that can be obtained is the most economical. 352. The qualities Required in a good road stone are hardness and toughness and ability to resist the disintegrating action of the weather. These qualities are seldom found together in the same stone. Igneous and silicious rocks., although frequently hard and tough, do not consolidate so well nor so quickly as limestone, owing to the sandy detritus formed by the two first having no cohesion,, whilst the limestone has a detritus which acts like mortar in bind- ing the stones together. 353. A stone of good binding nature will frequently wear much better than one without although it is not so hard. A limestone road well made and of good cross-section will be more impervious to wet than any other, owing to this cause, and will not disintegrate 294 HIGHWAY CONSTRUCTION". so soon in dry weather, owing partly to this and partly to the well- known quality which all limestone has of absorbing moisture from the atmosphere. Mere hardness without toughness is not of much use, as a stone may be very hard but so brittle as to be crushed to powder under a heavy load, when a stone not so hard but having a greater degree of toughness will be uninjured. By a stone of good binding quality is meant one that, when moistened by water and subjected to the pressure of loaded wheels or rollers, will bind or cement together. This quality is possessed to a greater or less extent by nearly all rocks when in a state of disintegration. The binding is caused by the action of water upon the chemical constituents of the stone contained in the detritus produced by crushing the stone, and by the friction of the frag- ments on each other while being compacted ; its strength varies with the different species of rock, but it exists in some measure .with them all, being greatest with limestone and least with gneiss. The essential condition of the stone to produce this binding ^effect is that it be sound. No decayed stone retains the property of binding, though in some few cases, where the material contains iron oxides, it may, by the cementing property of the oxide, un- dergo a certain binding. The first attempt to ascertain the cementing property of rocks was made by the Massachusetts Highway Commission. The method followed is described in Art. 35 Qa. These tests show in general that quartzites, sandstones, gran- ites, gneisses, and marble possess very little cementing power, some of them breaking down with two or three blows; whereas lime- stones and some trap-rocks show a high p&ver of cementation and stand thirty or forty blows before giving way. Other trap-rocks have not proved so good. 354. The durability of stones used for roads depends partly upon resistance to chemical decomposition and partly upon resist- ance to mechanical abrasion. The former character is influenced mainly by the chemical composition of the constituent materials, while the latter depends upon the manner in which and the ma- terial by which these component minerals are aggregated into a compact mass. To know thoroughly the qualifications of any rock as a road-stone, therefore, involves an intimate knowledge of both BROKEN STONE PAVIME.VTS. 205 its mineralogical composition and its structure. Some of the ap- parently hard and durable rocks, such as certain granites and ba- salts, which remain comparatively unaltered when in the solid crust of the earth and removed from the disintegrating influence of air and water, when broken up and exposed to the chemical in- fluences prevailing on the surface of a road rapidly decompose into clayey mud. Other rocks, such as many of the sandstones, are chemically almost indestructible, but are so loosely aggregated to- gether that under the action of traffic they crumble into powder. As regards the structure, its character is influenced by the size of the grains (within certain limits the coarser the grain the weaker the crushing-strength of the stone), the orientation of the crystals, and the nature of the base or matrix in which these crystals are imbedded. Man) 7 of the crystalline rocks are merely an aggregate of crystal grains wedged together into a tight-fitting mosaic. The breaking down or decomposition of one of the component minerals seriously diminishes the cohesion of such rocks. In other cases there is much more intimate union of the crystals, which are interlocked in such a manner that the cohesion is increased. In others the crystalline particles are firmly set in a more or less com- pact siliceous paste or cement of considerable hardness and dura- bility, and forming a continuous matrix, which would hold to- gether even if the crystals themselves decayed. As regards the mineralogical constituents, a vast difference exists in the chemical durability of different minerals. Feldspar, which forms a consid- erable proportion of the composition of the great majority of rocks used for roads, occurs in many different varieties, some of which the potash feldspars are much more durable than those which contain a large proportion of soda or lime. With regard to the durability of minerals a distinction must be drawn between chem- ical disintegration or decomposition and alteration. Many minerals are liable to alteration without any loss of cohesive power. In some cases there is often a distinct gain in the chemical durability of such altered minerals. Among minerals of this kind may be men- tioned the ferro-magnesian silicates, which readily alter into ser- pentinous products of great stability. The mere presence, there- fore, of an unstable element in a rock is not necessarily of itself unfavorable, unless the result of its alteration is such that disinte- HIGHWAY CONSTRUCTION. gration ensues, as when feldspar breaks down into a powdery clay. Hardness, though important when combined with other qualities, is singly not of great consequence. Quartz, the hardest of the- common minerals, used alone does not make a desirable road-stone, as its dust is lacking in cementing power; it has a low specific gravity and is very brittle. Brittleness promotes crumbling under the impact of traffic. Soft rocks, as limestones and slates, are quickly ground to powder and are rapidly carried away by water and wind action. The most efficient road-stones are obtained from the class of rocks called traps, or dike-stones, and technically known as diabases and diorites. These rocks are not uniformly desirable, but nearly all of them are better than the best of other rocks. The normal composition of the diabase rocks is feldspar and pyroxene, with or without black mica. The diorites may be considered as the same rock with the mineral hornblende replacing the pyroxene. The structure of these rocks is such that the minerals composing them are interlocked with one another in the most perfect manner, thus producing great toughness. To the effect of this structure must be added the uniform toughness of the individual minerals pyroxene and hornblende. The feldspars present in the diabases and diorites are essentially alumino-silicates of calcium and sodium, and they form one of the unstable compounds, under the influences of their environment, on which depends so largely the rapid disintegration of these rocks. When these rocks are fresh, little loss from this cause is to be apprehended during the life of the road; but where the weathered portion of the rock, the sap, is used, the loss sus- tained by chemical and mechanical means is considerable. The alteration of feldspar to clay, quartz, and calcite in many cases so weakens the coherency of the rocks that they readily crumble to powder under pressure and are converted into fine sand. The calcite derived from the alteration of the feldspar, when deposited from solution during dry periods, acts to a limited extent as a bind- ing material, tending to strengthen the rock-dust and increase its attachment to the broken stone. The experiments of the Massa- chusetts Highway Commission shows that the maximum cementing value of powdered rock was obtained from an olivine diabase which was much weathered. Some diabases carry a considerable percent- BROKEN-STONE PAVEMENTS. 29? age of black mica, which, owing to its tabular form and the readi- ness with which it cleaves into thin plates, is quickly and easily transported by the winds. The essential mineral pyroxene and the occasional mineral pyrite in diabases, and the hornblende in diorite, are also prone to decomposition, a change which is aided by the presence of acids. The granite rocks are undesirable for use as road-stones. Many of them contain more or less of the soda and lime-bearing feld- spars, in addition to the potash variety, and their durability is in consequence adversely affected. No granite can be found whose feldspar is free from some secondary alteration to clay, and when this change has gone on to a degree sufficiently great to affect the strength of the stone it should be discarded as unfit for broken - stone roads. Granites in this condition quickly crumble to sand and clay, and the winds sweep away the fine material in dry weather, while in rainy times the road is in a muddy state. There are several kinds of mica present in granite rocks. Of these mus- covite or white potash mica is much more durable than the black ferro-magnesian mica, biotite. This circumstance is proved by the fact that white mica is a much more frequent constituent of the sedimentary sands and clays derived from the breaking up of granite rocks than is biotite or black mica. The mica is very easily transported both by wind and water action, owing to its tabular character, and this mineral under all circumstances is unde- sirable in road-stone. Other constituents of granite, such as pyrites and iron oxides, are also notably unstable. A true granite is composed of quartz, orthoclase, feldspar, and two micas biotite and muscovite. The micas are not always present, their place being wholly or in part taken by hornblende or pyroxene. When a granite is free from mica it offers great resistance to wear, but its brittleness and its granular structure operate to increase the rate of abrasion. Granite differs from the trap-rocks not only in mineral composition, but also in an entire difference in the form and arrangement of the constituent minerals; in the granites the structure is granular, with little tendency toward an interlocking arrangement. The brittleness of granite is due principally to the quartz, one of the hardest as well as most brittle minerals of com- mon occurrence. When the necessities of the case force the use of 398 HIGHWAY CONSTRUCTION. granite rocks it is well to select those, such as syenites or granites, containing as small a percentage of mica and quartz as possible. Syenite if badly weathered is considered even more objectionable than granite. Although granite and syenite contain a great amount of feldspar, the cementing value of these rocks is much less than that possessed by the diabases and diorites. Gneiss and mica schists are either too soft or too brittle to withstand the action of traffic. The micaceous element causes the stones to break up and grind away quickly. The hornblende schists, although rather soft and easily ground up, have consider- able toughness, and in the absence of better material will make tol- erable roads. Limestone rocks, though they vary considerably in hardness, are in general much too soft for economical use in road-making, provided any other more suitable material can be obtained. The variety of such stone which is known as dolomite commonly affords a better rock than calcite, or ordinary limestone. Where the lime is commingled with clay the effect is generally to improve its value as a road material; where the mixture is of sand and the mass is an arenaceous limestone, it is generally poor road-stone. Where the surface of a limestone road can be covered with iron ore the firmness of the mass is much increased. Crystalline limestone or marble is unsuitable, for, while the mate- rial binds well together, it is brittle, and consequently quickly passes into a condition of dust under the action of the traffic. Its granular or crystalline structure has a very pronounced tendency to break up into rhombic grains, a tendency which serves further to increase the weakness of the stone. The white powdery dust produced is very offensive. The limestones suffer a considerable loss from the ready solubility of the calcite in rain-water and water impregnated with acids. Rain-water charged with carbonic acid will dissolve when cold one part of lime carbonate in 10,800 parts of water. In the magnesian or dolomitic limestones the loss from this cause is -omewhat less, but still important. The carboniferous and transi- tion limestones are fairly durable and make smooth and pleasant roads for light traffic and pleasure-drives. Quartz, when it is found, as is sometimes the case, in large veins in which it has been deposited from water at depths below BROKEN STONE PAVEMENTS. 299 the original surface, often affords a tolerable material for macadam purposes. Owing to the very angular forms which the material assumes when crushed, it mats weir together. The bits, however, are not really cemented into a mass, for the dust, unlike that from most other rocks, does not form a binding cement. Moreover, under the pressure of wheels and the beating of horses' feet, the material passes rapidly into the state of fine sand, which is blown or washed away. Eoads of this material rarely attain a very smooth state, and they wear out rapidly. Quartzites are rocks which were originally sandstone the frag- ments of which have to a greater or less extent been dissolved and recemented into a firm mass. The nature of quartzites varies greatly. They are generally hard, but brittle, and break up rap- idly under the action of traffic, forming a fine sand much like pow- dered glass. The smooth surface of the fragments prevents their forming a bond. Mixed with limestone they form fair roads. Chert consists of quartzose material which has been segregated in beds of limestone rock. When the limestone decays and is washed away, the cherty matter is often left in a rubble-like mass. In many cases the material verges into quartzite and is indistin- guishable from it. The cherty residuum arising from the decay of limestone is of value in road-making in the southern portion of the Appalachians and in other portions of this country beyond the gla- ciated field, and also in some of the States of the Northwest. Field-stone and river-stone have been much used in some dis- tricts of England; they generally make a rough road, as they are composed of the hardest parts of those stones which have resisted the action r.f the weather, and are, though frequently very hard, of unequal hardness, so that they wear very irregularly. From the results obtained on experimental paving-strips and in the laboratory the following conclusions have been deduced as to the relative wearing value of different rocks : One cubic yard of basalt having a resistance to crushing of 24,040 pounds per square inch is equal to Pounds per square inch. 1.10 cubic yards of basalt with a crushing strength of 21,015 1 34 ts (t t( (< (f t( <( (t "19 ^00 1.70 " " " 16,780 oOO HIGHWAY CONSTRUCTION. Pounds per square inch. 3.00 cubic yards of coral limestone with a crushing strength of 11,750 3.80 " " " coral limestone with a crushing strength of 10,810 5.80 " " " Triassic with a crushing strength of 9,670 7 to 8 " " " sandstone " " " " 8,390 9 to 11 " " " cretaceous " " " " 7,260 355. Coefficients of quality for various road materials have been obtained by the engineers of the French "Administration des Fonts et Chausees." The quality was assumed to be in inverse pro- portion to the quantity consumed on a length of road with the same traffic, and measurements were systematically made of the traffic and wear to arrive at correct results, these processes re- quiring great care and considerable time. Direct experiments on resistance to crushing and to abrasion and collision were made on 673 samples of road materials of all kinds. The coefficients obtained by these experiments were found to agree fairly well with those arrived at by actual observation of the wear in the roads, and are summarized in Table XXXVIII. The coefficient 20 is equiva- lent to "excellent/' 10 to "sufficiently good/' and 5 to "bad." 356. The experiments were conducted as follows : The apparatus employed to determine the resistance to wear consisted of cylindrical boxes of iron about 8 inches in diameter and 13 inches long, mounted on an axle revolving horizontally, and so cranked as to hold the axes of the boxes at an angle of 30 degrees with the axis of revolution. In each box was placed 5 kilograms of the broken materials to be tested, carefully cleansed from dust by washing, and the boxes put in motion at a rate of 2000 revolutions per hour. The stones rolled against one another, and were thrown from one end of the box to the other at each revolution. After 5 hours or 10,000 revolutions the boxes were opened, the detritus resulting from the rubbing and collision was carefully collected and sorted, and the weight of all of less diameter than T ^ inch, compared with that of the original samples, gave the degree of wear. It was found that the best materials seldom gave less than 20 grams of detritus per kilogram, and the coefficient of 20 was therefore, adopted, BKOKEN-STONE PAVEMENTS. 30 L for materials having that proportion of wear. For other materials the coefficient was derived from the proportion Grams of detritus : 20 : : 20 : coefficient. Resistance to crushing was determined hy means of an hydraulic press. Experience having shown that cubes of the hardest ma- terials rarely resisted more than 3000 kilograms per square centi- meter (equal to about 19 tons per square inch) the coefficient of 20 was given to materials presenting that degree of resistance, and other coefficients were derived from the proportion 3000 : crushing weight per square centimeter : : 20 : coefficient. In the experiments every precaution to insure accurate results was taken. When the materials were already rounded, as pebbles, they did not wear much in the machine, and obtained a coefficient far above their value ; and there were anomalies with a few other materials, such as chalk flints with a softer coating, and stones with cavities. The size to which the stones were broken did not seem to have much influence on the wear. TABLE XXXVIII. COEFFICIENTS OF QUALITY. Materials. Coefficient of Wear. Coefficient of Crushing. Basalt . ... 12.5K 14.1 10.3 7.3 11.6 14.5 13.8 14.3 12.9 9.8 3.5 6.6 )24.2 22.9 19.0 18.0 12.7 15.3 30.0 26.2 17.8 21.3 16.8 15.7 12.1 t 8.3 13.4 7.7 12.4 7.2 12.3 9.9 12.3 14.2 17.8 6.5 j!6 16.3 14.8 15.8 13.0 11.1 21.6 16.6 13.2 17.6 25.5 13.5 G ranite Slag Quartzite Quartzose sandstone fcilex Chalk flints 356a. Abrasion and Cementation Tests of Stone. The report of the Massachusetts Highway Commission for 1896 describes in detail the methods employed at the Lawrence Scientific School of Harvard University for testing the qualities of road-building stone. 303 HIGHWAY CONSTRUCTION. In making the tests the aim has been to determine the nature of the qualities which constitute fitness or unfitness of the different rocks used for road-making, the effects of diverse methods of treat- ment used in the process of construction, and the relative value of the bed-rocks and gravels which are found in different parts of the State. The machines used were designed by Prof. L. W. Page. The abrasion-machine was modelled after the Deval machine used by the French engineers for determining the relative value of the stone used in the construction and maintenance of the national highways of France. The machine employed for the abrasion tests consists of four cylinders, each 7.9 inches in diameter and 13.4 inches deep, fast- ened to a shaft so that the axis of each makes an angle of 30 degrees with the axis of rotation. Each cylinder is closed at one end and has a tightly fitting cover at the other. At one end of the shaft is a pulley by which the cylinders are revolved, and at the other end is a revolution-counter. Four tests can be carried on at the same time. The stone to be tested is broken into pieces, between 2| inches and li inches in diameter, and carefully washed to remove any foreign matter. In a test 5 kilograms (11.15 pounds) of stone are placed in a cylinder, the cover is bolted on, and the cylinder is rotated at the rate of 2000 revolutions per hour for five hours. At each revolution of the shaft the fragments of stone are thrown twice from one end of the cylinder to the other, grinding them against each other and against the sides of the cylinder. At the end of five hours the machine is stopped, the cylinder opened, and the contents are emptied into a sieve having Jg-inch meshes. The material passing through the sieve is put aside for the cementation test. The sieve and the stone remaining in it are thoroughly washed, and the cylinder is washed to remove the dust that adheres to it. The washed stones are thoroughly dried and weighed, the decrease giving the weight of the detritus worn off by the test. The percentage of the detritus is rarely less than 20 grams per kilogram of stone used (2^); therefore 20 has been adopted as the standard, and the coefficient of quality is obtained by the following formula : BROKEST-STONE PAVEMENTS. 20 400 a = 20 x = , u = per cent, 2 ni ni * U U in which u represents the weight in grams (15.43 grains) of detri- tus per kilogram (2.23 Ibs.) of stone. After several tests had been made in the manner above de- scribed, it was recognized that the very important property or cementing value of the stone was not investigated. The commis- sion, recognizing this deficiency, accordingly directed its attention to devising some means of supplying it. As no previous attempt had been made in this direction, the commission had to invent its own method, which is as follows: The stone-dust to be tested is obtained either from the detritus of the abrasion test or by specially reducing the stone. The dust is prepared by passing it through an automatic screen, which con- sists of a cylinder (39.37 inches long by 4 inches in diameter) of brass wire netting of five different meshes: 100 meshes per inch at one end and decreasing by 20 meshes each time to 20 meshes per inch at the other end, the smallest size being at the end where the dust enters. The screened dust is mixed with distilled water and placed in a circular metal die; a closely fitting plug is then inserted on top of the wet dust, and a pressure of 1422 pounds per square inch is applied. The compressed briquette, circular in section, 0.98 inch in diameter, and of the same height, is removed from the die and laid aside for two weeks, so that it may become thoroughly dry. The weight of the dust varies with the density and compressi- bility of the stone, but generally about 0.9 ounce, and 0.24 cubic inch of distilled water is required to make a briquette of the above dimensions. The dried briquettes are tested by impact in a specially devised machine, which consists of a hammer, weighing 2.2 pounds, ar- range^, like the hammer of a pile-driver. It is raised by a screw, and dropped automatically from any desired height, falling on a plunger which rests on the briquette. The plunger is held in two guides, and attached to it is a lever pivoted at of its length from the plunger, and carries a pencil at its free end. The pencil has a vertical parallel movement five times as great as that of the plunger, 304 HIGHWAY CONSTRUCTION. and its movement is registered on a drum against which the pencil presses. The drum rotates through a small angle at each stroke of the hammer; thus an automatic diagram is taken on the behavior of the briquette throughout the whole test. The standard fall of the hammer for a test is 0.39 inch, and the blow is repeated until the bond of cementation of the material is destroyed. The final blow is easily ascertained, for when the hammer falls on the plunger, if the material beneath it can withstand the blow, the plunger re- bounds; if not, the plunger stays at the point to which it is driven. The number of blows needed to break the bond is taken as repre- senting the binding power of each stone, and is so used in compar- ing this property in road materials. As the surface of a broken-stone road is constantly abraded and recemented, it was considered desirable to determine the recement- ing properties of the stone tested. Briquettes differing from those described above only in that they were of constant weight instead of constant height were made and tested in the manner described above, and then were remade and retested. The table on page 305 contains some of the results of these tests. 356b. Coefficients of wear and cementing quality of the rocks of Maryland have been obtained by the Highway Division of the Maryland Geological Survey by the same methods described in Art. , and are as follows: Coefficient of Wear. Cementation Test. Trap-rocks 5.7-26.1 1- 10 Serpentine 5.8-21.2 10-300 Granitic and quartzitic 2.6-16.3 1-13 Limestones 4.8-16.8 1- 73 Sandstones 5. -13. 0-28 The figures signify: - Wear. Cementation. 1-7 1-4 bad. 7-12 4-10 fair. 12-17 10-20 good. 17- 20- . excellent. BROKEN-STONE PAVEMENTS. 305 h4 > C5 fc *4 Si H S OH II OGQ fe S D 3 S III! II II It "C D.O 0) I?*- 1I - . o a ^o so .O^ s - a - .t3 3 .2 w t: X! Q O rn 306 HIGHWAY CONSTRUCTION. 357. Size of Stones. The stones should be broken into frag- ments as nearly cubical as possible. The size of the cubes will depend upon the character of the rock. If it be granite or trap, they should not exceed 1 inches in their greatest dimensions; if limestone, they should not exceed 2 inches. The broken stone used on the Massachusetts State roads is separated into three sizes by passing it through a screen with meshes J inch, 1J inches, and 2J inches in diameter. 358. The smaller the stones the less the percentage of voids. Small stones compact sooner, require less binding, and make a smoother surface than large ones, but the size of the stone for any particular section of a road must be determined to a certain extent by the amount of traffic which it will have to bear and the character of the rock used. 359. It is not necessary nor is it advisable that the stones should be all of the same size; they maybe of all sizes under the maximum. In this condition the smaller stones fill the voids between the larger and less binding is required. FIG. 24.-SIZE AND SHAPE OF STONE FOR BROKEN- STONE PAVEMENTS. The proper shape of broken stone is shown in Fig. 24. 360. Breaking the Stone. Breaking stone for the purpose of using it as a road-covering was until quite recently always effected by hand; now by the use of machinery it is more quickly and cheaply broken. 361. Hand-broken stone still finds favor with European en- gineers ; they claim that it is better broken and has sharper angl es than that broken by crushing: and in many districts the occupa- tion affords employment for persons who otherwise would be- thrown upon the public for support. BROKEN -STOKE PAVEMENTS. 307 362. In breaking stone by hand the breaker sits and strikes the stone with a small cast-steel chisel-faced hammer, weighing about one pound, fixed at the end of a long, straight-grained but flexible ash stick. The breaker also has another hammer, weighing about five pounds, with which he reduces the size of the large stones before breaking them into proper size. Each breaker is furnished with a gauge-ring through which the stones must pass in every direction. 363. The great cost of hand-broken stone led to the employ- ment of machine crushers; their use effected a reduction in the cost of from 50 to 200 per cent, and increased the amount of daily output from 1 to 50. 364. The objections to machine-broken stone are principally: (1) Want of uniformity in the size of stones. (2) The stone is frequently flaky with rounded edges, which is a very disadvantageous form for compacting. (3) Very tough stones have frequently to be passed several times through the machine before they get properly broken. (4) Very soft stones are crushed to powder. 365. Cost of Breaking Stone. The cost of breaking stone by hand will vary considerably in different localities on account of the character of the stones to be broken and the value of labor. 366. The average amount of stone broken by a good sione- breaker is given by Mr. Codrington in his work on the Mainte- nance of Macadamized Eoads as follows : Hard silicious stones and igneous rocks, 1 to 1J cubic yards per day; granite, J cubic yard per day ; river gravel, field-stones, or flints, 3 to 4 cubic yards per day. 367. The cost of a stone-crushing plant and expense of operat- ing may be taken as follows : Cost of crusher, engine, aud boiler set up, complete .$2500.00 Cost of operating: 1 enginernan and fireman $3.00 2 laborers feeding 3.50 2 tons of coal 8.00 Oil, waste, etc 2.00 Repairs 10.00 $26.50 The product will vary with the toughness of the stone to be broken and the size of the machine. 368. The wear and tear of a stone-crusher is very considerable; it has been known to reach as high as 62.5 per cent of the first cost of the machine in one year. 308 HIGHWAY CONSTRUCTION. 369. To make a stone-breaking machine pay, it is necessary (1) To give it nearly constant work. (2) To exercise care in feeding, to give a sufficient supply with- out allowing an undue quantity of stone to pass in at one time. (3) That the machine shall be so located as to reduce to the minimum the expense of handling both the unbroken and the broken stone. The dimensions and capacity of several crushers are given in Chap. XXIII. 370. It is impossible to estimate the cost of getting the un- broken stone to the crusher and the broken stone back to the road, for that depends entirely upon the distance which must be trav- ersed in cartage and the condition of the grounds over which the loads are hauled. If the loads have to be hauled a considerable distance to or from the crusher, or if heavy grades have to be as- cended or rough ground traversed, the time occupied in hauling each load will be increased and less can be hauled in a day, thus lessening the work done by horses and drivers for each day's wages. Where stone is to be obtained in more than one place along the line of the projected road, it is sometimes more economical to take the crusher to the stone than to have to haul the broken stone a great -distance. For this purpose the crusher can be mounted on wheels and the steam roller used to haul and drive the crusher, without the expense of a fixed plant for crushing stone. 371. Cost of Quarrying and Crushing Stone. The report of the Board of Street Commissioners of the city of Hartford, Conn., for the year 1890 contains the following table of the cost of quarrying and crushing stone for the past ten years. The increase in the cost of quarrying and crushing stone during the past year is in part chargeable to the extra cost of hauling the stone to the crushers, on account of the added distance at which the stone was procured, also in part by the expense connected with the opening of new quarries. (See Table XXXIX.) 372. Voids in the Broken Stone. The voids of broken stone in which the size and shape of the pieces are nearly uniform are about one half the mass. If the pieces are not uniform, the voids are about four tenths of the mass. The voids in gravel vary, but aver- age about one half of the mass. The greatest amount of rolling will not reduce the voids more than one half of the primitive bulk. A well-rolled road-covering contains from 70 to 80 percent of stone. BROKEX-STOXK PAVEMENTS. 309 TABLE XXXIX. COST OF QUARRYING AND CRUSHING STONE. Year. Cost of Quarrying per cubic yard. Cost of Crushing per cubic yard. Cost of Carting to Breaker per cubic yard. Total Cost of Crushed Stone at thn Quarry per cubic yard. Average Cost Delivered on the Streets per cubic yaid. 1881 . 655 Ct. .536 Ct. .283ct. $1.47 $1.70 1882 .781 ct. .348 ct. .237ct. 1.36 1.87 1883 .... 638 ct. .265 ct. . 247 ct. .15 1.59 1884 . 665 ct. . 372 ct. .228ct. .26 1 70 1885 658 ct . 342 ct . 224 ct. .23 1.66 1886 .... . 590 ct . 289 ct. . 233 ct. .12 1.65 1887 . 595 ct .345 ct. .281ct. .22 1.64 1888 658 ct 221 ct 288 ct 17 1.63 1889 694 ct 319 ct . 263 ct 1 28 1.69 1890 .889 ct 407 ct . 301 ct. 1.597 2.045 Experiments made by the Department of State Engineer and Surveyor, New York, show that sandstone ranging in size from. H to 3 inches contains 40 per cent of voids, which by rolling with. a 10-ton roller was reduced to 35 per cent. 373. Determination of the Voids in Broken Stone. The pro- portion of voids may be determined by experiment in either of the following ways : (1) Determine the specific gravity of the material,, and from that the weight of a unit of volume of the solid. Weigh a unit of volume of the loose material. The difference between the weights divI 1o .d by the first gives the proportion of the voids* (2) Wet the lot ^ material thoroughly, fill a vessel of known capac- ity with it, and then pour in all the water the vessel will contain;. Measure the volume of water required and divide this by the volume of the vessel; the quotient represents the proportion of voids. The smaller the stone is broken the less the percentage of voids and the heavier a cubic yard will weigh. 374. Weight of Broken Stone. To ascertain the weight of a cubic yard of broken stone, multiply the weight of a cubic yard of the given stone by the proportion of voids (usually 0.50) ; the result will be the weight of a cubic yard *>f the stone when broken. 375. Area covered by One Cubic Yard of Broken Stone. A cubic yard of ordinary broken stone will, when properly spread, cover an area of about 32 square yards of surface of a road way. Since a cubic yard of loose broken stone contains only one half 310 . HIGHWAY CONSTRUCTION. of its volume, or 13 cubic feet of solid stone, its weight, allowing 12 cubic feet of solid granite to one ton, is approximately Again, one cubic yard is equivalent to 36 square yards 1 inch deep; and 1 ton of stone laid without compression to a depth of 1 inch covers an area of 36 X ..-r = 32 square yards. When the stone is ^5 laid and rolled the primitive volume is reduced by about one fourth ; and 1 ton of rolled stone laid to a depth of one inch covers an area one fourth less than 32, or 32 x f = 24 square yards. 376. To Find the Area that can be covered by One Ton of Stone, when the Thickness of the Layer is given. Divide 32 by the thick- ness of the layer in inches if unrolled ; or divide 24 by the thick- ness of the layer in inches when rolled. The quotient is the area in square yards. 377. To Find the Area that can be covered by One Cubic Yard of Broken Stone, when the Thickness of the Layer is given. When the stone is not rolled, divide 36 by the thickness in inches; the quotient is the number of square yards that can be covered. When the stone is rolled, divide 27 by the final thickness in inches; the quotient is the number of square yards. 378. Thickness of the Broken Stone. The offices of the stone are to endure friction and shed water; its thickness must therefore be regulated by the quality of the material and the amount of the traffic, and not by any consideration as to its own independent power of bearing weight. Macadam considered 10 inches as suffi- cient for any traffic on any substratum: experience has proved this true in the well-drained and well-kept roads of Europe. 379. The proper rule is to vary the thickness according to the traffic and the grade. Eoads of sharp descent do not require as thick covering as those having flat grades. Mr. J. Owen, County Engineer of Essex County, N. J, adopted the following thicknesses with good results : For grades flatter than \% ............................... 10 inches " between \% and 4 ........................... 8 " " " over4 ..................................... 6 " ;; BROK EX-STONE PAVEMENTS. 3H The roads of Bridgeport, Conn, (upwards of 50 miles), built under the direction of Mr. B. D. Pierce, are, with the exception of two short pieces, only 4 inches thick. These roads are subjected to a regular traffic of loads averaging 6000 pounds each; they give entire satisfaction to the public using them, and an ordinary team hauls a net load of 3000 pounds over them. 380. Many roads of 4 and 6 inches thickness have been built that have not proved satisfactory. Their failure is generally attributed to their thinness. This is erroneous ; the fault does not always lie in the thinness of the stone covering, but in the method of construc- tion followed. The thin roads that fail are as a rule made by throwing the broken stone on an undrained and unrolled earth roadway, frequently without even removing the mud which covers its surface. In some few cases the stones are rolled with a horse roller, but in the majority the stone is left to be consolidated by the traffic. If roads are to be built in this manner, they must be massive; but no matter how massive they be made, they will have no cohesive strength, they will never be impervious to the rnud from below or the rain from above, and will always be unsatis- factory. 380a. The Massachusetts Highway Commission has estimated that non-porous soils drained of ground water will support in their worst condition a load of about 4 pounds per square inch, and the thickness of the broken stone is adjusted to the traffic on this basis. If a division of the load in pounds at any one point by the square of twice the depth of the stone gives a quotient of 4 or less, then the road foundation will be safe at all seasons of the year. On sand or gravel the commission believes that 20 pounds per square inch may be safely placed. Acting on this theory the thickness of stone on State roads varies from 4 to 16 inches; the smallest thickness being placed over good gravel or sand and the greatest over heavy clay. Where the surfacing exceeds 6 inches in depth, the excess may be broken stone, gravel, or ledge stone, the choice depending entirely on the cost, for all are equally effective. 380b. Foundation. The preparation of the natural soil over which the road is to be constructed to enable it to sustain the superstructure and the weights brought upon it requires the observ- ance of certain precautions the neglect of which will sooner or later result in the deterioration or possible destruction of the road cover- ing. These precautions vary with the character of the soil. 312 HIGHWAY CONSTRUCTION. Soils of a siliceous and calcareous nature do not present any great difficulty, as their porous nature generally affords good natural drainage which secures a dry foundation. Their surface, however, requires to be compacted; this is effected by rolling. The rolling should be carried out in dry weather, and any depressions caused by the passage of the roller should be made good with the same class of material as the surrounding soil. The rolling must be repeated until a uniform and solid bed is obtained. The argillaceous and allied soils, owing to their retentive nature, are very unstable under the action of water and frost, and in their natural condition afford a poor foundation. The preparation of such soils is effected by drainage and by the application of a layer of suitable material to entirely separate the surface from the road material. This material may be sand, furnace ashes, or other material of a similar nature spread in a layer from 3 to 6 inches thick over the surface of the natural soil. When the road is formed in rock cuttings it is advisable to spread a layer of sand or other material of light nature, so as to fill up the irregularities of the surface as well as to form a cushion for the road materials to rest on. 381. Sand Core for Broken-stone Pavement. On a well-drained foundation a sand or gravel core will be found as mechanically serviceable as the most costly stone foundation. Such a core covered with a layer of stone measuring when compacted 4 inches thick will form a finer and more lasting surface than a greater thickness of stone laid upon the earth soil and compacted. Telford was aware of this fact; he was willing to prevent by almost any means available the coming in contact of his road material with the earth subsoil, and suggested gravel, sand, or chalk as alternatives to bottoming stones. A requisite, whatever the medium, was that " this bottoming should be made perfectly firm and regular, so as to re- ceive the top workable metal of equal thickness." Thus, although he always advised a paved bottom when it could be had, many miles of roadway were made under Telford's direction without the paved bottom with which his name is associated. The observations of the Massachusetts Highway Commissioners indicate that the employment of a Telford foundation gives un- satisfactory results. In a few cases the large stones have come to the surface in a manner indicating frost action. It is thought BROKEN-STONE PAVEMENTS. that there are few if any cases where equally good results cannot be obtained by the use of sand, gravel, or small stones in the place of Telford, and at a less cost. 382. The quantity of broken stone required per mile of road for different widths and thicknesses is given in Table XL. 383. Spreading the Stone. The stone should be hauled upon the roadbed in broad-tired two-wheeled carts and dumped in heaps, TABLE XL. NUMBER OF CUBIC YARDS OF BROKEN STONE REQUIRED PER MILE OF ROAD. Depth of Width of Pavement in E'eet. stone in Inches. 8 16 24 30 3-2 10 48 60 4 645 1,290 1,935 2,421 2,580 3,225 3.870 4.842 6 968 1.935 2,903 3,632 3,872 4840 5,808 7,264 8 1,290 2,580 3,870 4,842 5,160 6,450 7,740 9,684 10 1,613 3,225 4,838 6,053 6,452 8065 9,678 12,106 12 1,935 3,870 5,805 7,263 7,740 9.675 11,610 14,526 14 2,258 4,515 6,773 8,474 9,032 11,290 13,548 16,948 16 2,580 5,160 7,740 9,684 10,320 12,900 15,480 19,368 and be spread evenly with a rake in a layer of as nearly uniform thickness as may be. . 384. Thickness of the Layers. The thickness of the layers will depend upon the final thickness of the covering. If the finished thickness is to be 6 inches, each layer should be of a depth of 4^- inches. 385. Macadam insisted that the stone should not be laid in shovelfuls but scattered over the surface, one shovelful following another and spreading over considerable space. His object in this was to avoid an accumulation of soft stones at one spot, for the rocks from which the stone was obtained were not of uniform hard- ness, but of all qualities gathered from adjoining fields. The application of this method to stone of uniform quality would be detrimental and have the same effect as screening. 386. Binding. One half of the volume of loosely spread broken stone is space, and no amount of rolling will reduce it more than one half; therefore to thoroughly consolidate the broken stone some fine material must be added. It may consist of the fragments and 314 HIGHWAY CONSTRUCTION. detritus obtained in crushing the stone. When this is insufficient, as will be the case with the harder rocks, the deficiency may be made up of clean sand or gravel. The proportion of binder should slightly exceed the voids in the aggregate; it must not be mixed with the stones, but should be spread uniformly in small quantities over the surface and rolled into the interstices with the aid of water and brooms. 387. The fragments of stone should be proportioned according to t.ieir size, so that the voids in the mass will be the least possible. The stones should be separated into the various sizes by screening, the voids determined, and the stones mixed in the calculated propor- tions. The voids in the mixture should then be ascertained; the amount of binder to be used should be slightly in excess of the voids in the final mixture. 388. By using a large quantity of binding material mixed with the stones the amount of rolling is lessened, but at the expense oi durability. If there is an excess of binding material in the joints of the stones, the first heavy rain washes it out and the surface of the roadway quickly goes to pieces. 389. The French engineers use clay, sand, or earth from the road excavation when such is suitable, in the proportion of one fourth to one sixteenth of the bulk of the stone. They apply it after the steam roller has been once over the broken stones. 389a. As the quality of the binding used is of vital importance, the employment of inferior material, such as road scrapings or material of a clayey nature, should be avoided, even if the initial cost of the work should be greater when a good binding material is used. Stone consolidated with improper binding material may present a good appearance immediately after being rolled and be otherwise an apparently good piece of work, still in damp weather a con- siderable amount of "licking up" by the wheels of the vehicles will take place, which reduces the strength of the coating and causes the surface to wear unequally, By the application of 'an immoderate quantity of binding of any description the stone coating will become unsound or rotten in condition, and if the binding be of an argillaceous nature, will expand during frost owing to its absorbent properties, and cause the displacement of the stones. The surface will become sticky, BROKEN-STONE PAVEMENTS. 315 which seriously affects the tractive power of horses, while the road itself will suffer by the irregular deterioration of the surface. The use of such material for binding as mentioned enables roll- ing to be accomplished in much less time than when proper binding is used, and the cost of consolidating the stone may be reduced by 25 per cent; but on the other hand the stone coating, which will probably contain under these circumstances from 30 to 40 per cent of soft and soluble material, and possibly present a smooth surface immediately after being rolled, will quickly become " cupped " by the wheel traffic, a bumpy surface being the result. This is caused by the irregular wear, while the lasting qualities or " life " of the coating will be shortened, giving unsatisfactory results to those travelling over the road, and the work of renewing the surface of the road in this manner may prove a failure on economical grounds. There can be no doubt, and it is now being more gen- erally recognized, that sand as a material for binding in connection with rolling operations, when applied in a limited but sufficient quantity, promotes the durability of the stone coating, while the general results are equally satisfactory ; a firm, compact, and smooth surface is obtained, and the subsequent maintenance of the road is minimized. A great amount of rolling is necessary when sand is employed as a binding material, but economy is promoted, and the results are more satisfactory when sand is used than by the use of a material which gives to the stone an appearance only of having been properly consolidated. If clean sand be used in combination with the screenings from the crusher a very sound and satisfactory road surface will be obtained. It should always be remembered that the best road is made, other things being equal, with the least amount of binding consist- ent with cohesion ; provided the crust of the road is properly formed transversely and of sufficient strength, a smooth, even- wearing surface and an economically maintainable road will be the result. If the use of motor vehicles equipped with pneumatic tires becomes general, it is possible that some other description of bind- ing material will be necessary. The pumping action or suction created by pneumatic tires, especially when propelled at a high 316 HIGHWAY CONSTRUCTION. speed, causes a considerable movement of the fine particles of the binding material, which on being displaced will convert the cover- ing into a mass of loose stones. This objection can probably be overcome by watering. This will cause an additional expenditure for maintenance, but the cost of sprinkling will be infinitesimal compared with the saving effected in the other items of mainte- nance, the surface wear of the roads will be greatly decreased and the sanitary condition will be much improved. In the report of the Commissioner of Public Roads of New Jersey the effect of automobiles is described as follows: "The displacement of the surface due to automobiles is becom- ing a subject of grave consideration on the part of those having charge of road repair. There seems to be a double action in the process: first, a grinding action, somewhat similar to the ordinary wheel travel; second, a kicking action, throwing the loosened mate- rial to the side. In dry, dusty weather the surface of a macadam pavement, after the passage of a heavy automobile at a high velocity, shows an incipient rut of light dimensions, but plainly to be discerned. This is not like the rut formed by ordinary vehicles, which merely displace the dusty surface, but is due to the tearing out of a portion of the consolidated macadam, and the result is a great increase in the rate of deterioration. Fortunately auto- mobiles do not travel in a straight line like a horse and wagon; therefore the tendency to continuous ruts is not apparent, and so far there is no tendency of the automobiles to break up the surface in any more serious manner. With the steady increase of their use, however, such a condition might arise." Investigations on the roads of France indicate that speeds up to fifteen miles an hour cause little injury, but higher speeds do much damage. 389b. Clay Binder on Sand Subgrade. Some years ago an interesting experimental road was built in Truro, near the extreme end of Cape Cod, and has proved a success. The soil here is loose sand with practically no surface loam. The drainage is perfect. There is not much snow or frost during winters, and the traffic is light and small in volume. The loose sand subgrade was shaped to the desired cross-section, and on this was spread a natural mix- ture of 1 part of sand to 2 parts of clay; this layer was 2 inches deep. Over it was spread a 3-inch layer of stone broken to sizes ranging from i to 1 inches. This broken stone was covered with BROKEN-STONE PAVEMENTS. 317 a 1-inch layer of clay and a long-toothed spike harrow was dragged back and forth until the clay and broken stone were well mixed. The entire surface was finally watered and rolled with a 2-ton horse roller, and since its completion an occasional sprinkling of sand to prevent the clay from becoming muddy is all the work that has been needed to keep the road reasonably smooth and free from loose stone. 390. Necessity of Binding Material. With reference to the recessity of binding material, the following facts are interesting. Mr. Wm. H. Grant, Superintending Engineer of the New York Central Park, in his report upon the park roads, says: " At the commencement of the macadam roads, the experiment was tried of rolling and compacting the stone by a strict adherence to Macadam's theory, that of carefully excluding all dirt and foreign material from the stones, and trusting to the action of the roller and the travel of teams to accomplish the work of consolidation. The bottom layer of stone was sufficiently compacted in this way to form and retain, under the action of the rollers (after the com- pression had reached its practical limit), an even and regular sur- face; but the top layer, with the use of the heavy roller loaded to its greatest capacity, it was found impracticable to solidify and reduce to such a surface as would prevent the stones from loosening and being displaced by the action of wagon-wheels and horses' feet. No amount of rolling was sufficient to produce a thorough binding upon the stones, or to cause a mechanical union and adjustment of their sides and angles together as to enable them mutually to assist each other in resisting displacement. The rolling was persisted in with the rrvPcr adjusted to different weights up to the maximum load (12 tuns;, until it was apparent that the opposite effect from that intended was being produced. The stones became rounded by the excessive attrition they were subjected to, their more angular parts wearing away, and the weaker and smaller ones being crushed. " The experiment was not pushed beyond this point. It was conclusively shown that broken stones of the ordinary sizes and of the best quality for wear and durability, with the greatest care and attention to all the necessary conditions of rolling and compression would not consolidate in the effectual manner required for the sur- face of a road while entirely isolated from and independent of other substances. The utmost efforts to compress and solidify them while in this condition, after a certain limit had been reached, were unavailing." 318 HIGHWAY CONSTRUCTION. 391. Mr. Deacon, Engineer of Liverpool, England, describes the effect of binding material as follows : " Under a 15-ton steam roller preceded by a wacering-cart, 1200 yards of trap-rock macadam, without binding, can only be moder- ately consolidated by twenty-seven hours' continuous rolling. If the trap-rock chippings from the stone-breaker are used for binding, the same area may be moderately consolidated by the same roller in eighteen hours. If silicious gravel from f inch to the size of a pin's head, mixed with about one fourth part of macadam sweepings obtained in wet weather, be used, the area may be thoroughly con- solidated in nine hours. " Macadam laid according to the last method wears better than that laid by the second, and that laid by the second much better than that laid by the first." 391a. experiments with Binders. At Providence, R. I., binders composed as follows have been tested: I. Ironstone (peridotite, about 40% iron) and limestone crushed and passed through a J-inch screen. The proportions used were nine tenths iron and one tenth lime. II. Bituminous macadam or a tar binder. III. Diamond Hill quartz crushed to J inch in size and dust. IV. Field-stone crushed to J inch in size and dust. V. Trap-rock crushed to ^ inch in size and dust. The relative merits of the binders, as so far shown by experi- ment, are: (1) Tar or bituminous macadam. (2) Iron and limestone. (3) Trap-rock. (4) Field-stone. (5) Diamond Hill quartz. "The combination of ironstone (peridotite) and lime, while not accomplishing all that was supposed in the matter of oxidizing or rusting, yet it has furnished the best binder we have used except the tar; but owing to its extra cost to quarry and deliver in the city (a distance of fourteen miles), it is not deemed advisable to use it in place of trap-dust, the latter material of excellent quality being obtained in the suburbs of the city. "The work of testing the binders was performed in July, during the dry season, yet neither binder permitted the surface to loosen or become friable. The tar binder gave good results, producing a BROKEJST-STONE PAVEMENTS. 319 pavement very similar to an asphalt surface and emitting little noise when struck by horses' hoofs." The cost of laying the pavements, exclusive of excavation, is: Bituminous macadam 85 cts. per sq. yd. Iron and limestone binder 51 " " " " Trap-rock-dust binder 41 " " " ' The city crusher was located seven eighths of a mile from the work. 39 Ib. Oil Binder. Asphaltic oil has been extensively used in California as a binder for the surface of broken-stone pavements. The method employed for its application is as follows: The surface of the broken stone is covered with either screen- ings, fine gravel, or coarse sand to a depth varying from one-fourth to one-half inch. The asphaltic oil, heated to a temperature of not less than 150 F. and not more than 200 F., is then applied at the rate of one half to one gallon per square yard and allowed to remain undisturbed for twenty-four hours. The oiled surface is then cov- ered with a layer of sand or screenings to a depth of about one half inch and another coat of oil applied. The. second coat of oil is immediately covered with a layer of sand or gravel in quantity sufficient to completely fill the liquid oil and remove the stickiness. The surface is then compacted by a roller weighing not less than two tons; if the surface " picks up " under the rolling, sufficient sand to remove it is applied, and the rolling continued until sufficient compaction is attained. The roadway is then opened to traffic and watched for two or three weeks, and any spots showing an excess of oil are sanded; if the traffic is light the rolling is repeated at inter- vals until the surface has hardened. 392. Watering. Wetting the stone expedites the consolidation, decreases crushing under the roller, and assists the filling of .the voids with the binder. It should be applied by a sprinkler and not be thrown on in quantity or from the plain nozzle of a hose. Excessive watering, especially in the earlier stages, tends to soften the foundation, and care should be exercised in its application. 393. Compacting the Broken Stone. Three methods of com- pacting the broken stone are practised : (1) by the traffic passing over the road ; (2) by rollers drawn by horses ; (3) by rollers pro- pelled by steam. 394. The first method is both defective and objectionable. (1) It is destructive to the horses and vehicles using the road. (2) It is wasteful of material; about one third of the stone is worn away in the operation. (3) Dung and dust are ground up with the stone, and the road is more readily affected by wet and frost. 395. The first recorded allusion to the consolidation of roads 320 HIGHWAY CONSTRUCTION. by rolling seems to have been made in 1619 by John Shotbolt in England. The first practical application of rollers appears to have been made by the French engineers in 1829. Their first applica- tion in England appears to have been made by Sir John E. Bur- goyne. Since these dates rolling has been universally adopted on the continent of Europe, not as a refinement but as a necessity, and no road is considered complete until it has been thoroughly com- pacted by a roller. 396. Advantages of .Rolling. The advantage of rolling broken- stone pavement may be summed up as follows : (1) The saving of wear and tear of horses and vehicles. Roads should be made for the traffic and not by it. (2) Comfort of persons using the roads. (3) Economy, as a saving of from 30 to 50 per cent is effected by reason of the roads being better made, thus obviating the neces- sity for such frequent sweeping and scraping. If a portion of a road that has not been rolled is broken up and the material washed, it will be found that as much as half of it is soluble matter, mud, dirt, and fine sand. The stones having been thrown loosely upon the road-bed have lain so long before becoming consolidated by the traffic, and have undergone in the mean time such extensive abra- sion, that the proportion of mud, dirt, and pulverized material is increased to that extent, and the stones are really only stuck to- gether by the mud. This accounts for the fact that although an unrolled road may indeed after long use have a surface that is pretty good and hard in dry weather, and may offer then a very slight resistance to traction, yet it will quickly .become soft and muddy when there is rain. By the employment of a roller of com- petent weight the stones are well bedded at once, and the surface is consolidated into a sort of stone felt capable of resisting most effect- ually the action of the traffic, and containing the smallest quantity of soluble matter to form mud in wet weather. (4) The avoidance of cruelty to horses, as in the case of newly metalled unrolled roads. 397. Horse-rollers.* Rollers drawn by horses are unsatjsfac- * Many improvements have beeu made in the construction of horse-rollers during the past few years, such as the use of hollow iron cylinders, which may be weighted by water or sand, and the rotary table, which renders no longer necessary the difficult task of turning the roller bodily, and avoids the plough- ing up of a portion of the newly rolled stone. BROKEX-STO^E PAVEMENTS. 321 tory for compacting the broken stone. They are expensive to use, requiring a large number of horses and attendants. The horses' feet displace as many stones as the roller compacts, and if they are of great weight they become clumsy and difficult of manipulation. 398. Steam-rollers. Steam-rollers were first successfully intro- duced in France in 1860, since which time they have been almost universally adopted on account of the superiority and economy of the work done. Their use shortens the time required for construc- tion or repair, and effects an indirect saving by the reduced wear and tear of horses and vehicles. They are made in different weights ranging from 3 to 30 tons. For the compacting of broken stone roads the weights in most favor are from ten to fifteen tons; the heavier weights are considered unwieldy and their use is liable to -cause damage to the underground structures that may be in the roadway. 399. The advantages of steam rolling may be summed up as follows : (1) They shorten the time of construction. (2) A saving of road metal, (a) because there are no loose stones to be kicked about and worn; (b) because there is no abrasion of the stones, only one surface of the stone being exposed to wear; (c) because a thinner coating of stone can be employed ; (d) because no ruts can be formed in which water can lie to rot the stone. (3) Steam-rolled roads are easier to travel on account of their even surface and superior hardness and have a better appearance. (4) The roads can be repaired at any season of the year. (5) Saving both in materials and manual labor. 400. Form of Rollers. The advantage of the present form of rollers is generally overestimated. The heaviest roller in use does not exert the same pressure per inch of width nor in the same man- ner that a heavily loaded wagon does, but the demand that a roller should be as heavy per inch of width as a loaded wagon- wheel is per inch of tire cannot be successfully met. The wheels of the rollers now in use have too wide a bearing on the road surface. The smaller soft spots are bridged over and remain unseen until the road is completed and thrown open for use. The traffic will quickly find these soft spots, and hollows and ruts will form. To obviate this and obtain the best effect from rollers, they should be constructed with both front and rear rolls. The front roll should be formed of disks, having diameters varying about six inches, HIGHWAY CONSTRUCTION. set alternately on the axle. The rear roll may be formed of two or more disks of uniform diameter. The ridges left by the front roll will be levelled by the rear roll. The effect produced by a roller of this form will approximate more nearly the effect of loaded wagon- wheels. Weight of Roller. The most suitable weight of roller for any given work must necessarily be determined by the nature and char- acter of the material to be consolidated and the object to be attained. Experience shows that for consolidating trap, granite, and similar rocks, the greatest amount and the best work are obtained by the employment of a roller which exerts a compressive force of from 550 to 600 pounds per inch width of wheel. In the compact- ing of soft and brittle stones the employment of too heavy a roller will result in crushing the material, thus rendering it useless; therefore it is obviously necessary to make use of a roller adapted to the character of the material to be consolidated. The best wear- ing results are generally obtained by employing a roller whose weight is slightly in excess of the displacing force or weight carried by vehicles of ordinary construction provided that the material is capable of withstanding the pressure without failure during the process of rolling. Speed of Rollers. The travelling speed for all weights of rollers varies from 2 to 3 miles per hour, and they can be operated on grades up to 20 per cent, but 7 per cent seems to be the economical limit. 401. The driving rolls of steam-rollers usually have holes bored in their faces to receive spikes, in order that they may be used for breaking up or disintegrating the road-surface. These, however, apparently do not answer; the working of a machine in this manner shakes and strains it considerably, and the holes in the rollers, which are plugged with wood when not in use for this purpose, are objectionable; the plugs wear out and the road metal gets into holes, and the surface of the road is picked up as the rolling pro- ceeds. Besides this, the spikes seem to have no effect unless the surface of the roadway being operated upon is soft. 402. Amount of Work Performed by Steam-rollers. The amount of work performed in a given time by the different classes BROKEN -STONE PAVEMENTS. 32 3 of steam-rollers necessarily varies, and is less in proportion as their weight and width of rolling surface decrease. The quantity of material which a steam-roller is capable of consolidating in one day will depend on the quality and nature of the stone, the thickness of the layer, the amount and nature of the binding used, the available water supply, the amount used, the time lost by compulsory stoppages for the passing traffic, and the gradient of the surface under consolidation. On roads with grades ranging from level to 1 per cent a 10-ton, roller working nearly continuously during 10 hours, will thoroughly consolidate a layer of stone 4^ inches in thickness (measured before consolidation) and using just sufficient binder to fill the interstices between the stones and a moderate amount of water, about 30 cubic yards. When working on gradients over 1 per cent a less quan- tity of material can be rolled, diminishing in amount as the incline becomes steeper. When the number of compulsory stoppages are great, as when working on suburban roads or in streets from which vehicular traffic is not excluded, the quantity of stone consolidated per day will be reduced considerably. 403. Cost of Maintaining Steam Rollers. The annual cost of maintaining steam rollers as given in the reports of city engineers, is as follows : HARTFORD, CONN. One 10-ton roller $4,000.00 Wages of engineer and tenders $888.57" Coal (40,730 pounds) 111.01: Wood (54- cords) 31.20> Water for boiler 12.00' Repairs, tools, etc . . 210.70- Oil, waste, and packing , 43.59 Insurance 15.00- Total for year $1,312.07 TOLEDO, OHIO. Wages , .... $951. 50 Fuel, supplies, and repairs 316.29 Total for year $1.267.79 DULUTH, MINN. Wages, fuel, repairs, etc $2, 087.41 324 HIGHWAY CONSTRUCTION". In England the cost per annum for 9 hours per day is abou^ $2000. 404. Amount of Rolling. The number of superficial yards rolled per day must vary extremely with circumstances the class of material, the amount of binding and water used, the gradient and pressure of steam maintained, and the amount of rolling considered necessary. The number of square yards rolled varies from 500 to 3000 per diem, the average of 42 English towns being 1105 square yards per diem. In Paris 2 to 3.75 ton-miles of roller are applied to every cubic yard of stone. The weight of steam rollers per inch of run is speci- fied to be 448 and 336 pounds, and for horse rollers 263 pounds. The ton-miles necessary to make a square yard of porphyry wheel - way, or to compact a cubic yard of the same metal, is given as follows: The mean for two models of machines weighing 448 pounds per inch run was, per square yard, with the thickness of 3.9 inches, 0.41 ton-mile; while for the roller of 336 pounds, with , thickness of 2.8 inches, 0.234 ton-mile was required, or 3.78 and 2.99 ton-miles per cubic yard respectively; and for horse rollers, where the thickness was 2.6 inches, the ton-miles required were 0.194 per square yard and 2.69 per cubic yard. The amounts con- solidated per ton per hour are in the following proportions : 467 for the heavy rollers, 539 for the light rollers, and 297 for the horse roller, and the number of passages of the rollers were 98.5, 75, and 92. The maximum speed is stated at 2.3 miles per hour. The roll- ing is done by contract (the city furnishing the water) at a rate per ton-mile varying from 15.26 to 7.63 cents, according to the amount, with an increase of one third in price where the grade exceeds 6 per cent. The Southern Boulevard, New York City, constructed by Mr. E. P. North, received 0.859 ton-mile per square yard or 5.177 ton- miles per cubic yard. From careful experiments with blue limestone in England, it has been found that to obtain consolidation with the usual coating of two stones in thickness (each cubic yard broken to 2-inch gauge, and made to cover about 17 square yards of surface), the steam roller must traverse a patch equal to its own width about 35 times. From this it appears that a cubic yard of broken stone requires 1 ton-miles to produce consolidation. For binding about BROKEN-STONE PAVEMENTS. 325 5 per cent of well-weathered road -scraping was used, being spread over the surface when consolidation was nearly effected. Without the use of binding, consolidation was found impossible. The only guide for the proper amount of rolling is that it must be continued until the stones cease to creep in front or sink under the rolls, and the surface has become smooth and firm. To ascertain the number of ton -miles per square yard or the number of passages of a roller of given weight, the following iormula (deduced by Prof. C. H. Brown) may be used : Let R = weight of roller per lineal inch in pounds ; P = number of passages of roller over a given spot ; T = number of ton-miles per square yard ; 36 = inches in 1 yard ; 1760 = yards in a mile ; 2240 = pounds in 1 ton. 1095117 7 R 405. Manner of Applying the Roller. The stone should be- spread in a uniform layer 4| inches thick. This depth will consoli- date better than either thicker or thinner. Commence the rolling at the edge or border of the roadway; move up along this edge and return on the other in such manner that during each succeeding trip the edge of the strip previously rolled is overlapped while covering a strip closer to the middle of the road. The trips or passages of the roller should proceed in this manner and be continued until such a degree of firmness is attained that when the roller passes over the centre or the crown of the road its weight, which tends to spread the metal or make it work off towards the sides, may be re- sisted by the consolidation. The surface of a well-constructed broken-stone road should, after being rolled, look almost like an encaustic pavement. The rolling should be done slowly, as nothing is gained by a rapid motion; the fuel consumption being considerably increased without any advantage to the work. 326 HIGHWAY CONSTRUCTION. In the execution of rolling it is an important advantage to be able to change, within considerable limits, the weight of the roller, because: 1st. The newly spread stone fragments are most readily fixed in position when exposed to moderate pressure in the beginning; once bedded, they should be rolled under maximum pressure. This has the convenience that the movement of the unballasted roller requires about the same tractive force on loose road metal as the ballasted roller on the more compacted surfacing. 2d. Experience teaches that the time needed for finishing diminishes with the increased weight of rollers. It appears that, with average road metal, a pressure of the unballasted roller of from 72 to 110 pounds per inch and of from 370 to 460 pounds per inch of width of ballasted roller is preferable. 3d. Not only the character of the broken stone, but also the resistance of the substratum, must be considered in the selection of roller weight. On soft or wet subsoil heavy rollers will cause a dis- tortion of the road-bed. In order to secure the best result, the rolling should be com- menced with a roller of light weight, say 3 tons, either steam or horse, provided with hollow cylinders for ballasting with sand or water. After the loose fragments have been crowded together, in- crease the weight by means of ballast, and when the stones near the edges have been compacted so that there is no noticeable settle- ment, the rolling with the heaviest roller may be commenced and continued to completion. The following rules on the rolling of broken-stone roads are given by the Massachusetts Highway Commission: " When possible roll the subgrade with a steam-roller. "If the subgrade is too sandy to roll, cover with coarse gravel laid on to a depth of three inches, or as much more as may be needed to give a good foundation. " Fill any depressions with the same material until the surface is true and even. " All broken stone must be rolled in screened layers. " After spreading the first course of broken stone, begin rolling at the sides, and continue thus by running ahead so as to allow from two to five inches of the driving-wheel to pass over the shoul- BROKEN- STONE PAVEMENTS. 327 der, and backward with the outer edge of the driving-wheel from five to ten inches inside the edge of the broken stone. Roll until the stone ceases to ' wave ' in front of the wheels, and until it seems firm underfoot as you walk over it. Next begin on the other side and roll in the same manner. Then work towards the centre until the .stone is rolled. Roll each layer of stone in the same manner. " If the road shows a wavy motion after passing the roller over it three, four, or more times, it may indicate too much moisture in the subgrade. If, on examination, you find this to be true, stop roll- ing and move ahead, allowing time for the subgrade to dry out. " With some coarse, hard granite rocks it has been noted that after the roller passes over them a few times they begin to * crawl/ and the sharp edges break off. A slight sprinkling of sand or stone screenings or water may prevent this. Try one after another of these means until the work progresses to your satisfaction. You must not expect to prevent the stone from shaking as you walk over it, but you need 'to continue the rolling until the fragments of stone adjacent to where the foot presses do not move as you walk. Most of the rolling must be done before you spread the screenings. After spreading the screenings, water and roll until the mud flushes to the surface. You cannot expect to prevent the stone from kicking out if the teams pass over the road. Keep watch, and in a few days have the roller pass once or twice over the road, after watering, until the loose stones are pressed down out of sight. " Before spreading any broken stone, great care must be taken to have the subgrade carefully shaped and thoroughly compacted. "All shoulders must be shaped and left sufficiently high to roll to the proper grade before any broken stone is spread on the road. "In the case of heavy fills you must not run the roller to the edge of the shoulders unless the fill has had time to settle. Work out slowly on this kind of work. "In every case the screenings used on the surface as a binder course must be of the same material as the top course of the road. " Excepting where it may be needed to compact hard granite rocks, as before referred to, you will use water only on the top or binder course. "You will wet this binder course thoroughly before rolling, but ~>ot to the extent of saturating the foundation. You will get 328 HIGHWAY CONSTRUCTION. better results and prevent the screenings from being picked up by the wheels of the roller if you apply water and allow it to settle down below the top surface before passing the roller over it. Too much water or too little will give trouble by causing the surface to be picked up. "You must not under any conditions roll the screening while dry. "You must not under any conditions allow teams to pass over the road after the screenings are spread and before they are rolled." 406. Cost of Rolling. The average cost of rolling varies con- siderably by reason of the amount of rolling considered necessary. In England it varies between one and two cents per square yard. In the United States it varies between 0.015 to 14 cents per square yard. 407. Cost of Broken-stone Pavement. What the cost of broken- stone pavements will be must depend upon the accessibility and cost of material and labor, which will be quite variable. TABLE XLI. COST OF BROKEN- STONE ROADS. Locality. Thickness of Stone. Inches. Width of Pavement. Feet. Method. Cost per Mile. 4 18 to 20 Macadam $3,000 Fairfield Conn 4 20 Macadam 5,000 Fanwood, Conn . . . . < Franklin Township, N. J. . . Kingston R I 12 4 8 16 15 16 to 20 Telford Macadam Macadam 9,530 4,700 5,500 Linden Township, N. J Plainfield N. J 12 4 to 6 16 16 Telford Macadam 11,600 3,000 Rahway N J 12 16 Telford 9,349 Westfield N J 12 16 Telford 9,640 Union Township, N. J 12 16 Telford 11,900 BROKEN-STONE PAVEMENTS. 329 TABLE XLII. EXTENT OF BROKEN-STONE PAVEMENT IN THE PRINCIPAL CITIES OF THE UNITED STATES IN 1903. City. Area. Square Yards. Length. Miles. Akron Ohio . 53 212 3 00 Albany N. Y 60 108 3 40 Allentown, Pa 232,900 9 50 Altoona, Pa 10,240 1 30 Atlanta, Ga 2 50 Atlantic City N J 313 836 16 30 Auburn NY. 761 552 43 30 Augusta Ga 412 836 19 80 Baltimore Md 629 940 47 30 Bay City, Mich 35 169 2 30 Bayonne, N. J 281 500 10 00 Binghamton, N. Y 15200 1 00 1,172700 49 10 Boston, Mass 5,829 269 317 80 Bridgeport Conn 1 500 000 80 00 Brockton, Mass 162,951 12 90 Buffalo NY. 263 523 12 30 Cambridge Mass . 1 454 182 77 5Q Camden N. J 40 331 2 81 Cedar Rapids, Mich 65 264 5 10 Charleston, S. C 83 981 4 10 Chattanooga, Tenn 34 646 3 20 281 600 16 00 Chester, Pa 52800 3 00 Chicago, 111 7 646 000 465 50 Cincinnati, Ohio 3 350 000 2 9 5 00 Columbus, Ohio 111 979 6 40 Council Bluffs, Iowa 22 400 2 50 Covington, Kv 428 472 27 1Q Dallas, Tex 428 736 20 00 Davenport, Iowa 130 960 15 50 Dayton, Ohio 10000 80 Denver, Colo 99 962 5 70 Des Moines, Iowa 10 145 i oo Detroit, Mich 353 265 12 40 1 973 165 88 10 Duluth, Minn 470 586 25 40 Easton, Pa 677 927 2Q no Elizabeth, N. J 401 573 18 ^O Elmira, N. Y 113 579 4 80 E. St. Louis, 111 82 826 3 60 Evansville, Ind 93 866 4 00 Everett, Mass 465 168 26 40 Fall River, Mass 412 750 ?4 oo Fitchburg, Mass 101 482 9(\0 Fort Worth, Tex 80 00 Galveston, Tex 23 050 i 40 Gloucester, Mass 79 493 5 40 330 HIGHWAY CONSTRUCTION. TABLE XLII Continued. City. Area. Square Yards. Length. Miles. Grand Rapids, Mich. . 110,019 6 30 Harrisburg, Pa 609,039 31.80 Hartford Conn 1 551 000 88 10 Haverliill Mass 171 644 12 40 Ploboken N. J. 4000 30 Holyoke Mass. . 85,770 4 30 Houston, Tex 1.40 Indianapolis, Ind. ... 128,752 6.10 Jackson, Mich 35,000 2.00 Jacksonville, Fla 8,999 0.60 Jersey City N J 17 30 Johnstown Pa 14 500 70 Joliet 111 . . 402 609 20 40 Joplin, Mo. . . 739 200 35 00 Kalamazoo Mich. . . . 6 163 30 Kansas City, Kan 72,642 3 70 Kansas City, Mo 823,233 36.50 Kingston, N. Y 607,780 37.00 Knoxville, Tenn 1,200,000 60.00 La Crosse Wis 544 849 24 40 Lancaster Pa . . 626 040 30 50 Lawrence, Mass. . 381 839 22 10 Lexington, Ky 422,400 24.00 Lima, Ohio 575,360 48.00 Little Rock, Ark 262,190 11.40 Los Angeles Cal 96 213 4 10 Louisville Ky 1 827 314 91 40 Lowell Mass. . . 330 325 29 60 Lynn, Mass .. 248 771 10 00 Maiden, Mass 162,529 5 80 Manchester, N. H 316 166 15.90 Meriden, Conn 76,665 4.00 Milwaukee, Wis 9,240 0.50 Minneapolis Minn 167 930 10 60 Mobile Ala 27 700 1 00 Nashua N. H. . . . 73994 4 00 Nashville, Tenn. . 3 196 160 181.60 Newark, N. J 19.10 New Bedford Mass 784 2 7 4 63 20 New Britain Conn 520 000 30 00 Newburg NY. ... . 14 466 60 Newcastle Pa 10000 60 New Haven, Conn 1,003,720 64.00 New Orleans La Newport Ky 470 000 20 40 Newton Mass .... . . . 2 279 640 77 70 New York N. Y 10,164 051 779 . 30 No. Adams, Mass 55,051 5.20 Oakland Cal 3 443 440 150 50 Omaha Neb . . . 52 246 3 10 Orange, N. J 274 560 26 00 BROKEN-STONE PAVEMENTS. 331 TABLE XLII Continued. City. Area. Square Yards. Length. Miles. Oshkosh, Wis 148,900 5 50 Passaic, N. J . 270,466 26.60 Paterson N J 1,108 800 63 00 Pawtucket R I .... 173 078 16 40 Pec ia 111 ..." ... 17 264 1 00 Philadelphia Pa 2,722 976 262 70 Pittsburg Pa . 157 580 10 30 l Portland, Me. . 139 747 9 40 Portland, Ore 1,315 200 48 10 Providence, R. I 2,993 760 170 10 Quincy, 111 236 544 11 20 Quincy, Mass 228,800 15 00 Racine, Wis 48,798 2 40 1 032 257 51 80 Rochester, N. Y 378,887 26 90 Rockford, 111 802,560 40 00 Sacramento Cal 231 000 12 00 Sa^inaw Mich 134 718 12 30 Salem Mass 590 749 40 50 Schenectady N Y 44 301 3 10 Seattle Wash 36 380 2 70 Sioux Citv Iowa 6 600 30 Somerville Mass 1 113 200 63 30 So. Bend Ind 5 757 20 So. Omaha Neb 11 111 20 Springfield 111 58 819 2 go Springfield Mass . . 880 786 49 oo Springfield, Ohio 353 656 15 10 St. Joseph, Mo. 517 493 26 70 St. Louis, Mo. . 4 935 955 233 70 St. Paul, Minn 246 780 12 90 Taunton, Mass 331 689 20 90 Terre Haute, Ind 286 317 12 20 Toledo, Ohio 140 067 13 50 Topeka, Kan 7 767 60 Trenton N j 112 933 5 50 Troy N Y 52 743 Q HO Washington D C 3 427 534 78 00 Waterbury Conn . . 80 783 4 60 West Hoboken N. J 112 992 3 20 Wheeling, W. Va 135 542 6 70 Wilmington, Del 278 988 18 70 Woonsocket, R. I. 281 600 16 00 Worcester, Mass 745 000 42 30 Yonkers, N. Y 1,158,504 83 30 York, Pa 530 000 30 80 Youngstown, Ohio 42 800 2 90 407a. Cost of Broken-stone Roads in Massachusetts. In Massa- chusetts the cost of State highway construction under the contract 332 HIGHWAY CONSTRUCTION. system has ranged from $6600 to $24,547 per mile and has aver- aged $10,033, divided as follows: For excavating and grading $1 t 24l " gravel 520 " Telford and drains 367 " Macadam and shaping 5,694 Masonry ^ Guard-rails Paved gutters Engineering, superintendence, and inspection. Minor constructions, catch-basins, culverts. . . Stone bounds Advertising , Weighing stone Sundries 448 188 191 679 431 54 18 24 178 Total $10,033 408 Difference in the Cost of European and American Broken- stone Pavements. As an example exhibiting the difference in the cost of constructing macadam roads in Europe and the United States, we select a first-class highway of the broadest type, one which was built about ten years ago over a level expanse between the villages of Langenfeld and Burgwald, Germany. The road in question is 2100 meters (6888 feet) long, 26 feet in width, the macadamized wagon track 13 1 feet wide and 8 inches thick. With labor estimated at 36 cents per day except for stone masonry, which costs in country districts from 60 to 75 cents per day, the construc- tion account of this road foots up as follows : Germany. Jimerica. GrnidinfiT roadwav $707 61 $1748 00 89.96 268.88 154.70 464.10 Macadamizing .. 3647.35 7843 50 11.38 34.14 Tools 75 68 151 36 Damages to adjacent property during work . . . 155.65 61.88 155.65 185.64 Superintendence of construction 369 85 784 35 49.98 49.98 $5324.04 $4092.00 $11680.00 $8947.60 per mile per mile BROKEN-STONE PAVEMENTS. 333 409. Wear of Broken-stone Pavements. The wear of road ma- terials resulting in their gradual reduction to detritus is due to the joint action of the traffic and the weather. When the wear is con- fined to the abrasion of the surface, it is the least possible; but when a road is weak from insufficient thickness, or from a yielding foundation, bending and cross-breaking take place under passing loads, and a movement is produced in the body of the road which causes internal wear by the rubbing of the stones against each other; this wear is aggravated by the softening action of water finding its way into the roadbed through cracks in the surface, and by the disintegrating action of frost; the wear and waste are thus far greater than on roads of sufficient strength properly maintained, 410. The relative proportions in which a road is deteriorated by the action of atmospheric changes, wheels, and horses feet for the generality of roads is approximately as follows : Atmospheric causes 20 per ceat Wheels 35.5 " Horses' hoofs 44.5 " 411. The effect of horses' feet is to form depressions which, if not immediately eradicated, prepare the way for further injury by the wheels. Horses moving at a walk and drawing heavily-loaded wagons do far more injury than horses travelling quickly and draw- ing lightly-loaded vehicles. Rain. The effect of rain upon a highway is, first, to soften the bed, and next to wash off the portion of the material which the temporary streams can bear along. On an earth road the soften- ing action is highly injurious, as it permits the feet of animals and the wheels of vehicles to penetrate below the surface. On a prop- erly constructed broken-stone road, as well as on all forms of block pavement, the pavement acts as a roof, shedding the water from its surface. If the roadway be skilfully planned, the penetration of water from the sides is avoided, and thus the damage arising from the softening action, as well as from the influence of frost, is done away with. On all forms of earth roads, and on the most of those made of gravel as well, the effect of the penetration of water in loosening the mass of the road-bed is serious, in most cases up to the margin of disaster. Where a hard road of broken stone or blocks or other material impervious to water is properly shaped, the rainfall is quickly 334 HIGHWAY CONSTRUCTION. carried to the side ditches by the arched form of the road. On such roads the water never courses over the roadway for a much greater distance than its width. Thus arranged, the streams, even in a very heavy rainfall, do not gain much volume or attain great speed; therefore 1 hair scouring effect is but small. Nevertheless, the storm-water, by removing the dust from the roads and by washing out the binding material between the stones, hastens the wearing of the roadway. This is especially the case where the broken stone is of the softer sort. Where the pavement is com- posed of the basaltic trap-rocks, the washing influence of the waters is not so serious. On dirt roads the rainfall, especially after times of frost, is the most serious agent of destruction. The power of water to move and transport materials depends upon the specific gravity, the size and form of the fragments, and upon the velocity of the water, or, what amounts to the same thing, the slope of the roadway. Hence the steeper the grade, the greater the transporting power of the water, and the longer the distance the water will flow over the roadway before it is dis- charged into the gutters or side ditches. On steep grades the carrying power is made apparent by gullies; on gentle slopes the grains of the least weight and specific gravity and of the most tabular form are made to occupy the surface of the road, where, after drying, they fall an easy prey to the power of the wind. This sorting action arises from the fact that, other things being equal, the sand grains will arrange themselves in water in the order of their specific gravities, the heaviest at the bottom. An exception to this rule is found where minerals even of a high specific gravity are characteristically of a tabular form r since the resistance they offer to descent, owing to their relatively large surfaces, causes them to arrange themselves at the top with minerals of the lowest density. The rain falling upon a road serves to concentrate the minerals into layers in the order of their specific gravity. This will not be found true of the micas, for these will be found concentrated near the surface with the minerals of a less density and both made accessible to the action of the wind. The impact of falling rain-water causes a certain amount of injury by attrition and loosening of those grains which it is able to BROKEX-STONE PAVEMENTS. 335 move about, and a certain weakening of the coherency of the surface as far down as the water is able to penetrate. Frost. The immediate effect of frost action on a broken- stone road, where care has not been taken to keep the foundation dry, is to heave the pavement irregularly, the amount of the up- lifting depending on the quantity of water which has become frozen. The effect of this irregular motion is to pull the cemented stones apart, and sometimes to form cracks through which the water can penetrate. Where the broken stone is not well cemented, or where on an earth or gravel there are stones near the surface, the effect is often to push the larger fragments upward to the sur- face. It may in general be said that all frost action is highly detri- mental to a road, and that therefore the utmost care to exclude the water from the hardened part of the way, as well as from the under earth, needs be taken. When the frost enters the ground the first effect is to convert into ice the water within the zone of its influence. In undergoing this change the fluid expands to the amount of about one-ninth of its bulk. The energy with which this expansion occurs is in all cases sufficient to thrust about the materials of the soil. So long as the road permits water to pass into it, and wherever ground - water can penetrate from the sides beneath a roadway, however well compacted, even if it be quite water-proof, the action of frost is destructive. The presence of frost in stones is promotive of weakness and rapid crumbling. In fragments of broken stone it operates to increase their brittleness to a considerable degree, and for this reason gives rise to a more rapid disintegration of the screenings and upper portion of the road. Wind. The action of wind on roads of all descriptions is con- siderable. The effect is to remove all the loose material of a fine- grained nature as soon as it becomes dry. On earth roads and those of gravel the wearing action thus accomplished, though it takes place in a more even way, and therefore is less conspicuous, is often as great as that brought about by the rain. On broken- stone roads the effect is considerable, but on the whole not seri- ously damaging, except where the pavement is made of rocks which easily powder, such as limestone and slate. The diabase 336 HIGHWAY CONSTRUCTION. rocks, which carry a considerable percentage of black mica, and the mineral feldspar, which decomposes to clay, also furnish abun- dant material for the wind's work. The sorting action of the wind tends to remove the minerals having the least specific gravity, and this will be particularly true xvhen the grains possessing the least density happen to coincide with those of a brittle nature, and which for this reason are most liable to be ground to a condition of fine dust under the action of the wheels. Wind-blown material is not only objectionable, since it increases the cost of road maintenance, but is an intolerable nuisance to the users of the road and adjacent residents. The ability of the wind to take up and bear away grains of any rock depends upon several factors. These in the order of their importance are: (1) The form of the particles subjected to the wind's influence; (2) the specific gravity and size of the individual grains; and (3) their accessibility to the action of the wind. The form of the grains will depend upon their original shape in the rock and that which they may be induced to take as an effect of road wear or as a result of chemical change. The most suitable stone to be used for highways, to withstand the action of the wind, is one whose products of abrasion are of a high but uniform specific gravity, and which is free from all minerals that by their tabular form are prone to be thus transported. A small amount of dust is of value on a road, acting like a cushion to protect the broken stone from the action of the wheels and the animals" feet. The value of this dust-film is further en- hanced by a small quantity of moisture. Disintegration * and Decomposition of Road Materials by the Chemical Action of the Elements and Organic and Inorganic Acids. Rain-water impregnated with carbonic acid alone acts as a slow solvent on all the common minerals occurring in the stones used for road covering, attacking even quartz; but a mixture of the vari- ous acids, organic or inorganic, acts more rapidly. The organic acids occurring in all water circulating through the soil in fertile regions are carbonic, humic, crenic, and apocrenic. Near cities we must add to the organic acids those derived from gas-plants * See foot- note, p. 337. BROKEX-STONE PAVEMENTS. 337 and manufacturing establishments. These acids are largely nitric, sulphuric, and hydrochloric. The injurious effects of organic and inorganic acids on road- stones are confined for the most part to rocks containing calcite or dolomite, minerals which they readily dissolve and carry away. Shrinkage of the Subgrade.* A road-bed may suffer disruption by shrinkage of the subgrade. It has been determined experi- mentally that clay shrinks one fifth of its bulk in excessively dry weather and increases to a corresponding degree when wet, and that silicious sands and gravels undergo no change in volume. From this it follows that when a road passes over a clay bed which may become dessicated, injurious results are likely to follow, par- ticularly at a point where the clay abuts a sand substratum which is unaffected by weather changes. Gravity * also plays an important part in the work done by run- ning water and falling rain. Through its operation alone there is always a tendency exercised for grains and fragments of rock to work down the slopes towards the sides of the road. Under some circumstances the effect of gravity may completely destroy a road- bed. When the roadway is constructed along a mountainside whose soil is slowly creeping toward the valley, the cut made necessary for the roadway is often sufficient so to weaken the hold of the soil as to precipitate the surface of the country down the slope as a landslide, or cause a slower movement which in the end entails a long-continued and serious expense in the way of repairs. Such movements are particularly common in loose materials in countries where the frost penetrates deeply and the ground be- comes soft in the time of thawing. Roads may also be destroyed by avalanches of trees and stones from a point farther up the slope. Changes of Temperature * produce expansions and contractions of the rock forming the road-covering, which in extreme cases break the bond holding together the broken stone and cause cracks and fissures. * Abbreviated from "The Geology of the Common Roads of the United States," by N. S. Shaler, and " The Forces which Operate to Destroy Roads," by C. I. Whittle. 338 HIGHWAY CONSTRUCTION. 412. The quantity of stone worn away annually from the sur- face of roads is an exceedingly variable quantity, dependent not only upon the character of the stone and the quantity of the traffic, but also upon the mode of maintaining the road. Mud is an ex- cellent assistant in rapidly grinding down the surface. Many attempts have been made to measure the wear on roads, but no definite conclusions can be arrived at. 413. The wear or loss of thickness on some of the heavily trav- elled streets of London and Paris has been as much as four inches per annum. In Birmingham, England, the macadam streets have worn down six inches in one year under a traffic of 2484 vehicles in ten hours. ; The average loss of thickness on the European roads appears not to exceed one inch per year. 414. The amount of material used annually in England to re- place the wear on main roads varies from 40 cubic yards per mile in the country districts to 1000, and in some cases to 1500 cubic yards in the vicinity of large towns. The general average appears to be from 70 to 80 cubic yards per mile, the least being 10 cubic yards per mile. The average annual consumption of broken stone to replace wear in France and Austria appears to be about 70 cubic yards per mile. Table XLIIa shows the loss of stone on five typical State roads in Massachusetts. TABLE XLIIa. Loss OF STONE ON MASSACHUSETTS STATE HIGHWAYS. Road No. Material. Length. Miles. Loss in Pounds per Sq. Yard per Annum. Remarks. 1 2 Soft native rock Good native stone and trap-rock 1.905 6.973 1.80 0.98 Long grades, light country traffic. 3 4 5 Soft native rock Good native stone. . . . Trap-rock 2.222 17.008 3 610 2.00 O.Ob 2.20 6% grades, fairly large traffic . Is at all times kept cov- ered with sand and is ap- parently in as good condi- tion as when built. Built over clayey soil; fairly heavy traffic, and great wear due to weather. PAVEMENTS. 339 415. The loss of thickness by wear should be restored annually by spreading coats of two or more stones thick and consolidating it with the roller. Before applying the coating the surface of the road should be broken up with picks in cross-courses about 4 inches apart; the depth to which the surface is broken should not exceed 2 inches. Steam rollers are furnished with picks for this purpose, but their employment is not satisfactory or advantageous; if the spikes are short ; they have no effect on the road unless it is soft; if tbtjy are long, they penetrate the body of the road, breaking the bond, and leave the road a mass of loose stones. Besides the employ- ment of the roller for this purpose shakes and strains it consider ably. 416. The practice of spreading the new coating and leaving it to be consolidated by the traffic is open to the same objections as the construction of unrolled roads. It is an obstacle instead of an aid to traffic. The methods employed for ascertaining the amount of wear are . (1) Indirect measurement, by estimation from the amount of stone consumed in a given period to maintain the road in good condition; (2) Direct measurement, at fixed intervals, of the changes in the elevation of the road surface, by levelling from a bench mark. The amount obtained by either method is only approximate: in the first it is impossible to know the volume of the stone when spread loose and when compacted, or what amount was used to fill up de- pressions, wash-outs, etc.; in the second the changes in elevation may be due to settlement of the road bed. The French road en- gineers make observations by cutting trenches across the road and estimating the amount of detritus in the coating. The results are too complex to be of much practical use. When the stone is spread, the sooner it is rolled solid the better. 417. Recoating the road should be done at that season of the year which will interfere the least with the movement of the traffic. Wet or damp weather is most suitable, but when water is obtainable it may be done at any season. 340 HIGHWAY CONSTRUCTION. 417a. Effect of Climate on Broken-stone Roads. Regarding the effect of climate on broken-stone roads, Prof. N. S. Shaler says: *' As a roadway is, of all constructions, the most exposed to the action of the weather, the climate of the district in which it lies lias a greater effect upon it than upon any other class of buildings. This effect is exercised by the rainfall, changes in temperature, :and the winds. A secondary influence arising from the above- mentioned natural conditions is found in the character of the vegetation, which, under favorable conditions, may advantageously affect a road by covering the unused portion of its surface with a network of low-growing plants, such as the grasses. " In a moderately humid climate, exempt from continuous summer droughts, creeping plants, nourished by the dust from the Toads, which in most cases has a considerable fertilizing value, take hold on the shoulders and sides of the way in such a manner as to protect those exposed parts from washing or from the action of the winds. When these conditions prevail it is generally practicable to build a relatively narrow, hardened way with wide shoulders on either side, onto which the passing teams can turn out, finding there, by virtue of the plant-covering, a surface so firm that it will not rut from an occasional passage of wheels. If, however, the shoulders are overdry, as they are sure to become in an enduring ^drought, the plants are killed and the surface is left exposed." 418. Cost of Maintenance. The cost of maintaining broken- stone pavements varies between very wide limits. A road with little traffic, well drained, and exposed to the sun and air, with fairly good materials at hand, can be kept in repair at a very small yearly cost, while a suburban or city street may cost several hun- dred dollars. Unless the amount of the traffic, the quantity of ma- terials used, their price, and other particulars be taken into account, the cost per mile or square yard at which a road is maintained affords little real information, and may be misleading. In London the cost of maintaining macadam pavements is -stated as follows : BROKEN-STONE PAVEMENTS. 341 ID heavy-traffic streets 62$ cts. per sq. yd. In moderate-traffic streets 29f In light- " ' 14 IQ lightest- " " 6 ". In Paris macadam costs about 45 cents per square yard per year. In Boston, Mass., about 50 cents. The cost of maintaining the high-roads of Austria ranges from $1032 to $1571 per mile per annum; of these amounts about 50 per cent (49 to 52) is for materials. The highways of Belgium cost be- tween 6 and 10 cents per square yard per year. The French roads cost from 1 to 10 cents per square yard per year. The annual cost of maintaining the government roads of Bavaria in 1877 was, per kilometer, or .62 English mile, as follows : Cost of material $54.26 Extra labor 11 42. Bridges and culverts 2 52- Retainiug-walls and gutters 31 Road-paving. ... N 2.45 Cost of tools 1.02 $71.98- or about $116.09 per English mile. Total number of men em- ployed on the government roads was 1089. The average cost of regular roadmen per English mile was $45.25. Total length of government roads : The total length of government roads macadamized 4,223 miles. " paved 29 " " " " " " " over bridges 6 ' e 4, 258 miles The cost of maintaining the Massachusetts State roads ranges from $54 to $100 per mile per annum. 419. Descriptions of Modern Broken-stone Roads. "First-class metropolitan roads, England : The ground is excavated or filled to the required level, then thoroughly consolidated by rolling. On the earth-bed thus prepared a bottoming or bed 12 inches thick, of " hard core/' consisting of brick rubbish, clinker, old broken con- crete, broken stone or shivers, or any other hard material in pieces, , is spread and rolled down to a thickness of 9 inches, and any loose or hollow places made up to the level. 342 HIGHWAY CONSTRUCTION. " Next comes a layer of Thames ballast 5 inches thick, rolled solidly to a thickness of 3 inches. The ballast serves to fill up the vacancies in the bottoming, and, being less costly, saves so much of the cost for broken granite." Broken granite, or macadam, is laid upon the prepared surface of the ballast in two successive layers 3 inches thick, rolled succes- sively to a combined thickness of 4 inches; a layer of sharp sand % or f inch thick is scattered over the second layer, and rolled into it with plenty of water. 420. The method adopted in Chicago is as follows : The roadbed is prepared to the required contour and well consolidated with a steam roller. On this surface rubble-stone is carefully placed by hand, with its broadest side dowmvards, then 12 inches of broken stone are spread, 6 inches at a time, thoroughly rolled, to bond it ; it is then topped with 4 inches of crushed trap or other equally hard rock; this is again thoroughly rolled, so as to compact and bind it together. 421. The method adopted in the construction of the Bridgeport, Conn., roads is as follows : The ground is graded and regulated with a gutter 18 inches deep on each side; the soil is then thoroughly rolled with a 15-ton roller, and the stone spread on the surface so pre- pared. Three varieties of soil are met with-in Bridgeport : (1) a fine " dead " sand, which sometimes cannot be rolled on account of its pushing before the roller, without covering it with coarse broken stone this expedient, acting as a pavement, prevents movement; (2) loam, and (3) a hard-pan with mica disseminated through it. Underdraining has in no case been resorted to, the 18- inch gutters being depended on for drainage. After the broken trap-rock is rolled to a bearing, screenings are added as a binder and the road metal is well and thoroughly filled with them, the whole being rolled until the water flushes on the surface. A strong silicious sand is sometimes used, in part, in place of screenings, and when, in dry weather, the road commences to break up or " ravel," out of easy access by watering-carts, sand is spread over the spot, which quickly consolidates the road. No loam or clay is used as a binder or filler in the construction of the roads, nor in their repair, except when the surface over a ditch is to be replaced and it is too small a patch to justify bringing the roller; then the broken trap is laid down after being mixed with the proper quantity of screen- BROKEN-STONE PAVEMENTS. 343 ings, and the whole covered with loam. The traffic consolidates it in a short time. It should be noticed, in connection with the low cost of those roads stated in Table XLII, about 28 cents per square yard, that Bridgeport, in addition to the possession of particularly good trap- rock, is exceptionally favored in the location of its quarry almost exactly two miles from the centre of the city; so that the cost of the stone is 82 cents per gross ton of 21 or 22 cubic feet, delivered to the wagons ; and the cost of hauling varies, depending on the distance, from 50 to 75 cents per ton, or between $1.32 and $1.57 per gross ton delivered on the road. The trap-rock is broken to 2- inch size by three 7 X 10-inch Marsden crushers, placed side by side on a platform, to which cars are drawn from the quarry by a wire rope, wound by the same engine which runs the crushers. The in- terest on the cost of the roller an Aveling & Porter, now twenty years old is not reckoned in the above-mentioned cost. That the cost of the Bridgeport roads has not been underesti- mated is apparently made certain by the contract price of such work in the neighboring town of Fairfield, where, with a longer haul, a 4-inch road 20 feet wide was built for 85 cents per lineal foot or 38.3 cents per square yard. This sum included regulating, some grading, and the use of a roller, as well as the contractor's profit. 422. Extracts from Specifications for forming Telford Roads in St. Louis, Mo. Drainage. All drains considered necessary by the Street Com- missioner to carry off the water shall, when required, be made by the contractor for the work, and shall be paid for at a price agreed upon by the Street Commissioner. Sub-foundation. After the curbstones are set, the second grad- ing and shaping of the roadway shall be done. All surplus earth and other material shall be removed and the sub-foundation formed to a depth of eighteen (18) inches below the intended surface of the street, the cross-section thereof to conform in every respect to the cross-section of the pavement when finished. The roadbed shall then be rolled with a roller weighing not less than five (5): tons, when required by the Street Commissioner. All depressions which may appear shall be carefully refilled before any stone is put on. 344 HIGHWAY CONSTRUCTION. Lower Course of Telford. When the street shall be thus graded and formed, a bottom course or layer of limestone of approved quality shall be laid by hand in regular straight courses at right angles with the line of the streets, so as to break joints; the bot- tom surfaces of the stones shall form as close joints as possible. The stones to be used shall not be less than three (3) inches nor more than eight (8) inches thick, and from five (5) to ten (10) inches long on their bottom surfaces, and must be thoroughly set- tled to place with hammers. The interstices shall then be filled with stone chips firmly wedged by hand with hammers, and all projecting points shall be broken off. The tops of the stones when levelled off shall have a surface not greater than one third of the base. The foundation or bottom course when finished shall have a regular and uniform depth of not less than' seven (7) inches. The bottom course along the curb and under the gutter for a width of four (4) feet, and under the cross-walk for a width of eight (8) feet, shall be thoroughly consolidated by rolling or ramming, and the surface be made even by filling the spaces between the stones with sand in such manner as the Street Commissioner may direct. Guttering. After the Telford foundation has been prepared the gutter shall be put down upon a bed of clean coarse sand at least two (2) inches deep. The paving-blocks shall be from six (6) to seven (7) inches deep, four {4) to six (6) inches thick, and eight (8) to twelve (12) inches long. The faces shall be straight, free from bunches, depressions, and inequalities exceeding one half (|) inch. The faces shall meet at right angles, and the corresponding dimensions of opposite faces shall not vary more than one-half (|) inch. They must be set vertically on edge, in close contact with each other, in straight rows at right angles with the curb, the blocks in different rows breaking joint by a space not less than four (4) inches. The joints between the blocks shall be filled with clean, sharp sand. Cross-gutters. The cross-gutters shall be of such width and shape as may be directed. The stone used therefor shall be from three (3) to six (6) inches thick, nine (9) inches deep, and from six (6) to twelve (12) inches long. The bottom course of stone shall be eight (8) inches thick, nine (9) inches deep, and not lesa than twelve (12) inches long. BROKEN- STONE PAVEMENTS. 345 Quality and Finish of Stone Work. All stones used for gutters, cross-gutters, and cross-walks shall be limestone of the best quality, from ledges known to withstand the effects of frost, and free from seams and all other defects. All paving-stone shall be dressed so as to make close joints at least four (4) inches deep, and have a square bottom not less than three quarters (f) of the super ficial surface of the top of the same stone. All materials shall be fuiiy dressed before they are brought onto the street to be im- proved. The whole paving must be made tight, compact and smooth, and be fully fed with sand, and must be laid true and uni- form^ with broken joints, and have a full bond of at least four (4) inches. After the paving is laid it must be sanded on top, the* sand swept into the joints with a broom, and be settled down evenly and firmly with a rammer of not less than forty (40) pounds weight. Macadam or Second Course. When the Telford foundation has thus been formed, there shall be placed thereon a layer of clean, hard limestone macadam, free from clay, earth, rubbish, or other foreign matter, so broken that the largest pieces shall pass through a two and one half (2J) inch ring in all their dimensions, and shall be fully broken before it is brought on the line of work. This course shall have such a depth and form of cross-section as may be directed by the Street Commissioner, and shall be thoroughly con- solidated by rolling with a roller weighing not less than fiv3 (5) tons. Sand. The macadam course having been finished, the spaces between the stones shall be well filled with clean, coarse sand, or so much sand as may be directed by the Street Commissioner, which shall be washed in with water from a hose having a rose attached to the nozzle, and then the whole shall be rerolled to the satisfac- tion of the Street Commissioner. A sprinkling-cart shall not be used unless it is impossible to make a connection with a fire-plug, and then only with the consent of the Street Commissioner. A water license and a permit from the Water Commissioner must first be obtained before a fire-plug can be opened. Gravel. The macadam course with binding material having been finished, there shall be placed thereon a layer of good clean gravel, free from clay, animal, or vegetable matter, and containing not more than fifteen (15) per cent of loam or sand, nor shall the largest pebbles exceed one inch in diameter; to be well wetted down or slushed with water and thoroughly rolled to a perfect surface, 346 HIGHWAY CONSTRUCTION. TYPE SECTIONS OF BROKEN-STONE PAVEMENTS. <\, f .^ ^SXV^/Vy^V FIG, 25. COUNTRY ROAD, SIDE-DITCH FILLED WITH COBBLE. FIG. 26, COUNTRY ROAD, WITH EARTH BERM AND TILE-DRAIN. 1\%fasz?;4^%i&ft^ :'.& . FIG. 27. CITY STREET s* FIG, 28. CITY STREET, WITH STONE-BLOCK GUTTER, BROKEN-STONE PAVEMENTS. 3-17 having such form of cross-section and depth as may be directed by the Street Commissioner. 423. Heads of Specifications for Broken-stone Pavements. (1) Preparation of roadbed. (2) Foundation (sand, gravel, etc.). (3) Quality of the stone. (4) Size of the stone. (5) Cleanness of the stone. (The stone must at all times be clean and free from clay or other dirt.) (6) Spreading the stone. (7) Thickness of layers. (8) Rolling : weight of roller and amount of rolling. (9) Watering. (10) Binding, quality and quantity of. (11) Interpretation of specifications. (12) Omissions in specifications. (13) Engineer defined. (14) Contractor defined. (15) Notice to contractors, how served. (16) Preservation of engineer's marks, etc. (17) Dismissal of incompetent persons. (18) Quality of materials. (19) Samples. (20) Inspectors. (21) Defective work, responsibility for. (22) Measurements. (23) Partial payments. (24) Commencement of work. (25) Time of completion. (26) Forfeiture of contract. (27) Damages for non-completion. (28) Evidence of the payment of claims. (29) Protection of persons and property. (30) Indemnity bond. (31) Bond for faithful performance of work, (32) Power to suspend work, (33) Right to construct sewers, etc. , ,> (34) Loss and damage. ,{ , (35) Old materials, disposal of. 348 HIGHWAY CONSTRUCTION. (36) Cleaning up. (37) Personal attention of contractor. (38) Payment of workmen. (39) Prices. (40) Security retained for repairs. (41) Payment, when made. Final acceptance. 423a. State Road Construction Methods. Lower Course. Upper Course. Surfacing. 03 Binder, Size of. State. Size of It Size of Inches. Size of ^2 Stone. II Stone. Thickness. Inches. Stone. _fi ^"* Inches. *rt ^ Inches Inches. P P Connecticut. .. 4 |-2 2 1-1 * Dust to \ in. 1 Dust Rolled dry, to \ in. * then sprinkled Massachusetts 4 1 J 2 2 1 -1 J No binder in Sufficient t o lower course form smooth surface; wa- tered and rolled New Jersey. . . 4 2-3 2 1-2 Dust to in. Sprinkled and < t H rolled New York 4 1J-3 2 1-2 Hard stone ^in., f i soft stone fin. Rolled dry; swept with brooms; sprin- kled and roll- ed CHAPTER VIII. MISCELLANEOUS PAVEMENTS. 424. Gravel Roads. Gravel, though not as durable as broken stone, has proved very serviceable as a road covering. In selecting gravel for this purpose, the chief quality to be sought for is the property of binding. The binding properties are two : the presence of ferruginous clay, which causes the gravel to set or become hard as soon as it is exposed to the action of the atmosphere ; and the angular shapes and sizes of the stones. 425. Gravel from the sea-beach and shores of rivers, and that in which the stones are round or oval, with regular smooth sur- faces, never forms a good binding material, even if mixed with ferruginous clay. The reason is that the stones which are on the surface have no mechanical hold on those which are beneath or be- side them, but being merely cemented by means of the clay they are easily loosened and thrown out of place by the action of the traffic or frost, and even by the alternate actions of drought and moisture. 426. When no gravel but that found in rivers or on the sea-shore can be obtained, one-half of the stones should be broken and mixed with the other half; o the stone so mixed a small quantity of clay or loam, about one-eighth of the bulk of the gravel, must be added : an excess is injurious. Sand is unsuitable : it prevents packing in proportion to the amount added. 427. Preparing the Gravel. Pit-gravel usually contains too much earth, and should be screened before being used. Two sieves should be provided, one with meshes of one and one-half inches, so that all pebbles above that size may be rejected, the other with meshes of three quarters of an inch, and the material which passes through it should be thrown away. The expense of screening will be more than repaid by the superior condition of the road formed 349 350 HIGHWAY CONSTRUCTION. by the cleaned material, and the diminution of labor in keeping it in order. The pebbles larger than one and a half inches may be broken to that size and mixed with the cleaned material. 428. Laying the Gravel. On the roadbed properly prepared a layer of the prepared gravel four inches thick is uniformly spread over the whole width, then compacted with a roller weighing not less than two tons, and having a length of not less than thirty inches. The rolling must be continued until the pebbles ceases to rise or creep in front of the roller. The surface must be moistened by sprinkling in advance of the roller, but too much water must not be used. Successive layers follow, each being treated in the above-described manner until the requisite depth and form has been attained. 429. The gravel in the bottom layer must be no larger than that in the top layer; it must be uniformly mixed, large and small together, for if not so the vibration of the traffic and the action of frost will cause the larger pebbles to rise to the surface and the smaller ones to descend, like the materials in a shaken sieve, and the road will never be smooth or firm. The pebbles in a gravel road are simply imbedded in a paste and can be easily displaced. It is for this reason, among others, that such roads are subject to internal destruction. 430. The binding power of clay depends in a large measure upon the state of the weather. During rainy periods a gravel road becomes soft and muddy, while in very dry weather the clay will contract and crack, thus releasing the pebbles, and giving a loose surface. The most favorable conditions are obtained in moderately damp or dry weather, during which a gravel road offers several advantages for light traffic, the character of the drainage, etc., largely determining durability, cost, maintenance, etc. 431. Repair. Gravel roads constructed as above described will need but little repairs for some years, but daily attention is required to make these. A garden rake should be kept at hand to draw any loose gravel into the wheel-tracks, and for filling any depressions that may occur. In making repairs, it is best to apply a small quantity of gravel at a time, unless it is a spot which has actually cut through. Two inches of gravel at once is more profitable than a larger amount. Where thick coating is applied at once it does not all pack, and if, MISCELLANEOUS PAVEMENTS. 351 after the surface is solid, a cut be made, loose gravel will be found; this holds water and makes the road heave and become spouty under the action of frost. It will cost no more to apply six inches of gravel at three different times than to do it all at once. At every one-eighth of a mile a few cubic yards of gravel should be stored, to be used in filling depressions and ruts as fast as they appear, and there should be at least one laborer to every five miles of road. 432. Cost of Construction in Illinois. The cost has been about $900 per mile for a roadway 12 feet wide, 12 inches deep at the centre and 9 inches at the sides. Table XLIII shows the extent and cost of gravel pavements in some of the principal cities in the United States. TABLE XLIII. EXTENT AND COST OP GRAVEL PAVEMENTS IN SOME OP THE PRINCIPAL CITIES OF THE UNITED STATES. Cities. Extent. t Miles. Cost of Construction per square yard. 160.00 $0.75 67.91 Richmond Vs. 46.44 $0 15 to $0 20 Washington D C 33.50 32.37 11.92 Haverhill Mass $025 433. Weight of Gravel. A cubic yard of pit gravel weighs about 3300 pounds. When the distance is not greater than 1 miles, a team will haul about 7 cubic yards a day ; even with hauls of six miles the work can be done at reasonable cost. 434. Bituminous Macadam. In some towns in England bitu- minous or asphalt macadamized roadways are made. This consists in mixing ordinary coal-tar with the road metal ordinarily employed for macadamized roads ; only it must be borne in mind that the metal employed must be limestone or some other soft material, otherwise it will not wear down evenly with the tar, and thus a lumpy surface will be produced in course of time. The method of mixing is by heating the stone, which has of course been previously broken to the required size, and then thor- 352 HIGHWAY CONSTRUCTION. oughly mixing and incorporating it with the tar. This is carried to the roadway, is spread in the ordinary manner, and well rolled to the proper contour, a surface being afterwards given to it by a coating of about 2 inches thick, composed of a similar mixture, the stones of which are of much smaller size. Another method is to place about 6 inches of the broken stone upon the necessary foundation. Upon this a boiling mixture, com- posed of about 50 gallons of creosote oil and 1 ton of pitch, is poured until every interstice is filled with the mixture. Whilst this is still warm, a thin layer of small broken stone is spread upon the surface and well rolled; more small stones or chippings are added, and the whole is rolled until the surface of the roadway has attained its proper contour and presents a perfectly smooth and clean appearance, little inferior to that of real asphalt. Dry weather is essential whilst this class of roadway is in course of construction, and careful watching is required, as when the skin breaks the whole roadway soon disintegrates. This class of pave- ment has, however, many advantages over ordinary macadamized roadways when finished, not the least of them being impervious- ness to moisture, and the ease with which it may be cleaned. 435. In repairing some of the macadam roads and pavements in Paris, fragments of old asphalt were mixed with the broken stone. The results, as regards wearing qualities, show little improvement over the unmixed stone, but such a pavement keeps remarkably clean during dry weather and does not become as muddy as the true macadam during rainy seasons. In the middle of summer an unpleasant odor is given out, and the surface has a dirty black color. 436. Concrete Macadam, introduced by Mr. J. Mitchell, London Eng., is composed of broken stone, sand, and Portland cement so proportioned that the spaces, otherwise vacant, and ultimately filled with muddy cementing matter of worn macadam, are filled with an admixture of Portland cement or other hydraulic cement-grout. The concrete thus formed rapidly becomes a uniform and impervious mass which is wholly unaffected by heat or moisture. It is mixed in these proportions : Broken stones 4 measures Clean, sharp sand li to 1| Portland cement 1 " MISCELLANEOUS PAVEMENTS. 353 So for a cubic yard, or 27 cubic feet, of broken metal 6f cubic feet, or 1 barrels (of 4| cubic feet), of Portland cement are re- quired. The broken stone should be of the hardest quality, of uniform size, thoroughly screened; and it should be thoroughly wetted before being incorporated with the cement. Cement of the best quality must be employed, and the sand should be sharp, clean, and gritty. The surface of the ground is brought to form, and rolled several times. The concrete is then laid on the surface in a layer 3 or 4 inches, and is left for three days to harden. The second layer of 3 or 4 inches is next laid on the first, and immediately rolled to form with a heavy iron roller, as heavy as two or three men can draw. The cement should be left for three weeks, to allow it to become quite hard before the road is opened for traffic, although a week has been found to be a sufficient interval. Mr. Mitchell states that a concrete road, 7 inches deep at the middle and 5 inches at the sides, is sufficient for ordinary traffic. For heavy traffic a depth of 8 inches is recommended. The first piece of concrete road was laid in 1865 in Inverness, and consisted of 45 lineal yards of the approach to the freight sta- tion of the railway. In 1870, after the road had been under traffic for 4^ years, it was reported that the wear of the surface was scarcely appreciable, whilst the adjoining macadamized road had been coated frequently every year. Another specimen, 50 yards long and 15 yards wide, was laid in 1866, on George IV. Bridge, Edinburgh, where the traffic is heavy and continuous. At the end of three years and a half under traffic the surface was perfectly sound and immovable. The amount of vertical wear during the periods above named appears not to have exceeded inch. But Mr. J. H. Cunningham, writing in January, 1875, stated that it was then much worn at the surface, in consequence, he thought, of its great hardness and rigidity. 437. Stone Trackways (Figs. 29 to 32). Trackways formed of stone slabs were first employed by the Egyptians for moving great weights. In modern-times they reappeared in northern Italy, where they are in general use not only in the streets of the principal cities, but also in the smaller towns. Telford employed a stone trackway on the Holyhead Road to 354 HIGHWAY CONSTRUCTION. ''-%/>_ _ SAN D OR CONCRETE if'J^ffl ;-y.v GRAVEL. VoJj^vlV/t; FIG. 29 SECTION OF STONE TRACKWAY. FIG. 30.-PLAN OF TRACKWAY. FIG. 31. PLAN OF CROSSING^ MISCELLANEOUS PAVEMENTS 355 r FIG. 32. JUNCTION OF CURVES WITH STRAIGHT LINE. 356 HIGHWAY CONSTRUCTION. avoid excessive work of construction. There were two hills each a mile in length, with an inclination of 5 : 100. To reduce this to a 4 per cent grade would have cost $100,000, but nearly the same advantage in diminishing the amount of tractive force required was obtained by making stone trackways at a total expense of one half the former amount and retaining the 5 per cent grade with moderate -cutting and embankment. To draw one ton over the original hills required a tractive force of 294 pounds; to draw the same load over the trackways laid on the same inclinations required only 132 pounds. Trackways of both stone and iron have been used in London, Liverpool, Manchester, Glasgow, and other cities. 438. The Italian trackways consist of two parallel lines of granite blocks, usually 14 inches wide, 8 inches deep, and 5 feet in length, bedded in a layer of sand. The lines are 28 inches apart, and the in- terspace, or footway for horses, as well as the other portions of the roadway, is paved with cobbles obtained from the Po, or from other rivers. These stones should be egg-shaped, with a maximum diame- ter of from 3J to 4 inches and a depth of from 4| to 5J indies. The roadway is usually formed with a slight inclination downwards towards the centre. By this arrangement the space between the trams serves as a channel to receive the surface-water, and is provided with stone gratings, placed at suitable intervals, by which the water escapes into the sewers. The surfaces of the trams are slightly in- clined towards each other, the inner edges being f inch lower than the outer edges ; whilst the interspace is concave, having a versed sine or depression of 1^ inches. The foundation of the roadway consists of a layer of screened gravel, about 6 inches deep, watered so as to form a compact mass. Two inches of sand is laid on the gravel, as a bed for the paving-stones. The upper surfaces of the trams are dressed flat and the ends square, to form close joints. The stone gratings for the gulleys are 32 inches long, formed with three slots 12 inches long and 1-J- inches wide. After the trams are placed, the other portions of the pavement are completed. After the surface has been well rammed with a wooden rammer, it is watered and covered with a bedding of sand f inch deep, so as to fill the joints by degrees. On steep gradients the surfaces of the trams are grooved diagonally. 439. Trackways are expensive to construct (cost about $14,000 MISCELLANEOUS PAVEMENTS. 357 per mile for two lines of track and intermediate paving in the neighborhood of New York), but cost little for repairs and mainte- nance. Their advantages are many: they combine the opposite qualities req7iired for easy haulage, viz., a smooth surface for the wheels, on which the friction is reduced to the least possible amount, and a rough footway, affording a firm foothold for horses, thus enabling them to exert their utmost tractive power. For this reason they ought to receive more attention than is now accorded them. The friction of their surface is only about T -|- of the load, or about one half that of the best block pavement. It is stated that on such trackways in London a horse weighing about 700 pounds could draw on a level 15 tons, and a horse weighing about 1600 pounds could draw 30 J tons. 440. In Glasgow, Scotland, there was a trackway down for forty yeL M s. It consisted of cast-iron plates 2 inches thick, 8 inches wide, and cast in lengths of 3 feet. It was laid in Buchanan Street on a 5 per cent grade. 441. The trackways for the wheels may be of granite, or compact sandstone slabs 12 to 24 inches wide, 6 inches thick,, and in lengths of 2 to 6 feet. The footway for the horses to be int all cases paved with cobblestones the other portions of the road- way may be paved with cobblestones, granite, or other pavement. The foundation for the trackways should be constructed as shown in Fig. 29, with all the joints filled with asphaltic paving-cement. The roadway may be formed in the usual manner with the trackways level (transversely), the surface falling from their outer edge to the gutters; but at frequent intervals in the horse-path catch-basins with iron or stone covers should be placed, connecting with the sewer. At track-crossings or junctions the surface of the slabs should be grooved, so as to afford good foothold for the horses, passing over them. 442. " Jasperite." Jasperite, under what is known as " Drake's Patent," consists of quartzite crushed to sizes of J, , and -J- of an inch, and known as Nos. 3, 4, and 5, respectively. The foundation is composed of irregularly broken stone set to form a rough pave- ment similar to that used for a Telford road. . On this is spread a layer of concrete 1| inches thick, composed as follows : 1 part of Portland cement, 1 part of sand, and 3 parts of quartzite of the sizes Nos. 3 and 4. This is well mixed, spread, and rammed inta 358 HIGHWAY CONSTRUCTION. place in such a manner as to form blocks one yard square. These blocks are separated by tarred paper. On the bed so formed is spread a layer one-half inch in thickness, prepared in the same way, but substituting quartzite of the size known as No. 5. This pave- ment is in use in Sioux Falls, S. D., and Wichita, Kan. The cost per square yard is about $2.50, with a five-year guarantee. 443. Artificial Granite "Slocks are formed from the chippings of granite quarries. It is mixed at the place where it is to be used with Portland cement in sufficient quantity to make a thorough bond between the pieces, and put down in blocks or squares so as to form separate stones as it were. Its surface is kept compara- tively rough by the cement wearing below the points of the granite. Its advantage is, presumably, cheapness. 444. Plank Roads. In localities where timber is abundant and -other materials are unobtainable, planks may be employed to form pavements. When new and well laid they form a comfortable car- riageway both for haulage and pleasure, but make when worn and -displaced a very disagreeable road. 445. The method most generally adopted in constructing plank roads consists in laying a flooring or track 8 feet wide, composed of boards from 9 to 12 inches in width and 3 inches in thickness, which rest upon two parallel rows of stringers or sills laid length- wise in the road and having their centre lines about 4 feet apart or 2 feet from the axis of the road. Sills of various-sized scantling have been used, but experience seems in favor of scantling about 12 inches in width, 4 inches in thickness, and in lengths of not less than 15 to 20 feet. Sills of these dimensions laid flatwise and nrnily embedded present a firm and uniform bearing to the boards and distribute the pressure they receive over so great a surface that, if the soil upon which they rest is compact and is kept well drained, there can be but little settling and displacement of the road-surface from the usual loads passing over it. The better to secure this uni- form distribution of the pressure, the sills of one row are so laid as to break joints with the other, and to prevent the ends of the sills from yielding the usual precaution is taken to place short sills at the joints, either beneath the main sills or on the same level with them. The boards are laid perpendicular to the axis of the road, ex- perience having shown that this position is more favorable to their MISCELLANEOUS PAVEMENTS. 359 wear and tear than any other, and is besides the most economical. Their ends are not in an unbroken line, but so arranged that the ends of every three or four project alternately, on each side of the axis of the road, 3 or 4 inches beyond those next to them, for the purpose of presenting a short shoulder to the wheels of vehicles to facilitate their coming upon the plank surface when from any cause they may have turned aside. On some roads the boards have been spiked to the sills, but this is unnecessary, the stability of the boards being best secured by well packing the earth between and around the sills, so as to present a uniform bearing surface to the boards, and by adopting the usual precautions for keeping the sub- soil well drained and preventing any accumulation of rain-water on the surface. The boards for plank roads should be selected from timber free from the usual defects, such as knots and shakes, which would render it unsuitable for ordinary purposes, as durability is an essential element in the economy of this class of road-construction. Boards of 3 inches in thickness offer all the requisites of strength and durability that can be obtained from timber in its ordinary state, in which it is used for plank roads. Besides the wooden track of 8 feet, an earthen track of 12 feet in width is made, which serves as a summer road for light vehicles and as a turnout for loaded ones. This, with the wooden track, gives a clear road-surface of 20 feet, the least that can be well allowed for a frequented road. It is recommended to lay the wooden track on the right-hand side of the approach of a road to a town or village, for the proper convenience of the rural traffic, as the heavy trade is to the town. The surface of this track receives a cross-slope from the side towards the axis of the road outwards of 1 in 32. The surface of the summer road receives a cross-slope in the opposite direction of 1 in 16. These slopes are given for the purpose of facilitating a rapid surface for draining. The side drains are placed for this purpose parallel to the axis of the road and connected with the surface in a suitable slope. Where from the character of the soil good summer roads cannot be had, it would be necessary to make wooden turnouts from space to space, to prevent the inconvenience and delay of miry roads. This can be effected by laying at these points a wooden track of double width, to enable vehicles meeting to pass each other. It is recommended to lay these turnouts on four or five sills, to spring 3GO HIGHWAY CONSTRUCTION. the boards slightly at the centre, and spike their ends to the ex- terior sills. In some of the earlier plank roads a width of 16 feet was given to the wooden track, the boards of which were laid upon four or five rows of sills. But experience soon demonstrated that this was not an economical plan, as it was found that vehicles kept the centre of the wooden surface, which was soon worn into a beaten track, whilst the remainder was only slightly impaired. This led to the abandonment of the wide track for the one now usually em- ployed, which answers all the purposes of the traffic and is much more economical, both in the first outlay and for subsequent re- newals and repairs. Plank roads possess great advantages in a densely-wooded country, and will be found superior to every other kind as a temporary expedient. 446. The cost per mile ranges from $1000 to $4000, and the life is about eight years. 447. Log Roads. When a road passes over soft swarnpy ground, always kept moist by springs which cannot be drained without too much expense, and which is surrounded by a forest, it may be cheaply and rapidly made passable by felling a sufficient number of young trees, as straight and as uniform as possible, and laying them side by side across the road at right angles to its length. This arrangement is well known under the term "corduroy road." Though its successive hills and hollows offer great resistance to draught and are very unpleasant to persons riding over it, it is nevertheless a very valuable substitute for a swamp, which in its natural state would at times be utterly impassable. 448. Charcoal. In some of the Western States, where wood is abundant and cheap, roads covered with charcoal have been made as follows : Logs from six inches to two feet in diameter and from twelve to twenty-four feet long are cut and piled lengthwise along the road about six feet high, being nine feet on the bottom and two on top, and then covered with straw and earth, or simply with sods, and burned in the manner of coal-pits. The covering is taken from the sides of the road, and the ditches thus formed afford good drainage. After the timber is converted into charcoal, the earth is removed to the side of the ditches, the coal raked down to a width of fifteen feet, leaving it two feet thick at the c.n- ter and one at the sides, and the road is completed. MISCELLANEOUS PAVEMENTS. 361 449. A road thus made in Michigan cost $660 per mile, and is said to.be very compact and free from mud or dust. At a season when the mud on the adjoining earth road was half-axletree deep, on the coal road there was not the least standing, and the impress of the feet of a horse passing rapidly over it was like that made on hard -washed sand, as the surf recedes, on the shore of the lake. The water was not drained from the ditches, and yet there were no ruts or inequalities in the surface of the coal road, except what was produced by more compact packing on the line of travel. It is probable that coal will fully compensate for the deficienc}'' of lime- stone and gravel in many sections of the West, and, where a road is to be constructed through forest land, that coal may be used at a fourth the expense of limestone. 450. Iron. Iron is eminently durable, but as a pavement it is a failure. It is so slippery even when roughened that horses can- not gain a foothold on it. About thirty years ago Cortlandt Street in New York was paved with it. In order to guard against slipper- iness the surface was made rough and consisted of hexagonal pro- jections about an inch in size, separated by depressions of about the same size. It was both rough and noisy; the horses caught their calks in the depressions and twisted off their shoes, and in spite of its roughness the horses fell frequently and with disastrous results in tearing their knees on the sharp projections. It remained in use but a short time and was replaced with stone. Combinations of wood and iron, concrete and iron, are frequently introduced and experimented with, but so far none have been a practical success. 450a. Furnace Slag. Slag and cinders from iron and copper works may be employed with advantage when they are procurable, and when no stone sufficiently tough to withstand the action of heavy traffic can be obtained. They are both very durable,, but care is required in the selection of the tougher sorts. They have no binding properties, and on this account are sometimes used with limestone; a rough surface will, however, always result from the unequal wear of two materials so different in hardness. Limestone scrapings, coal ashes or clay, laid on as a binding material, aid con- solidation very much, and also prevent injury to horses 5 i'eet from the sharp edges of the fresh-laid sla^. In Queen Anne County, Md., experiments with furnace slag have proved successful. "The slag used was obtained from the 362 HIGHWAY CONSTRUCTION. Sparrows Point furnaces. It is the material run off from the furnace before the iron is drawn; it cools in a sponge-like mass. Its chemical composition is complex, and varies with the different ores and fluxes used. It is composed for the most part of an anhydrous lime silicate with sulphur compounds, to which its peculiar odor is due. The action of the weather on this slag is to harden it, and because of its cementing properties it readily compacts and becomes harder the longer it is down. The slag was put on the road 10 inches thick in the center and 7 inches at the sides measured loose. On the surface of the coarse slag there was spread a thin coating of fine material or ladle scrapings. This fine material when wet becomes hard and cements the pieces of slag together. The roller used was a 3^-ton horse-roller." The slag requires much less rolling than broken stone, but more water. After the material has been thoroughly drenched it should be allowed to stand for 10 or 12 hours before rolling, and after the roller has passed over it once or twice it may be watered again. Three trips over every part of the surface with a 10-ton steam-roller are considered sufficient to consolidate it. The estimated cost of a slag road for the Eastern Coast of Maryland is $3476 for one mile 15 feet wide. 450b. Blocks formed by casting furnace slag in moulds are in use in England and other parts of Europe. Their quality varies with the amount of silica contained : if this be about 35 per cent, the resulting blocks are tough ; hut if below 30 per cent, the block is brittle and easily broken. The process employed in England for the manufacture of these blocks, and which seems to produce a tough and durable article, is to run the slag from the furnace into a ladle, then pour it from this into iron moulds of the desired shape and size contained on an iron plate arranged to revolve; contact with the moulds chills the outside of the slag block immediately, and as the plate makes a half revolution the bottom of the mould is opened by mechanical means and the chilled block dropped either on a bed of sand or a conveyor. From here, and while the interior of the block is still in a molten condition, it is placed in an annealing oven, which, when fully charged, is sealed and allowed to cool, no heat being used other than that furnished by the blocks themselves.* * Scoria blocks are rarely free from internal cavities. When these are located near the upper surface the destruction of the block is materially accelerated. The dimensions of the blocks are 3^X4X8 inches; the four edges of the wearing surface are usually chamfered. MISCELLANEOUS PAVEMENTS. 363 450c. Chert. This material is employed for street and road paving in some of the Southern States, notably Alabama, where it is found in inexhaustible quantities overlying the red sandstone, which forms the covering of the red hematite iron ore, and underlying the sub-carboniferous limestone. The cities of Montgomery and Bir- mingham, Ala., and Macon and Savannah, Ga., have several miles of streets paved with it. There is also in both States several miles of country roads covered with it. Chert is a valuable substitute for broken stone, especially where stone is scarce or of unsuitable character; it furnishes an excellent surface and .wears well under traffic with but little dust or mud. The material is usually laid upon a foundation of furnace slag or other convenient material, but in the absence of such it is laid di- rectly upon the earth surface. The thickness employed varies from 3 to 5 inches. It is simply spread, sprinkled, and rolled. In Bir- mingham, Ala., the cost of the chert is 80 cents per cubic yard on the street, and the cost of the furnace slag, including hauling, spreading, and rolling, is from 30 to 40 cents per cubic yard. The name "chert" is also applied to the slag derived from the blast furnaces in Alabama. This material is also employed for street and road paving. 450d. Florida Clay. This name is given to a sandstone rock de- posit found in Florida, the material from which has been extensively used in several towns of Florida for street and sidewalk paving. Its use has been the means of converting streets so sandy that travel over them was very slow and difficult into driveways over which travel is easy and pleasant. The composition of this "clay" is as follows : Moisture 4.20 per cent. Silica 69.03 " " Aluminum silicate -. . . . 18.21 " " Ironoxide 8.53 " " Calcium carbonate trace. The most valuable constituent of this material, when used as a covering for roads, is, no doubt, the oxide of iron, which acts as a ce- ment, rendering the material capable of becoming compact and hard. For use the material is quarried and without any preparation is spread over the roadway to the depth of several inches, then sprinkled with water and compacted with a roller. It is of a red- dish color, due to the presence of the oxide of iron. After being 364 HIGHWAY CONSTRUCTION. travelled over for a short time it becomes very compact and nearly as hard as it was in its native bed. 450e. Tar-macadam. A paving composition called "tar-mac- adam" has been introduced in England; it consists of granite, coal-tar, refined asphaltum, and creosote oil in the proportions of 1 ton of granite broken into 1^-inch fragments, 12 gallons of coal-tar, 28 pounds of asphaltum, and 2 gallons of creosote oil; the ingredients are heated and thoroughly incorporated. The pavement is formed as follows : The foundation is composed of a layer of hard clinkers and broken stone, 10 inches in thickness, well consolidated by rolling with a 12-ton steam-roller; this- is covered with a layer 4 inches thick of stone broken into 2^-inch fragments. This is also compacted by rolling; upon this is spread a 3-inch layer of the "tar-macadam"; this is thoroughly compacted by rolling and then covered with a 1-inch layer of limestone screenings mixed with the same cementing materials that are used in the macadam. This last layer is sprinkled with clean dry limestone screenings and rolled. The work should only be done in dry weather; the rolling should average 10 hours for each 100 square yards, and the traffic should not be admitted until at least 24 hours after the work is completed. The cost is from 84 cents to $1.00 per square yard. Tar-macadam has been used with more or less success in several English and Canadian towns, and recently samples have been laid in several towns in the State of New York. Experience indicates that the life varies from three to ten years, according to the traffic; with fairly heavy traffic it would probably need to be entirely relaid at the end of seven years. COST OF CONSTRUCTION. Hamilton, Ont $0 . 95 per sq. yd. . . The stone used is a bastard lime- stone costing about $1.15 per cu. yd. for hand-broken and $0.95 for machine-broken, de- livered upon the work. Coal- tar $3.75 per bbl. of 50 gallons. Labor 18 cts. per hour. Ex- tent, 1901, 12| miles. London, Ont 1,20 " " Toronto, Ont 1.40 " " Nottingham, Eng 0.43 " " Geneva, N. Y 0.90 " " Fredonia, N. Y 1 .06 " " ' .. .Experience unsatisfactory. Aurora, N. Y Pawtucket, R. I .. .Used as a binder for macadam on steep grades. MISCELLANEOUS PAVEMENTS. , o65 COST OF MAINTENANCE. No statistics available. City Engineer Wingate, Hamilton, Ont., estimates cost under heavy traffic 8J cents, and under light 5 to 6J cents per square yard. Road Surveyor Owen, Nottingham, England, estimates cost of repairs 28 cents, and cost of floating 14 cents per square yard. ADVANTAGES AND DISADVANTAGES. It is claimed that coal-tar macadam possesses many advantages over ordinary macadam. For the first couple of years it offers very little resistance to trac- tion, and after being thoroughly compressed the cohesion is so great that the wear of the stones caused by attrition is reduced to a minimum. It is impervious to moisture, and it produces less mud and dust. It can be more easily cleaned in all weathers; for whereas sweeping-machines and scrapers remove the binding and thereby weaken an ordinary macadam road, they do no injury whatever to a tar-macadam road, and a shower of rain washes it clean. Snow and the subsequent thaw after frost do not cause the surface to disintegrate. In suburban roads where trees are planted on each side of the road, with ordinary macadam, the drops of rain falling from the trees wash out the binding and loosen the stones, and the foliage prevents the sun from drying the road. With tar-macadam the drops of rain do no injury, and the foliage protects it from the slight softening which occurs when the sun's rays are directed upon it. Traction-engines and motor vehicles cause but inappreciable damage. The chief objection raised against it is its slipperiness and that it is dangerous for horses in frosty weather; that it will not stand heavy traffic ; that it is not suitable for grades over 2J per cent. MAINTENANCE AND REPAIRS. It is found that coal-tar macadam, if properly mixed and laid, does not begin to wear as soon as traffic commences to pass over it, as, owing to its elastic nature, some time elapses before it is completely consolidated, and it acts like a cushion to the foundation for a couple of years. When it does begin to wear, and little ruts and hollows make their ap- pearance, they should be " picked out," swept clean, painted with a little hot tar, and a layer of tarred chippings put on and rolled. When the road is very much worn it is best to thoroughly pick the surface to a depth of 3 inches, clean all dirt and old material away, paint or sprinkle lightly with hot tar, and put on a layer of 366 HIGHWAY CONSTRUCTION. 2|-inch stone, which, when rolled, should be followed by a coat of J-inch chippings and finished off in the same manner as new work. The old material if screened free from dirt can be treated with a little hot tar (not so much will be required as for new stone) and used again. A very good way of preserving tar-macadam is to thoroughly clean the surface, paint with hot tar, and sprinkle with slag dust or fine gravel. This is called " floating," and is chiefly adopted where there is very little traffic. FAILURE. "The failures of tar-macadam are caused by not having the proper knowledge pertaining to the tar-mixing, which is essentially a job that must be left to the discretion of the man in charge, as it is quite difficult to fix any hard and fast rule, as so much depends upon the quality of the tar, the temperature while heating, the dryness-of the stone, and the quantity of pitch. Then, too, it is absolutely necessary to have hard, porous rock which is found in the limestone. With the use of granite for a tar-macadam roadway one would have very little success, owing to the granite being so close-grained that it will not absorb the tar unless thor- oughly dried and baked on hot plates, which makes it expensive." W. C. Wingate, City Engineer, Hamilton, Ont. COMPOSITION. Broken stone ranging from 2J inches to dust, cemented together with coal-tar, or a mixture of coal-tar and asphalt, to which sometimes creosote-oil is added. Quality of Stone. As regards the character of the stone to be used, it is found that the tar adheres better to a porous stone, such as limestone or slag, than it will to granite or trap. "It has been found next to useless to tar granite or syenite, because the material itself will not absorb the tar. The result has been that after forming the road well 'to start with, exposure has caused the tar to melt, wear, or disappear, with the result that after a short period the road has become not only rough through disintegration, but from a surveyor's point of view a hopeless failure. Many kinds of material have been tried for tarring, but they have almost always been found either too soft to stand traffic though they would absorb tar or too hard to absorb tar, being, however, hard enough to stand traffic. After repeated trials it has been found that the most satisfactory material yet produced is furnace slag of the very best hand-picked quality, but that, unless this is MISCELLANEOUS PAVEMENTS. 367 well warmed and perfectly dried before being used, it has too often baen only a failure." Report of ^Ir. E. P. Hooley, County Sur- veyor, Nottinghamshire, England. Quality of the Tar. The tar must be pure coal-tar free from all foreign substances and containing not more than 5 per cent of water. Coal-tar is of very complex composition, varying with the nature of the coal and the processes employed in the manufacture of gas or coke, of which it is a by-product; consequently no two tars are identical in every respect, although many tars are identical in every essential respect. The amount of bitumen contained varies between 60 arid 90 per cent; the non-bituminous matter contained is generally carbon and is insoluble in carbon bisulphide or in the lighter coal-tar oils, while all of the bitumen is soluble in coal-tar, benzine, or naphtha. Petroleum light oils or carbon bisulphide do not furnish a perfect solvent for coal-tar bitumens. The process of determining the amount of bitumen in a coal- tar is to liquefy it further by the use of coal-tar benzole, and all of the solution will pass through the filter-paper except the carbon. About 2 per cent of the carbon is so fine that it will go through the filter-paper and will appear by this test as bitumen. Coal-tar Cement is a residue by distillation of coal-tar. Hard- ness is produced in coal-tar cements, as in other bituminous sub- stances, by removing part of the oils contained in the bitumen, leaving the residue of the consistency desired. Flexibility is maintained by sacrificing a certain amount of hardness. Tar Mixture. The tar mixture to be applied varies consider- ably, as the quality of the tar differs so much. Thin tar requires more boiling than thick tar, or it should be stiffened by the addition of some pitch. Tar that has been distilled must not come to a boil, or it will become unworkable and will not incorporate freely with the stone. The use of pitch is not recommended unless the mixture is to be used immediately, for if the tar is boiled sufficiently it will be found to equal the tar-and-pitch mixture in cementing properties and be far superior in elasticity and covering power. Tar properly boiled has much more life in it and will not perish so quickly as when pitch and creosote-oil are added to it. The average time required for boiling the tar is 1J hours; it 368 HIGHWAY CONSTRUCTION. should be stirred frequently to prevent it from boiling over or burning. To test the consistency of the tar, boil a small quantity over a Bunsen burner and at intervals mix some with a quantity of stone chippings. From these samples it can be determined what time will be required for boiling to bring it to the proper consistency. It may also be tested by taking a little between the forefinger and thumb and trying if it is sticky. If it rubs off the finger easily it has not been boiled long enough. The quantity of tar varies according to the quality of the tar and the nature and size of the stone. Generally from 8 to 9 gal- lons of tar are required to coat 1 ton of warm stone. When pitch is used the amount is usually 10 Ibs. to the gallon of tar. Manipulation. The stone must be perfectly dry and mixed with the tar while hot. Care must be taken that the stone is not too hot, otherwise it will injure the tar. Both fixed and rotary driers are employed for drying and heating the stone. Specifications for Tar-macadam. Hamilton, Out. (E. G. Barrow > Engineer). "All earth or other material above the sub- grade shall be excavated so as to conform to the level of the sub- grade, which will be 12 inches below the finished surface of the roadway; and should the subgrade be above the level of the natural ground, then earth shall be deposited until the level of the subgrade is reached. The subgrade shall be shaped to the profile and cross-section^ which will be furnished by the city engineer. After the subgrade has been formed to the proper camber of the road, then it shall be thoroughly rolled with the steam foad-roller / and if by this means soft spots are revealed they shall be filled with good solid material. The first 6 inches shall be made in the ordi- nary way for a macadam or Telford roadway, thoroughly rolled. If so required it may be made of hard broken stone, furnace clinkers, or brick rolled smooth, and finished to the required camber of the road. Upon this shall be placed the tarred stone; the first layer 4 inches thick to be composed of stones capable of passing through a 2-inch ring. On this a layer composed of fine gravel or quarry chippings, f inch thick, shall be placed and well rolled in so as to fill all interstices. Before finishing a dressing of screenings shall be scattered broadcast, to be worked in by the traffic. All these layers except the last shall be thoroughly compacted by roll- MISCELLANEOUS PAVEMENTS. 369 ing. The stone to be tarred shall be heated on an iron floor, under which are flues from a fire, until the moisture is driven out. The material in its heated state is then to be thoroughly mixed with a sufficient quantity of tar. The tar should be boiled in iron kettles holding 50 imperial gallons, to which should be added a bucketful of pitch ; 8 imperial gallons should be added to each cubic yard of the coarser material, and 10 gallons to 12 gallons of the finer kinds of stone. The work must be done in the summer months, and all work must be suspended during wet weather. "The tar must be pure coal-tar free from all foreign substances and containing not more than 5 per cent of water, and shall con- tain upon analysis not less than 56 per cent of pitch." Geneva, N. Y. (E. G. Seybolt, Superintendent Public Works). "On the subgrade prepared as for ordinary macadam a layer of 2-inch stone was spread, sprinkled, and rolled; over this was spread 2^-inch stone to a depth of 5 inches, with enough screen- ings added to fill the voids; this was rolled down to 4 inches. Next a course of stone ranging in size from inch to 2 inches was spread; this stone was heated in a sand-drum and coated with tar in an asphalt-mixer. It was rolled while hot with a 5-ton roller. The top dressing, J inch thick, was composed of a mixture of tar, screen- ings, dust, and sand spread hot and rolled with a 5-ton roller until the tar flushed to the surface. This surface was then covered with limestone screenings and rolled. Sixteen gallons of tar were used to the cubic yard of the large stone and 39 to the finer." Experience with Coal-tar Macadam. Glasgow, Scotland. " Generally speaking, our experience of trr-macadam as a paving material in Glasgow is that it is not sufficient where t'lere is con- siderable traffic. In quiet residential streets, as a substitute for ordinary macadam, it is, I believe, an excellent material, but as a substitute for stone setts or wood-block paving it is not a good one. It is comparatively noiseless, non-slippery, unless in frosty weather, when all smooth pavements are slippery; and it is easily cleaned. I think also if laid during the summer-time, in dry weather, the ordinary weather conditions will not affect it." 450f. Artificial Stone. Pavements formed of artificial stone or concretes composed of hydraulic cement, crushed stone, sand, and gravel, with sometimes the addition of some indurating mineral .substance, as baryta, litharge, etc., have been tried ; they are usually 370 HIGHWAY CONSTRUCTION. manufactured under a patent, either in place or in the form of blocks at a factory. While artificial stone is eminently suitable as a paving material for foot walks, it quickly fails under the action of horses' hoofs and wheels when used as a carriageway pavement. 450g. Portland-cement Concrete. Portland-cement concrete is used in several cities as a paving material for alleys, and is found very suitable for this purpose. It has also been used for carriageway pavements in several cities, among which may be mentioned Belief ontaine, Ohio; Sioux Falls, S. Dak.; Chicago, 111.; Grenoble, France; several cities in Germany; and in Havana, Cuba. The usual method of construction is about as follows: The base is composed of cinders spread to a depth of 6 inches on the subsoil, which has been compacted by rolling. On the cinder foundation the concrete is laid in two courses, the lower 5J inches thick, composed of Portland cement 1 part, 5 parts sand and crushed stone. The wearing coat, If inches thick, is spread on the first course before the latter has taken its initial set. It is com- posed of 1 part cement and 1J or 2 parts of crushed granite or other hard stone screened to an average size of J inch. The surface of the second course is divided into blocks 3^X8 inches. A -inch transverse expansion joint is left at each 50 feet, and a longitudinal expansion joint is left at the curb. Artificial stone pavement has been used between the car-tracks on the neutral ground of Canal Street, New Orleans. The pave- ment consists of a 4-inch concrete foundation formed of 1 part Atlas cement, 3 parts sand, and 7 parts washed river-gravel; the top course consists of mortar 1 inch thick, formed of 1 part cement and 1 part sand. A considerable portion of the pavement has failed, due probably to the subsidence of the car-tracks and the vibration occasioned by the cars moving over the tracks. Some of the pavement has failed because the top course never thoroughly bonded with the foundation, and the top course, being subjected to greater contraction and expansion, due to exposure in a greater degree to the influences of the weather, separated from the foundation, being extremely brittle and easily fractured it has disintegrated. 450h. Clinkers. The clinkers produced by burning street sweepings and garbage and the debris produced in the manufacture of gas, consisting of the clinkers, old retorts, fire-bricks, ash-pan and coKe refuse, have all been tried for paving both footpaths and MISCELLANEOUS PAVEMENTS. 371 carriageways; in the former they are generally satisfactory, but in the latter they quickly fail. The materials are prepared for use by crushing to a size of about one inch; the crushed material is screened; the portion that will not pass through a one-quarter inch screen is used for the top finish, and the coarser portion for the foundation. The materials so separated are mixed with either Portland cement or coal-tar, and laid in place in the usual manner; or they may be formed into blocks at a factory and shipped to the place of use. (Mixed with cement it is used at Hersey, a suburb of London, and is said to give satisfaction.) 450i. Glass. An experiment with this material is being made in Lyons, France; the Kue de la Eepublique has been paved with ceramocrystal, or devitrified glass. This new product is obtained from broken glass heated to a temperature of 1250 F. and com- pressed in matrices by hydraulic force. The glass pavement is laid in the form of blocks 8 inches square, each block containing sixteen parts in the form of checkers. These blocks are so closely fitted together that water cannot pass between them, and the whole pavement looks like one gigantic checker-board As a pave- ment it is said to have a greater resistance than stone, it is a poor conductor of cold, and ice will not form on it readily; dirt does not accumulate upon it so easily as upon stone, and it will not. retain microbes. 450j. Novaculite (from the Latin novacula, a razor) is an un- crystallized quartzite, very much like flint, and occurs in large quantities in southern Illinois, Missouri, and Arkansas. It is em- ployed for carriageway and sidewalk paving (under a patent) and appears to give satisfaction. Its composition is stated to be as* follows : Silica 94.48 Alumina 1.28 Iron oxide 3.12 Loss by ignition 1.13 100.00 Prof. J. B. Johnson says it is the hardest of rocks, scratches glass like a diamond, and resists all disintegrating action of the weather. 372 HIGHWAY CONSTRUCTION. 450k. Destructor Concrete. In several English cities where cre- matories are employed for the destruction of the garbage, etc., the clinker therefrom is used for making concrete slabs. The clinker is ground very fine, and mixed in the proportion of one of Portland cement to two of clinker. The mass of clinker and cement, after being mixed, is passed through a hydraulic press and formed into slabs 2 inches in thickness, and are used for footpath paving under the name of "Destructor" concrete. 4501. Cork. Pavements made from granulated cork mixed with asphalt and other cohesive substances are employed in London and other European cities to deaden the noise in the neighborhood of hospitals and churches. The ingredients are compressed into blocks measuring 9 by 44 by 2 inches. The blocks are imbedded in tar and rest upon a concrete foundation 6 inches thick. The cost per square yard (32 blocks), including jointing material, but exclu- sive of laying and foundation, is about $2.50. It is claimed that as a paving material it is non-absorbent, non- slippery, practically noiseless, more durable than wood, perfectly sanitary, and not subject to expansion and contraction. Blocks which have been under traffic for a number of years seem to have come through the ordeal with a satisfactory result which the name of the material would hardly suggest. 450m. Copper Slag. Paving-bricks are made in Germany from copper slag. The slag is run into heated cast-iron moulds having a capacity of 36 bricks; immediately after filling the moulds and their contents are thickly covered with sand and allowed to stand undisturbed for seventy-two hours. When thoroughly cooled each brick is struck a strong blow with a hammer, and those containing blow-holes crack. ' 450n. Steel Trackways. The experimental pieces of these trackways which have been constructed consist of two parallel lines of steel plates, eight inches wide, laid at a sufficient distance apart to receive the wheels of vehicles of the standard gauge. The plates are provided on one edge with a flange one-half inch wide, and on the under side with a flange about 6 inches deep, which, when bedded in the earth of the roadway, supports the rail without the use of cross-ties. Tie-rods are used at intervals of about 10 feet. MISCELLANEOUS PAVEMENTS. The advantages claimed for this style of road by its advocates are: 1. That it can be built without greater cost in most cases, and probably with less cost in many cases, than any other hard and durable road; 2. That it will last many times as long as any other known material for road purposes, and with much less repair; 3 That the power required to move a load over the steel trackway io only a small fraction of the power required to move the same over any other kind of road. FIG, 32A. CROSS-SECTION OF STEEL TRACKWAY, During 1892 a steel trackway was constructed between Valen- cia and Grao, Spain, at a cost of $28,518. It is traversed daily by an average of 3200 vehicles, each of which pays a toll of about eight-tenths of a cent. The annual cost of maintenance is about $380. The trackway replaces a stone road which cost $5470 a year to maintain. In Germany several experiments with steel trackways have 1 been made. The first track was laid on a highway in tlie province of Hanover by Engineer Gravenhorst. The length of this ex- perimental section was 1600 feet; the rails were of flat section, 5 inches wide, 33 feet long, and weighed 6.7 Ibs. per foot. The joints were made on cast-iron seats, which also held the track in position. The foundation was concrete, the rails being laid in a bed of cement mortar without cross-ties. The rails were de- pressed about 0. 1 inch from the level of the pavement, and longi- tudinal depressions were made to provide foothold for the horses. The use of this trackway showed: 1. That it was wrong to depress the rails in the pavement: the rough edges of the projecting stones were not sufficient to form a guide for poorly horsed, carelessly driven, and badly maintained vehicles; besides, the stones caused shocks to the vehicles and caused rapid abrasion of the wheel- rims. 2. That it was not sufficient to secure the flat rails c.,t their joints to the concrete foundation. When the sun heated the 374 HIGHWAY CONSTRUCTION. track, the loosely lying rails became wavy and began to rattle, wliile in rainy weather water and mud collected under them and was scattered about by the passing vehicles. Experiments with rails of T section having a guiding rib gave such favorable results that upwards of 40 miles of trackway were built; but continued use showed that the T rail had a tendency to rotate or overturn, due to the narrow bearing of the base on the foundation, which the use of cross-ties did not prevent. ____ - FIG, 32e, T RAIL USED IN GERMANY, FIG. 32c. SECTION OF Box RAIL. After extended experiments Engineer Gravenhorst developed the box section, shown in Fig. 32c, and about 10 miles of such section have been laid. The rail weighs 12 pounds per lineal foot. The joints are made by a splice-box of similar section; the rails are pushed in from both sides and are secured with thin metal wedges. The hollow space of the rail is filled either with bricks or concrete. The bricks are grouted with a thin cement mortar and the concrete is made up with a stiff mortar. The filling adheres firmly to the metal, so that the rail can be overturned after 36 to 48 hours with- out loosening it. The apprehension that the filling would gradually loosen under the effect of he vibrations of traffic and the unavoid- able changes caused by temperature has not been realized so far. The rails are supported for their whole length by a concrete foundation and are secured by the pavement against displacement .side wise. The grades of the trackways laid range from 2.5 per cent to 3.8 per cent with many curves. As to what is the maximum allow- able grade no experiments have been made curves offer no diffi- culties and the rails are easily bent in the shop. Observations made to determine the most suitable height of MISCELLANEOUS PAVEMEKTS. 375 the guiding rib showed that a height from f to J inch is sufficient to prevent involuntary derailment and is not objectionable to vehicles crossing or leaving the track. A height of f inch was found to cause much inconvenience and difficulty to vehicles leav- ing and crossing the track, and breaking of wheels frequently happened. As to the best inclination to be given to the inside of the guiding rib, experience indicates that about 25 per cent is the best, this being the inclination to which the ribs show a tendency to wear. FIG. 32o. SECTION OF RAIL LAID IN MURRAY STREET, N. Y. For paving between the tracks cobblestones will be found sufficient. If the tracks are to be laid on a macadam road having a Telford foundation, the latter will prove sufficient for the rails; but the joints between the broken-stone surface and the rails are difficult to make, unenduring, and troublesome to maintain. As to the effect of the use of trackways on the cost of mainte- nance of the highways no data are available at present. Fig. 32d shows a section through one of the rails recently laid in Murray Street, New York, under the direction of General Roy Stone. The rails are spaced 5 feet apart \ center to center, and every 13J feet longitudinally they are tied together with f-inch 376 HIGHWAY CONSTRUCTION. rods bolted through both flanges of each rail, and fitted with a nut on the outside and a gas-pipe separator between the inner flanges of the rails. The rails are 40 feet long, weigh about 25 Ibs. per lineal foot, and are riveted together by means of three splice-plates: one, 9X5 inches, on the under side of the web of the channel, with three rivets for each rail countersunk on the, rolling surface; the other two plates, 10x3 inches, connect the flanges, with two rivets to each flange. The foundation for the rails is 12 inches of broken stone resting on the old paving-blocks removed from the street. The under surface of the rails was coated with tar and the rails bedded on a thin layer of fine gravel. The resistance to traction on this wheelway is stated by General Stone to be 14 pounds per ton. After about one year's experimenting the trackway was found to be impracticable, owing to the constant slipping and stumbling of the horses. It has been removed and wood-block pavement laid in its place. FIG- 32E- GIBBON PATENT TRACKWAY. The resistance to traction on steel wheelways is shown by Prof. I. O. Baker to range from 19 to 40 pounds per ton, the variation being undoubtedly due to the deflection of the track under the load and to the state of cleanliness of the rail. Fig. 32e shows the Gibbon patent steel trackway now being introduced by the Steel Highway Track Construction Company of America. It consists of steel base-plates, rail-supports, tie-bars and rails. The rails are 32 feet long and 7 to 8 inches wide, with flanges on both sides; the one designed to guide the wheels is } of an MISCELLANEOUS PAVEMENTS. 377 inch in height. The track is intended to be ballasted between the rails and three or more feet outside each rail. The cost of con- struction is said to be about $6000 per mile. 450o. India Rubber in large sheets about 1 inch in thickness has been tried in Hanover, and is said to be an excellent paving mate- rial. A sample 2 inches thick was laid at the entrance to the Euston Railroad Station, London, in 1881, at a cost of $32.70 per square yard. In 1902 it was examined and found to have worn down to f of an inch at the incoming edges where the horses first step on to it from the street pavement. An area of about 3000 square feet has recently been laid at the Savoy Hotel, London, at a cost of $4.54 per square foot. The thickness is 2 inches and the weight is 15J pounds per square foot. It is laid on a concrete foundation, fin- ished with a cement floating to make a smooth bed, upon which the sheets of rubber are laid and held in place by strips of iron. It is said to meet nearly all the requirements of a perfect paving material, being exceedingly durable, not slippery, absolutely noiseless and impervious. Its cost, however, prohibits its general use. 450p. Artificial Paving-stones are manufactured in Germany from a mixture of coal-tar, sulphur, chlorate of lime, glass or fur* nace slag. The process employed is to mix the tar and sulphur at a moderate temperature, and to this mixture add the chlorate oi lime. The mixture is allowed to cool, then broken into small frag- ments and mixed with fragments of glass or blast-furnace slag This mixture is heated to a moderate temperature, placed in moulds of the desired form, and subjected to a pressure of about 3000 pounds per square inch. The specific weight of the stone is 2.20, and the resistance to crushing 315 pounds to the square centi- metre; the resistance to wear and tear in use is said to be half as great as that of Swedish granite. The advantages claimed are: Durability equal to that of many stone roads; resistance to changes of temperature; a roughness of surface which gives horses a good foothold; non-transmission of sound; facility of cleansing on account of the closeness of the joints. 450q. Asphaltina is a patented material composed of coal-tar, resin, and sulphur. 450r. Asphalt-granite Pavement. In this pavement the binder is laid on a concrete foundation in the ordinary manner, and while it is still soft fragments of granite or other hard stone, broken to a roughly pyramidal shape, are imbedded in the asphalt with their 378 HIGHWAY CONSTRUCTION. points upward, and just below the level of the surface of the finished pavement. The final layer of asphalt is put on over these stones and fills the interstices between them, and appears as smooth as an ordinary pavementt The object of this construction is to render the pavement non-slippery. 450s. Asphalt Macadam. WHINERY'S PATENT. This pavemei consists of broken stone cemented with asphaltic cement prepared in the same manner as that for use in asphalt pavements. The method of construction is described as follows: "Foundation. The foundation may be either of broken stone, as in ordinary macadam roads, or it may be of hydraulic-cement concrete, such as is generally used with asphalt pavements. The question as to which foundation is advisable will depend on local conditions, such as the character of the subgrade and the relative cost of each kind of foundation, of such depth as will furnish the requisite support to the wearing surface. "The wearing surface consists of a layer of sufficient thickness of broken stone, the voids of which are filled and the inequalities of the surface are levelled up with the bituminous composition. The stone is broken to a suitable size, and all fragments above and fragments and dust below the required dimensions are carefully screened out as it comes from the crusher. The selected material is spread over the prepared foundation in an even layer of the requisite thickness. Either before or after it is thus spread it is heated to a temperature of about 300 F. This is done to facilitate the filling of the voids in the mass with the bituminous composition^ and to insure a close bond and firm adhesion between the stone and the bituminous composition. " The bituminous composition is substantially of the same mate- rials and is prepared in much the same manner as the wearing surface of sheet-asphalt pavements, the component parts and the consistency of the mass being varied so as to secure the best prac- tical results. This composition, when prepared and while still at a sufficiently high temperature to be very plastic, is spread over the top of the layer of hot crushed stone in quantity sufficient to fill the voids in the stone and to level up the unevenness of its surface, and is properly graded with paving-rakes. When this operation is completed a steam-roller weighing not less than ten tons, of the * asphalt ' type, is operated over the surface until the plastic com- position is forced into every void in the mass of stone, the uneven- MISCELLANEOUS PAVEMENTS. 379 ness of the surface filled up, and the whole mass thoroughly com- pressed and solidified. The roadway is then complete, and after giving it time to become cold and hard the street is opened to travel. "No pavement of this kind has yet (1907) been constructed, but the inventor believes that it will possess the following merits: " 1. The first cost will be materially less than sheet asphalt. " 2. The surface should be almost, though probably not quite, as smooth and noiseless as a sheet-asphalt pavement, and should offer but little more resistance to traction. " 3. It will afford a better foothold for horses than sheet asphalt. "4. It will be at least as durable and will probably prove more durable than sheet asphalt, and will not be subject to the defect called 'scaling. 7 "5. It will not shift under travel into ridges and hollows as does a sheet-asphalt pavement. " 6. It is believed that it will not crack. "7. It can be repaired more cheaply and with less skilled labor than sheet asphalt. " 8. It will be free from dust. "9. It will be free from the defect called 'ravelling/ " 10. Since the bituminous part of the pavement will be made with a greater percentage of bitumen than is used in sheet asphalt, and will be, in a measure, shielded from the effects of excessive travel by the crushed stone, it should be possible to use a com- posite asphaltum cement, which, while it may not have as great strength and endurance as the best paving asphalts, will not be affected by water to the same extent as these asphalts." 450t. Bitulithic or Bituminous Macadam. WARREN'S PATENT. This pavement is composed of stone ranging in size from 2 inches to dust, mixed in predetermined proportions so as to reduce the voids to about 10 per cent, cemented by a bituminous cement manufactured either from coal-tar, asphalt, or a combination of both. The method of construction is as follows: The foundation is composed of a layer 4 inches thick of broken stone spread upon the subsoil and thoroughly compacted by rolling. On the surface of the compacted stone there is spread a thin coat of bituminous cement which fills the interstices and forms a binding surface for the wearing coat. 380 HIGHWAY CONSTRUCTION. The wearing coat is composed of broken stone, varying in size from 2 inches to dust, the various sizes being so pioportioned that the voids are reduced to about 10 per cent. The stone is mixed, with or without heating, with Warren's bituminous compo- sition heated to about 250 F. The mixture is spread while hot to such a depth that after compression with a roller weighing from 10 to 15 tons it shall have a thickness of 2 inches. After rolling the surface is coated with Warren's quick-drying bitu- minous flush coat composition, the purpose of which is to thoroughly fill any unevenness and porous spots in the surface. While this coat is still sticky there is spread over it a layer of sand or fine stone chips, which are then rolled and the surface is ready for traffic. The purpose of the stone chips is to form a gritty surface and prevent slipperiness. THE ADVANTAGES CLAIMED are : 1. Greater durability than asphalt by reason of the use of a softer cement. 2. Provides a foothold for horses equal to macadam and at the same time maintains the relative or general smoothness of an asphalt surface. 3. Overcomes the necessary muddy or dusty condition of mac- adam. 4. Provides a pavement that, while having the density of solid stone, at the same time has great elasticity, is unaffected by heat, cold, or water, is sanitary, and presents a good appearance. 5. Adapted to all grades. It is in successful use on a street with a grade of 12 per cent in Pawtucket, R. I. The life is assumed to be equal to that of a block pavement of the same kind of stone. The cost ranges from $2 to $2.50 per square yard according to the local price of stone. SPECIFICATIONS FOR BITULITHIC PAVEMENT. Foundation. On top of the sub-foundation shall be spread a layer of hard crushed stone to a depth of 6 inches, which shall then be com- pressed with a 12-ton steam road-roller. This shall be coated with a thin layer of Warren's No. 1 Puritan brand bituminous semi-liquid cement, said bitumen to be sufficiently flexible to unite freely with the cold stone. On top of this No. 1 composition shall be spread a heavy coat- MISCELLANEOUS PAVEMENTS. 381 ing of Warren's No. 24 Puritan brand hard bituminous cement for the purpose of firmly binding the foundation together and making- it readily unite with the bituminous concrete wearing surface. One gallon of the bituminous cement will be used to each square yard of surface. On this prepared foundation shall be laid the wearing surface or pavement proper, which shall be composed of carefully selected, sound, hard crushed stone, mixed with bitumen and laid &s hereinafter specified. Wearing Surface. After heating the stone in a rotary mechani- cal drier to a temperature of about 250 F., it shall be elevated and passed through a rotary screen having six or more sections with vary ing-sized openings, the maximum of which shall be If inches and the minimum y 1 ^ inch in diameter. The several sizes of stone thus separated by the screen sections shall pass into a bin con- taining six sections or compartments. From this bin the stone shall be drawn into a weigh-box, resting on a scale, having seven beams. The stone from each bin shall be weighed in the propor- tion which has been previously determined by laboratory tests to give the best results. From the weigh-box each batch of stone shall pass into a "twin pug" mill or other approved form of mixer. In this mixer shall be added a sufficient quantity of Warren's Puritan brand bituminous water-proof cement to thoroughly coat all the particles of stone and to fill all the voids in the mixture. The bituminous cement shall, before mixing with the stone, be heated to between 200 and 250 F.; the amount used shall be accurately weighed and recorded. The mixing shall be continued until the co ruination is a uniform bituminous concrete. In this condition L o-iall be spread on the prepared foundation to such depth that, after thorough compression with a steam road-roller, it shall have a thickness of 2 inches. Surface Finish. After rolling, the wearing surface shall be coated with a thin layer of Warren's quick-drying bituminous flush coat composition. This in turn will be covered with a layer of stone chips and the whole thoroughly rolled. General. Each layer of the work shall be kept free from dirt. The bituminous composition or cement shall in each case be free from water, petroleum oil, water-gas, or process tars, and shall be especially refined with a view to remove the light oil, naphthalene, and other crystalline matter susceptible to atmospheric influences. CHAPTER IX. FOUNDATIONS. 451. THE stability, permanence, and maintenance of any pave- ment depends upon its foundation. If the foundation is weak, the surface will quickly settle unequally, forming depressions and ruts. With a good foundation the condition of the surface will depend upon the material employed for the pavement and the manner of laying it. 452. The essentials necessary to the forming of a good founda- tion are: (1) The entire removal of aS vegetable, perishable, and yielding matter. It is of no use to lay good material on a bad substratum. (2) The drainage of the subsoil wherever necessary. A perma- nent foundation can only be secured by keeping it dry; for, where water is allowed to pass into and through it, its weak spots will be quickly discovered and settlement will take place. (3) The thorough compacting of the natural soil by rolling with a roller of proper weight and shape until it forms a uniform and unyielding surface. (4) The placing on the natural soil so compacted a sufficient thickness of an impervious and incompressible material which will effectually cut off all communication between the soil and the bot- tom of the pavement. 453. The character of the natural soil over which the roadway is to be built has an important bearing upon the manner of forming and the kind of foundation; each class of soil will require different treatment. Whatever its character, it must be brought to a dry and tolerably hard condition by draining and rolling. Sands and gravels which do not hold water present no difficulty in secu ring a solid and secure foundation; clays and soils retentive of water are the most difficult. Clay should be excavated to a depth of at leas); 18 inches below the surface of the finished covering, and the space 393 384 HIGHWAY CONSTRUCTION. so excavated filled in witn sand, furnace-slag, ashes, coal-dust,, oyster-shells, broken brick, or other materials which are not exces- sively absorbent of water. Whichever of these materials is used, it should be thoroughly consolidated before laying the pavement. In ground saturated with water a foundation may be formed of logs or layers of fascines; but unless the nature of the ground is such as will always insure the timber being kept in a wet or damp state, it will soon rot and the road will go to pieces. Therefore they should never be employed unless under unavoidable circumstances. 454. Sand. Sand and planks, gravel, and broken stone have been successively used to form the foundation for pavements; but although eminently useful materials, their use for this purpose has been and always must prove a failure. They are inherently weak and possess no cohesion, and the main reliance both for strength and wear must be placed upon the surface-covering. This cover- ing, being usually (except in case of sheet asphalt) composed of small units with joints between them varying from one half to one and a half inches possesses no elements of cohesion, and under the blows and vibrations of traffic the independent units or blocks will settle and be jarred loose. They are porous and the subsoil quickly becomes saturated with urine and surface-waters percolating through the joints; winter frosts upheave them and the surface of the street becomes blistered and broken up in dozens of places. The defects of plank foundations are stated in Art. 186. Although sand, gravel, etc., by themselves are unsuitable as foundation materials for block pavements, still when used with judgment they form excellent foundations for broken-stone roads. 455. Sand Foundation. The natural soil having been trimmed and thoroughly compacted by rolling to the cross-section which is to be given to the covering, a layer of sand four inches thick is spread uniformly, thoroughly wetted by sprinkling, and rolled; two other layers of four inches each are in like manner added and rolled. The compression effected by a roller weighing ten tons will reduce the thickness of twelve inches to eight a greater final thick- ness than this is unnecessary unless the natural soil is very yield- Ing, when it may be increased to twelve or sixteen inches. 456. Blast-furnace Slag. The ordinary brittle slag makes a very good foundation for a road, particularly on clay or wet soils, as by rolling the top pieces form a powder that fills the interstices. FOUNDATIONS. 385 between the lower fragments so thoroughly that neither clay nor mud can work up through the layer, and on this the more durable wearing materials can be placed. It was found impossible to form any roads on the soft clay surface of the Centennial Fair grounds at Philadelphia until their beds had been prepared by a layer of well-rolled furnace-slag, after which they stood heavy teaming without under-drainage; the binding of the fragments of slag with the thorough filling of the interstices preventing any mud from working up through the first or cover layer, thus keeping the road' from breaking up. 457. Concrete. As a foundation for all classes of pavement (broken stone excepted) hydraulic-cement concrete is superior to> any other. When properly constituted and laid it becomes a solid coherent mass capable of bearing great weight without crushing,, and which if it fail at all must fail altogether. It is the most costly, but this is balanced by its permanence and saving in the cost of repairs to the pavement which it supports. It admits of access to subterraneous pipes with less injury to the neighboring pavement than any other, for the concrete may be broken through at any point without unsettling the foundation for a considerable distance around it, as is the case with sand or other incoherent - material; and when the concrete is replaced and set, the covering may be reset at its proper level without the uncertain allowance for. settlement which is necessary in other cases. 458. Thickness of Concrete. The thickness of the concrete bed must be proportioned by the engineer; it should be sufficient to> provide against breaking under transverse strain caused by the set- tlement of the subsoil. On a well-drained soil six inches will be- found sufficient, but in moist and clayey soils twelve inches will not be excessive. On such soils a layer of sand or gravel, spread and compacted before placing the concrete, will be found very bene- ficial. 459. Concrete (called beton by the French engineers) is a species of artificial stone composed of (1) the matrix, which may be either lime or cement mortar, usually the latter, and (2) the aggregate, which may be any hard material, as gravel, shingle, broken stone, shells, brick, slag; etc. The essential quality of concrete seems to be that the material of the aggregate should be of small dimensions, so that the cement- - 386 HIGHWAY CONSTRUCTION. ing medium may act in every direction round them, and that the latter should on no account be more in quantity than is necessary for that purpose. The aggregate should be of different sizes, so that the smaller shall fit into the voids between the larger. This requires less mortar and with good aggregate gives a stronger con- crete. Broken stone is the most common aggregate. It is usual to require that the stone shall be broken so as to pass any way through a 2-inch ring. To insure compact packing the aggregate should consist of a mixture of broken stone ranging from 1 to 3 inches, and pebbles which are at least equal to the strength of the mortar. Sun-dried or rain-soaked material is to be strictly avoided. The choice of the cementing substance, lime or cement, depends upon the use of the concrete. 460. The strength of concrete depends upon the cohesion of the matrix, adhesion to the aggregates, irregular bonding or inter- locking of the coarser fragments, and upon the strength and proportion of each ingredient. Concrete for pavement foundations should be dense and homo- geneous, with the voids of the aggregate thoroughly filled with mortar, and the latter must again be so constituted that the voids between the grains of sand shall be closely filled by the cement paste. Good concrete has a specific gravity of 1.5 to 2.5, according to its composition of crushed bricks or heaviest stones, A cubic yard weighs from 2500 to 3900 pounds. 461. Proportions. The proportions of the ingredients required for the manufacture of concrete may be ascertained by measuring the respective voids. The proportion of voids may be determined by experiment in either of the ways described in Art. 373. The voids of broken stone, in which the size and shape of the pieces are nearly uniform, are about 0.5 of the mass. If the pieces are not uniform, the voids are about 0.4 of the mass. The voids in gravel vary, but average about 0.5 of the mass. 462. The voids between the grains of sand will probably average 33 per cent; that is to say, 67. per cent of the cubic contents t M Quick-setting cement Slow- " Portland Hydraulic lime Portland Quicklime Lime and cement Hydraulic lime Portland . Quick-setting cement Slow- " Rosendale Portland Blue lias lime ii it Robertson, 1858 I. t J. Mann, 1883 Dr. Bohme, 1883 Prof. Warren, '87 Boistard Dr. Bohme, 1G83 Prof. Warren, '87 Rober son, 1858 Gen. Gillmore, '63 I. J. Mann, 1882 tt . (I Building News, '80 J. White, 1832 Bauschinger, 1873 Dr. Bohme, 1883 Bauschinger, 1873 Rondolet, 1831 Robertson, 1858 I. J. Mann, 1883 J. White, 1832 Gen. Gillmore, '63 Vicat, 1818 it tt Mallet, 1829 J. Grant, 1871 < tt a t (i ( t ti t tt (i 57 41 38 19 24.1 168 21 102 117 18.7 38 53 9-15 *, 15.3 20 26 isia 9 16 35.1 213 30.4 105 146 25.5 45 73 *59 20.9 24 48 17.5 14 45 3o!s 27.5 78 1197 l| 71 1166 49 is'. 7 20.8 *30 12.3 12.0 6.8 9.2 5^2 7.9 *io *36 *18 68!s 39i3 "54 41.9 *5 46.9 W.Q 38.9 *33 *15 24^2 28!i 14.2 12.8 22!e =MO '|I62 1155 II 75 "68 *18 "40 *8 24 *ai *51 .'"" 45 78 96 48 40 126 123 "70 99 44 63 70 47 29 83 62 *85 *140 .... .... * Proportions of sand not given, but presumably about those indicated in headings of table. t Standard sand used in mixture. \ Clean river sand used in mixture. Crushed sandstone used in mixture. f Fine river sand used iu mixture. || Coarse particles in cement sifted out before testing. 410 HIGHWAY CONSTRUCTION. 501. Shearing Strength. In recent times elaborate experiments to ascertain the shearing strength of mortar, both in the joints of brickwork and separate blocks, have been made by Prof. Bausch- inger of Munich. The results are too numerous for a verbal description, and they are accordingly given in Table XLVI. None of the values obtained are very large, ranging after ninety days from 70 to 7 pounds per square inch on brickwork with mortal- mixed in the proportion of three parts of relatively fine river sand to one of cement-lime. The shearing strength of cubes of mortar also appears to be considerably greater than that of the compara- tively thin joints in brickwork, and to be influenced by the quality of the sand. TABLE XLVI. SHEARING STIIENGTH OP CEMENTS AND MORTARS. o ti Average Shearing Strength 1 . in Ibs. per sq. in. S,l| Kind of Cement. e . Authority. ""* ?oi ^,eo ^-* t || C r-T 11 ji Ji Ji If I. Shear in, and parallel to, bed-joints of brick- work. 42 Portland (Bonn)* 72.5 Prof. Bauschinger, 1873 49 44 44 * 73.9 64 .... .... 44 44 52 " " *.. iss 106.6 44 44 44 90 90 on " (Perlmoosj*. 23 7 44 44 44 44 (I 44 44 11 44 76 8 Quicklime* 7.1 yu II. Shear in cubes of ce ments and mortars dried in air. 50 60 1 w'k Portland (Bonn)* (Perlmoos)t. % " " 369.7 256.0 224.7 369.7 405.3 284.4 383.9 142.2 362.6 108.1 320 '.0 '66!8 Prof. Bauschinger, 1873 44 44 44 1878 301.5 123.7 78.2 ** " Sw'ks * . 270.2 !!!! 128 93.9 14 '.'. T c 322.8 . 163.5 122.3 U 14 A I \T I 257 4 153.6 112.3 44 *. i* * 1 34l'.3 .. 199.1 137.9 44 44 Sw'ks t 258.8 196 2 167.8 44 *1 r I- 376.8 237 5 199.1 * Fine river sand. t Coarse sand. \ Average values for series of four different brands of quick-setting cements. Clean, medium sand. 1 Average values for series of four different brands of slow-setting cements. FOUNDATIONS. 411 As in the case of adhesion, no exact relation between the tensile and the shearing strengths of mortar placed in brickwork can yet be deduced, owing to the lack of sufficient data; but, on the other hand, the experiments show that the shearing strength of blocks or cubes of mortar is about 20 per cent greater than the tensile strength under the same circumstances. 502. Compressive Strength. But few experiments have been made upon the compressive strength of mortar. An examination of the results of about sixty experiments made with the Watertown testing-machine seems to show that the compressive strength of mortar, as determined by testing-cubes, is from 8 to 10 times the tensile strength of the same mortar at the same age. Data deter- mined by submitting cubes of mortar to a compressive strain are of little or no value as showing the strength of mortar when employed in thin layers, as in the joints of masonry. The strength per unit of bed area increases rapidly as the thickness of the test-specimen decreases, but no experiments have ever been made to determine the law of this increase for mortar. 503. Tensile Strength. The following table, carefully compiled from a large number of reliable experiments, gives the tensile strength of cement-mortar : TABLE XLVII. TENSILE STRENGTH OP CEMENT-MORTAR. Composi ion Age of Mortar. Mortar Rosendale. Portland. Cement Sand. 1 Week. 1 Month. 6 Months 1 Year. 1 Week. 1 Month. 6 Months 1 Year. 1 100 180 275 300 300 400 450 500 1 1 60 100 180 225 175 250 340 375 1 2 25 60 125 170 120 150 245 290 1 3 20 40 80 120 90 110 175 220 1 4 15 26 60 90 75 75 130 170 1 5 10 15 50 80 60 65 110 130 1 6 6 10 45 75 50 35 90 100 504. Fineness of Sand. Vicat, in the course of elaborate ex- periments with limes and mortars in the early part of this century, 412 HIGHWAY CONSTRUCTION. established standards for size of grain of what he termed coarse sand and fine sand, as follows; coarse sand being such as will pass through a sieve of 64 meshes per square inch and be retained on one of 289 meshes per square inch, while fine sand will pass through a sieve of 289 meshes per square inch and be retained on one of 625 meshes per square inch. On this definition he ranked the superi- ority of coarse, mixed, and fine sands with limes according to the following schedule : For eminently hydraulic limes, 1, fine; 2, mixed; 3, coarse. For slightly hydraulic limes, 1, mixed; 2, fine; 3, coarse. For fat or quick limes, 1, coarse; 2, mixed; 3, fine. It will suffice to say that with cement-mortars much better results are obtained when the sand is of the size of grain above described and is sharp and clean. Mr. Clarke says that when the sand was formed of a mixture of fine and coarse grains nearly as good results were attained as with, coarse grains alone. Before leaving this subject it may be of interest to refer briefly to the experiments made at Wilhelmshaven in 1877 by H. Arnold,. C.E., as published in the Journal of the Hanoverian Architects and Engineers' Society for 1883, and from which was found that the size of grain and quality of the sand used in Portland -cement mortar are important factors in its ultimate strength. With six different kinds of substantially clean sands and the same brand of cement mixed into mortar in the proportions of three volumes of sand to one volume of cement, the tensile strength after seven days, . ranged from 101 to 243 pounds per square inch, and after twenty- eight days from 133 to 311 pounds per square inch, thus exhibiting extremely wide variations, depending largely upon the size and roughness of the grains of sand. In every instance it was found that a greater strength was de- veloped with a coarse-grained sand free from very fine particles and dust than with a fine-grained sand, both being equally sharp. Mr. Arnold also points to the fact deduced from his experiments, that with the same cement but different sands of similar size oi' grain, the cohesion of the mortar may be found to vary consider- ably, and will probably depend upon the chemical composition of the sand. He therefore concludes that in order to obtain satis- factory results from the cement-mortar used in the construction of FOUNDATIONS. 413 public works, the quality of the sand available in the particular locality should first be taken into careful consideration. If no other than a fine sand happens to be available and a given strength of the mortar is to be attained at the end of one week, experiments should be made to earn whether the proportions of sand to cement named in the specifications should be changed, since the strength diminishes rapidly with the quantity of sand used; and in such an event it may also be advisable to use an entirely different kind of cement. It is a necessary condition of success in mortar-making that every particle of the sand or " aggre- gate " be completely covered with the cement or " matrix ;" and since, when the grains in a given volume are small, the magnitude of the total surface to be covered is greater than when the grains are large, it follows that fine sand requires a larger proportion of cement than coarse sand. Any specification or plan contemplating the use of a good coarse sand must, therefore, be altered if fine sand alone is used, or else the quality of the work will be im- paired. In support of the foregoing remarks, it has been quite generally observed by engineers that when most of our American natural cements are mixed entirely with fine sand the process of hardening is greatly retarded, even if not entirely prevented; while the same cements, when tested neat, exhibit a cohesive strength ranging from 50 to 136 pounds in twenty-four hours, thus showing conclu- sively the effect of admixing the fine material. An instructive in- stance of this kind was noticed some years ago, when an excellent quality of Akron "Star" cement was mixed with very fine sand from the Pinnacle pits in the proportion of 2| parts sand to 1 part of cement. For several days the mass remained in a plastic state in the tin can in which it had been deposited, and upon being /emoved and exposed to the air upon a window-sill for several months it displayed very little strength and broke in handling. On the approach of cold weather the largest fragment was kept in an apartment constantly heated by steam, and after lying undis- turbed therein for three months pieces could easily be broken off with the fingers. At the present time, after having attained an age of one year, it is still quite friable and entirely unfit for use. Another mass of mort-ar prepared at the same time from the same cement, but with clean, coarse sand, mixed in the proportions 414 HIGHWAY CONSTRUCTION. of 3 parts of sand to 1 part of cement, indurated promptly and exhibited far better qualities. TABLE XLVIII. EFFECT OF SIZE OF GRAIN OF SAND ON TENSILE STRENGTH OP CEMENT-MORTAR. Denomination of Size of Grains. Dangast Sand after Crushed Granite after 7 days. 28 days. 7 days. 28 days. Hailed barley 177 162 131 134 141 64 213 ' 191 177 164 160 87 194 176 164 144 136 87 255 234 242 192 193 134 Grass-seed Grit Coarse dust ) Fine dust j Tensile Strength of Mortar mixed 3 : 1 with TABLE XLIX. CHARACTER OF SIEVES FOR SIFTING SANDS. Number of Sieve. Number of Holes per lineal inch. Number of Holes pei- square inch. Size of Hole of Length of Side in inches. Diameter of Wire in inches. 1.. 20 400 .03101 .01899 2 30 900 .02119 .01214 3 50 2500 .01119 .00881 4 80 6400 .00599 .00510 5 170 28900 . 00309 . 00279 505. Portland cement acquires its strength, more quickly than Rosendale. Both cements, but especially the Rosendale, harden more and more slowly as the proportion of sand mixed with them increases ; and whereas neat cement and rich mortars attain nearly their ultimate strength in six months or less, weak mortars con- tinue to harden for a year or more. It has also been found that after a period of about a year weak mortars often lose in strength or tenacity what they may gain in hardness, from the fact of their FOUNDATIONS. 415 becoming brittle. Specimens of such mortar two years old break very irregularly. Mortars less than one month old are relatively weak, and hence the advantage of waiting as long as possible before loading masonry structures. Portland-cement mortars are especially useful in cases where the structure is necessarily subjected to severe strains within so short a period as one week, as frequently happens in the case of pavements. 506. Permeability of Mortar. The permeability of mortar is increased as the proportion of the cement decreases. It increases with the coarseness of the sand. Mortars made with a mixture of sand of various sizes are relatively non-porous and non-permeable. Mortars mixed dry are more permeable than those mixed wet or of a " normal consistency." 507. Effect of Frost upon Mortars. It is a matter of common knowledge that ordinary quick-lime mortar which is exposed to the action of frost before it has become well set or indurated will thereby become greatly injured in its adhesive and cohesive properties ; and hence where such mortar is used it is customary to suspend all build- ing operations on the arrival of the cold season. Should, however, it be necessary to proceed with the construction, experienced masons and builders sometimes make use of a quick-setting cement-mortar in place of lime, and cease work when the weather is at all severe. It is, therefore, of importance to learn something of the behavior of cements under such circumstances. The impression seems to prevail quite extensively that cement - mortars are not appreciably injured by freezing, and that masonry may safely be constructed at any temperature below the freezing point at which a man can still work, provided that either brine or salt be used instead of fresh water, or that the materials be first heated. With regard to the use of brine or salt it may be remarked that whether the mortar will be injured thereby or not seems to depend principally upon the character of the cement. Most of the natural or " Roman" cements suffer a considerable loss of strength if mixed with salt water, while the Portland cements do not appear to be materially affected. Respecting the practice of heating the cement, sand, and water before mixing, and then using the hot mortar in cold weather upon frosty stones or bricks, or depositing it in icy water, the experiments of William W. Maclay, C.E., submitted in 1877 to the American 416 HIGHWAY CONSTRUCTION. Society of Civil Engineers, show indisputably that such a method of treatment is erroneous, and that a great amount of injury is effected when heated mortar, even if made of Portland cement, is immersed directly in cold water. The tests were all made with Burham Portland cement, which, when tested neat at ordinary temperature, gave a tensile strength of 278 pounds per square inch aftei seven days. In one series of experiments the ingredients of the mortar all had a temperature oi; about 40 degrees Fahr., and in another they were heated to 100 degrees Fahr. These two sets of briquettes were kept for seven days in precisely the same manner, and were broken on the same day, so that any changes in tempera- ture during this period would necessarily affect them alike. The averages of the tensile strengths acquired show that by first heating the ingredients to about 100 degrees, then mixing them in air having a temperature of from 13 to 37 degrees, and afterward exposing the briquettes for six days to the winter weather, their strength in the case of neat cement was only from 7 to 20 per cent of that attained when the materials were mixed without heating, or with the temperature of the mortar at 40 degrees; and in the case of mortar mixed in the proportion of 2 sand to 1 cement, the tensile strength of the heated mortar after 28 days was only 30 per cent of that reached by the cold mortar at 40 degrees. From these and other similar experiments Mr. Maclay concludes that the mixing of cement-mortar with highly-heated materials for use above water in very low temperatures greatly reduces its normal strength, and that for use below icy water its value will thereby be almost entirely destroyed. If mortar must be used at all in such weather, it should be used cold, and the only condition to be observed is that the materials shall be free from frost at the time of using. " In the experiments where the materials were mixed cold and then exposed to the winter weather, Portland-cement mortar appeared to set without freezing even in as low a temperature as 13 degrees Fahr., except when it was windy; but where the briquettes were made of hot mortar they invariably froze, as was proven by their becoming soft again when the temperature rose." Portland cement was found to possess the peculiarity, also noticed by many other writers on the subject, of setting in a low temperature wherein other varieties of cement will surely freeze. No definite limits of this action, however, have yet been assigned. FOUNDATIONS. 417 Mr. E. Leblanc exposed cakes of Portland-cement mortar to frost immediately after mixing and before any setting had occurred, with the result that " they cracked deeply and in part became disinte- grated, but the detached fragments after being thawed were found perfectly hard." In Mr. Maclay's experiments none of the Port- land-cement briquettes when mixed cold cracked in the slightest degree even when exposed to as low a temperature as 11 degrees Fahr., and they all became hard after thawing. This seems to be the prevailing opinion among engineers. Mr. J. Button Steele r C.E., in discussing the paper of Mr. Maclay, states that " cement- mortar is not seriously impaired by being laid in frost, as its prop- erty of setting is simply held in suspense during the time it remains frozen." Gen. Q. A. Gillmore, U.S.A., in his work on Beton, etc., remarks that "when the temperature is not much below the freezing point during the day, work may be safely carried on if care be taken to cover over the new material at night. After it has once set and has had a few hours to harden, neither severe frost nor alternate freezing and thawing has any eifect upon it." In the report of the work performed at the Royal Testing; Laboratory of Berlin in 1886 there is an account of a number of experiments for ascertaining the effect of frost upon the strength of Portland cement, both neat and when mixed into mortar in the proportion of 3 parts of sand to 1 part of cement. These tests were made in two distinct series, the first one involving only a single exposure to frost on and during the sixth day after mixing, while in the second series the briquettes were treated as follows : First, allowed to indurate for twenty-four hours in the air of a warm room; second, exposed for twenty-four hours to a freezing tem- perature of from -j- 10 degrees to + 5 degrees Fahr. ; third, thawed four hours in a warm room; fourth, placed under water until tested. The experiments were made with six different brands of cement, and for each set of briquettes exposed to frost another similarly constituted set was kept in temperatures above the freezing point to serve as a basis of comparison of tensile strength. Upon test- ing the frozen and unfrozen samples, it was found that the effect of frost varied greatly with the quality of the cement ; the loss in tensile strength incurred by such freezing ranging after seven days ; from 2 to 22 per cent in the case of neat cement, and from 3 to 24 418 HIGHWAY CONSTRUCTION. per cent in the case of the mortar mixed as above described ; also ranging after 28 days from 2 to 12 per cent in the case of neat cement, and from 1 to 33 per cent in the case of the mortar. It should be noted particularly that the foregoing results were de- rived when pure, clean, and standard materials only were used. On the other hand, where the cement was adulterated with 30 per cent of pulverized slag from a blast-furnace the loss in strength by freezing was much greater than above given, especially in the case of the mortar. After seven days this loss ranged from 6 to 62 per cent, and after 28 days from 21 to 44 per cent, standard sand hav- ing been used. Other interesting experiments with regard to the effect of frost on Portland-cement mortar were carried out early in 1886 at Ham- burg, Germany, by Mr. Moeller, C.E., and an account thereof is contained in the Deutsche Bauzeitung for November 17, 1886. The results showed that Portland-cement mortar, whose time of setting is lengthened by the addition of sand or lime, or both, suf- fers severely in loss of tensile strength by the action of frost, and tnat such loss becomes greater as the proportion of sand or lime is increased; further, that a quick-setting Portland cement will indu- rate in spite of the frost, provided that it be protected therefrom for two days after having been tempered, and that it be as dry as possible before exposure to the cold. It was also found that the mixing of such materials with brine renders the mortar more capa- ble of resisting the influence of frost, and that this statement like- wise holds true for slow-setting compounds, such as 1 part of cement, 1 part of lime, and 3 parts of sand. Mortars thus prepared and mixed with fresh water instead of brine, and kept for two days at a temperature of -j- 41 degrees Fahr., and then exposed to the frost, lost nearly all strength, so that even after four months pieces could easily be broken off from the briquettes with the fingers; whereas when tempered with strong brine their strength after seven months was about fourteen times greater. Accordingly, if the mortar can be kept from freezing for a few days by the use of salt or brine, so as to allow the setting to take place, much benefit is sure to be derived. It may also be deduced from these experiments that when it becomes absolutely necessary to lay masonry in freezing weather, quick-setting Portland cements, mixed with small proportions of FOUNDATIONS. 419 sand and water, should alone be employed ; and when a satisfactory quality of work is expected or required, the use of brine or salt should be resorted to, as well as the protection of the newly-laid masonry at night by means of adequate coverings. In case, how- ever, that the temperature is lower than 23 degrees Fahr. even these precautions will not prevent more or less damage. Under such circumstances, moreover, it is self-evident that the stones or bricks should be free from snow or ice and as dry as prac- ticable; also that all the materials, including the sand and cement, be free from frost by being kept at a temperature above the freez-^ ing point for some days before being used in the work. The safest rule, however, is to cease operations with mortars of any kind dur- ing the prevalence of frost. In a paper read before the American Society of Civil Engineers in July, 1886, its author, Alfred Noble, C.E., states that " in the construction of the lock at the St. Mary's Falls Canal, the laying of masonry was discontinued about October 20 of each year, on account of the frequent recurrence of freezing weather. On the last day of the work done in 1877 mortars made of Portland, cement and of a good quality of American natural cement were used in adjoining portions of the same wall. Both mortars were mixed in the proportions of 1 cement to 1 sand, and the masonry- was laid during a light rain. The following spring the surface of the Portland-cement mortar was sound, showing perfectly the marks of the rain-drops, while the natural-cement mortar was dis- integrated to a depth of three or four inches." Mr. .Noble also mentions a few other cases where Portland-cement mortar was used in laying masonry during very cold weather without affecting the subsequent induration of the mortar noticeably. The inference to be drawn from his paper is that if it becomes imperative to use mortar in freezing weather, Portland cement should be used. Similar effects of frost were also noticed by Mr. Francis Colling- wood, C.E., on the Rosendale-cement mortars, mixed in the pro- portion of 2 sand to 1 cement, used for the masonry of the East Kiver Bridge, since he states that " the tops of the various pieces of masonry were always gone over carefully in the spring. The concrete which had been put in late would usually be found disin- tegrated to a depth of from one to four inches, but below this it was found sound. The rule seems to be that it was unsound only 420 HIGHWAY CONSTRUCTION. so far as it was exposed alternately to freezing and thawing; and wherever it had taken a set before freezing, and had not been thawed out for some time, it was sound." The experience of Mr. George S. Morison, C.E., with cements as given in his discussion of Mr. Noble's paper, was in full accord with what was therein stated, and in his extensive practice as a designer and builder of large bridges he uses Portland cement exclusively in all places where the mortar is liable to freeze before setting. Mr. Eliot C. Clarke, C.E., also mentioned that in experimenting with concretes of Eosendale and Portland cements which had been exposed to the weather for three years he found that the former was injured and disintegrated from year to year, while the latter were not affected .at all. Eecent expressions of opinion from many other excellent au- thorities respecting the action of frost on cement-mortars are to the same effect as above recited. It is generally agreed that the freezing of freshly-prepared cement-mortar will not destroy its capacity to harden after becoming thawed, but exactly how much its cohesive and adhesive strength will thereby become impaired? does not appear to be definitely known ; neither is the effect of re- peated freezing and thawing very clearly pointed out. In our winters it frequently happens that water freezes in the shade, while at the same time ice melts in the sunlight, and hence under such circumstances in a wall facing south a slow-setting mortar in the face will be alternately frozen and thawed, while that in the rear will continue to remain frozen. This condition of the work can- not fail to be prejudicial to its ultimate strength, and manifestly demands that a strong and quick-setting mortar be used if the lay- ing of masonry be continued in freezing weather. Numerous in- stances of failure of walls and abutments built in winter may be cited which are fairly attributable to the thawing out of the frozen mortar after the warm weather has set in, whereby it becomes almost as soft as when first mixed. In such cases the thawed mortar acts rather as a lubricant than as an efficient binding mate- rial, and if the structure is then subjected to lateral forces of con- siderable magnitude, deformation or failure is sure to follow unless a very wide margin of safety has been allowed in the design. When, however, the dimensions are fixed with reference to econ- omy and the use of ordinarily good materials and workmanship, as FOUNDATIONS. 421 generally happens, the action f frost becomes a very serious factor in the stability and durability of the work, and therefore care should be taken in the proper selection of the cement. It musk always be remembered that frozen cement-mortar will not set so long as it remains frozen, and that when it becomes thawed it is simply in the condition of material freshly mixed, which, while in. that state, imparts no more strength to the structure than sand^ ashes, mud, or other inert matter. A rather close observation for a number of years of the effects of frost on Buffalo and Akron cement-mortars, mixed in the pro- portion of two sand to one cement and three sand to one cement, leads to the conclusion that such mortars entirely disintegrate to a depth of several inches in exposed joints of masonry laid in cold weather; also that when used as coatings or renderings of rough stone surfaces a flaking thereof occurs by frost which leads to rapid disintegration. If it is imperative that masonry be built in freezing weather, a quick-setting Portland cement-mortar should be used, instead of such as is prepared with natural cements; also that even when Portland cement is used with brine, work should be suspended when the temperature is lower than 25 degrees Fahr., if good results are to be expected ; and finally, smaller pro- portions of sand shoud be used than during the prevalence of higher temperatures. 508. The standard of tensile strength required by German engineers of Portland-cement mortar, prepared by mixing one unit of weight of cement with three like units of normal sand, and four tenths of such a unit of clean fresh water, and tested after an exposure of one day in air and twenty-seven days in water, is 227 pounds per square inch and a resistance to compression of 2300 pounds per square inch. 509. English Specifications for Portland Cement. The follow- ing is a summary of the specifications used by Mr. Henry Faija, an accepted English authority : Fineness. To be such that the cement will pass through a sieve having 625 holes (25 2 ) to the square inch, and leave only 10 per cent residue when sifted through a sieve having 2500 holes <50 2 ) to the square inch. Expansion or Contraction. A pat made and submitted to 422 HIGHWAY CONSTRUCTION. moist heat and warm water at a temperature of about 100 degrees Fahr. shall show no sign of blowing in twenty-four hours. Tensile Strength. Briquettes of slow-setting Portland, which have been gauged, treated, and tested in the prescribed manner, to- carry an average tensile strain, without fracture, of at least 176 pounds per square inch at the expiration of three days from gaug- ing; and those tested at the expiration of seven days to show an increase of at least 50 per cent over the strength of those at three days, but to carry a minimum of 350 pounds per square inch. For quick-setting Portland at least 176 pounds per square inch at three days, and an increase at seven days of 20 to 25 per cent, but a minimum of 400 pounds per square inch. Very high tensile strengths at early dates generally indicate a cement verging on an unsound one." 510. Data for Estimates. The following data will be found useful in estimating the amounts of the different ingredients neces- sary to produce any required quantity of mortar : One barrel of lime (230 pounds) will make about 2J barrels (0.3 cubic yard) of stiff lime-paste. One barrel of lime-paste and three- barrels of sand will make about three barrels (0.4 cubic yard) of good lime-mortar. One barrel of unslaked lime will make about 6.75 barrels (0.95 cubic yard) of one to three mortar. A barrel of Portland cement weighs 400 pounds gross, or about 375 net. Hudson River Rosendale weighs 300 pounds net per bar- rel. Western Rosendale weighs 265 pounds net per barrel. A barrel of Rosendale, as packed at the manufactories on the Hudson will measure from 1.25 to 1.40 barrels if measured loose. A barrel of Western Rosendale will make about 1.1 barrels if measured loose. A commercial barrel of Portland will make about 1.2 barrels if measured loose. One cubic foot of dry cement (shaken down but not compressed) mixed with 0.33 cubic foot of water will give 0.63 cubic foot of stiff paste. One barrel (300 pounds) of finely ground Rosendale cement will make from 3.70 to 3.75 cubic feet of stiff paste; or 79 to 83 pounds of cement-powder will make about one cubic foot of stiff paste. Volume for volume, Portland will make about the same amount of paste as Rosendale; or 100 pounds of Portland will make a cubic foot of stiff mortar. 511. Machine-mixed mortars and concretes are superior to hand- FOUNDATIONS. 423: mixed. In hand-mixing the first drawback is the liability to error in measuring out correct and uniform proportions of prescribed materials. Mortar men make mistakes which generally happen to- be against the proper proportions of cement. The quantity of sand will also vary according to whether it is measured in wet or dry condition, packed or loose. Next the workmen fail to intermix, thr- ee ment and sand thoroughly before adding the water an important point. Again, they will ease up on the labor required to mix all well together after applying water, and to facilitate the operation will over-dose the water. A further error occurs in assuming that all barrels of cement contain equal quantities. The necessity of a close supervision will be recognized in these particulars. 512, Specifications for Concrete (Boston). The American cement- concrete shall be made of one part of American hydraulic cement,, two parts of clean, sharp sand, and five parts of clean broken stone or screened gravel-stones by measure. The Portland-cement concrete shall be made of one part Port- land cement, three parts of clean, sharp sand, and seven parts of clean broken stone or screened gravel-stones by measure. The stone for the concrete shall be free from clay, dirt, or other objectionable material; no stone shall be larger than 2 inches and but very few less than j- inch in their greatest dimensions. The mixing shall be done in proper boxes, in a manner satisfac- tory to the engineer; and after the materials are wet the work must proceed rapidly until the concrete is in place and is so thoroughly rammed that water flushes to the furface and all the interstices be- tween the stones are entirely filled with mortar. The surface of the concrete foundation must be floated and made exactly parallel with the crown of the pavement to be laid, and must be suitably protected from the action of the sun and wind until set. It shall be allowed to set a sufficient time, to be determined by the engin- eer, before walking over or working upon it shall be allowed . 513. Specifications for Concrete (Berlin). The concrete is to be prepared from a mixture of cement and sand or a mixture of cement, sand, and broken granite or limestone. In making it at least one barrel of cement in the standard proportion of 180 kilos gross or 170 kilos net weight is to be used with one cubic meter of sand or of sand and stone. The proportions of sand and broken stone are to- be determined in each case by the inspector. If in exceptional 424 HIGHWAY CONSTRUCTION. cases a greater proportion of cement is employed to obtain quicker setting, a corresponding payment will be made for each barrel used, as given in the schedule of prices. The cement is to be weighed whenever the inspector desires. In order that the proportions may exactly conform to the specifica- tions, the sand or mixture of sand and stone is to be measured in boxes holding exactly one half or one cubic meter. The mixing is done on a platform that must be 30 centimeters (11.8 inches) larger all around than the bottom of the measuring- boxes. The sides are to be provided with strips to prevent the falling of the material. In order to insure regular work at least iive mixing-boards are to be set up at each place of working. Sand and cement are to be twice mixed dry before water is added. After the addition of the water the mass must be immedi- ately worked to a stiff condition. During the preparation of the concrete, all the foreign bodies in the cement or sand are to be carefully removed. If, during the process of mixing, a portion of the concrete, of sand or stone, falls from the platform, it must not be again added to the mass and used in the concrete, but must be removed. Laying the Concrete. In order to insure the exact formation of the concrete foundation, a series of templates are to be laid on the road-bed from 4 to 5 meters apart and parallel to the axis of the street. The greatest care must be taken to have these templates at the proper height, and all out of alignment must be immedi- ately removed. When the road-bed has been finally brought to the proper grade the concrete is to be laid between the templates and thoroughly tamped and worked into a profile corresponding to that of the finished street surface. Use of the Concrete after its Preparation. While the concrete is setting, it is to be sprinkled with water so that the surface is continually moist, and as long as it remains soft the work must b<3 protected by suitable guards from intruders. No concrete shall be prepared at a temperature below 2 degrees Reaumur (36 degrees Fahr.). Concrete just laid is to be pro- tected for two days, when frost begins, by a covering of mats or bundles of straw. The foundation must have exactly the same profile as the upper FOUNDATIONS. 425 surface of the finished pavement is to receive. It is especially necessary that the surface be free from all inequalities, elevations as well as depressions. Work must not begin on the construction of the foundation until the inspector has definitely stated that the work on the roadbed has been finished in the manner prescribed in the regulations. 514. 'Specifications for Concrete (New York). One part of American cement, equal to the best quality of freshly burned Rosendale cement, two parts of clean, sharp, washed sand, free from clay, to be thoroughly mixed dry and then made into mortar with the least possible amount of water; to this shall be added three parts of sound stone, broken with a hammer, the largest of which will pass through a 2-inch ring, the broken stone to b'e wet before being added to the mortar. The whole mass shall then be shoveled over until it is thoroughly mixed before it is put in place : it shall then be put in place and rammed until it is thoroughly compacted and has a clean mortar surface. The whole operation of mixing and laying each batch will be performed as expeditiously as possible, by the employment of a sufficient number of skilled men. The upper surface will be made exactly parallel with the pave- ment when laid, and, if necessary, will be protected from the action of the sun and wind until set. No concrete will be allowed to be used which has been mixed more than three hours. The concrete shall be laid to a depth of 6 inches. 515. Concrete for Foundations, as used in Paris. The proper tions by bulk are: Cement ... c 1 part Sand 4 parts Gravel 6 " Water H " or one of cement to ten of sand and gravel. The concrete is mixed on a large mortar-board, the mixers mov- ng the board ahead as the work advances, and never being more than a few feet from the spot where the concrete is to be placed. A square wooden form is placed on the mortar-board; into this is dumped successively, in the order named, 2 barrows of gravel. 426 HIGHWAY CONSTRUCTION. sack of cement, 1 barrow of gravel, \ sack of cement, 2 barrows of sand. The form is then removed, and the mass turned over dry with the shovel by two men working side by side. It is then turned a second time by the two men, while a third sprinkles on the water from a pot. The mass is then turned over a third time, and shoveled from the board directly into place. This concrete sets quickly, and every evening the surface of that laid during the day is covered with a thin coat of pure cement. 516. Specifications for Preparation of Roadbed. The subsoil or other matters (be it earth, rock, or other material) shall be excavated and removed to a depth of inches below the top line of the proposed pavement. Should there be any spongy material, vegetable or other objectionable matter, in the bed thus prepared, all such material must be entirely removed, and the space filled with clean gravel or sand carefully rammed. The roadbed shall be truly shaped and trimmed to the required cross-section and grade, and rolled to ultimate resistance with a roller weighing not less than ten tons; such portions of the road- bed as cannot be reached by the roller shall be consolidated with hand rollers or tampers. Note. The employment of ashes, garbage, or other objectionable matter should not be permitted for filling on the streets of cities and towns. Eock shall be excavated to a depth of 2 feet below the level of the finished grade, and the space so excavated shall be refilled to subgrade level with gravel, steam ashes, or other approved material, and thoroughly consolidated. 516a. Foundation employed in Liverpool. The foundation em- ployed in Liverpool for heavy-traffic pavements is described by Mr. P. H. Boulnois, City Engineer, as follows: "The ground having been prepared in the usual way, and the channel (gutter) and curb stones fixed in position, a stratum of stones (which should by preference be of a non-absorbent character), broken so as to pass all ways through a 3-inch ring, is spread evenly over the surface of the ground, and upon this is placed a layer of cement mortar mixed in the propor- tions of one of Portland cement to six of fine, sharp, clean gravel in the method to be described hereafter. Upon this layer of mor- tar is placed another layer of broken stone the whole of the stones FOUNDATIONS. 427 in each layer to be thoroughly watered while the work is proceed- ing and this stone is forced into the interstices of the first layer by the use of flat beaters of wrought iron, weighing 16 pounds each, shaped like square shovels, with handles at an angle of 33 degrees. " This process is repeated until the proper level and contour ie reached, and the surface is finished off parallel to the exact curva- ture of the carriageway. "The foundation thus prepared is left until the concrete is suffi- ciently set or hardened to receive the pavement, which, if possible, should not be less than ten days, although this period may be shortened, where the exigencies of the traffic render it imperative, by strengthening the proportion of cement to gravel, care to be taken in all cases to periodically water the surface of the concrete to assist the ultimate hardening, and in very hot weather it is advisable to cover the surface of the concrete with old cement-bags saturated with water. " The proportions of broken stone, gravel, and cement used in such a concrete are as follows: "Before Mixing. Broken stone, 8 parts; gravel, 6 parts; cement, 1 part. " After Mixing. Broken stone and gravel, mixed together, 11 parts; cement, 1 part; three parts of gravel having been expended in filling the interstices of the stones. " The method adopted for insuring that the cement mortar shall contain the proper proportions as carried out in Liverpool is as follows: An apparatus is used consisting of a set of double mixing- boards, each 7 feet by 3^ feet, having 1^-inch deal sides and back 9 inches high, and 1^-inch deal bottom lined with sheet iron. A partition in the centre divides the board into two compartments; at the back of each compartment is a box for measuring the gravel, with a capacity of 1 cubic foot, 14 inches square at the top, 10 inches square at the bottom, and 12 inches deep. It is hinged to the back of the board by strong iron eyes and bolts. " Any number of mixing-boards being placed side by side, about ] foot apart, the water-supply is arranged as follows : A length of flexible hose is attached at one end to the nearest hydrant, and at the other end to the ball-tap of a sheet-iron regulating-cistern; 428 HIGHWAY CONSTRUCTION. containing 18 gallons, fixed on a light angle-iron frame, about 4 feet from the ground to the bottom of the cistern; this is placed at one end of the series of mixing-boards. Opposite to the inlet-pipe is an outlet-pipe of flexible tubing attached to the cistern by brass unions; water is conveyed through this pipe to a horizontal wrought-iron. pipe, 7 feet long, supported upon light iron stand- ards placed over the back of each mixing-board. Attached to this pipe is a pair of brass swivel rose-ended pipes with stop-taps; these roses are so arranged as to discharge the water in a gentle rain- like spray over the centre of each mixing-compartment. This ar- rangement may be extended to any number of boxes, the service- pipes being connected by flexible tubing. " The cement is measured in light iron bowls having a capacity of J cubic foot. " The usual arrangement for mixing concrete is as follows : The mixing-boards are placed with their backs to a heap of gravel, the cement being stored at one end, also at the back of the boxes; a laborer with a mixing-shovel is detailed off to each mixing-com- partment; a man at the back fills each measuring-box with gravel; the mixer in front tips over this box with his shovel, emptying the gravel into the mixing-board; a boy brings a bowlful of cement from the store and spreads it over the gravel; the mixer turns over the contents of his board until the cement and gravel are thor- oughly mixed in a dry state; he then turns the tap of the rose- pipe, and allows the water to flow over the mixture until sufficient moisture for setting is obtained, the quantity of water used vary- ing with the dampness of the gravel. The concrete is now thrown into wheelbarrows and conveyed to its destination. One mixer in nine hours can turn out ninety such mixings, which are equal to 6 cubic yards." . 516b. Specifications for Concrete (Chicago). PROPORTIONS. One part cement, three parts sand, seven parts broken stone; sand and cement mixed dry; water then added to make a stiff mortar, to which the stone is immediately added and mixed (water being added if necessary) until each particle of stone is covered with mortar. The concrete is deposited in one layer and rammed to a, true and smooth surface. The subgrade is kept moist, and fthe- FOUNDATIONS. 429 concrete is sprinkled as necessary and left exposed for at least seven days. MATERIALS. Portland Cement, 92 per cent passing through a No. 100 sieve, passing the "boiling test," setting in 45 minutes or more; tensile strength (neat) 400 pounds in 7 days, 175 pounds for 1 cement to 3 sand, with 15 per cent increase, in 28 days. Sand, clean, dry; grains -J inch and less, not more than 30 per cent voids; weighing 109 pounds per cubic foot. Stone, limestone, clean, between 1^ inches and 1 inch in largest dimensions. 516c. Reinforced Concrete for pavement foundation has been used at Hattiesburg, Miss., under the following specification: "If, in the opinion of the city engineer, it is deemed necessary to rein- force the concrete foundation over filled trenches, the contractor shall furnish, and place under the direction of the city engineer, expanded metal of not more than 3-inch mesh and No. 10 gauge steel. The cross-section area of tame shall not be less than 0.185 square inch per foot in width. The contractor shall be paid for actual work at the schedule price bid " (90 cents per square yard). CHAPTER X. RESISTANCE TO TRACTION. 517. The resistance to traction on highways is occasioned (1) by the want of uniformity in the surface of the road, the weight of the load having- to be lifted over the projecting points and out of hol- lows and ruts, thus diminishing the effective load which the horse may draw to such as it can lift. (2) The want of strength of the roadbed itself, however free its surface may be from asperities or cavities, if its substructure be of such a nature that it will yield to the pressure of the wheels, adds another impediment to the movement of a load over it, with the additional disadvantage that while the horse is endeavoring to lift the load from a cavity or hollow, the fulcrum, which in the first case was supposed to be fixed and rigid, is in the latter yielding and variable, subjecting the horse to the constant effort of lifting, instead of simply drawing. 518. Want of Uniformity in the Surface. The power required to draw a wheel over a stone or any obstacle, such as S in Fig. 36, may be thus calculated. Let P represent the power sought, or FIG. 36. that which would just balance the weight on the point of the stone, and the slightest increase of which would draw it over. 430 RESISTANCE TO TRACTION. 431 This power acts in the direction CP with the leverage of SO or DE. Gravity, represented by W, resists in the direction CB with the leverage of BD. The equation of equilibrium will be p X CB = Wx BD, whence CB~ CD - AB Let the radius of the wheel CD = 26 inches, and the height of the obstacle = AB = 4 inches. Let the weight W = 500 pounds, of which 200 pounds may be the weight of the wheel and 300 pounds the load on the axle. The formula then becomes P = 500 - = 500 = 314.7 pounds. The pressure at the point D is compounded of the weight and the power, and equals riT\ oq W~ = 500 X | = 591 pounds, and therefore acts with this great effect to destroy the road in its collision with the stone, in addition there is to be considered the effect of the blow given by the wheel in descending from it. For minute accuracy the non-horizontal direction of the draught and the thickness of the axle should be taken into account. The power required is lessened by proper springs to vehicles, by enlarged wheels, and by making the line of draught ascending. 519. Resistance of Penetration. This resistance is that of a, medium distributed over the submerged portion of the circum- ference of a wheel, in advance of the perpendicular line drawn from the centre of the wheel to the plane of the road. The following investigation furnishes a formula for calculating, with sufficient degree of accuracy, the resistance of gravel, loose stones, soft earth, or clay. Let AOB, Fig. 37, be a wheel drawn over the horizontal surface CDE of the road, in the direction OF, and let the road be of such a consistency that the wheel penetrates to the depth 432 HIGHWAY CONSTRUCTION. DB below the surface, leaving a track BG behind it. The aro BO is the submerged portion of the circumference, and it may be assumed to be identical with the chord of the arc BC. Now the, resistance is distributed over the surface BC, and it may be taken FIG. 37. as acting on this surface perpendicularly to the plane of the road,, or vertically and directly opposed to the gross weight, consisting of the weight of the wheel and the load upon it. To simplify the^ investigation, let it be supposed that the upper portion of the road is homogeneous, as clay or sand; then the resistance to penetra- tion is nothing at the surface, and it increases as the depth; and the upward resistance along the line of submersion, BC, is a maximum at B and it vanishes at C, and the varying intensity of the graduated pressure may be represented by an isosceles triangle, of which the centre of gravity, H, situated at one third of its length, BH, from the base, B, is also the centre of resistance, and therefore also the centre of pressure under the load ; and the radial line OH is the resultant of the pressure of the load, measured in force and direction by the vertical 01, and the tractive force, measured by the horizontal line HI or OK. But the vertical 01 may be taken as equal to the radius OB, and the horizontal HI may be taken as one third of the semi-chord of submersion CD', whence the proportion Load : tractive force : : OB : CD : : radius of wheel : | semichord; RESISTANCE TO TRACTION". 4S3 and the resistance to traction is equal to the product of the load by the third of the semichord divided by the radius of the wheel. But the length of the semichord CD may be more easily deter- mined by calculation from the measured depth of submersion D B. It is equal to the square root of the products of the segments into which the diameter AB is divided by the plane of the road CDE, or to 4/^J/Tx DB] an d the whole of the calculations is embraced by the equation Tractive force OK = X WVADxBD OB (1) The work done in compressing the material of the road is easily indicated diagrammatically, by supposing the wheel to advance through a space equal to the semichord CD, or the length of the submersion. Thus, in Fig. 38, the wheel AB is supposed to roll FIG. 38. FIG. 39. forward and to occupy the position A'B'. The work done in compressing the road is proportioned to the four-sided area BCC'B', comprised between the circumferential segments BC and B'C', and this area is, by the properties of the circle, equal to the original rectangular area BDCB f . Now, suppose a wheel ABA, Fig. 39, of larger diameter with the same gross weight, to travel over the same surface. It is obvious that, if it could sink to the same depth, db, as that for the smaller wheel, the length of immersion, dc, would be increased, and the rectangle, db X do, representing work, would be greater 434 HIGHWAY CONSTRUCTION. than that performed by the smaller wheel in the first example. Such a supposition cannot be admitted : the depth of immersion, dB, for the larger wheel, must be less than that, clb, for the smaller wheel, though the length of immersion dC, must be greater than that dc, for the smaller wheel, but not so much greater as if the wheel were sunk to the first depth, db. In fine, larger wheels sink less but spread more into the surface than the smaller wheels, in such proportion that the area of the rectangle representing work of submersion is constant for all sizes of wheels. In this instance, accordingly, the rectangle db X dc = the rectangle dB x dC. It might be thought that, on this principle of the constancy o:f the work of submersion, in a soft road, the resistance to traction must be the same for all diameters of wheels. But, as the rect- angle of work is spread over a longer space, dC, for the larger wheel, than the space, dc, for the smaller wheel, it follows, on the contrary, that the resistance or force of traction varies in some proportion inversely as the diameter, being less as the diameter is greater. This conclusion accords with experience; but though the actual law of variation may not be strictly deducible in the line of reasoning here traced, it is nevertheless useful to carry the reason- ing to its logical conclusion. Let a and A be the diameters respec- tively of the smaller and the larger wheels, b and B the depths of immersion, and c and the lengths of immersion, or dc and Dc, respectively. As already stated, the areas of immersion are equal to each other, or (2) Also, the values of c and C are, by the properties of the circle, ex- pressible by the products Vab and VAB, for all cases that need occur in practice; and, by substitution in the equation (2), ....... (3) and, squaring both sides, (4-) RESISTANCE TO TRACTION. 435 Finally, extracting the cube root of each side of this equation (4), the equation (5) is obtained, which may be developed into the proportion showing that the depth of immersion varies as the cube root of th: diameter. But, as be = BC, and b:B:t0ic, then, (?) showing that the length of immersion is as the cube root of the diameter. It has already been seen that the force of traction is aL the length of immersion; therefore, finally, 020. The circumferential or rolling resistance of wheels tc traction on a level road is inversely proportional to the cube root of the diameter. On this principle of resistance, it follows that, to reduce the rolling resistance of a wheel one half, for instance, the diamete: must be enlarged to eight times the primary diameter. The deduction of M. Morin, that the resistance varies simply in the inverse ratio of the diameter of the wheel, so that, for exam- ple, a wheel of twice the diameter would only incur half the resist- ance, has been generally accepted. But this deduction is not supported by the foregoing analysis of forces, and there is good reason for renouncing it, in the more recent experiments of M. Dupuit. He placed model wheels or rollers ofvarious diameters at the summit of an inclined plane, succeeded by a horizontal plane, on which they rolled down by the force of gravity and arrived at a state of rest after having expended the energy acquired in falling through the height of the plane. From these and other experi- ments he drew the following deductions: On macadamized roads in good condition, and on uniform sur- faces generally, (1) The resistance to traction is directly proportional to the. pressure. 436 HIGHWAY CONSTRUCTION. (2) It is independent of the width of the tire. (3) It is inversely as the square root of the diameter. (4) It is independent .of the speed. M. Dupuit admits that on paved roads which give rise to con- stant concussion, the resistance increases with the speed, whilst it is diminished by an enlargement of the tire up to a certain limit. The resistance produced by the hollows between the stones of a pavement is of a different character. According to M. Gerstner, the resistance arising from such a surface is directly proportional to the load, to the square of the velocity, and to the ratio of the width of the cavity to the radius of the wheel, and inversely pro- portional to the width of the paving-stones. 521. Friction. The resistance of friction arises from the rub- bing of the wheels against the surfaces with which they come in contact, and will always exist. The friction of surfaces is variable, and can be determined only by experiment. Friction of the axles and resistance of the air are causes of resistance to motion but their consideration may be neglected, as their effects are constant, and independent of the imperfections of the road. 522. Many experiments have been made at various times to ascertain, in functions of the quality and condition of the road-sur- faces, the measure of the tractive force, or the force required to overcome the resistances which oppose themselves to the movement of a vehicle along horizontal roads of different degrees of smooth- ness and hardness and covered with different materials. Table L presents the results of those experiments. The frac- tions which are generally rounded off, indicate the part of the whole weight which is equivalent to the resistance of drawing it on a level road. An examination of this able will clearly show the great economy in horse-power by using the hardest and smoothest ma- terial for road-coverings. For instance, if 1 horse can just draw a load on a level road on iron rails, it will require 1 horses to draw it on asphalt, 3 on the best Belgian-block pavement, 7 on good cobblestone pavement, 13 on bed cobblestone, 20 on an ordinary earth road, and 40 on a sandy road. 523. The following deductions are from the experiments ol MM. Dupuit and Morin : 1st. The resistance to traction on uniform smooth surfaces is BESI8TANGB TO TRACTION. 437 TABLE L. RESISTANCE TO TRACTION ON DIFFERENT ROAD-SURFACES. Character of Surface, Resistance in Terms of Load. Pounds per Ton. Authority. Asphalt . T i 17-26 U. S. Dept. Agri. " temperature 42 F . . . . 34 Baker " " 84 F 70 Belgian block i 56 MacNeil Brick Tf?& 17-37 Baker Clay. . ff?r 98-112 Bevan, U.S. Dept. Cobblestone i-l 54-280 Agri. Earth, ordinary road TV - 224 Bevan ' ' dry and hard rfnfc 101-75 Morin Granite block ?W? 29-36 Baker i ( 1 1 A* 42 U. S. Dept. Agri. Gravel, loose y 320 Bevan hard A 75 < < common road * 140 MacNeil ' ' park road 51 U. S. Dept. Argi. Iron tramway JL 11 Gordon Macadam, little used TB-2T 140-97 Morin bad 160 Gordon old 1 90 Havier slightly muddy dfe 75-41 Morin best French. 45 Havier clean . 18 Baker best 38 U. S. Dept. Agri. Plank (oak) 32-40 Baker ' ' roadway. . . .... 56-40 Morin Sand, loose. . 320 U. S. Dept. Agri. Sandy road . i 187 Morin Steel trackway clean 19 Baker dirty 40 Stone " 14 Gordon (Sleigh) Snow 3 inches thick, temp- perature 26 F JL 75 Turf (wet) 36 Baker 37-90 Morin ( ( it t ( it 1 280 it Wood block (rectangular worn). . . . " (round) t 124 90 it Bevan 438 . HIGHWAY CONSTRUCTION. directly proportional to the load, and inversely as the square root of the diameter of the wheels. 2d. It is independent of the width of the tire when this quantity exceeds 3 or 4 inches. 3d. It is independent of the speed. 4th. On paved surfaces which give rise to constant concussion^ it increases with the speed. 5th. Upon soft roads of earth or sand or turf, or roads fresh and thickly gravelled, the resistance to traction is independent of the velocity. 6th. At a walking pace, the resistance is the same, under the same circumstances, for vehicles with springs and for vehicles with- out springs. 7th. The destruction of the road is, in all cases, greater as the diameter of the wheels is less, and it is greater in vehicles without than with springs. 524. The comparative ease of draft on various surfaces is largely influenced by the amount of foothold afforded, and it may be doubted if dynamometer experiments, however carefully made, are altogether conclusive. The tractive force is influenced by the di- ameter of the wheels, the friction of the wheels on the axles, and the speed, as well as by the resistance of the road surface; and these must be all taken into account to obtain accurate results. Recent experiments on London and Paris street pavements gave the f< lowing results, speed 2 to 6 miles per hour : RESISTANCE TO TRACTION. 439 TABLE LI. TRACTIVE FORCE. ON A LEVEL. Pounds per ton. surrace. London. Paris 40 . 7 to 44 29 32.12 to 39 38 39.0 "39.32 Wood 33 62 " 36.03 33 44 to 39 16 Granite . . 26.2 "21 00 35.20 525. Gravity. The grade of the road, or the quantity by which it differs from a level. The grade resistance is due to the force of gravity, and is the same on both good and bad roads, and unlike the others may be determined from the laws of mechanics, whilst the former are determinable entirely by experiment on the road in question. The resistance due to gravity on any incline in pounds 2240 per ton = ^ -=-. rate of grade TABLE LII. RESISTANCE DUE TO GRAVITY ON DIFFERENT INCLINATIONS. Grade 1 in . 90 30 40 50 60 70 80 90 100 900 300 400 Rise in feet per mile 264 176 132 105 88 75 66 58 52 26 17 13 Resistance in Ibs. per ton 112 74i 56 45 38 32 28 25 22 Hi 7* 54 526. The additional resistance caused by inclines may be inves- tigated in the following manner: Suppose the whole weight to be borne on one pair of wheels, and that the tractive force is applied in a direction parallel to the surface of the road. Let AB in Fig. 40 represent a portion of the inclined road, O being a vehicle just sustained in its position by a force acting in the direction CD. It is evident that the vehicle is kept in its position by three forces ; namely, by its own weight W acting in the vertical direction OF, by the force F applied in the direction CD parallel to the surface of the road, and by the pressure P which the vehicle exerts against the surface of the road acting in the direction CB perpendicular to the same. To determine the relative magnitude 440 HIGHWAY CONSTRUCTION. of these three forces, draw the horizontal line A G and the vertical one B G ; then, since the two lines CF and B G are parallel and are FIG. 40. both cut by the line AB, they must make the two angles C^E and ABG equal; also the two angles CEF and AGB are equal; there- fore the remaining angles FCE and BA G are equal, and the two triangles CFE and ABG are similar. And as the three sides of the former are proportional to the three forces by which the vehicle is sustained, so also are the three sides of the latter; namely, AB or the length of the road is proportional to W, or the weight of the vehicle ; B G, or the vertical rise in the same, to F, or the force re- quired to sustain the vehicle on the incline ; and A G, or the hori- zontal distance in which the rise occurs, to P, or the force with which the vehicle presses upon the surface of the road. Therefore and W:AB::F: GB, W:AB \\P\AG. And if to A G such a value be assigned that the vertical rise of the road is exactly one foot, then w W := = W. sin A, RESISTANCE TO TRACTION". . 441 and W.AG AB W.AG - = W. cos A. L VA a* -4- ] in which A is the angle BA G. 527. To find the force requisite to sustain a vehicle upon an inclined road (the effects of friction being neglected), divide the weight of the vehicle and its load by the inclined length of the road, the vertical rise of which is one foot, and the quotient is the force required. 528. To find the pressure of a vehicle against the surface of an inclined road, multiply the weight of the loaded vehicle by the hori- zontal length of the road, and divide the product by the inclined length of the same; the quotient is the pressure required. 529. The force with which a vehicle presses upon an inclined road is always less than its actual weight; the difference is so small that, unless the inclination is very steep, it may be taken equal to the weight of the loaded vehicle. 530. To find the resistance to traction in passing up or down an incline, ascertain the resistance on a level road having the same surface as the incline, to which add, if the vehicle ascends, or sub- tract, if it descends, the force requisite to sustain it on the incline; the sum or difference, as the case may be, will express the resistance. 531. Tractive Power and Gradients. The necessity for easy grades is dependent upon the power of the horse to overcome the resistance to motion composed of the four forces, friction, collision, gravity, and the resistance of the air. All estimates on the tractive power of horses must to a certain extent be vague, owing to the different strengths and speeds of animals of the same kind, as well as to the extent of their training to any particular kind of work. Authorities on the subject differ widely, and sometimes express themselves in a loose manner that throws doubt on their meaning. 532. The draught or pull which a good average horse, weighing 1200 pounds, can exert on a level, smooth road at a speed of 2 j- miles per hour is 100 pounds, equivalent to 22,000 foot-pounds per minute, or 13,200,000 foot-pounds per day of 10 hours. 533. The tractive power diminishes as the speed increases and perhaps, within certain limits, say from f to 4 miles per hour, nearly 442. HIGHWAY CONSTRUCTION. in inverse proportion to it. Thus the average tractive force of a horse, on a level, and actually pulling for 10 hours, may be assumed approximately as follows : TABLE LIII. TRACTIVE POWER OP HORSES AT DIFFERENT VELOCITIES. Miles per hour. Tractive Force. Pounds. Miles per hour. Tractive Force. Pouuds. . 333 33 21 Ill 11 1 250 g* . 100 11 . 200 3| 90 91 U 166 66 3 .... 83 33 1* . 142 86 31 . 71 43 2 125 4 62.50 534. The work done by a horse is greatest when the velocity with which he moves is ^ of the greatest velocity with which he can move when unloaded; and the force thus exerted is 0.45 of the utmost force that he can exert at a dead pull. TABLE LIV. DURATION OF A HORSE'S DAILY LABOR AND MAXIMUM VELOCITY UNLOADED. Duration of Labor. Hours. Maximum Velocity. Miles per hour. Duration of Labor. Hours. Maximum Velocity. Miles per hour. 1 14.7 6 6 2 . . . . . 10 4 7 . 5 5 3 8 5 8 5 2 4 7.3 9 . .. 4 9 5 6 6 10 4 6 535. The tractive power of a horse may be increased in about the same proportion as the time is diminished, so that when working from 5 to 10 hours, on a level, it will be about as shown in the fol- lowing table : TABLE LV. Hours per day. Traction (pounds). Hours per day. Traction (pounds). 10 100 7 146f 9 11H 6 166^ 8 125 5 200 RESISTANCE TO TRACTION. 443 The tractive power of teams is about as follows : 1 horse =1 2 horses 0.95 X 2 = 1.90 3 " 0.85X3 = 2.55 4 " 0.80x4 = 3.20 Table LYI is useful as showing the maximum amount of labor a horse of average strength is capable of performing at different rates of speed. TABLE LVI. Resistance to Useful Effect of One Horse working 1 day in tons drawn 1 mile.* Speed in Duration of the Traction Miles per hour. Day's Work. assumed at On Level Iron Rails. On Level Maca- Pounds. Tons. dam. Tons. 2* HI 83* 115 14 3 8 83* 92 12 3* 4 Iv 83* 8* 82 72 10 9 5 *& 83i 57 7.2 6 2 83* 48 6.0 7 H 83i 41 5.1 8 H 83i 36 4.5 9 A 83 32 4.0 10 83* 28.8 3.6 *The actual labor which a horse can perform is greater, but he is injured by it. 536. I oss of Tractive Power on Inclines. In ascending inclines a horse's power diminishes rapidly; a large portion of his strength is expended in overcoming the resistance of gravity due to his own weight and that of the load. Table LVIII shows that as the steep- ness of the grade increases the efficiency of both the horse and the road-surface diminishes; that the more the horse's energy is ex- pended in overcoming gravity the less remains to overcome the su rf ace-resistance. Table LVII shows the gross load which an average horse, weighing 1200 pounds, can draw on different kinds of road-surfaces, on a level and on grades rising five and ten feet per one hundred feet. 444 HIGHWAY CONSTRUCTION. TABLE LV1L Description of Surface. Level. 5 per cent. Grade. 10 per cent. Grade. Pounds. 13,216 6,700 4,700 3,000 1,840 3,600 1,400 1,100 8,300 6,250 1,500 1,087 Pounds. Pounds. l',060 1,000 890 740 930 660 600 1,090 1,040 390 21.7 . Broken stone (best condition) . . . . 1,840 1,500 1,390 1,040 1,500 900 780 1,920 1,800 675 445 " " (slightly muddy) " ' ' (ruts and mud) " " (very bad condition) Earth (best condition) " (average condition) " (moist but not muddy) Stone-block pavement (dry and clean). " " " (muddy) Sand (wet) 11 (dry) . . The formula which shows the relation of the tractive force to the weight of the load is a in which ^represents the mean tractive power of the horse, taken at -J of its weight, equal to 165 of its weight, equal to 165 pounds; fjt the coefficient of resistance to traction; Q the load, including the weight of the wagon; G the mean weight of the horse = 165 X 5 = 825 pounds; a the angle of inclination. Q, the load in the above expression, is equal to K G tan or - 1 f* -f- tan a and this form has been utilized for the computation of Table LVII# r showing the load (with vehicle) that the average horse, exerting an average tractive force, can pull up a continuous incline having various grades and different coefficients of resistance, without re- quiring reinforcement at any time. While the above formula holds good for all inclinations shown in the table, it must be stated that it is no longer applicable for ex- cessive grades, for the tractive force in reality diminishes so rapidly that at an angle of 30 degrees it becomes zero. KESISTANCE TO TRACTION. 445 TABLE LVIIa. Values n Values M, Grade tan a A * A A i Grade tan a *V & A iV i Load Q in Pounds. Load Q in Pounds. 0.000 8250 4950 3300 1650 825 0.022 3497 2654 2040 1204 661 0.002 7425 46-37 3141 1601 808 0.025 3-.'08 2476 1925 1155 642 0.004 6737 4335 2994 1555 793 0.028 2956 2315 1819 1109 623 0.008 5657 3835 2731 1467 761 0.033 2599 2078 1660 1036 591 0.010 5225 3620 2612 1425 747 0.040 2200 1800 1467 943 550 0.012 4847 3424 2502 1385 73-2 0.050 1764 1483 1238 825 495 0.016 4217 3079 2300 1309 703 0.066 1285 1113 953 666 415 0.020 3713 2786 2121 1237 &',5 0.100 687 610 550 413 275 537. The decrease in the load which a horse can draw upon an incline is not due alone to gravity; it varies with the amount of foothold afforded by the road-surface. The tangent of the angle of inclination should not be greater than the coefficient of tractional resistance; therefore it is evident that the smoother the road-sur- face the easier should be the grade. The smoother the surface the less the foothold, and consequently the load. Table LVIII shows the decrease in the loads caused by various road-coverings on grades from 1 to 20 per cent. TABLE LVIII. EFFECT OF GRADES UPON THE LOADS A HORSE CAN DRAW ON DIFFERENT PAVEMENTS. Grade. Earth. Broken Stone. Stone Blocks. Asphalt. Level 1.00 1.00 1.00 1 00 1 100 .80 .66 .72 .41 2 100 66 50 55 25 3 100 .55 40 .44 18 4-100 .47 .33 .36 .13 5: 100 .41 .29 .30 .10 10 100 26 16 14 04 15-100 .10 .05 07 20 100 04 03 538. The loss of tractive power on inclines is greater than any investigation will show ; for, besides the increase of draught caused by gravity, the power of the horse is much diminished by fatigue 446 HIGHWAY CONSTRUCTION. upon a long ascent, and even in greater ratio than man, owing to its anatomical formation and great weight. Though a horse on a level is as strong as five men, on a grade of 15 per cent, it is less strong than three; for three men carrying each 100 pounds will ascend such a grade faster and with less fatigue tjian a horse with 300 pounds. 539. A horse can exert for a short time twice the average trac- tive pull which he can exert continuously throughout a day's work ; hence, so long as the resistance on the incline is not more than double the resistance on the level, the horse will be able to take up the full load which he is capable of drawing. 540. Steep grades are thus seen to be objectionable, and partic- ularly so when a single one occurs on an otherwise comparatively level road, in which case the load carried over the less inclined por- tions must be reduced to what can be hauled up the steeper portion. 541. The bad effects of steep grades are especially felt in winter, when ice covers the roads, for the slippery condition of the surface causes danger in descending, as well as increased labor in ascending; the water of rains also runs down the road and gulleys it out, destroying its surface, thus causing a constant expense for repairs. The inclined portions are subjected to greater wear from the feet of horses ascending, thus requiring thicker covering than the more level portions, and hence increasing the cost of construction. 542. It will rarely be possible, except in a flat or comparatively level country, to combine easy grades with the shortest and most direct route. These two requirements will often conflict ; in such a case increase the length. The proportion of this increase will depend upon the friction of the covering adopted. But no general rule can be given to meet all cases as respects the length which may thus be added, for the comparative time occupied in making the journey forms an important element in any case which arises for settlement. Disregarding time, the horizontal length of a road may be increased, to avoid a 5 per cent grade, seventy times the height. Table LIX shows with sufficient exactness for most practical purposes the force required to draw loaded vehicles over inclined roads. The first column expresses the rate of inclination ; the second, the pressure on the plane in pounds per ton ; the third, the tendency down the plane (or force required to overcome the effect of gravity) in pounds per ton ; the fourth, the force required to haul one ton up [RESISTANCE TO TRACTION. 447 TABLE LIX. Rate of Grade. Feet per 100 feet. Pressure on the Plane in Ibs. per ton. Tendency down the Plane in Ibs. per ton. Power in Ibs. required to haul one ton up the Plane. Equivalent Length of Level Road. Miles. Maximum Load in Ibs. which a Horse can haul. 0.0 2240 00 45.00 1.000 6270 0.25 5.60 50.60 1.121 5376 0.50 11.20 56.20 1.242 4973 0.75 16.80 61.80 1.373 4490 1 * 22.40 67.40 1.500 4145 1.25 28.00 73.00 1.622 3830 1.50 33.60 78.60 1.746 3584 1.75 39.20 84.20 1.871 3290 2 45.00 90.00 2.000 3114 2.25 50.40 95.40 2.120 2935 2.50 56.00 101.00 2.244 2725 2.75 61.33 106.33 2.363 2620 3 2239 67.20 112.20 2.484 2486 4 2238 89.20 134.20 2 982 2083 5 2237 112.00 157.00 3.444 1800 6 2233 134.40 179.40 3.986 1568 7 2232 156.80 201.80 4.844 1367 8 179.20 224.20 4.982 1235 9 2231 201.60 246.60 5.480 1125 10 2229 224.00 269.00 5.977 1030 ;: Near enough for practice, actually 2239.888. Pressure on the plane weight X nat cos of angle of plane. the incline; the fifth, the length of level road which would be equivalent to a mile in length of the inclined road that is, the length which would require the same motive power to be expended in drawing the load over it as would be necessary to draw it over a mile of the inclined road; the sixth, the maximum load which an average horse weighing 1200 pounds can draw over such inclines, the friction of the surface being taken at -g^ of the load drawn. 543. Character of Vehicles. The character of the vehicles used upon a roadway has a great influence upon its endurance to the beat of the wheels. The great defect of our vehicles is that for a given load the tires of the wheels are too narrow. It has been proved by repeated and careful experiments that wheels with tires two and a half inches wide cause double the wear of wh*eels which have tires four and a half inches wide. It is true that on ill-con- ditioned and muddy roads a narrow wheel-tread is advantageous, for the reason that the thick mud has a less extended hold when it wraps around the felloes and spokes; but with this arrangement 448 HIGHWAY CONSTRUCTION. the interests of the roadway are sacrificed to the convenience of the individual who drives upon it. 544. Vehicles with Narrow Tires, Vehicles with narrow-tired wheels carrying heavy loads cause much damage, particularly on roads where they run in one track; the knife-like tire cuts into the road covering, forming ruts which each succeeding vehicle deepens ; thus the cost of maintenance is considerably increased. The proper width of tire, or proper load for a given width of tire, is a ques- tion that deserves more attention than is usually accorded to it. 545. The best width of tire measured when new is shown in Table LX. These widths are best for easy traction and the maximum wear of the road-surface. To make the tires wider does not diminish the force required to move the load, and unnecessarily increases the dead weight of the vehicles. For carriages, coupes, and vehicles for light passenger use the tires need not exceed 2-j- inches and should never be less than 2 inches. The width of tires should be established by law. The French Commission, presided over by Morin and Dupuit, recommends as maximum width of tire 4f inches, and as minimum width 2 inches. The best European practice allows only from 500 to 900 pounds per inch width of tire. In the United States loads ranging from 1000 to*5000 pounds per inch width of tire are quite common. TABLE LX. Description of Vehicles. Load on each Wheel. Two Wheels without Springs. Inches. Two Wheels with Springs. Inches. Four Wheels without Springs. Inches. Four Wheels with Springs. Inches. t ton i ;; 6 6 3 3 5 5 5 3 3 3A H 5 4 2 " 6 4A 546. The freight and market wagons of France have tires from 3 to 10 inches in width, usually from 4 to 6 inches. The four- NOTE. All laws regarding the width of tires in London have been abol ished. RESISTANCE TO TRACTION". 449 wheeled freight-wagons have tires rarely less than 6 inches and the rear axle is about 14 inches longer than the fore, so that the rear wheels run on a line about an inch outside of the line of the fore- wheels. The varied gauge is also usually observed with cabs, hacks, and other four-wheeled vehicles. 547. In Bavaria the width of the wheel-tires is laid down by law as follows : 2-wheeled carts with 2 horses 4.133 inches " 4 " .. 6.180 " 4-wheeled carts with 2 " 2.596 " " 3or4horses 4.133 " j " 5 to 8 "' 6.180 " Carts with more than four and wagons with more than eight horses are not allowed to use the road except under special permit from the authorities. 548. In Austria the width of tires for wagons carrying 2J tons tons is 4.33 inches, and for wagons carrying 4 tons 6.30 inches. 548a. In June, 1892, the Studebaker Bros. Mfg. Co. of South Bend,Ind., made a series of tests to determine the relative merits oi wide and narrow tires with regard to the resistance they offered to traction upon different road-surfaces. The wagon employed was a regular 3^-inch thimble-skein wagon having in one set of tests wheels 3 feet 8 inches and 4 feet 6 inches in diameter, and in another set 3 feet 6 inches and 3 feet 10 inches. A Fairbanks dynamometer was attached to the double-tree, and the team exerted their pull through the instrument to move the load. The tests showed that the width of tire has very little effect upon the power required to move loads upon hard surfaces, such as stone blocks, hard sand, or gravel, the power required to move a load of one ton (2240 pounds) being on Stone blocks with l^-in. tire 168 pounds; with 4-in. tire 180pounds. Hard sand " " " " 383 " " " " " 360 " Hard gravel " " " " 344 " " " " " 311 " Upon soft ground, such as mud and grass sods, into which the narrow tires would cut, the wide tires have a slight advantage, the power required to move one ton (2240 pounds) being on Soft rnud with 1-J-in. tire 476 pounds; with 4-in. tire 412 pounds. Sod " " " " 610 " <( 3 " " 537 " The power required to keep the load in motion after being started was found to range from 25 to 5.0 per cent less than 450 HIGHWAY CONSTRUCTION. that required to start it. It was also found that less power was required to start the load when wheels of large diameter were em- ployed, and that the diameter of the wheel had no apparent effect on the power required to keep the load in motion. Numerous tests of the influence of width of tire on draft of wagons have been made at the University of Missouri. The fol- lowing is a brief summary of the results : The width of the tires used was one and one-half inches and six inches. The draft was determined by a self-recording dynamometer. The net load in every trial was 2000 pounds. The loads which could be hauled with the same draft were on: l^-inch Tire. 6-inch Tire. Macadam 2000 Ibs. 2518 Ibs. Gravel, good condition 2000 " 2482 ' ' Dirt, dry and hard 2000 " 2500 " Clay, with mud, deep, and drying on top and spongy underneath (1) 2000 " 3200 " (1) In this condition of road the broad tires show to their great- est advantage. As the road dries and becomes firmer the difference between the draft of the broad and the narrow tires gradually dimin- ishes until it reaches about 25 to 30 per cent on dry, hard, smooth dirt, gravel, or macadam, in favor of the broad tire. On the other hand, as the mud becomes softer and deeper, the difference between the draft of the two types of tires rapidly diminishes until the con- dition is reached when the mud adheres to both styles of wheels. Here the advantage of the broad tires ceases entirely, and the draft required for the narro.w tires is considerably less. Clay, surface dry, with deep ruts cut by narrow tfres in the ordinary use of the road. The first run of the broad tire over the narrow-tire rut showed a materially increased draft when compared with that of the narrow tire run in its own rut. The second run of the broad tire in the same track where the rut was not deep completely eliminated this disadvantage, and showed a lighter draft for the broad tire than the narrow tire showed in the first run.. When the ruts were eight inches deep with rigid walls three runs of the broad tire in its own track over the ruts were required to eliminate the disadvantage. RESISTANCE TO TRACTION. 451 The conditions which showed results unfavorable to the broad tires were : Gravel f wet and sloppy. Dirt. 1. When sloppy, muddy, or sticky on the surface and firm or hard underneath. 2. When covered with a very deep, loose dust and hard under- neath. 3. When the mud is very deep and so sticky that it adheres to the wheels of both types. The experimenters concluded that the best width of tire for a combination farm and road wagon is six inches, and that both axles should be the same length, so that the front and hind wheels will run in the same track. 549. Size of Wheels. The wheels of a vehicle serve a twofold purpose. In the first place, they dimmish the friction on the ground by transferring it from the circumference to the nave and axle; and in the second place, they serve to raise the vehicle more easily over obstacles met with on roads. 550. The friction is diminished in the proportion of the circum- ference of the axle to that of the wheel ; and hence the larger the wheel and the smaller the axle the less is the friction. The mechanical advantage of the wheel in surmounting an obstacle may be computed from the principle of the lever. Let the wheel, Fig. 41, touch the horizontal line of traction in the point A and meet a protuberance BD. Suppose the line of draught A B FIG. 41. OP to be parallel to AB. Join CD and draw the perpendiculars DE and DP. We may suppose the power to be applied at E and the weight at F, and the action is then the same as the bent lever EDF turning round the fulcrum at D. Hence P : W : : FD : DE, 452 HIGHWAY CONSTRUCTION. but FD : DE :: tan FCD : 1, and tan PCD tan 2(DAB)-, therefore P = W tan 2(DAB). Now it is obvious that the angle DAB increases as the radius of the circle diminishes; and therefore, the weight W being constant, the power required to overcome an obstacle of a given height is diminished when the diameter is increased. Large wheels are therefore the best adapted for surmounting inequalities of the road. 551. There are, however, circumstances which provide limits to the height of the wheels of vehicles. If the radius A C exceeds the height of that part of the horse to which the traces are attached, the line of traction CP will be inclined to the horse, and part of the power will be exerted in pressing the wheel against the ground. The best average size of wheels is considered to be about 6 feet in diameter. 552. Wheels of large diameter do less damage to a road than small ones, and cause less draught for the horses. 553. With the same load a two-wheeled cart does far more damage than one with four wheels, and this because of their sud- den and irregular twisting motion in the trackway. 554. U rnpfenbach recommends the following wheel diameters for vehicles frequenting good roads : 1. For two-wheeled freight-carts, 5 feet 3 inches to 5 feet 9 inches. 2. For four-wheeled freight- wagons, front wheels 3 feet 1 inch, hind wheels 3 feet 9 inches to 4 feet 2 inches. These diameters should be increased from 6 to 12 inches for traffic on bad roads. 554a. Effect of Springs on Vehicles. Experiments have shown that vehicles mounted on springs materially decrease the resist- ances to traction, and diminish the wear of the road, especially at speeds beyond a walking pace. Going at a trot they were found not to cause more wear than vehicles without springs at a walk, all other conditions being similar. Vehicles with springs improperly fixed cause considerable concussion, which in its turn destroys the road covering. CHAPTER XL LOCATION OF COUNTRY ROADS. 555. THE considerations governing the location of country roads are dependent upon the commercial condition of the country to be traversed. In old and long-inhabited sections the controlling ele- ment will be the character of the traffic to be accommodated. In such a section the route is generally predetermined, and therefore there is less liberty of a choice and selection than in a new and sparsely settled district, where the object is to establish the easiest, shortest, and most economical line of intercommunication accord- ing to the physical character of the ground. 556. Whichever of these two cases may have to be dealt with, the same principle governs the engineer, namely, to so lay out the road as to effect the conveyance of the traffic with the least ex- penditure of motive power consistent with economy of construction and maintenance. 557. Economy of motive power is promoted by easy grades, by the avoidance of all unnecessary ascents and descents, and by a direct line; but directness must be sacrificed to secure easy grades and to avoid expensive construction. 558. Reconnoissance. The selection of the best route demands much care and consideration on the part of the engineer. To obtain the requisite data upon which to form his judgment he must make a personal reconnoissance of the district. This requires that the proposed route be either ridden or walked over and a careful examination made of the principal physical contours and natural features of the district. The amount of care demanded and the difficulties attending the operations will altogether depend upon the character of the country. 559. The immediate object of the reconnoissance is to select one or more trial lines, from which the final route may be ultimate- ly determined. 453 454 HIGHWAY CONSTRUCTION. When there are no maps of the section traversed, or when those which can be procured are indefinite or inaccurate, the work of reconnoitring will be much increased. 560. In making a reconnoissance there are several points which, if carefully attended to, will very considerably lessen the labor and time otherwise required. Lines which would run along the imme- diate bank of a large stream must of necessity intersect all the tributaries confluent on that bank, thereby demanding a corre- sponding number of bridges. Those, again, which are situated along the slopes of hills are more liable in rainy weather to suffer from washing away of the earthwork and sliding of the embankments ; the others which are placed in valleys or elevated plateaux, when the line crosses the ridges dividing the principal water-courses will have steep ascents and descents. 561. In making an examination of a tract of country, the first point to attract notice is the unevenness or undulations of its sur- face, which appears to be entirely without system, order, or arrange- ment; but upon closer examination it will be perceived that one general principle of configuration obtains even in the most irregular countries. The country is intersected in various directions by main water-courses or rivers, which increase in size as they approach the point of their discharge. Towards these main rivers lesser rivers ap- proach on both sides, running right and left through the country, and into these, again, enter still smaller streams and brooks. The streams thus divide the hills into branches or spurs having approx- imately the same direction as themselves, and the ground falls in every direction from the main chain of hills towards the water- courses, forming ridges more or less elevated. 562. The main ridge is cut down at the heads of the streams into depressions called gaps or passes; the more elevated points are called peaks. The water which has fallen upon these peaks is the origin of the streams which have hollowed out the valleys. Further- more, the ground falls in every direction towards the natural water- courses, forming ridges more or less elevated running between them and separating from each other the districts drained by the streams. 563. The natural water-courses mark not only the lowest lines, but the lines of the greatest longitudinal slope in the valleys through which they flow. 564. The direction and position of the principal streams give LOCATION OF COUNTRY ROADS. 455 also the direction and approximate position of the high ground or ridges which lie between them. 565. The position of the tributaries to the larger stream gener- ally indicates the points of greatest depression in the summits of the ridges, and therefore the points at which lateral communication across the high ground separating contiguous valleys can be most readily made. 566. The instruments employed in reconnoitring, are: The compass, for ascertaining the direction; the aneroid barometer, to fix the approximate elevation of summits, etc. ; and the hand-level, to ascertain the elevation of neighboring points. If a vehicle can be used, an odometer may be added, but distances can usually be guessed or ascertained by time estimates or otherwise, closely enough for preliminary purposes. More outfit than the above (the use of which is supposed to be understood), with the best maps ob- tainable and a succession of travelling companions who possess a local knowledge of the country, will not be particularly useful. 567. The reconnoissance being completed, instrumental surveys of the routes deemed most advantageous should be made. When the several lines are plotted to the same scale, a good map can be prepared from which the exact location of the road can be deter- mined. 568. In making the preliminary surveys the topographical features should be noted for a convenient distance to the right and left of the line, and all prominent points located by compass- bearings. The following data should be also obtained : the impor- tance, magnitude, and direction of all streams and roads crossed ; the character of the material to be excavated or available for em- bankments, the position of quarries and gravel-pits, and the modes of access thereto ; and all other information that may effect a selec- tion. 569. Topography. There are various methods of delineating upon paper the irregularities of the surface of the ground. The method of most utility to the engineer is that by means of "contour lines." These are fine lines traced through the points of equal level over the surface surveyed, and denote that the level of the ground throughout the whole of their course is identical ; that is to say, that every part of the ground over which the line passes is at a certain 456 HIGHWAY CONSTRUCTION. height above a known fixed point termed the datum, this height being indicated by the figures written against the line. The intervals between the lines vertically is equal and may be 1, 3, 5, 10, or more feet apart; 5 feet will be found the most useful. The rate of inclination of the ground may be estimated by the relative proximity or distance apart of the lines. Where the ground is comparatively level they are far apart; where the surface is very hilly they lie close together. These lines by their greater or less distance apart have the effect of shading, and make apparent to the eye the undulations and irregularities in the surface of the country. Fig. 42 shows an imaginary tract of country the physical features of which are shown by contour lines. 570. Map. The map should show the lengths and direction of the different portions of the line, the topography, rivers, water- courses, roads, railroads, and other matters of interest, such as town and county lines, dividing lines between property, timbered and cultivated lands, etc. Any convenient scale may be adopted ; 400 feet to an inch will be found the most useful. Fig. 43 shows a map of this kind. 571. Memoir. The descriptive memoir should give with minute- ness all information such as the nature of the soil, character of the several excavations whether earth or rock, and such particular fea- tures as cannot clearly be shown on the map or profile. Special information should be given concerning the rivers crossed, as to their width, depth at highest known flood, velocity of current, character of banks and bottom, and the angle of skew which the course makes with the line of the road. 572. Levels. Levels Should be taken along the course of each line, usually at every 100 feet, or at closer intervals depending upon the nature of the country. In taking the levels, the heights of all existing roads, railroads, rivers, or canals should be noted. " Bench-marks " should be es- tablished at least every half-mile that is, marks made on any fixed object such as a gate-post, side of a house, or, in the absence of these, a cut made on a large tree. The height and exact description of each bench-mark should be recorded in the level book. 573. Cross-levels. Wherever considered necessary levels at LOCATION OF COUNTRY KOADS. 45' 458 HIGHWAY CONSTRUCTION. LOCATION OF COUNTRY ROADS. 459 MSS- right angles to the centre line should be taken. These will be found useful in showing what effect a deviation to the right or left of the surveyed line would have. Cross-levels should be taken at the intersection of all roads and railroads to show to what extent, if any, these levels will have to be altered to suit the levels of the pro- posed road. 574. Profile. A profile is a longi- tudinal section of the route, made from the levels. Its horizontal scale should be the same as that of the map; the vertical scale should be such as will show with distinctness the inequalities of the ground. Fig. 44 shows the manner in which a profile is drawn and the nature of the information to be given upon it. 575. Bridge Sites. The question of choosing -the site of bridges is an im- portant one. If the selection is not restricted to a particular point, the river should be examined for a con- siderable distance above and below what would be the most convenient point for crossing; and if a better site is found, the line of the road must be made sub- ordinate to it. If several practicable crossings exist, they must be carefully compared in order to select the one most advantageous. The following are controlling conditions : (1) Good char- acter of the river-bed, affording a firm foundation. If rock is present near the surface of the river-bed, the foun- dation will be easy of execution and stability and economy will be insured. ZMf -OtW- W09- UJ a: a. o UJ 460 HIGHWAY CONSTRUCTION. (2) Stability of the river-banks, thus securing a permanent con- centration of the waters in the same bed. (3) The axis of the bridge should be at right angles to the direction of the current. (4) Bends in the river are not suitable localities and should be avoided if possible. A straight reach above the bridge should be secured if possible. 576. Principles to be observed in making the Final Selection. In making the final selection the following principles should be observed as far as practicable. (a) To follow that route which affords the easiest grades. The easiest grade for a given road will depend upon the kind of cover- ing adopted for its surface (b) To connect the places by the shortest and most direct route commensurate with easy grades. (c) To avoid all unnecessary ascents and descents. When a road is encumbered with useless ascents, the wasteful expenditure of power is considerable. (d) To give the centre line such a position, with reference to the natural surface of the ground, that the cost of construction shall be reduced to the smallest possible amount. (e) To cross all obstacles (where structures are necessary) as nearly as possible at right angles. The cost of skew structures in- creases nearly as the square of the secant of the obliquity. (f) To cross ridges through the lowest pass which occurs. (g) To cross either under or over railroads; for grade crossings mean danger to every user of the highway. Guards and gates fre- quently fail to afford protection, and the daily press is filled with accounts of accidents more or less serious; and while statistics fail to give total casualties, the aggregate must be great. 577. Examples of Cases to be Treated. In laying out the line of a road, there are three cases which may have to be treated, and each of these is exemplified in the contour map Fig. 42, page 393 First, the two places to be connected, as the towns A and B on the plan, may be both situated in the same valley, and upon the same side of it; that is, they are not separated from each other by the main stream which drains the valley. This is the simplest case. Secondly, although both in the same valley, the two places may be on opposite sides of the valley, as at A and C, being separated by the main river. Thirdly, they may be situated in different valleys, sep- LOCATION OF COUNTRY ROADS. 461 arated by an intervening ridge of ground more or less elevated, as at A and D. In laying out an extensive line of road, it frequently happens that all these cases have to be dealt with; frequently, per- haps, during its course. The most perfect road is that of which the course is perfectly straight and the surface practically level; and, all other things being the same, that is the best road which answers nearest to this description. Now in the first case, that of the two towns situated on the same side of the main valley, there are two methods which may be pur- sued in forming a communication between them. A road follow- ing the direct line between them, shown by the thick dotted line AB, may be made, or a line may be adopted which will gradually and equally incline from one town to the other, supposing them to be at different levels, or which should keep, if they are on the same level, at that level throughout its entire course, following all the sinuosities and curves which the irregular formation of the country may render necessary for the fulfilment of these conditions. According to the first method, a level or uniformly inclined road might be made from one to the other; this line would cross all the valleys and streams which run down to the main river, thus neces- sitating deep cuttings, heavy embankments, and numerous bridges; or these expensive works might be avoided by following the sinu- osities of the valley. When the sides of the main valley are pierced by numerous ravines with projecting spurs and ridges intervening, instead of following the sinuosities, it will be found better to make a nearly straight line cutting through the projecting points in such a way that the material excavated should be just sufficient to fill the hollows. Now, of all these, the best is the straight and uniformly in- clined, or the level road, although at the same time it is the most expensive. If the importance of the traffic passing between the places is not sufficient to warrant so great an outlay, it will become a matter of consideration whether the course of the road should be kept straight, its surface being made to undulate with the natural face of the country; or whether, a level or equally inclined line being adopted, the course of the road should be made to deviate from the direct line and follow the winding course which such a condition is supposed to necessitate. 462 HIGHWAY CONSTRUCTION. In the second case, that of two places situated on opposite sides of the same valley, there is, in like manner, the choice of a per- fectly straight line to connect them, which would probably require a high embankment if the road was kept level, or steep inclines if it followed the surface of the country; or by winding the road, it may be carried across the valley at a higher point, where, if the level road be taken, the embankment would not be so high, or, if kept on the surface, the inclination would be reduced. In the third case, there is, in like manner, the alternative of carrying the road across the intervening ridge in a perfectly straight line, or of deviating it to the right and left, and crossing the ridge at a point where the elevation is less. The proper determination of the question which of these courses is the best under certain circumstances involves a con- sideration of the comparative advantages and disadvantages of inclines and curves. What additional increase in the length of a road would be equivalent to a given inclined plane upon it; or, conversely, what inclination might be given to a road as an equivalent to a given decrease in its length ? To satisfy this ques- tion it is requisite to know the comparative force required to draw different vehicles with given loads upon level and upon variously inclined roads a subject which is treated in Chapter X. The route which will give the most general satisfaction con- sists in following the valleys as much as possible and rising after- ward by gentle grades. This course traverses the cultivated lands, regions studded with farm-houses and factories. The value of such a line is much more considerable than that of a route by the ridges. The water-courses which flow down to the main valley are, it is true, crossed where they are the largest, and require works of large dimensions, but also they are fewer in' number. 578. Intermediate Towns. Suppose that it is desired to form a road between two distant towns, A and B, Fig. 45, and let us for the present neglect altogether the consideration of the physical features of the intervening country, assuming that it is equally favorable whatever line we select. Now at first sight, it would ap- pear that under such circumstances a perfectly straight line drawn from one town to the other would be the best that could be chosen. On more careful examination, however, of the locality, we may find that there is a third town, C, situated somewhat on one side of the LOCATION OF COUNTRY ROADS. 463 straight line which we have drawn from A to B ; and although our primary object is to connect only the two latter, that it would nevertheless be of considerable service if the whole of the three \ \ ! ! _ N A D B FIG. 45* towns were put into mutual connection with each other. Now this may be effected in three different ways, any one of which might, under the circumstances, be the best. In the first place, we might, as originally suggested, form a straight road from A to B, and in a similar manner two other straight roads from A to C, and from B to 0, and this would be the most perfect way of effecting the object in view, the distance between any two of the towns being reduced to the least possible. It would, however, be attended with considerable expense, and it would be requisite to construct a much greater length of road than according to the second plan, which would be to form, as before, a straight road from A to B, and from C to construct a road which should join the former at a point D, so as to be perpendicular to it. The traffic between A or B and would proceed to the point D and then turn off to C. With this arrangement, while the length of the roads would be very materi- ally decreased, only a slight increase would be occasioned in the distance between C and the other two towns. The third method would be to form only the roads AC and CB, in which case the dis- tance between A and B would be somewhat increased, while that between AC or B and C would be diminished, and the total length of road to be constructed would also be lessened. As a general rule it may be taken that the last of these methods is the best and most convenient for the public ; that is to say, that if the physical character of the country does not determine the course of the road, it will generally be found best not to adopt a 4U HIGHWAY CONSTRUCTION. perfectly straight line, but to vary the line so as to pass through all the principal towns near its general course. 579. Mountain Roads. The location of roads in mountainoua countries presents greater difficulties than in an ordinary undulating country; the same latitude in adopting undulating grades and choice of position is not permissible, for the maximum gradient must be kept before the eye perpetually. A mountain road has to be constructed on the maximum grade or at grades closely approximating it, and but one fixed point can be obtained before commencing the survey, and that is the lowest pass in the mountain range; from this point the survey must be commenced. The reason for this is that the lower slopes of the mountains are flatter than those at their summit ; they cover a larger area and merge into the valley in diverse undulations. So that a road at a foot of a mountain may be carried at will in the desired direction by more than one route, while at the top of a mountain range any deviation from the lowest pass involves increased length of line. The engineer having less command of the ground, owing to the reduced area he has to deal with and the greater abruptness of the slopes, is liable to be frustrated in his attempt to get his line carried in the direction he wishes it to follow. 580. It is a common practice to run a mountain survey up-hill, but such practice should be avoided. Wherever an acute-angled zigzag is met with on a mountain road near the summit, the infer- ence to be drawn is that the line being carried up-hill on reaching the summit was too low and the zigzag was necessary to reach the desired pass. The only remedy in such a case is by a resurvey beginning at the summit and running down-hill. This method requires a reversal of the usual one. The grade line is first staked out and its horizontal location surveyed afterwards. The most appropriate instrument for this work is a transit with a vertical circle on which the telescope may be set to the angle of the maxi- mum grade, 581. Loss of Height. Loss of height is to be carefully avoided in a mountain road. By loss of height is meant an intermediate rise in a descending grade. If a descending grade is interrupted by the introduction of an unnecessary ascent, the length of the load will be increased over that due to the continuous grade by the length of the portion of the road intervening between the summit LOCATION" OF COUKTKY ROADS. 465 of the rise and the point in the road in a level with that rise a length which is double that due on the gradient to the height of the rise. For example, if a road descending a mountain rises at some intermediate point to cross over a ridge or spur, and the height ascended amounts to 110 feet before the descent is con- tinued, such a road would be just one mile longer than if the descent had been uninterrupted; for 110 feet is the rise due to a half-mile length at 1 : 24. 582. Water on Mountain Roads. Water is needed by the work- men and during the construction of the road ; it is also very neces- sary for the traffic, especially during hot weather; and if the road exceeds 5 miles in length provision should be made to have it either close to or within easy reach of the road. With a little in- genuity the water from springs above the road, if such exist, can be led down to drinking-fountains for men, and to troughs for animals. In a tropical country it would be a matter for serious considera- tion if the best line for a mountain road 10 miles in length or up- wards, but without water, should not be abandoned in favor of a worse line with a water-supply available. 583. Halting-places. On long lines of mountain roads halting- places should be provided at convenient intervals. 584. Alignment. No hard and fast rule can be laid down for the alignment of a road ; it will depend both upon the character of the traffic on it and upon the " lay of the land." To promote economy of transportation it should be straight; but if straight- ness is obtained at the expense of easy grades that might have been obtained by deflections and increase of length, it will prove very expensive to the community that uses it. 585. Where curves are necessary, employ the greatest radius pos- sible and never less than fifty feet. They may be circular or parabolic. The parabolic will be found exceedingly useful for join- ing tangents of unequal length, and for following contour lines; its curvature being least at its beginning and ending, makes the deviations from a straight line less strongly marked than by a circular arc (see Figs. 46 to 49). 586. When a curve occurs on an ascent, the grade at that place must be diminished in order to compensate for the additional resistance of the curve. 466 HIGHWAY CONSTRUCTION. TYPES OF CURVES. FIG. 46. SIMPLE CURVE. FIG. 47. COMPOUND CURVE. FIG. 48. REVERSE CURVE. FIG. 49. DOUBLE REVERSE CURVE. LOCATION OF COUNTRY ROADS. 467 587. The width of the wheel way on curves should be greater than that on tangents to permit the swinging of the teams and to prevent accidsnts; the amount of the increase in width depends upon the character of the traffic using the road. The position in which the additional width will be of the greatest service to the traffic is at the entry arcs, as shown at A and A in Fig. 49a, and FIG. 49A. WIDENING WHEELWAY ON CURVES. not at the center (B) of the curve, which is the point commonly widened. The minimum radius of the outer curve to provide the increased width may be determined by the formula in which R = radius of the inner curve of the road; W = width of road on tangents; w = width of vehicles; Z= maximum length of vehicles, including teams. 468 HIGHWAY CONSTRUCTION. If the traffic requires it a further widening may be obtained by flattening the inner curve as indicated by abc. The radius of the reversing curves DD should be not less than 15 feet. 588. Excessive crookedness of alignment is to be avoided, for any unnecessary length causes a constant threefold waste: first, of the interest of the capital expended in making that unnecessary portion; secondly, of the ever-recurring expense of repairing it; and thirdly, of the time and labor employed in travelling over it. 589. The curving road around a hill may be often no longer than the straight one over it, for the latter is straight only with reference to the horizontal plane, while it is curved as to the verti- cal plane; the former is curved as to the horizonal plane, but straight as to the vertical plane. Both lines curve, and we call the one passing over the hill straight only because its vertical curva- ture is less apparent to our eyes. 590. The difference in length between a straight road and one which is slightly curved is very small. If a road between two places ten miles apart were made to curve so that the eye could nowhere see farther than one quarter of a mile of it at once, its length would exceed that of a straight road between the same points by only about four hundred and fifty feet. 591. Zigzags. The method of surmounting a height by a series of zigzags, or by a series of reaches with practicable curves at the turns, is objectionable. (1) An acute-angled zigzag obliges the traffic to reverse its direction without affording it convenient room for the purpose. The consequence is that with slow traffic a single train of vehicles is brought to a stand, while if two trains of vehicles travelling in opposite directions meet at a zigzag a block ensues. (2) With zigzags little progress is made towards the ultimate destination of the road ; height is surmounted, but horizontal dis- tance is increased for which there is no necessity or compensation. (3) Zigzags are dangerous. In case of a runaway down-hill the zigzag must prove fatal. (4) If the drainage cannot be carried clear of the road at the end of each reach, it must be carried under the road in one reach only to appear again at the next, when a second bridge, culvert, or drain will be required, and so on at the other reaches. If the LOCATION OF COUNTRY ROADS. 469 drainage can be carried clear at the termination of each reach, the lengths between the curves will be very short, entailing numerous zigzag curves, which are expensive to construct and maintain. 592. Final Location. The route being finally determined upon, it requires to be located. This consists in tracing the line, placing a stake at every 100 feet on the straight portions and at every 50 or 25 feet on curves. At the tangent points of curves, and at points of compound and reverse curves, a larger and more permanent stake should be placed. Lest those stakes should be disturbed in the pro- cess of construction, their exact distance from several points out- side of the ground to be occupied by the road should be carefully measured and recorded in the note-book, that they may be replaced. The stakes above referred to show the position of .the centre line of the road, and form the base line from which all operations of construction are carried on. Levels are taken at each stake, and cross-levels are taken at every change of longitudinal slope. 593. Construction Profile. The construction or working profile is made from the levels obtained on location. It should be drawn to a horizontal scale of 400 feet to the inch and a vertical scale of 20 feet to the inch. Fig. 50 represents a portion of such a profile. The figures in column A represent the elevation of the ground at every 100 feet, or where a stake has been driven, above datum. The figures in column B are the elevations of the grade above datum. The figures in column C indicate the depth of cutting or height of fill; they are obtained by taking the difference between the level of the surface of the ground and the level of the road. The two straight parallel lines represent the grade of the road ; the upper line is intended to show the upper surface of the road when finished, while the lower line represents what is termed the sub- grade or formation level. All the dimensions refer to the forma- tion level, to which the surface of the ground is to be formed to receive the road-covering. At all changes in the rate of inclir ation of the grade line a heavier vertical line should be drawn. 594. Gradient. The grade of a line is its longitudinal slope, and is designated by the proportion between its length and the difference of height of its two extremes. The ratio of these two quantities gives it its name : if the road ascends or falls one foot in every twenty feet of its length, it is said to have a grade of 1 : 20 470 HIGHWAY CONSTRUCTION. z/u- o oow z 06W- H- o ^ m-J pr -MW- h- CO Z OO'W- g o in E 1 (xi LOCATION OF COUNTRY ROADS. 471 or a 5 per cent grade. Grades are of two kinds, maximum and minimum. The maximum is the deepest which is to be permitted and which on no account is to be exceeded. The minimum is the least allowable for good drainage. (For method of designating grades see Table LXIII.) 595. Determination of Gradients. The maximum grade is fixed by two considerations, one relating to the power expended in as- cending, the other to the acceleration in descending the incline. There is a certain inclination, depending upon the degree of per- fection given to the surface of the road, which cannot be exceeded without a direct loss of tractive power. This inclination is that in descending which, at a uniform speed, the traces slacken, or which causes the vehicles to press on the horses; the limiting inclination within which this effect does not take place is the angle of repose. 596. The angle of repose for any given road-surface can be easily ascertained from the tractive force required upon a level with the same character of surface. Thus if the force necessary on a level to overcome the resistance of the load is -fa of its weight, then the same fraction expresses the angle of repose for that sur- face. 597. On all inclines less steep than the angle of repose a cer- tain amount of tractive force is necessary in the descent as well as in the ascent, and the mean of the two drawing forces, ascending and descending, is equal to the force along a level road. Thus on such inclines as much mechanical force is gained in the descent as is lost in the ascent. From this it might be inferred that when a vehicle passes alternately each way along the road, no real loss is occasioned by the inclination of the road; such is not, however, practically the fact with animal power, for whilst it is necessary in the ascending journey to have either a less or a greater number of horses than would be requisite if the road were entirely level, no corresponding reduction can be made in the descending journey. On inclines which are more steep than the angle of repose, the load presses on the horses during their descent, so as to impede their action, and their power is expended in checking the descent of the load; or if this effect be prevented by the use of any form of drag or brake, then the power expended on such drag or brake corre- sponds to an equal quantity of mechanical power expended in the ascent, for which no equivalent is obtained in the descent. 472 HIGHWAY CONSTRUCTION. 598. Men and all animals can ascend steeper slopes than they can descend. A man walks slowly up-hill and quickly down-hill. A horse does the reverse : the steeper the ascent the faster, until fatigued, he attempts to travel, while in descending he moves at a slow trot which gradually subsides into a walk. Consequently the inclination which admits of high speed in descending practically controls the maximum grade. 599. The maximum grade for a given road will depend (1) upon the class of traffic that will use it, whether fast and light, slow and heavy, or mixed, consisting of both light and heavy; (2) upon the character of the pavement adopted; and (3) upon the question of cost of construction. Economy of motive power and low cost of construction are antagonistic to each other, and the engineer will have to weigh the two in the balance. 600. It is evident, therefore, that no fixed maximum gradient can be adopted in all situations. For fast and light traffic the grades should not exceed 2 per cent ; for mixed traffic 3 per cent may be adopted ; while for slow traffic combined with economy 5 per cent should not be exceeded. This grade is practicable but not convenient. 601. The maximum grade for various paving mate^^s is as follows : Stone blocks a? rades Wood 5 ^r cent Asphalt 2t Brick 5 Broken stone 3 " 602. The maximum grade adopted by the French engineers for macadamized roads is 5 per cent or 1 : 20. The maximum adopted by Telford was 1 : 30. 603. It is obvious from Table LVIII that the smoother the road- surface the easier must be the grade. From this fact it has been deduced that on rough-surfaced roads steeper grades are permissi- ble than on smooth roads. This deduction is misleading. The force of gravity which has to be overcome is the same whether the road-surface be rough or smooth. The rough surface affords better foothold for the horse than the smooth surface, and thus assists him to exert his utmost force, but the great friction produced be- tween the wheels and the rough surface requires the expenditure LOCATION OF COUNTRY EOADS. 73 of greater tractive force than would be required on a smooth, sur- face. In practice there is no pavement which combines the oppo- site requirements of an even smooth surface for the wheels and a sufficiently rough surface affording good foothold for the horses, and a compromise of advantages must therefore be made in most cases. Where the extent and importance of the traffic will warrant the expense, stone trackways afford an excellent method for over- coming the disadvantage of smooth pavements on inclines. 604. To Determine the Maximum Grade. Let L denote the gross load to be hauled up an incline; f, the proportion of the resistance to the load on a level ; S, the sine of the angle of the incline. Then (/-}-$). Z is the greatest resistance to be overcome in ascending the incline; and this should not exceed the greatest tractive force which the horse is capable of exerting. Let P be that force ; then (f -{- 8) . L should not be greater than P, or 8 p should not be greater than -= /. This condition is essential and Li fixes the maximum grade. To avoid excessive acceleration of speed in descending S should not exceed /. The proportion of the resistance/ differs, as shown in Table LXI very much for different sorts of road coverings. It consists of two parts, one arising from friction and another arising from vibration, and increases with the velocity of transit. TABLE LXI. VALUE OP/. Stoue pavement 0.015 = j^ Broken stone 0.020 = T V Gravel road 0.067 = T V Soft sand and loose gravel 0.143 = | For the allowable maximum grade Bockelberg proposes the following expression : 2f*Q = VQ + (& + Q) t <*, in which // = the coefficient of resistance to traction ; Q = the load, including the weight of the wagon; G = the mean weight of the horse = 165 X 5 = 825 pounds. a = angle of inclination. 474 HIGHWAY CONSTRUCTION". The mean tractive power (k) of the horse is taken at one-fifth of its weight = 168 pounds, which enables the animal to move on a level plane a load Q equal to its tractive pull divided by the coefficient of resistance; that is, K 165 Q = ; or, in the average horse, pounds. On macadamized roads having a coefficient of 5 V a horse will pull without exertion Q = 165 -5- -^ = 4950 pounds. The maximum allowable grade depends upon the additional effort that a horse is able to exert above its mean tractive pull, and it is generally conceded that on grades of moderate length, not over 2300 feet, it may exert twice the amount of the adopted mean. Now since // expresses the mean tractive force, we have 2/*Q for the maximum pull, which must equal the weight of the load, wagon, and horse, corrected for the grade, and the character of road-surface, or 2/^Q = ^.Q cos a -f- (Q -f- G) sin a. This expression may be simplified by dropping cos a from the first member, because on inclinations up to 1 in 10 it remains nearly unity; and in the second member the term sin a may be changed into tan a, for the reason that their difference is too small to affect the result, and "the tangent has the advantage of expressing in a more direct manner the amount of the grade. This reduces the formula down to %f*Q = j^Q + (Q + G) tan a. In the further consideration of this subject the weight of the horse may be omitted, which is perfectly admissible in grades of moderate length. Then the formula becomes Zj*Q = nQ -f- tan a, which is n tan a. This means that the tangent of the permissible inclination, which in a reach of moderate length does not require an additional horse to overcome it, is equal to the coefficient of resistance to traction. On a well-paved road, therefore, where /* = ^ rises greater than 1 in 50 ought not to occur, while on poor earth roads a grade of 1 in 10 is not excessive. The coefficient of resistance to traction for different road-surfaces is given in Table L. 604a. To Determine the Most Advantageous Grade (J. H. Stried- inger and Otto von Geldern). Although the maximum permissible degree of inclination has been set forth in the foregoing, it has not LOCATION OF COUNTRY ROADS. 475 been decided yet whether such grades are the most advantageous, or whether it would not be better to adopt a still smaller grade. In order to settle this question definitely, it is proper to consider every element that affects the actual cost of transportation, and to aim at reducing this as much as possible. The expenditures of moving a load upon a highway depend upon : 1. The angle of inclination a. 2. The coefficient of resistance to road traction //. 3. The tractional force k which draught-animals are able to ex- ert at a mean velocity c during a mean working time t. 4. The law according to which the tractional power of animals varies with the change in the mean velocity or working time. In consideration of this factor, Mascheck's formula has been used, which expresses the tractive force in this wise: In order to make this clear, it is well to refer to a short theo- retical consideration of this point. The work L of animal loco- motors is, like all mechanical work, the product of a power K^ (the tractive force) into the velocity v, and into a certain element of time ^during which that power is exerted; therefore L = K^vZ. These three factors differ in every draught-animal according to individual conditions, but they hold such a relation to each other that an increase in tractional force diminishes velocity and time; an acceleration of the velocity reduces the force and time; while a more extended duration of work will weaken the force and lower the velocity. The following formula of Mascheck has been generally em- ployed : -*[-:] in which K = a mean tractive force; c = a mean velocity; t = a mean working time. 476 HIGHWAY CONSTRUCTION. It may be readily demonstrated that with these mean factors the maximum work performed is L max = Kct. K is usually taken at 165 pounds; c = 3.6 feet per second; t 8 hours. Then the work done in one hour will equal 2,147,310 foot- pounds. If the values c, K and t, and with them the maximum day's work, cannot be reached (if, for instance, a greater velocity be required), we must endeavor to obtain a relative maximum, which is tied to v Z the condition 7 = 7-' c t Introducing this value reduces Mascheck's formula to the ex- pression This formula furnishes results in harmony with practical ex- perience as long as the values of K, c, and t do not exceed the mean values beyond reasonable limits. Bockelberg, for instance, assumes c = 4 feet; Sganzin places the most advantageous velocity that an animal will assume when it is neither held in nor urged on as follows : A heavy horse, 2.93 feet. A lighter animal, 3.66 feet. 5. The weight of the unloaded wagon Q, the mean of which has been taken at 1320 pounds, = 8K. 6. The weight of the load Q. 7. The weight of the draught-animal, taken at 5K = 825 pounds for one horse. 8. The monetary value of the daily work of the animal. 9. The probable cpst of both the new roadway construction and the maintenance of the highway. Considering all these factors, a mathematical deduction has led to certain results that express the most advantageous grade, which it is not necessary to carry out in detail here. Launhardt, by a careful analysis in this line, and by assuming the following values: u = -5*0, Q = 1320 pounds, and G. = 825 pounds, has arrived at the following conclusions: LOCATION OF COUNTRY ROADS. 477 Dependent upon the amount of traffic, and the cost of construc- tion and maintenance of the highway, the most advantageous grade varies: For mountainous country .................... between -$ and ^ " hilly country. .. ......................... between^ " ^ " level country ............................ between^ ^ and for an ordinary traffic on roads built at an average cost: In mountainous country ................................. 1 : 24 In hilly country ........................................ 1 : 80 In level country ....................................... 1 : 44 These deductions give results somewhat smaller than those laid down by the road regulations of European countries. In one item, in that of hilly country, however, there is shown considerable devi- ation from practice; the others nearly agree with the results of theoretical deduction. 604b. Cost of Grades. The increased cost of transportation caused by grades may be ascertained approximately by the formula in which R = percentage of resistance to traction on a level surface; I = percentage of resistance due to inclination of grade; _/V= number of full one-horse loads per day; V = value of horse, harness, and vehicle, and The amount which can be economically spent in reducing a grade is found approximately by the formula in which A = percentage of resistance due to the inclination of the lower grade. 605. Grade of Mountain Roads. Although mountain roads are in general projected for slow traffic, yet as civilization and wealth in a country increase, roads adapted to the use of wheeled vehicles gradu- ally become used by an increasing amount of quick traffic. Ascend- ing grades of 1 : 20, 1 : 18, 1 : 16 are too steep to permit of carriages drawn by horses ascending for any distance except at a foot-pace. Hack conveyances with relays at short distances can and do pro- 478 HIGHWAY CONSTRUCTION". ceed more rapidly over hill roads with these grades, but such ser- vice is accompanied with a great amount of cruelty to the draught animals. Private horses are not called upon to work like hired hackneys, which are supposed to be able to do double the work they were capable of in their younger, and better, days; therefore, con- tinuous grades of 1: 16, 1 : 18, 1 : 20 means, as respects private quick traffic, its conversion into slow traffic. On the descent of such inclinations horses can only travel with safety at a slow trot, which probably subsides into a walk at the turns and when meeting other traffic. To ride down a slope of 5 per cent for a long distance is disagreeable. With a gradient of 4 per cent on a mountain road the slow traffic would be so well suited that ten miles continuous ascent could be surmounted without a halt or undue exertion on the part of the draught animals. Such a grade would not reduce quick traffic to a walk throughout an ascent, and it would permit of horses descending with safety at six to eight miles an hour. 606. Minimum Grade. From the previous considerations it would appear that an absolutely level road was the one to be sought for, but this is not so ; there is a minimum or least allowable grade which the road must not fall short of, as well as a maximum one which it must not exceed. If the road was perfectly level in its longitudinal direction, its surface could not be kept free from water without giving it so great a rise in its middle as would ex- pose vehicles to the danger of overturning. The minimum grade established in France by the Corps des Fonts et Chaussees is .008, or 1 in 125; this may be adopted as the minimum, and in a perfectly level country the road should be artificially formed into gentle undulations approximating this minimum limit. 607. Undulating Grades. From the fact that the power re- quired to move a load at a given velocity on a level road is decreased on a descending grade to the same extent that it is in- creased in ascending the same grade, it must not be inferred that the animal force expended in passing alternately each way over a rising and falling road will gain as much in descending the several inclines as it will lose in ascending them. Such is not the case. The animal force must be sufficient, either in power or number, to draw the load over the level portions and up the steepest inclines LOCATION OF COUNTRY ROADS. 479 TABLE LXII. DIFFERENT METHODS OF DESIGNATING THE SAME GRADES. American Method, Feet per 100 feet. English Method. Feet per Mile. Angle with the Horizon. i 1:400 13.2 8' 36" I 1:200 26.4 17 11 1 : 150 39.6 22 55 i 1 : 100 52.8 34 23 u 1 :80 66 42 58 1} 1:66& 79.2 51 28 if 1 :57i 92.4 1 51 2 1:50 105.6 186 2* 1:44* 118.8 1 17 39 2i 1:40 132 1 25 57 2f : 36i 145.2 1 34 22 3 :33 158.4 1 43 08 8i :30f 171.6 1 51 42 8* :28i 184.8 2 16 3f :26f 198 2 8 51 4 :25 211.2 3 17 26 4* :23| 224.4 2 26 10 4* : 22| 237.6 2 34 36 4* :21 250.8 2 43 35 5 :20 264 2 51 44 6 :18| 316.8 3 26 12 7 :14f 369.6 4 15 8 :12i 422.4 4 34 26 9 :1H ' 475.2 5 8 31 10 : 10 528 5 42 87 480 HIGHWAY CONSTRUCTION. of the road, and in practice no reduction in the number of horses can be made to correspond with the decreased power required in descending the inclines. The popular theory that a gentle undulating road is less fatigu- ing to horses than one which is perfectly level is erroneous. The assertion that the alternations of ascent, descent, and levels call into play different muscles, allowing some to rest while others are ex- erted, and thus relieving each in turn, is demonstrably false, and contradicted by the anatomical structure of the horse. Since this doctrine is a mere popular error, it should be utterly rejected, not only because false in itself, but still more because it encourages the building of undulating roads, and this increases the labor and cost of transportation upon them. 608. Level Stretches. On long ascents it is generally recom- mended to introduce level or nearly level stretches at frequent in- tervals in order to rest the animals. These are objectionable when they cause loss of height, and animals will be more rested by halt- ing and unharnessing for half an hour than by travelling over a level portion. The only case wj^ich justifies the introduction of levels into an ascending road is where such levels, will advance the road towards its objective point; where this is the case there will be no loss of either length or height, and it will simply be exchang- ing a level road below for a level road above. 609. Establishing the Grade. When the profile of a proposed route has been made, a grade line is drawn upon it (usually in red) in such a manner as to follow its general slope, but to average its irregular elevation and depressions. If the ratio between the whole distance and the height of the line is less than the maximum grade intended to be used, this line will be satisfactory; but if it be found steeper, the cuttings or the length of the line will have to be increased : the later is generally preferable. 610. The apex or meeting point of all grades should be rounded off by a vertical curve shown in Figs. 51 to 53. The formula for these curves is given in Art. 935. LOCATION OF COUNTRY ROADS. 4S1 EXAMPLES OF THE APPLICATION OF VERTICAL CURVES. FIGS. 51 TO 53. 482 HIGHWAY CONSTRUCTION. 610a. .Geological Considerations. "The extent to which gradients can be diminished by curves or cuttings is often deter- mined by the geological structure of the country. The cost both of construction and maintenance of roads may be considerably increased by neglecting to investigate the geology of the area traversed. For this purpose both the nature of the rocks as well as the direction of their stratification must be taken into account. Where the road follows the natural surface of the ground, the stabil- ity of its foundation is largely influenced by the nature of the underlying rock. Bogs and marshy swamps present difficulties which ought particularly to be avoided, and all ground liable to floods should be carefully noted. Even in strata which are appar- ently solid and homogeneous the presence of springs may cause certain portions of a road to be continually wet. This difficulty is more especially common at the junction of pervious and imper- vious strata. It is usually the case that geological boundary lines coincide with marked changes in contour, so that a change of grade is generally one of the consequences resulting from a change of rock formation. It is therefore important to know exactly where the boundary lines of different strata intersect the line of the pro- posed road. A contour road will in general keep more closely to one geo- logical formation, that is to say, it will run along the line of outcrop of the strata; while a road which crosses successive outcrops will be marked by irregular grades, which may entail considerable expense in cuttings and embankments. The nature of the rock must in this case be carefully examined ; for it may happen that the cost of cuttings may be more than counterbalanced by the value of the rock for subsequent use in the construction and repair of the road. In this case a cutting would be more advantageous than a detour or a surface grade. " In making cuttings geological considerations often determine the best direction, especially on hillsides, where it might at first seem to be immaterial on which side of the hill it should run. In Fig. 53a is shown a road cutting in inclined strata on each side of a LOCATION OF COUNTRY ROADS. 483 hill. Such strata are extremely liable to slips, one bed sliding over another in the direction of the dip. This is more particularly the case after the action of frost or heavy rainfall, and when the strata consists of alternations of permeable rock with seams of im- FiG. 53A. permeable clay. The amount of inclination of the strata is also important in this respect. All rocks have a certain angle of repose, beyond which they will not stand in a cutting or embankment; so that if the angle of dip exceed the angle of repose for the par- ticular rock in question, there will* be danger of the occurrence of FIG. 53e. slips. It will now be seen how this question influence! the proper position of the road. If the cutting is made towards the rise of the beds, i.e., at A, Fig. 53a, there can be no possible danger of slips; but if the road be placed at B, Fig. 53a, the side of the cutting will be a source of continual trouble and expense. Not only in hillside cuttings, however, but also in other cases the dip of the strata must be taken into consideration before a proper estimate can be formed of the expense which will be incurred. In Fig. 536 it is obvious that if the dip of the strata is greater than the angle of repose, that side of the cutting which is towards the rise of the 484 HIGHWAY CONSTRUCTION. beds will need to be benched back until the slope of the cutting is less than the angle of repose of the strata. This, of course, involves an increased expense in excavation, which should be taken into consideration when weighing the advantages and disadvantages of certain lines of routed CHAPTER XII. WIDTH AND TRANSVERSE CONTOUR. 611. A road should be wide enough to accommodate Jie traffic for which it is intended, and should comprise a wheelway for vehicles and a space on each side for pedestrians. 612. The wheelway of country highways need be no wider than is absolutely necessary to accommodate the traffic using it; in many places a track wide enough for a single team is all that is necessary. But the breadth of the land appropriated for highway purposes should be sufficient to provide for all future increase of traffic. The wheelways of roads in rural sections should be double ; that is, one portion paved (preferably the centre) and the other left with the natural soil. The latter if kept in repair will for at least one half the year be preferred by teamsters. 613. The minimum width of the paved portion, if intended to carry two lines of travel, is fixed by the width required to allow two vehicles to pass each other safely. This width is 16 feet. If in- tended for a single line of travel, 8 feet is sufficient but suitable turnouts must be provided at frequent intervals. The most eco- nomical width for any roadway is some multiple of eight. 614. Wide roads are the best; they expose a larger surf ace to the drying action of the sun and wind, and require less supervision than narrow ones. Their first cost is greater than narrow ones, and that nearly in the ratio of the increased width. 615. The cost of maintaining a mile of road depends more upon the extent of the traffic than upon the extent of its surface, and unless extremes be taken the same quantity of material will be necessary for the repair of the road whether wide or narrow which is subjected to the same amount of traffic. The cost of spreading the materials over the wide road will be somewhat greater, but the cost of the materials will be the same. On narrow roads the 485 480 HIGHWAY CONSTRUCTION. traffic, being confined to one track, will wear more severely than if spread over a wider surface. 616. The width of land appropriated for road purposes varies in the United States from 49 to 66 feet; in England and France from 26 to 66 feet. And the width or space macadamized is also subject to variation: in the United States the average width is 16 feet; in France it varies between 16 and 22 feet; in Belgium 8J feet seems to be the regular width, while in Austria it varies from 14^ to 26J feet. In Massachusetts the standard width of broken-stone roads is 15 feet, and on each side there is a width of 3 feet shaped to the same cross-section as the broken stone. These side strips or shoulders are covered with gravel on much-travelled roads; on all others the natural soil is used. Roadways of 10 and 12 feet have been built and are satisfactory so far as their use is con- cerned, but the 10-foot roadway cannot be maintained economically, except where the traffic is exceptionally light. Figs. 85-92, pages 531-533, show the subdivision of the road- way into wheelway, sidewalks, and ditches. 617. Width of Mountain Roads. Mountain roads should be pro- portioned in width to the amount of traffic; they should be neither too wide nor too narrow. If of excessive width, the cost of con- struction is increased ; if too narrow, traffic will be interrupted by blockades. An economical width is 24 feet, and the stone covering should extend from gutter to gutter. If the center only is covered, the road will soon be destroyed, as, by reason of the curves on a mountain side predominating over straight reaches, the traffic will hug either one side of the road or the other. Table LXIII shows the number of acres required per mile for different widths of roadway. WIDTH AND TRANSVERSE CONTOUR. 487 TABLE LXIII. ACRES REQUIRED PER MlLE FOR DIFFERENT WlDTHS OF ROADWAY. Width. Feet. Acres per mile. Width. Feet. Acres per mile. Width. Feet. Acres per mile. Width. Feet. Acres per mile. Width. Feet. Acres per mile. i .030 19 2.30 40 4.85 59 7.15 80 9.70 \ .061 20 2.42 41 4.97 60 7.27 81 9.82 .121 21 2.55 41* 5.00 61 7.39 82 9.94 2 .242 22 2.67 42 5.09 62 7.52 824 10.00 3 .364 23 2.79 43 5.21 63 7.64 83 10.06 4 .485 24 2.91 44 5.33 64 7.76 84 10.18 5 .606 24f 3.00 45 5.45 65 7.88 85 10.30 6 .727 25 3.03 46 5.58 66 8.00 86 10.42 7 .848 26 3.15 47 5.70 67 8.12 87 10.54 8 .970 27 3.27 48 5.82 68 8.24 88 10.66 8 1.00 28 3.39 49 5.94 69 8.36 89 10.78 9 1.09 29 3.52 49 6.00 70 8.48 90 10.90 10 1.21 30 3.64 50 6.06 71 8.61 90f 11.00 11 1.33 31 3.76 51 6.18 72 8.73 91 11.03 12 1.46 32 3.88 52 6.30 73 8.85 92 11.15 13 1.58 33 4.00 53 6.42 74 8.97 93 11.27 14 1.70 34 4.12 54 6.55 74i 9.00 94 11.39 15 1.82 35 4.24 55 6.67 75 9.09 95 11.51 16 1.94 36 4.36 56 6.79 76 9.21 96 11.63 164 2.00 37 4.48 57 6.91 77 9.33 97 11.75 17 2.06 38 4.61 57* 7.00 78 9.45 98 11.87 18 2.18 39 4.73 58 7.03 79 9.58 99 12.00 100 12.12 HIGHWAY CONSTKUCTIOX. 618. Transverse Contour. The centre of all roadways should be higher than the sides. The object of this is to facilitate the flow of the rain-water to the gutters. Where a good surface is main- tained a very moderate amount of rise is sufficient for this purpose. Earth roads require the most and asphalt the least. The rise should bear a certain proportion to the width of the carriageway. The most suitable proportions for the different paving materials is shown in the following table : TABLE LXIV. AMOUNT OF TRANSVERSE RISE REQUIRED FOR DIFFERENT PAVEMENTS. Kind of Surface. Proportion of the Carriageway Width. Earth ............... Rise at centre ................ fa Gravel .............. " ................ -fa Broken stone ........ " ................ ^V Stone blocks ......... " ................ -fa Wood ................ " ................ yfo Brick ................ ............... & Asphalt .............. ................ fa 619. Form of Transverse Contour. All authorities agree that the form should be convex, but they differ in the amount and form of the convexity. Circular arcs, two straight lines joined by a circular arc and ellipses all have their advocates, but the best form for streets will be found to be a parabolic curve starting from the edge of the gutter next the carriageway or one foot from the curb line. Fig. 54 shows this form, which is obtained in the fol- lowing manner: Divide the ordinate or the width between the edge of the gutter and the centre of the street into 10 equal parts, and raise perpendiculars the length of which will be determined by multiplying the rise at the center by the respective number of each perpendicular in the diagram. The amounts thus obtained can be added to the rod readings, and the stakes set at the proper distance across the street with their tops at this level will give the true curve. 620. For country roads a curve of suitable convexity may be obtained as follows : Give -J of the total rise at J the width from the centre to the side, and f of the total rise at the width (Fig. 55). 621. Excessive height and convexity of cross-section contract the width of the wheelway, by concentrating the traffic at the WIDTH AND TRANSVERSE CONTOUR. 489 TRANSVERSE CONTOUR OF STREETS AND ROADS. '36 '31 /'CO 5.UTTER LEVEL 490 HIGHWAY CONSTRUCTION. centre, that being the only part where a vehicle can run upright. The force required to haul vehicles over such cross-sections is increased, because an undue proportion of the load is thrown upon two wheels instead of being distributed equally over the four. The continual tread of horses' feet in one track soon forms a depression which holds water, and the continuous travel of vehicles in one track soon wears ruts which retain water, and the surface is not so dry as with a flatted section, which allows the traffic to dis- tribute itself over the whole width. 622. Sides formed of straight lines are also objectionable. They wear hollow, retain water, and defeat the object sought by raising the centre. 623. Concave Form. In Triest, Austria, the early pavements were laid concave, i.e., inclining to the middle, along which, under the surface-canals or sewers extended with gratings at intervals for the admission of surface-drainage. The same method, but with open channels through the centre, is practised in several South American towns. Experience has proved that this plan is not desirable or convenient for traffic. 624. The required convexity should be obtained by rounding the formation surface, and not by diminishing the thickness of the covering at the sides. 625. On hillside and mountain roads it is generally recom- mended that the surface should consist of a single slope inclining inwards. There is no reason for or advantage gained by this method. The form best adapted to these roads is the same as for a road under ordinary conditions, viz., that described in Art. 619. 626. With a roadway raised in the centre and the rain-water draining off to gutters on each side, the drainage will be more effectual and speedy than if the drainage of the outer half of the road has to pass over the inner half. The inner half of such road is usually subjected to more traffic than the outer half. If formed of a straight incline, this side will be worn hollow and retain water. The inclined flat section never can be properly repaired to with- stand the traffic. Consequently it never can be kept in good order, no matter how constantly it may be mended. It is always below par. When heavy rain falls it is seriously damaged. CHAPTER XIII. EARTH-WORK. 627. Earth-work. The term " earth-work " is applied to all the operations performed in the making of the excavations and em- bankments to prepare them for receiving the road-covering. In its widest sense it comprehends work in rock as well as in the looser material of the earth's crust. 628. Equalizing Earth-work is a term applied to the process of so adjusting the formation or sub-grade level of an inter ied work that the earth from the cuttings shall be as nearly as possible sufficient to make the embankments and no more. The art of making this adjustment by the eye upon a profile of the ground with sufficient accuracy is soon acquired by practice. In most cases it is essential to economy in the cost of the work. For any sur- plus of embankment over cutting must be made up by borrowing, and the earth from any surplus of cutting over embankment must be wasted, both of these operations involve additional cost for labor and land. But cases sometimes occur in which it is more economi- cal to make an embankment from borrow-pits close at hand than to bring the necessary material from a far-distant cutting on the line of the works, or in which it is more economical to waste part of the material from a cutting than to send it to a far-distant embankment on the line of the works, and these points must be decided by the engineer to the best of his judgment in each par- ticular case. 629. Transverse Balancing. When the road lies along the side of a hill, so that it is partly in excavation and partly in embank- ment, it is necessary to so place its centre line that these two parts of cross-section may balance. When the ground has a uniform slope the desired end would be obtained (if the side slopes were the same for excavation and embankment and if no shrinkage existed), 491 492 HIGHWAY CONSTRUCTION. by locating the centre line of the road upon the surface of the ground. In other cases, as when the side of the excavation slopes 1 to 1 and that of the embankment 2 to 1, a formula to determine the position of the centre line may be readily established. 630. If earth be wanted for a neighboring embankment, the amount of excavation may be easily increased by moving the centre of the road farther into the hill, with the additional advan- tage of lessening its liability to sjip. The line may be thus changed on the map according to the notes of the cross-section in the level book, and be subsequently moved by a corresponding quantity on the ground. 631. When the slope of the ground is very steep the transverse balance must be disregarded and the road made chiefly in excava- tion, to avoid the insecurity of a high embankment. 632. Borrow-pits. ^hen the excavations on the line of the road do not furnish sufficient material for the embankments, the deficiency is obtained either by widening the excavations, or from an excavation termed a " borrow-pit," made in the vicinity of the embankment. 633. Spoil-banks. If the excavations furnish more material than is required for the embankments, the excess is generally deposited in a convenient place on the land adjoining the excava- tion, in banks termed " spoil-banks." Both these cases are expensive and objectionable. It is there- fore very desirable to make the excavation and embankment " balance " each other. If the calculations show much disparity in the two amounts, the location of the line should be changed in some way so as to effect the desired equality. 634. The equalization must, however, be restrained within certain limits, for it should evidently be abandoned when, in order to form sufficient excavation to make the embankment, it would be necessary to go to such a distance that the cost of transport would exceed the cost of borrowing for the banks and wasting the distant excavation in spoil-banks. 635. The comparison of the price of transport with that of excavation and land will therefore determine the distance within which the balancing must be established. 636. The form to be given to the borrow-pits and spoil-banks will depend in a great degree upon the locality ; they should as far as EARTH-WORK. 493 practicable be located so that the cost of removal of the earth shall be the least possible. 637. Staking out Borrow-pits. Borrow-pits should be staked out by the engineer and their contents calculated, unless the contractor is to be paid by embankment measurements. A number of cross- profiles are taken of the original surface, and (on the same lines) on the bottom of the pit, after it is excavated, which furnish the depth of cutting at each required point. Borrow-pits should be regularly excavated so that they may not present an unsightly ap- pearance when abandoned. 638. Shrinkage. The equality recommended must be taken with an important qualification, dependent upon the fact that earth transferred from excavation to embankment shrinks, or settles so as to occupy less space in the bank than it did in its natural state. Eock, on the contrary, occupies more space when broken. 639. In estimating the relative amounts of excavation and em- bankment required, allowance must be made for difference in the spaces occupied by the material before excavation and after it is settled in embankment. The shrinkage of the different materials is about as follows : Gravel 8 per cent Gravel and sand 9 Clay ami clay earths 10 Loam aud light sandy earths. 12 Loose vegetable soil 15 Puddled clay 25 Eock, on the other hand, increases in value by being broken up, and does not settle again into less than its original bulk. The in- crease may be taken at fifty per cent. Thus an excavation of loam measuring 1000 cubic yards will form only about 880 cubic yards of embankment, or an embankment- of 1000 cubic yards will require about 1120 cubic yards measured in excavation to make it. A rock excavation measuring 1000 yards will make from 1500 to 1700 cubic yards of embankment, depend- ing upon the size of the fragments. 640. The lineal settlement of earth embankments will be about in the ratio given above; therefore either the contractor should be instructed in setting his poles to guide him as- to the 494 HIGHWAY CONSTRUCTION. height of grade on an earth embankment to add the required per- centage to the fill marked on the stakes, or the percentage may be included in the fill marked on the stakes. In rock embankments this is not necessary. 641. Failure of Earth- work. The failure of earth -work is due to the slipping or sliding of its parts on each other, and its stability arises from resistance to the tendency so to slip. In solid rock, that resistance arises from the elastic stress of the material, when subjected to a shearing force ; but in the mass of earth, as commonly understood, it arises partly from the friction between the grains, and partly from their mutual adhesion ; which latter force is considerable in some kinds of earth, such as clay, especially when moist. But the adhesion of earth is gradually destroyed by the action of air and moisture, and of the changes of the weather, and especi- ally by alternate frost and thaw ; so that its friction is the only force which can be relied upon to produce permanent stability. 642. The temporary additional stability, however, which is produced by adhesion, is useful in the execution of earth-work, by enabling the sides of a cutting to stand for a time with a vertical face for a certain depth below its upper edge. That depth is greater, the greater the adhesion of the earth as compared with its heaviness ; it is increased by a moderate degree of moisture, but diminished by excessive wetness. The following are some of its values : Greatest depth of tern. vert. face. Earth. Clean dry sand and gravel from to 1 foot. Moist sand and ordinary surface mould from 3 " 6 feet Clay (ordinary) from , 10 " 16 " Compact gravel from 10 " 15 " 643. One of the effects of the temporary stability due to adhesion is seen in the figure of the surface left after a " slip " has taken place in earth-work. That surface is not a uniform slope, inclined at the angle of repose, but is concave in its vertical section, being vertical at its upper edge, and becoming less and less steep down- wards. It is not capable, however, of preserving that figure ; for fche action of the weather, by gradually destroying the adhesion of the earth, causes the steep upper part of the concave face to crumble EARTH-WORK. 495 down, so that the whole tends to assume a uniform curved slope in the end. 644. The Permanent Stability of earth, which is due to friction alone, is sufficient to maintain the side either of an embankment or of a cutting at a uniform slope, whose inclination to the horizon is the angle of repose, or angle whose tangent is the coefficient of friction. ' This is called the natural slope of the earth. The cus- tomary mode of describing the slope of earth- work is to state the ratio of the horizontal breadth to its vertical height, which is the reciprocal of the tangent of the inclination. 645. The angles of repose for different earths are given in Table LXV. But for all practical purposes it may be said that all earths, sand, and gravel, stand at a slope of 33 degrees 41 minutes, or 1-J to 1. If the slopes of an excavation in sand are to be left unprotected by sodding, they should be given a slope of 2 to 1. The ratio of slopes, their angles and length, are given in Table LXVI. TABLE LXV. NATURAL SLOPES OF EARTHS (WITH HORIZONTAL LINE). Gravel (average). . . 40 Dry sand .38 Wet " 22 Vegetable earth .28 Compact earth 50 Shingle ,39 Rubble 45 Clay (well drained). 45 " (wet) 16 TABLE LXVI. LENGTHS AND ANGLES OF SLOPES. Slope. Angle with Horizon Length. (Height taken as J. 00.) Slope. Angle with Horizon Length. (Height taken as 1.00). *:1 75 58' 1.0307 U:l 33 41' 1.802 i : 1 63 26 1.118 If: 1 29 44 2.016 *:1 53 8 1.25 2 : 1 26 34 2.236 1 : 1 45 1.4142 3 : 1 18 26 3.162 U:l 38 40 1.6 4 : 1 14 2 4.124 49(5 HIGHWAY CONSTRUCTION. 646. The inclinations generally given in practice to the various materials are as follows: Loose earth, loain and gravel 1| to 1 Sand 2 " 1 Soft greasy clay 3 " 1 Rock (sound) OJ " 1 647. Effect of Moisture. The presence of moisture in earth to an extent just sufficient to expel the air from its crevices seems to increase its coefficient of friction 'slightly; but any additional moisture acts like a lubricant in diminishing friction, and tends to reduce the earth to a semi-fluid condition, or to the state of mud. In this state, although it has some cohesion, or viscidity, which resists rapid alteration of form, it has no f rictional stability ; and 'its coefficient of friction and angle of repose, are each of them null. Hence it is obvious that the frictional stability of earth depends to a great extent on the ease with which the water that it occasion- ally absorbs can be drained way. The safest materials for earth- work are fragments of rock, shingles, gravel, and clean sand ; for these materials allow water to pass through without retaining more of it than is beneficial. The cleanest sand, however, may be made completely unstable and reduced to the state of " quick sand " if it is contained in a basin of water-holding materials so that water mixed amongst its particles cannot be drained off. The property of retaining water and forming a paste with it belongs specially to clay, and to earths of which clay is an ingre- dient. Such earths, how hard and firm soever they may be when first excavated, are gradually softened, and have both their fric- tional stability and their adhesion diminished by exposure to the air. In this respect mixtures of sand and clay are the worst; for the sand favors the access of water, and the clay prevents its escape. The properties of earth with respect to adhesion and friction are so variable that the engineer should never trust to tables or to information obtained from books to guide him in designing earth- works, when he has it in his power to obtain the necessary data either by observation of existing earth-works in the same stratum or by experiment. EARTH-WORK. 497 648. Inclination of Side Slopes. The proper inclination for the side slopes of cuttings and embankments depends on the nature of the soil and the action of the atmosphere and of internal moisture upon it. " In common soils, as ordinary garden earth formed of a mixture of clay and sand, compact clay, and compact stony soils, although the side slopes would withstand very well the effects of the weather with a steeper inclination, it is best to give them two base to one perpendicular, as the surface of the roadway will, by this arrange- ment, be well exposed to the action of the sun and air, which will cause rapid evaporation of the moisture of the surface. Pure sand and gravel may require a greater slope according to circumstances. In all cases where the depth of the excavation is great the base of the slope should be increased. " In excavations through solid rock, which does not disintegrate on exposure to the atmosphere, the side might be perpendicular; but as this would exclude in a great degree the action of the sun and air, which is essential to keeping the road-surface dry and in good order, it is necessary to make the side slopes with an inclina- tion varying from one base to one perpendicular, to one base to two perpendicular, or even greater, according to the locality; the inclination of the slopes on the south side in northern latitudes being the greater, to expose better the road-surface to the sun-rays. " The slaty rocks generally decompose rapidly on the surface when exposed to moisture and the action of frost. The side slopes in rocks of this character may be cut into steps and then be covered by a layer of vegetable mould sown in grass-seed, or else the earth may be sodded in the usual way." 649. Form of Side Slopes. The natural, strongest, and ultimate form of earth slopes is a concave curve, in which the flattest portion is at the bottom. This form is very rarely given to the slopes in constructing them ; in fact, the reverse is often the case, the slopes being made convex, thus saving excavation for the contractor and inviting slips. In cuttings exceeding 10 feet in depth the forming of concave slopes will materially aid in preventing slips, and in any case they will reduce the amount of material which will eventually have to be removed when cleaning up. Straight or convex slopes will con- tinue to slip until the natural form is attained. 498 HIGHWAY CONSTRUCTION. A revetment or retaining wall at the base of a slope will save excavation. In excavations of considerable depth, and particularly in soils liable to slips, the slope may be formed in terraces, the horizontal offsets or benches being made a few feet in width with a ditch on the inner side to receive the surface-water from the portion of the side slope above them. These benches catch and retain earth that may fall from the slopes above them. (See Fig. 56.) FlG, 56. HILLSIDE ROADS. 650. overing of Slopes. It is not usual to employ any artificial means to protect the surface of the side slopes from the action of the weather; but it is a precaution which in the end will save much labor and expense in keeping the roadways in good order. The simplest means which can be used for this purpose consists in cov- ering the slopes with good sods, or else with a layer of vegetable mould about four inches thick, carefully laid and sown with grass- seed. These means are amply sufficient to protect the side slopes from injury when they are not exposed to any other causes of deterioration than the wash of the rain and the action of frost on the ordinary moisture retained by the soil. A covering of brushwood or a thatch of straw may also be used with good effect ; but from their perishable nature they will require frequent renewal and repairs. " Where stone is abundant a small wall of dry stone may be constructed at the foot of the slopes to prevent any wash from them being carried into the ditches." 651. Slips. "The stratified soils and rocks in which the strata have a dip or inclination to the horizon are liable to slips, or to give way by one stratum becoming detached and sliding on another, EARTH-WORK. 499 which is caused either from the action of frost or from the pres- sure of water which insinuates itself between the strata. The worst soils of this character are those formed of alternate strata of clay and sand, particularly if the clay is of a nature to become semi-fluid when mixed with water. The best preventives that can be resorted to in these cases are to adopt a system of thorough drainage, to prevent the surface-water of the ground from running down the side slopes, and to cut off all springs which run towards the roadway from the side slopes. The surface-water may be cut off by means of a single ditch, termed a catch-water ditch, exca- vated a, few feet back from the crest of the slope, so that it inter- cepts the water before it reaches the slope of the excavation, and convey it off to the most convenient natural water-courses. Usu- ally this ditch will be required only on the up-hill side of the road ; for in almost every case it will be found that the side slope on the down-hill side is, comparatively speaking, but slightly affected by the surface-water. "Where slips occur from the action of springs, it frequently becomes a very difficult task to secure the side slopes. If the sources can be easily reached by excavating into the side slopes, drains formed of layers of fascines or brushwood may be placed to give an outlet to the water and prevent its action upon the side slopes. The fascines may be covered on top with good sods laid with the grass side beneath, and the excavation made to place the drain filled in with good earth well rammed. Drains formed of broken stone or cobbles covered in like manner on top with a layer of sod to prevent the drain from becoming choked with earth may be used under the same circumstances as fascine drains. Where the sources are not isolated and the whole mass of the soil forming the side slopes appears saturated, the drainage may be effected by excavating trenches a few feet wide at short intervals to the depth of some feet into the side slopes, and filling them with boulders or broken stone, or else a general drain of stone may be made throughout the whole extent of the side slope by excavating into it. When this is deemed necessary it will be well to arrange the drain like an inclined retaining-wall with buttresses at inter- vals projecting into the earth farther than the general mass of the drain. The front face of the drain should, in this case, also be covered with a layer of sods with the grass side next to the stones 500 HIGHWAY CONSTRUCTION. forming the drain, and upon this a layer of good earth should be compactly laid to form the face of the side slopes. The drain need only be carried high enough above the toe of the side slope to tap all the sources, and it should be sunk sufficiently below the roadway to give it a secure footing." "The drainage has been effected, in some cases, by sinking wells or shafts at some distance behind the side slopes, from the top surface to the level of the bottom of the excavation and lead- ing the water which collects in them by pipes into the drains at the foot of the side slopes. In others a narrow trench has been excavated, parallel to the axis of the road, from the top surface to a sufficient depth to tap all the sources which flow towards the side slope, and a drain formed either by filling the trench wholly with stone or else by arranging an open conduit at the bottom to receive the water collected, over which a layer of brushwood is laid, the remainder of the trench being filled with stone." 652. Embankments. The best materials for embankments are those whose frictional stability is the greatest and the most perma- nent, such as fragments oi rock, shingle, gravel, and clean sand. Clay forms safe embankments, provided it is dry, or nearly dry, when laid down. Wet clay, vegetable mould, and mud are unfit for use in embankments; so also is peat, except when dry. 653. An embankment may be made in three ways : (1) In one layer. (2) In two or more thick layers. (3) In thin layers. (1) In One Layer. This being the cheapest and quickest FIG. 57. method consistent with stability, is that followed in all earth-works in which there is no special reason requiring it to be performed by the other methods. In Fig. 57 BAG represents the natural surface of EARTH-WORK. 501 the ground ; DA, part of the base of a cutting ; AEG, an embank- ment the construction of which is carried forward in the direction AE of its full width and height (including a sufficient allowance for settlement),, by running dump-carts on temporary tracks from the cutting along the top of the embankment, and tipping them at E, so that the earth runs down and spreads itself over the sloping end EC of the bank, which is called the "tip." Embankments formed in this manner are deficient in compactness, for the par tides of earth which are emptied from the top of the bank will temporarily stop in their descent at the point of the slope at which the friction becomes sufficient to balance their gravity; and when more earth conies upon them, they will give way and slide lower down, causing the portions above them to slip and crack, and thus delay for a long time the complete consolidation. Tipping or dumping the earth over the sides of banks made in the above manner should not be allowed, for the earth so dumped is liable afterwards to slip off. The solidity of embankments formed in the above manner may be increased by filling from the sides towards the centre in order that the earth may arrange itself in layers with a dip from the sides inwards. FIG. 58. CROSS-SECTION OF EARTH EMBANKMENT, SHOWING METHOD OF PLACING THE LAYERS. As the rapidity with which a bank can be made by this method is dependent upon 'the number of tipping or dumping points, it is usual to form the bank wider at top and narrower at the bottom than it is finally to be, maintaining of course the requisite area o cross-section; the excess at the top (the angles AB, Fig. 59) be- ing subsequently moved down to the bottom, thus securing the required width of base and inclination of side slopes. It is mistaken economy to first form embankments narrow and 502 HIGHWAY CONSTRUCTION". afterwards widen them by lateral additions, for the new material will never unite perfectly with the old. (2) In Thick Layers. This process has been used in some em- bankments of great height. It consists in completing the con- struction of the embankment up to a certain height by the process of end-dumping already described; leaving that layer for a time to settle, and then making a second layer in the same way, and so FIG. 59. on. It involves much additional time and labor, and is seldom employed. It is, however, useful in making embankments of hard clay or shale, which, when first dumped, consists of angular lumps that lie with vacant spaces between them and do not form a com- pact mass until partially softened and broken down by the action of air and moisture. (3) In Thin Layers. This process consists in spreading the earth in horizontal layers of from 9 to 18 inches deep, and rolling or ramming each layer so as to make it compact and firm before laying down the next layer. Being a tedious and costly process, it is used in special cases only, of which the principal are the filling in behind retaining walls, behind wings and abutments of bridges and culverts, and over their arches. 654. Side Slopes of Embankments. In forming the embank- ments the side slopes should be made with a greater inclination than that which the earth naturally assumes, for the purpose of giving them greater durability, and to prevent the width of the top surface along which the roadway is made from diminishing by every change in the side slopes, as it would were they made with the natural slope. To protect the side slopes more effectually they should be sodded, or sown in grass-seed, and the surface water of the top should not be allowed to run down them, as it would soon wash them into gulleys and destroy the embankment. In EARTH-WORK. 503 localities where stone is plentiful a sustaining wall of dry stone may be advantageously substituted for the side slopes. The toe or foot of embankments has a tendency to spread ; this may be resisted by excavating a small trench along the toe, or by buttressing with a low stone wall. 655. Drainage of Embankments. The only drains required for embankments over good ground are the ordinary side ditches, with occasional culverts to convey the water from them into the natural water-courses. When springs are crossed, stone drains or culverts may be built to carry the water clear of the embankment. 656. Embankments over Plains. When a roadway is carried across an extensive plain, it is almost always necessary, in order to keep its surface dry, that it should be raised above the general level of the ground; and where inundations occur, the requisite height may be considerable. In Fig. 60, A represents a cross-sec- FIG. 60. SECTION OF EMBANKMENTS OVER PLAINS. tion of an embankment for this purpose, the materials for which are obtained by digging a pair of trenches alongside of it. These trenches, by collecting surface-water and discharging it into the nearest river or other main drainage channel, tend to shorten the duration of floods in the neighborhood of the line. 657. Embankments across Marshes. When the ground is so soft that an embankment made in the ordinary way would sink in it, different expedients are to be employed according to the kind and degree* of difficulty to be overcome. The following list of expedients is arranged in the order of an increasing scale of dif- ficulty : (1) By digging side drains parallel to the site of the intended embankment, the firmness of the natural ground may be increased. (2) If the material of the natural ground has a definite angle of repose, though much flatter than that of the material of the embankment, the slopes of the embankment may be formed to the same angle, thus giving it a broader foundation than it would have with its own natural slope. 504 HIGHWAY CONSTRUCTION. (3) A foundation may be made for the embankment by digging a trench and filling it with a stable material. (4) The ground may be compressed and consolidated by driving short piles. (5) The embankment may be made of materials light enough to form a sort of raft, floating on the soft ground, such as hurdles, fascines, timber platforms, or dry peat. Dry peat was the material used by George Stephenson to carry the Liverpool and Manchester Railway across Chat Moss. Its heaviness, when well dried in the air, is about 30 pounds per cubic foot; and when saturated with water, 63 pounds. On the dry-peat embankment was placed a platform of two layers of hurdles to carry the ballast. (6) Should all other expedients fail, a marsh or bog may still be crossed by throwing in stones or gravel and sand, until an embankment is formed resting on the hard stratum below, and with its top rising to the required level. It is found that the material of the embankment assumes the same natural slope that it would do in the air. Mr. George W. Waite, C.E., gives the following description of a road constructed by him in 1868 in the village of Hyde Park (now in the city of Chicago) : " The line crossed a marsh about one mile wide which extended from about two miles west, easterly to Lake Michigan, and south- easterly to Calumet River, a distance of two miles, and was at that time all covered with water from a few inches to two feet deep. Wild rice grew all over that portion of the marsh, about 8 feet high, and the stalks were from J to % inch in diameter at the bottom. Through the central portion of the marsh was an open water-way about 10 feet wide in the channel proper, with no per- ceptible current, which widened out into small lakes every few hundred feet. " The channel and lakes had from 3 to 4 feet of water and about the same depth of black slush or decayed vegetable matter. " Soundings showed the turf to be about 1 foot thick, with from 2 to 6 feet of soft black vegetable mould underneath, then a hard bottom of blue clay. " The method of construction was as follows : Beginnirg at the dry ground on the south end, an 18-foot inch board, 1 foot wide, was placed lengthwise on the outside, 9 feet from the centre, then EARTH-WOKK. 505 one in the centre, 6 feet in advance of the first, and then one on the opposite side, 6 feet in advance of the middle one. Then the three pieces laid lengthwise were covered with 18-foot sound boards 1 inch thick, laid crosswise and nailed as fast as laid to keep them in their places. On these were placed three more, lengthwise as at first, one in the centre and one on each side, and these were nailed through into the under ones. Next all the wild rice for a space of about 75 feet on each side was cut down and pitched with forks onto the floating platform or roadbed. It made a compact cover- ing about 2 feet thick. At the end of the first 500 feet a turn- around for teams on one side was made of boards doubled, 36 feet square, thoroughly nailed. " Then the whole 500 feet of roadbed was covered 16 feet wide with about 15 inches thick of stone, and on this was placed 3 inches of crushed stone. " After finishing the first 500 feet the turn-around was removed to the end of the second 500 feet, and so on to completion. Near the middle of the marsh was a lake which the line crossed, some 200 feet wide. This was covered with a bent bridge 50 feet long, and the balance with floats, the same as the marsh but wider. The bridge was placed on the pond-lily roots that everywhere abounded in the bottom of all these small lakes, and left about 2 feet higher than needed to allow for settling, but it has not yet settled more than some. 6 inches, although a pole can be run down between the network of roots and into the slush underneath about 3 feet below the bottom of the sills before the hard bottom is reached. " The road settled on an average about 2 feet, with the excep- tion of two or three short distances where it settled 3 feet, but it did not break through the turf in any place. At a high stage of water some places for a few feet in length would be 1 foot under water. " The road has stood over 23 years and has been considerably travelled, and is in good condition at the present time (1892). It- has had but very little top-dressing during the whole time. Since the road was constructed the marsh has nearly all been drained, and has mostly become solid, and the land in it, which at that time was not worth $25.00 per acre, has just been sold for $2500.00 per acre." 658. Embankments across Bogs. Undrained moss consists of 506 HIGHWAY COXST.UUCTIOIT. - - - - - ' ^ about 90 per cent of water and 10 per cent of vegetable matter, and consequently while in that condition it is quite incapable of sus- taining a roadway.; but in most cases the surface of the underlying solid ground is above the level of the waterways of the district, and by gradual drainage the fluid mass may be condensed into a more or less solid peat. The drainage should not be effected at too rapid a rate, as there is a liability of the escaping water carrying off with it the particles of vegetable matter, causing the sides of the ditches to collapse, and producing fissures on the surface of the moss which, becoming filled with water or ice, extend more and more. The drainage of the strip of moss along the site of the intended roadway should be effected by side drains, carried gradually down and into the solid underlying ground. And if this can be done, it is probable that the moss by conversion into peat will be reduced by about one third of its total thickness. The sides of the drains, instead of being sloped, should be cut in a series of steps or benches, each of about three feet deep and three feet broad, down to the re- quisite level, so as to expose as large a surface as possible to the influence of wind and sun, and thereby produce a comparatively hard skin of peat, and consequently lessen the destructive action of frost. The side ditches should be cut parallel to the axis of the road- way and at a distance from the centre line on each side of 30 or more feet, depending upon the width of the berm intended to be left between th eedge of the roadway and the side ditch. The berm should not be less than six feet. Transverse drains should be cut at right angles to the side drains, and at distances apart not exceed- ing 30 feet. These transverse drains should extend across and beyond the side drains from 50 to 100 feet. The material exca- vated from these drains should not be deposited near their edges, or slips will probably occur; it may be spread on the roadway site. After the draining is completed, the roadway may be formed of sand and surfaced with broken stone. 659. Embankments on Hillsides. When the axis of the road- way is laid out on the side slope of a hill, and the road is formed partly by excavating and partly by embanking, the usual an4 most simple method is to extend out the embankment gradually along the whole line of the excavation. This method is insecure ; the EARTH-WOKK. 507 excavated material if simply deposited on the natural slope is liable to slip, and no pains should be spared to give it a secure hold, par- ticularly at the toe of the slope. The natural surface of the slope FIG. 61. SHOWING METHOD OF CONSTRUCTION ON HILLSIDES. should be cut into steps as shown in Figs. 61, 62. The dotted line AB represents the natural surface of the ground, CEB the excavation, and ADC the embankment, resting on steps which have been cut between A and C. The best position for these steps is perpendicular to the axis of greatest pressure. If AD is inclined FIG. 62. SHOWING METHOD OF CONSTRUCTION ON HILLSIDES. at the angle of repose of the material, the steps near A should be inclined in the opposite direction to AD, and at an angle of nearly 508 HIGHWAY CONSTRUCTION. 90 degrees thereto, while the steps near C may be level. If stone is abundant, the toe of the slope may be further secured by a dry wall of stone. On side hills of great inclination the above method of construc- tion will not be sufficiently secure; retaining- walls of stone must be substituted for the side slopes of both the excavations and em- bankments. These walls may be made of stone laid dry, when stone can be procured in blocks of sufficient size to render this kind of construction of sufficient stability to resist the pressure of the earth. But when the blocks of stone do not offer this security, they must be laid in mortar. The wall which forms the slope of the excavation should be carried up as high as the natural surface of the ground. Unless the material is such that the slope may be safely formed into steps or benches as shown in Figs. 61 and 62, the wall that sustains the embankment should be built up to the surface of the roadway, and a parapet wall or fence raised upon it, to pro- tect pedestrians against accident. (See Figs. 56 and 63.) 660. Roadways on Rock-slopes. On rock-slopes when the inclination of the natural surface is not greater than one perpen- dicular to two base, the road may be constructed partly in excava- tion and partly in embankment in the usual manner or, as shown in Figs. 63, 64, 65, by cutting the face of the slope into horizontal FIG. 63. SHOWING METHOD OF CONSTRUCTION ON HILLSIDES. steps with vertical faces, and building up the embankment in the form of a solid stone wall in horizontal courses, either dry or laid in mortar. Care is required in proportioning the steps, as all attempts EARTH-WORK. 509 to lessen the quantity of excavation by increasing the number and diminishing the width of the steps require additional precautions against settlement in the build-up portion of the roadway. FlG. 64, SHOWING METHOD OF CONSTRUCTION ON HILLSIDES. When the rock-slope has a greater inclination than 1. : 2 the whole of the roadway should be in excavation. In some localities roads have been constructed along the face of nearly perpendicular cliffs on timber frameworks consisting of hori- zontal beams, firmly fixed at one end by being let into holes drilled in the rock, the other end being supported by an inclined strut which rests against the rock in a shoulder cut to receive it. There are also examples of similar platforms suspended instead of being sup- ported. 661. The vertical faces of rock-cliffs present the most formida- ble obstacles to the formation of roads. When the rock is suffi- ciently hard and not liable to early disintegration a half -tunnel like DEF, Fig. 66, may be formed by blasting; but if it be too soft and rotten to admit of this being done, the best plan, if the cliff be of any great height BE above the formation level, is to blow out the whole piece GEF by a large mine at E. Mining should not, as a rule, be employed where there is a chance of the strata being blown out downwards according to the dip, for a piece may be blown out, like the shaded portion Fig. 67, when much time and expense are entailed in rectifying the level. The general mode of attacking a vertical cliff and of forming a half-tunnel is shown in Fig. 68. The large blasts, a, a, a, a, driven 8 feet in depth, at an angle of 45 degrees, are 7 feet 3 inches apart horizontally and 5 feet vertically. The small holes, b, b, etc., 3 feet 510 HIGHWAY CONSTRUCTION. EXAMPLES OF ROADS ON ROCK SLOPES- Tig 6 5 Fig 66. Fig. 67. ** ^ 1 " ' J - \;,J ?V* Fig.68. EARTH-WORK. 511 apart and 3 ieet deep, which are not fired, serve to determine and facilitate rupture at the proper level. These blasts, when fired, generally blow out or loosen a piece like. AECD. The remaining space, BEF, is blown out in the same manner. 662. Rock Excavation. Excavation in hard rock is usually per. formed by means of some explosive material inserted in a hole bored in the rock, and when ignited it loosens the mass and permits of its being broken up into pieces of the required size. The diameter and depth of the hole vary with the quantity of rock to be loosened at each blast, and also with the strength of the explosive used. The quantity of rock loosened, other conditions being the same, is roughly proportional to the cube of the " line of least resistance," which is generally the shortest distance from the centre of the charge to the surface of the rock. If E = the quantity of the explosive in pounds, and L = the line of least resistance in feet, then E= CL 3 ', C = .032 blasting powder; = .005 " cotton; = .003 nitroglycerine or dynamite. Ordinary blasting powder, 1 pound of which occupies about 30 cubic inches, is ignited by means of a fuse, which burns at the rate of about 2 feet per minute, varying slightly with each coil. In estimating it is usual to allow f of a pound of powder to each cubic yard of solid rock. The actual quantity required will vary with the nature of the rock and its degree of compactness or loose- ness, the latter requiring most powder. Dynamite and nitroglycerine should be fired by percussion. Detonating tubes or caps are made for the purpose, which explode :on being ignited either by an ordinary fuze or by a galvanic battery. 663. Blasting. If L = least line of resistance in feet; X = number of ounces of powder required to blast any rock when L = 2 feet; P = quantity of powder in ounces required, then 512 HIGHWAY CONSTRUCTION. r ~ XL* or, when X = 4 ounces, should not exceed one half the depth of hole. TABLE LXVII. AMOUNT OF CHARGE WHEN X = 4 OUNCES. L Charge of Powder. L Charge of Powder. feet. Ibs. oz. feet. Ibs. oz. 1 1 5 3 14* 2 4 6 6 12 3 13* 8 16 4 2 In small blasts one pound of powder will loosen about 4| tons. In large blasts one pound of powder will loosen about 2f tons. Thirty cubic inches of powder weigh one pound. Hence we have the following table, showing the capacity of drill-holes : TABLE LXVIII. CAPACITY OF DIULL-HOLES. Diameter of Hole in inches. Area in square inches. Ounces of Powder in one inch deep. Powder in one foot deep. Depth of hole in inches to contain one Ib. of Powder. 1 0.7854 0.419 Ibs. oz. 5.028 38.197 1* 1.7671 0.942 11.300 16.976 2 3.1416 1.676 1 4.112 9.549 2* 4.9087 2.618 1 15.416 6.112 3 7.0686 3.770 2 13.240 4.244 664. In blasting no loud report should be heard nor stones be thrown out. The best effect is produced when the report is trifling, and when the mass is lifted and thoroughly fractured without the projection of fragments. If the rock be only shaken by a blast and not moved outward, a second charge in the same hole will be very effective. EARTH- WORK. Any kind of compact brush, such as pine or cedar boughs, laid on rocks about to be blasted, will almost completely prevent the flying of fragments, and thus lessen the danger to persons and buildings in the vicinity. So much, however, depends upon the character of the rock to be excavated, whether it is hard or soft, stratified or unstratified, and whether the position of the excavation allows of arranging the drill- holes in the most advantageous manner, that the above figures must be regarded as only approximately correct. 665. Holes for blasting rock are bored either by hand or machine drills. Shallow cuts, loose boulders, etc., are more cheaply bored by hand, but deep and extensive cuttings are more economically car- ried out by the use of machine drills operated either by steam or compressed air. 666. Hand-drilling. The speed with which holes may be bored in rock varies of course with the hardness of the rock and the diameter of the hole. The smaller the diameter of the hole the greater the depth that can be bored in a given time; and the depth will be greater in proportion than the decrease of the diameter. The average rate of progress made by a good drillman working a churn-drill in granite and the harder rocks is about as follows : Diam. of Drill. Depth bored per hour. Inches. Inches. 3 4 2| .5 2J 6 2 8 If 10 When the hole exceeds four feet in depth two men are required 1 to operate the drill. 667. Machine-drilling. Machine drills bore holes from f to 6 inches in diameter. The rate of progress is controlled by the same conditions as hand-drilling, and ranges from three to ten feet per hour, depending on the character of the rock and the size of the machine. 668. Cost of Rock Excavation. The cost of simply excavating rock is from four to six times that of earth, and is largely con- trolled by the skill of the overseer, especially as regards carrying the excavation to its full depth. If this is not done, the amount left in 514 HIGHWAY CONSTRUCTION. the bottom, especially if it is of little depth, will cost several times more per yard to remove it than the cost per yard of the main cut. 669. Earth Excavation Loosening the Earth. The loosening of the material in shallow cuttings and in light soils is done best by the plough, and its removal is economically executed with drag or wheeled scrapers. Gravel, clay, and hardpan require to be loosened by the pick, or if the depth be great, explosives may be employed. 670. Transport of Earth. The transport of earth is effected in the following ways : (a) Thr oiving with a Shovel, when the distance horizontally does not exceed 12 feet nor vertically 6 feet. (b) Wheelbarrows may be employed running upon a plank for distances up to 200 feet. (c) Carts. Between 200 and 500 feet two-wheeled dump-carts may be used. (d) Scrapers. The economical limit for drag-scrapers is about 150 feet. Wheeled scrapers may be employed up to 500 feet. (e) For hauls over 500 feet, where a large amount of work is to be done, a track with dump-cars drawn by horses will be found profitable. (/) Dump-wagons. The dump-wagon is a recent invention; it consists of a four-wheeled wagon, the body of which turns on a horizontal axle, so that it can be tipped over by a single movement of a lever and the earth dumped out. Their capacity varies from 35 to 45 cubic feet. They may be economically employed in long hauls. The distance, however, depends much upon the difficulty of getting out the earth. With hard clay, requiring two picks to a shovel, and with a small surface to work upon, two carts upon an ordinary road will take away all that a dozen men can get out ; while with an easy soil, where one pick will keep half a dozen shovels busy, a larger number of vehicles will be required, or a quicker haul, which may be obtained by putting down a track. The less the haul, or the greater the speed of transport, the fewer may be the number of vehicles to remove a given amount of material. The chief point to be gained is to arrange the different classes of laborers so that none shall be kept waiting. Everything depends upon the tact for management possessed by the overseer. 671. Loosening and Transporting by Machinery. A machine EARTH-WORK. 515 called the New Era Grader (Fig. 211) (Chap. XXIII) has been developed for both loosening the earth and automatically transport- ing and depositing it in the bank when the material is obtained from side ditches, as in the case of building a bank across a plain. The machine consists of a plough which loosens and raises the earth, depositing it upon a transverse carrying-belt, which conveys it from the excavation to the bank. The carrier-belt is of heavy three-ply rubber 3 feet wide, and can be adjusted to deliver the earth at 14, 17, 19, or 22 feet from the plough. The machine will work in any material that can be loosened with a plough. The motive power is horses, usually twelve in number. The capacity of the machine varies from 100 to 150 cubic yards per hour, depending upon the resistance of the material to be moved. The number of attendants required to operate the machine is three. The cost per cubic yard loosened and placed in bank will depend upon wages and team-hire. With wages at 20 cents per hour for laborers, and horsehire at 10 cents each per hour, the cost per cubic yard would be 1.80 cents. The machine can also be used to excavate material in deep cuts. When so employed, dump-wagons are used to transport the earth. The carrier of the machine is set to deliver at 10 feet ; the wagons are driven under it and automatically loaded with from 1.J to 1 yards of earth in from 20 to 30 seconds. The machine can thus load from 60 to 80 wagons per hour. 672. Cost of Earth- work. Regarding the cost of executing earthwork, no fixed rules can be given ; it depends largely upon the location, kind and cost of labor, and character of the management. In general it ranges from 10 to 35 cents per cubic yard. The several items that go to make up the total cost of earth- work are the loosening of the earth, either by ploughs, picks, or explosives, the loading it into the barrows, carts, or other vehicles, the moving and emptying it, the spreading it out upon the em- bankment, the return of the vehicle, the keeping of the road in order, the wear and tear of tools and vehicles, the interest on the cost of the equipment, the wages of the overseers, and the contract- or's profit. 673. Haul. The cost of removing excavated material when the 5iG HIGHWAY CONSTRUCTION. distance does *not exceed a certain specified limit is included in the price per cubic yard of the material as measured in the cutting. But whan the material must be carried beyond this limit, the extra distance is paid for at a stipulated price per cubic yard per 100 feet. Ths extra distance is known by the name of " haul/' and is to be computed by the engineer with respect to so much of the material as is affected by it. The contractor is entitled to the benefit of all short hauls (less than the specified limit), and material, so moved should not be aver- iiged against that which is carried beyond the limit. Therefore, in all cuts the material of which is all deposited within the limiting distance, no calculation of haul is to be made. The contractor must haul free that portion of the cutting no one yard of which is carried beyond the specified limit. There- fore this portion is first to be determined in respect to its extent, and the number of cubic yards contained in it is to be deducted from the total content of the cutting, before estimating the haul upon the remainder. Find on the profile of the line two points, one in excavation and the other in embankment, such that while the distance between them equals the specified limit, the included quantities (allowing for shrinkage) of excavation and embankment shall just balance. These points are easily found by trial with the aid of the cross-sections and calculated quantities, and become the starting points from which the haul of the remainder of the material is to be estimated. B Y - D FlG. 69. ILLUSTRATING CALCULATION OF OVERHAUL, Fig. 69 represents a cut and fill in profile. The distance AB is the limit of free haul. The materials taken from AO just make the fill OB and without charge for haul; but the haul for every cubic yard taken from AC and carried to the fill BD is subject EARTH- WORK. 517 to charge for the distance it is carried, less AB. It would be impossible to find the distance that each separate yard is carried, but we know from mechanics that the average distance for the entire number of yards is the distance between the centres of gravity of the cut AC, and of the fill BD, which is made from it. If, therefore, X and Y represent the centres of gravity, the actual average haul is the sum of the distances {AX -J- BY), and this (expressed in feet) multiplied by the number of cubic yards in the cut A C gives the product to which the price for haul applies. If a cut is divided and parts are carried in opposite directions, the calculation of each part terminates at the dividing line. If a portion of the material in AC is wasted, it must be deducted and the haul calculated on the remainder. The specified limit is sometimes made as low as 100 feet, some- times as high as 1000 feet. A limit of about 300 feet, however, is usually most convenient, as it includes the wheelbarrow work and a large part of the carting, while it protects the contractor on such long hauls as may occur. 674. Calculating the Amount of Earth-work. The quantity of excavation and embankment expressed in cubic yards is required to be known, in order to compare the amount of work to be done upon the different trial lines which may have been surveyed. For this purpose the method of averaging end areas is sufficiently exact; or if expedition is desired, the quantities may be taken from any of the many tables of quantities which for level cross-section are reliable. For other than level cross-section the tables will be in error, even with the use of the auxiliary formula given with them for the purpose of ascertaining the extra amounts to be added for irregular sections. The error in the quantities obtained by using the tables for irregular sections will be of no practical moment ; in fact, it will be more an advantage by allowing a leeway of about 3 or 4 per cent in excess. 675. After final location a more accurate calculation is required, for the reason that the contractors who usually perform the work are paid, not by the day, nor in the lump, but at a certain price per cubic yard, the exact determination of which is therefore required to ascertain their just dues. For this purpose the pris- moidal formula is the only one to use. It is as follows : To the sum 518 HIGHWAY CONSTRUCTION". of the end areas add four times the middle area. Multiply th& sum by one sixth of the length. Divide the product by 27. 676. Calculation of Half- widths and Areas. The boundaries of a piece of earth-work in general are as follows : (1) The base, or subgrade surface, which forms the bottom of a cutting or the top of an embankment. (2) The original surface of the ground, which forms the top of a cutting and the bottom of an embankment. (3) The sides, or slopes, which connect the base with the natural surface, and whose inclination is the steepest consistent with the permanent stability of the material. 677. Examples of Cross-sections. Figs. 70 to 76 represent examples of cross-sections of pieces of earth-work, in each of which DE is the base, AB the natural surface, and DA and EB are the slopes. In Fig. 70 the natural surface is horizontal; in Figs. 73, 74, 75, 76 it slopes sideways, being what is termed " side-long ground." Figs. 71, 72 represent forms that occasionally occur. Figs. 70 to 76 represent cuttings; to represent embankments it is only necessary to conceive them to be turned upside down. Figs. 75, 76 represent pieces of earth- work, of which one side, CEB, is in cutting called " side cutting " and the other, CD A, in embankment. The half -width of a piece of earth-work is the horizontal dis- tance measured at right angles from a given point in the centre- line of the base to one edge of the cutting or embankment ; and although it is called " half-width," it is very generally diif erent at opposite sides of that centre line. Each half -width consists of two parts : the real half-width of the base, which is fixed by the design of the work, arid the horizontal breadth of one slope, which is to be found by calculation or by drawing. In each of the figures 70 to 76, C represents a point in the centre-line, as marked on the ground; F, the point vertically above or below it in the centre-line of the base; DG and EH are vertical lines through the edges of the base; DF and FE are the half widths of the base. In Fig. 70, where the ground is level across, GA and EB are the widths of the slope, and GA and GB the half-widths of fcn-o earth-work. In Figs. 74, 75, and 76, where the ground slopes sideways, the EARTH -WORK. 519 EXAMPLES OP EARTH-WORK CROSS-SECTIONS. A 6 C H B Kg.76. 520 HIGHWAY CONSTRUCTION. vertical lines through D, F, and E are produced, if necessary, and are cut at right angles by horizontal lines, ALM and BNP, drawn through the edges of the earth-work. AL and BN are the widths of the slopes; and MA and PB are the half -widths of the earth-work. When the natural surface of the ground is rugged, the best method of determining the widths of the slopes is by measure- ment upon a series of cross-sections of the proposed work plotted to the same scale horizontally and vertically. 678. Calculation of Sectional Areas of Earth-work. The com- putation of the areas of a series of cross-sections of a piece of earth-work is necessary to ascertain its volume or cubical quan- tity. If the ground is rugged, it may be necessary to find the area of each cross-section by measurements made upon a drawing; but if the ground is nearly or exactly level across, or has nearly or exactly a uniform sidelong slope, the area of a given cross-section can be computed from the same data which serve to compute the width of the slopes. 679. Formulas for the Calculation of Areas. FT? Pig. 70. Area = ^f . (A B + DE). Figs. 71, 72, 73. Area = AB Fig. 74, Area = ^(cotan X - cotan F) 2 - DE\ K. (For values of JTsee Table LXIX.) (PB + FO)EH Fig. 75. Area of the larger triangle =- -- ^ -- (AM- OF).DQ Fig. 75. Area of the smaller triangle = - - - ' --- . Fig. 76. In this figure C and F coincide, that is, there is neither cut nor fill, the triangles are similar, and the area is expressed by the same formula given for Fig. 75. EARTH-AVOKK. The letters on Figs. 70 to 76 denote : L = angle of side slopes with horizon. X = angle of natural surface with horizon. S = ratio of slopes, usually H : 1. Y HB AB -DE S = cot L = CF AQ and HB = CF . S = CF . cot L. 2CF TABLE LXIX. VALUES OF K FOR DIFFERENT SLOPES. (G. L. MOLESWOBTH.) Angle of Values of K. Ground. X. Jtol. frtol. Jtol. 1 tol. H to 1. 10 .0922 .0967 .1016 .107 .1199 12 .1123 .119 .1265 .1351 .1562 14 .1329 .1424 .1533 .1661 .1992 16 .1543 .1672 .1794 .2008 .2512 18 .1766 .1937 .2145 .2407 .3164 20 .2 .2222 .25 .2857 .4009 22 .2252 .2538 .2907 .3389 .5128 24 .25 .2857 .3342 .4012 .6702 26 .2777 .3225 .3846 .4761 .909 28 .3067 .362 .4421 .5675 1.3123 30 .3373 .4058 .5091 .6830 2.1551 32 .3703 .4545 .5882 .8333 34 .4058 .5091 .6830 1.0373 36 .444 .5707 .7987 1.3297 38 .4854 .641 .9434 1.7857 40 .5307 .7225 1.131 2.6041 42 .5807 .8183 1.385 44 .6364 .9345 1.754 46 .6983 1.0729 2.315 48 .7692 1.25 50 .8488 1.475 Fig. 77 shows a profile and cross-sections of a piece of earth- work. The letters denote : = a zero point, or the point at which a cutting ends and an embankment begins. L = the distance between two parallel cross-sections. I = the distance from a cross-section to the zero point. 522 HIGHWAY CONSTRUCTION. EARTH-WORK. 523 TAB.LE LXX. (EARTH- WORK.) CONTENTS OF I-FOOT LENGTH IN CUBIC FEET. (For lengths of 100 feet move decimal two places.) J fa 4J Central Portion. Base in feet. Contents of Both Slopes. & 1 20 30 33 40 50 60 66 *:l i: 1 ,:l 1 : 1 H :1 2:1 3:1 I 1 20 30 33 40 50 60 66 .25 .75 . 1.5 2 3 j 2 40 60 66 80 100 120 132 1 2' 3 4 6 8 12 2 60 90 99 120 150 180 198 2.25 4. 6.75 9 13.5 18 27 3 4 80 120 132 160 200 240 264 4 8 12 16 24 32 48 4 5 100 150 165 200 250 300 330 6.25 12. 18.75 25 37.5 50 75 5 G 120 180 198 240 300 360 396 9 18 27 36 54 72 108 6 7 140 210 231 280 350 420 462 12.25 24. 36.75 49 73.5 98 147 7 8 160 240 264 320 400 480 528 16 32 48 64 96 128 192 8 9 180 270 297 360 450 540 594 20.25 40. 60.75 81 121.5 162 243 9 10 200 300 330 400 500 600 660 25 50 75 100 150 200 300 10 11 220 330 363 440 550 660 726 30.25 60. 90.75 121 181.5 242 363 11 240 360 396 480 600 720 792 36 72 108 144 216 288 432 12 13 260 390 i 429 520 650 780 858 42.25 84. 126.75 169 253.5 338 507 13 14 280 420 462 560 700 840 924 49 98 147 196 294 392 588 14 15 300 450 495 600 750 900 990 56.25 112. 168.75 225 337.5 450 675 15 16 320 480 528 640 800 960 1056 64 128 192 256 384 512 768 16 17 340 510 561 680' 850 1020 1122 72.25 144.5 216.75 289 433.5 578 867 17 18 360 540 594 720 900 1080 1188 81 162 243 324 486 648 972| 18 19 380 570 627 7601 950 1140 1254 90.25 180.5 270.75 361 541.5 722 1083 19 20 400 600 660 8001 1000 1200 1320 100 200 300 400 600 800 1200 20 21 420 630 693 840! 1050 1260 1386 110.25 220.5 330.75 441 661.5 882 1323 21 440 660 880| 1100 1452 121 242 363 484 726 968 1452 22 23 460 690J 759 920 1150 1380 1518 132.25 264.5 396.75 529 793.5 1058 1587 23 24 480 720 792 960 1200 1440 1584 144 288 432 576 864 1152 1728 24 25 500 750 825 1000 1250 1500 1650 156.25 312.5 468.75 625 937.5 1250 1875 25 | 26 520 780 858 1040 1300 1560 1716 169 338 507 676 1014 1352 2028 26 27 540 810 891 1080 1350 1620 1782 182.25 364.5 546.75 729 1093.5 1458 2187 27 28 560 8^0 924 1120 1400 1680 1848 196 392 588 784 1176 1568 2352 28 29 580 870 957 1160 1450 1740 1914 210.25 420.5 630.75 841 1261.5 1682 2523 29 30 600 900 990 1200 1500 1800 1980 225 450 675 900 1350 1800 2700 30 31 620 930 1023 1240 1550 1860 2046 240.25 480.5 720.75 961 1441.5 1922 2883 31 640 960 1056 1280J 1600 1920 2112 256 512 768 1024 1536 2048 3072 32 33 660 990 1089 1320 1650 1980 2178 272.25 544.5 816.75 1089 1633.5 2178 3267 33 34 680 1020 1122 1360 1700 2040 2244 289 578 867 1156 1734 2312 3468 34 35 700 1050 1155 1400 1750 2100 2310 306.25 612.5 918.75 1225 1837.5 2450 3675 35 36 720 1080 1188 1440 1800 2160 2376 324 648 972 1296 1944 2592 3888 36 37 740 1110 1221 1480 1850 2220 2442 342.25 684.5 1026.75 1369 2053.5 2738 4107 37 3S 760 1140 1254 1520 1900 2280 2508 361 722 1083 1444 2166 2888 4332 38 39 780 1170 1287 1560 1950 2340 2574 380.25 760.5 1140.75 1521 2281.5 3042 4563 39 40 800 1200 1320 1600 20001 2400 2649 400 800 1200 1600 2400 3200 4800 40 41 820 1230 1353 1640 2050 2460 2706 420.25 840.5 1260.75 1681 2521.5 3362 5043 41 840 1260 1386 1680 2100 2520 2772 441 882 1323 1764 2646 3528 5292 42 43 860 1290 1419 1720 21501 2580 2838 462.25 924.5 1386.75 1849 2773.5 3698 5547 43 44 880 1320 1452 1760 2200 2640 2904 484 968 1452 1936 2904 3872 5808 44 45 900 1350 1485 1800 2250 2700 2970 506.25 1012.5 1518.75 2025 3037.5 4050 6075 45 4li 920 1380 1518 1840 2300 2760 3036 529 1058 1587 2116 3174 4232 6348 46 47 940 1410: 1551 1880 2350 2820 3102 552.25 1104.5 1656.75 2209 3313.5 4418 6627 47 48 960 14^0: 1584 1920 2400 2880 3168 576 1152 1728 2304 3456 4608 6912 48 49 980 14TO 1617 1960 2450 2940 3234 600.25 1200.5 1800.75 2401 3601.5 4802 7203 49 50 1000 1500 1650 2000 2500 3000 3300 625 1250 1875 2500 3750 5000 7500 50 524 HIGHWAY CONSTRUCTION. The cubical contents between sections 5 and 6 and between sections 7 and 8 may be ascertained by the prismoidal formula; the contents between the zero point and the continuous cross-sections by the following formula : (fVTfl O 7) Tji\ - o" --- 1 -- o"~) 680. Zero Point. The zero point should be found on the ground. If this has not been done, it may be ascertained as follows: Take the cut and the fill at the stations between which it lies ; then, the sum of the cut and the fill : the cut : : the distance from the cut to the fill : the distance from the cut to the zero point. 681. Earth-work Table. Table LXX contains the contents in cubic feet for each foot in length of the central portion and side slopes of embankments or cuttings. To use table, note the con- tents for the central portion due to the required base and depth, add contents given for the required slope and depth, and multiply- by the length; the product divided by 27 gives cubic yards. CHAPTER XIV. DRAINAGE-CULVERTS. 682. Drainage. The drainage of roadways is of two Kinds, viz., surface and subsurface. The first provides for the speedy removal of all water falling on the surface of the pavement; the second provides for the removal of the underground water found in the body of the road, a thorough removal of which is of the utmost importance and essential to the life of the road-covering. A road- covering placed on a wet undrained bottom will be destroyed by both water and frost, and will always be troublesome and expen- sive to maintain; perfect subsoil drainage is a necessity and will be found economical in the end even if it requires considerable expense to secure it. 683. The methods employed for securing the subsoil drainage must be varied according to the character of the natural soil, each kind of soil requiring different treatment. 684. The natural soils may be divided into the following classes: silicious, argillaceous, and calcareous; rock, swamps, and morasses. 685. The silicious and calcareous soils, the sandy loams and rock present no great difficulty in securing a dry and solid founda- tion. Ordinarily they are not retentive of water and therefore require no underdrains; ditches on each side of the road will gener- ally be found sufficient. 686. The argillaceous soils and softer marls require more care: they retain water and are difficult to compact, except at the surface; and they are very unstable under the action of water and frost. The drainage of these soils may be effected by transverse drains and deep side ditches of ample width. The transverse drains are placed across the road, not at right angles but in the form of an in- 525 526 HIGHWAY CONSTRUCTION. verted V (y\), with the point directed up-hill; the depth at the angle point should not be less than 18 inches below the subgrade surface, and each branch should descend from the apex to the side ditches with a fall of not less than 1 inch in 5 feet. The distance apart of these drains will depend upon the wetness of the soil; in the case of very wet soil they should be at intervals of 15 feet, which may be increased to 25 feet as the ground becomes drier and firmer. 687. The transverse drains are best formed of unglazed circular tile of a diameter not less than 3 inches, jointed with loose collars. The tiles are made from terra-cotta or burnt clay, are porous, and far superior to all other kinds of drains. They carry off' the water with greater ease, rarely if ever get choked up, and only require a slight inclination to keep the water moving through them. The tiles are made in a variety of forms, as horseshoe sole, double sole, and round, the name being derived from the shape of their cross-sections. Round tile is superior to all other forms. The inside diameter of these tiles varies from 1^ to G inches, but they are manufactured 'as large as 24 inches. Pieces of the larger pipe serve as collars for the smaller sizes. They are made in lengths of 12, 14, and 24 inches, and in thickness of shell from $ of an inch to 1 inch. The collar which encircles the joint of the small tile allows a large opening, and at the same time prevents sand and silt from entering the drain. Perishable material should not be used for jointing. When laid in the ditch they should be held in place by small stones. Connections should be made by proper Y-branches. The outlets may be formed by building a dwarf wall of brick or stone, whichever is the cheapest or most convenient in the locality. The outlet should be covered with an iron grating to prevent vermin entering the drain-pipes, building nests and thus choking up the water-way. (See Fig. 82.) Silt-basins should be constructed at all junctions and wherever else they may be considered necessary; they may be made from a single 6-inch pipe (Fig. 83), or constructed of brick masonry as shown in Fig. 84. The trenches for the tiles should be excavated at least 3 feet wide on top and 12 inches on the bottom. After the tiles are laid the trenches must be filled to subgrade level with round field or DRAINAGE CULVERTS. 527 cobble stones; stones with angular edges are unsuitable for this purpose. Fine gravel, sand, or soil should not be placed over the drains. Bricks and flat stones may be substituted for the tiles, and the trenches filled as above stated. Figs. 78 to 81 show different forms of underdrains. 688. Cost of Drains per Foot. The cost (including labor and materials) of different drains may be taken as follows : 2-inch round tile $0.19 to $0.28 per foot 3- " " " 0.22 " 0.35 " " 4-" " 0.25" 040" " Triangular brick 0.22" 0.35" " Brick, 4 inches by 4 inches 0.40" 0.95" " Stone ;... 0.35" 0.50" " Drainage with tiles will cost less than with any other material and will be more satisfactory in the end. 689. As tile-drains are more liable to injury from frost than those of either brick or stone, their ends at the side ditches should not in very cold climates be exposed directly to the weather, but may terminate in blind drains, or a few lengths of vitrified clay- pipe reaching under the road a distance of about 3 to 4 feet from the inner slope of the ditch. 690. Another method of draining the road-bed offering security from frost is by one or more rows of longitudinal drains. These drains are placed at equal distances from the side ditches and from each other, and discharge into cross-drains placed from 250 to 300 feet apart, more or less, depending on the contour of the ground. The cross-drains into which they discharge should be of ample dimensions. On these longitudinal lines of tiles the introduction of catch-basins at intervals of 50 feet will facilitate the removal of the water. These catch basins may be excavated 3 or more feet square and as deep as the tiles are laid. After the tiles are laid the pit is filled with gravel and small stones. 690a. The drain used by the Massachusetts Highway Com- mission is vitrified clay pipe laid with open joints in a trench 3 to 3^ feet deep and 12 to 16 inches wide. The pipe is placed on a 2-inch layer of fine gravel free from sand or dirt, and is sur- rounded and covered to a depth of 6 inches by the same kind of gravel. The remaining part of the trench is filled with stone from 1 to 3 inches in diameter. Such a pipe is found to remove 528 HIGHWAY CONSTRUCTION. the water quickly to an outlet; the fine gravel allows a free flow of water, and at the same time prevents the passage of silt into TYPES OF DRAINS. FIG, 78, BLIND DRAIN, FIG, 79, POLE DRAIN. FIG, 80. STONE DRAIN.. FIG. 81. -TILE DRAIN, FIG. 83. SILT-BASIN. FIG. 82. OUTLET. FIG. 84. SILT-BASIN, the pipe; the removal of sand or dirt from the fine gravel sur- rounding the pipe removes the possibility of its entering the pipe;. DRAINAGE CULVERTS. and the coarse stone in the upper part of the trench intercepts the ground- water in its flow toward the subgrade. These drains are placed on either or both sides, as the contour of the ground requires. 691. Fall of Drains. It is a mistake to give too much fall to small drains, the only effect of which is to produce such a current through them as will wash away or undermine the ground around them, and ultimately cause their own destruction. When a drain is once closed by any obstruction no amount of fall which could be given it will again clear the passage. A drain with a considerable current through it is much more likely to be stopped from foreign matter carried into it, which a less rapid stream could not have. transported. A fall of 1 inch in 5 feet will generally be sufficient, and 1 inch; in 30 inches should never be exceeded. 692. Side Ditches are provided to carry away the subsoil-water from the base of the road, and the rain-water which falls upon its' surface; to do this speedily they must have capacity and inclina- tion proportionate to the amount of wa,ter reaching them. The width of the bed should not be less than 18 inches; the depth will. vary with circumstances, but should be such that the water-surface; shall not reach the subgrade, but remain at least 12 inches below the crown of the road. The sides should slope at least 1 to 1. The longitudinal inclination of the ditch follows the configura- tion of the general topography, that is, the lines of natural drain- age. When the latter has to be aided artificially, grades from 1 in 500 to 1 in 800 will usually answer. In absorbing soil less fall is sufficient, and in certain cases level ditches are permissible. The slopes of the ditches must be pro- tected where the grade is considerable. This can be accomplished by sod revetments, riprapping, or paving. These ditches may be placed either on the road or land side of the fence. In localities where open ditches are undesirable they may be constructed as shown in Figs. 87 to 89, and may be formed of stone or tile pipe, according to the availability of either material. If for any reason two cannot be built, build one; it is better than none. Springs found in the road-bed should be tapped and led into the side ditches. 693. Drainage of the Surface. The drainage of the roadway surface depends upon the preservation of the cross-section, with. regular and uninterrupted fall to the sides, without hollows or ruts in which water can lie, and also upon the longitudinal fall of the, 530 HIGHWAY CONSTRUCTION. road. If this is not sufficient the road becomes flooded during heavy rain-storms and melting snow, and is considerably damaged. The removal of the surface-water from country roads may be effected by the side ditches, into which, when there are no sidewalks, the water flows directly. When there are sidewalks, gutters are formed between the roadway and footpath, as shown in Figs. 85 to 90, and the water is conducted from these gutters into the side ditches by tile-pipes laid under the walk at intervals of about 50 feet. The entrance to these pipes should be protected against washing by a rough stone paving. In the case of covered ditches tinder the footpath, the water must be led into them by first passing through a catch-basin. These are small masonry vaults covered with iron gratings to prevent the ingress of stones, leaves, etc. Connection from the catch-basin to the ditch is made by a tile-pipe about 6 inches in diameter. The mouth of this pipe is placed a few feet above the bottom of the catch-basin, and the space below it acts as a depository for the silt carried by the water, and is cleaned out periodically. The catch-basins may be placed from 200 to 300 feet apart. They should be made of dimensions sufficient to con- vey the amount of water which is liable to flow into them during heavy and continuous rain. 694. If on inclines the velocity of the water is greater than the nature of the soil will withstand, the gutters should be roughly paved. In all cases the slope adjoining the foot-path should be covered with sod. A velocity of 30 feet a minute will not distuib clay with sanjf and stone. 40 feet per minute will move coarse sand. 60 feet a minute will move gravel. 120 feet a minute will move round pebbles 1 inch in diameter, and 180 feet a minute will move angular stones If inches in diameter. The scour in the gutters on inclines may be prevented by small weirs of stones or fascines constructed by the roadmen at a nominal cost. At junctions and cross-roads the gutters and side ditches require careful arrangement so that the water from one road may not be thrown upon another; cross-drains and culverts will be re- quired at such places. 695. Water-breaks to turn the surface-drainage into the side ditches should not be constructed on improved roads. They in- crease the grade and are an impediment to convenient and easy travel. Where it is necessary that water should cross the road a culvert should be built. DRAINAGE CULVERTS. 531 CROSS-SECTIONS OF ROADS, SHOWING METHODS OF DRAINING AND DIVISION INTO WHEELWAY, WALKS. ETC. Fig.87 696. On side hill or mountain roads catch-water ditches should be cut on the mountain side above the road, to cut off and convey the drainage of the ground above them to the neighboring ravines. The size of these ditches will be determined by the amount of rainfall, extent of drainage from the mountain which they inter- cept, and by the distances of the ravine water-courses on each side.. The inner road-gutter should be of ample dimensions to carry '532 HIGHWAY CONSTRUCTION. off the water reaching it ; when in soil it should be roughly paved with stone. Where paving is not absolutely necessary, but it is desirable to arrest the scouring action of running water during heavy rains, stone weirs may be erected across the gutter at conveni- ent intervals. The outer gutter need not be more than 12 inches wide and 9 inches deep. The gutter is formed by a depression in the surface of the road close to the parapet or revetted earthen protection-mound. The drainage which falls into this gutter is to be led off through the parapet, or other road-side protection at fre- quent intervals- The guard-stones on the outer side of the road ;are to be placed in and across this gutter, just below the drainage- holes, so as to turn the current of the drainage into these holes or channels. On straight reaches with parapet protection, drainage- lioles with guard-stones should be placed every 20 feet apart. "Where earthen mounds are used and it may not be convenient to have the drainage-holes or channels every 20 feet, the guard- stones are to be placed in advance of the gutter to allow the drain- age to pass behind them. This drainage is either to be run off at the cross-drainage of the road, or to be turned off as before by a ; guard-stone set across the gutter. At re-entering turns, where the outer side of the road requires particular protection, guard-stones should be placed every 4 feet. As all re-entering turns should be protected by parapets, the drainage-holes through them may be formed as close together as desired. 697. Culverts. Culverts are necessary for carrying under a road the streams it crosses, and also for conveying the surface- water collected in the side ditches from the upper side to that side on which the natural water-courses lie. 698. Especial care is required to provide an ample way for the water to be passed. If the culvert is too small, it is liable to cause a washout, entailing interruption of traffic and cost of repairs, and possibly may cause accidents that will require the payment of large sums for damages. On the other hand, if the culvert is made un- necessarily large, the cost of construction is needlessly increased. Any one can make a culvert large enough; but it is the province of the engineer to design one of sufficient but not extravagant size. 699. The area of water-way required depends (I) upon the rate of rainfall; (2) the kind and condition of the soil; (3) the oharacter and inclination of the surface; (4) the condition and in- clination of the bed of the stream ; (5) the shape of the area to be DRAINAGE CULVERTS. 533 drained, and the position of the branches of the stream ; (6) the form of the mouth and the inclination of the bed of the culvert ; STH I (0 u u tr fe CO (T CD ID co 6 Fig. 96b. DOUBLE PIPE CULVERT. bulkhead, although it is often omitted. A parapet wall of rubble masonry or brick-work laid in cement is best (see Fig. 93). The foundation of the bulkhead should be deep enough not to be dis- turbed by frost. In constructing the end wall, it is well to increase tho fall near the outlet to allow for a possible settlement of the in- terior sections. When stone and brick abutments are too expensive, a fair substitute can be made by setting posts in the ground and spiking plank on, as shown in Fig. 95. When planks are used, it is 540 HIGHWAY CONSTRUCTION. best to set them with considerable inclination towards the roadbed to prevent their being crowded outward by the pressure of the Fig. 96c. TRIPLE PIPE CULVERT. BROK STONES OR BRICK Fig. 96d. SECTION OF PIPE CULVERT. embankment. The upper end of the culvert should be so protected that the water will not readily find its way along the outside DKAINAGE CULVERTS. 541 of the pipes, in case the mouth of the culvert should become submerged. When the capacity of one pipe is not sufficient, two or more may be laid side by side as shown in Figs. 96a to 96c. Although two small pipes do not have as much discharging capacity as a sin- gle large one of equal cross-section, yet there is an advantage in laying two small ones side by side, since the water need not rise so high to utilize the full capacity of the two pipes as would be neces- sary to discharge itself through a single one of larger size. 707. Cost. Price of earthenware and cement pipe vary greatly with the conditions of trade, and with competition and freight. Current (1892) prices, subject from 40 to 65 per cent discount for culvert-pipe in car-load lots, f. o. b. at the factory, are about as follows : TABLE LXXI. COST AND WEIGHT OF VITRIFIED CULVERT-PIPE. Inside Diameter. Inches. Price per foot. Cents. Area. Square feet. Weight per foot. Pounds. Number of feet in Car-load of 24,000 Ibs. 12 85 .78 48 500 15 125 1.23 67 358 18 170 1.76 84 286 20 225 2.18 99 242 24 325 3.14 140 172 TABLE LXXII. COST AND WEIGHT OF PORTLAND CEMENT-PIPE. Inside Diameter. Inches. Price per foot. Cents. Area. Square feet. Weight per foot. Pounds. Number of feet in Car-load of 24,000 Ibs. 12 85 .78 57 450 15 125 1.23 77 320 18 178 1.76 110 230 20 225 2.18 135 180 24 325 3.14 165 150 708. Iron Pipe-culverts. During recent years iron pipe has been used for culverts on many prominent railroads, and may be used on roads in sections where other materials are unavailable. 542 HIGHWAY CONSTRUCTION. In constructing a culvert with cast-iron pipe the points requir- ing particular attention are (1) tamping the soil tightly around the pipe to prevent the water from forming a channel along the outside, and (2) protecting the ends by suitable head walls and, when neces- sary laying riprap at the lower end. The amount of masonry re- quired for the end walls depends upon the relative width of the embankment and the number of sections of pipe used. For ex- ample, if the embankment is, say, 40 feet wide at the base, the culvert may consist of three 12-foot lengths of pipe and a light end wall near the toe of the bank; but if the embankment is, say, 32 feet wide, the culvert may consist of two 12-foot lengths of pipe and a comparatively heavy end wall well back from the toe of the bank. The smaller sizes of pipe usually come in 12-foot lengths, but sometimes a few 6-foot lengths are included for use in adjust- ing the length of the culvert to the width of the bank. The larger sizes are generally 6 feet long. 709. Cost. Prices of cast-iron pipe vary greatly with com- petition and the conditions of trade. Table LXXIII shows current prices (1892), subject to commercial discount: TABLE LXXIII. DIMENSIONS, WEIGHT, AND PRICES 05 IRON PIPE. Inside Diameter. Thickness. Weight per foot. Price per foot. 12 inches & inch 60 pounds 96 cents 16 86 140 20 118 188 24 175 280 30 | 240 384 36 1 320 512 42 400 640 48 1 510 616 710. The approximate relative cost of the different forms of culvert per lineal foot for each square foot of waterway is as follows : Rubble 40 cents Earthenware or cement pipe 30 " Iron pipe 46 " 711. Stone Box-culverts. The simplest form of stone culvert is what is known as the box-culvert. It consists of two side walls, DRAINAGE CULVERTS. 543 EXAMPLES OF BOX-CULVERTS. r~ \ EDDDH3ZEE VmW99 1 FIG, 97. END ELEVATION, D FIG, 99. PLAN, FIG, 98. SECTION AB. FIG. 1 OO.-SECTION CD, FIG, 101. SECTION OF CULVERT ON A HILLSIDE, 544 HIGHWAY CONSTRUCTION. which may be built of stone laid dry or in mortar, and a covering of flags. Where large flat stones can readily be procured it forms a very economical structure. Under high embankments the thick- ness of the covering-stone must be increased. Figs. 97 to 101 show the form of this class of culverts and the dimensions given in Table LXXIV will serve as an approximate guide for general use. TABLE LXXIV. DIMENSIONS FOR BOX-CULVERTS. Area. Opening. Side Wall. Depth of Cover. Length of Cover. 4 feet 2' X 2' 2' X 2' 12 inches 5 feet 9 " 3X3 3 X 2* 16 " 6 " 16 " 4X4 4x3 20 " 7 " 25 " 5X5 5 X 3i 22 " 8 " 36 " 6X6 6X4 24 " 9 " 712. Arch-culverts. The form of an arch may be the semi- circle, the segment, or a compound formed of a number of circular curves of different radii. Full-centre arches or entire semicircles offer the advantages of simplicity of form, great strength, and small lateral thrust; but if the -span is large they require a correspond- ingly great rise, which is often objectionable. The flat or segmental arch enables us to reduce the rise, but it throws a great lateral strain on the abutments. The compound curve gives, when prop- erly proportioned, a strong arch, with a moderate lateral action, is easily adjustable to different ratios between the span and the rise, and is unsurpassed in its general appearance. In striking the com- pound curve, the following conditions are to be observed: the tangents at the springing must be vertical, the tangent at the crown horizontal, and the number of centres must be uneven. 713. The depth of the arch-stone, or thickness of voussoir, de- pends upon the form and size of the arch, the character of the masonry, and the quality of the stone. The following table gives the depths for semicircular arches, the second column being foi hammer-dressed beds, the third for beds roughly dressed with the chisel, and the fourth for brick masonry. DRAINAGE CULVERTS. 545 EXAMPLE OF ARCH-CULVERTS. FIG, 102. SECTIONAL ELEVATION, h, : c FIG. 1 04. SECTION AB, FIG. 1 03,-PLAN, FIG, 105, SECTION CD, 546 HIGHWAY CONSTRUCTION. TABLE LXXV. Thickness of Arch in inches. 01 >an 111 tccL. First-class Masonry. Second-class Masonry. Brick Masonry. 6 12 15 12 8 13 16 16 10 14 17 20 12 15 19 20 14 16 20 24 16 17 21 24 18 18 23 24 20 19 24 24 25 20* 25 28 30 21 26 28 35 22 28 28 40 23 29 32 45 1 24 30 32 50 25 31 32 Professor Eankine remarks that the precise determination of the depth of the keystone of an arch would be an almost imprac- ticable problem from its complexity, and that the best course in practice is to assume a depth for the keystone according to an empirical rule founded upon the dimensions of good existing ex- amples of bridges. For such a rule he gives the following : Depth in feet = |/(.12 radius at crown) for a single arch. Depth in feet = 4/(.17 radius at crown) for an arch of a series. Mr. Trautwine gives the following rule : For first-class cut stone of hard material take 0.36 of the square root of the radius of the crown ; for second-class work, .40 of the square root ; and for brick or rubble arches, 0.45 of the square root. The results by the latter are slightly in excess of those by Professor Kankine's formula. 714. Thickness of Abutments. Numerous rules have been given for obtaining the thickness of the abutments for arches. The most elaborate of these are from their form applied with difficulty to the cases commonly occurring in practice, and many of the elements entering into the solution of the problem are quite indeterminate, de- pending as they do upon the character of the masonry and upon the workmanship. In place of rules, therefore, we present merely an empirical table, embracing the results of a considerable degree of practice. DRAINAGE CULVERTS. EXAMPLE OF ARCH-CULVERTS. 547 FIG. 106.-END ELEVATION. FA FIG. 108.-SECTION AB. 548 HIGHWAY CONSTRUCTION. Table LXXVI gives the minimum thickness of abutments for arches of 120 degrees where the depth of crown does not exceed 3 feet. Calculated from the formula 2H' in which D = depth or thickness of crown in feet; H = height of abutment to springing in feet; R = radius of arch at crown in feet ; T = thickness of abutment in feet. TABLE LXXVI. MINIMUM THICKNESS OF ABUTMENTS FOR ARCHES OF 120 DEGREES WHERE THE DEPTH OF CROWN DOES NOT EXCEED 3 FEET. Height of Abutment to Springing, in feet. Arch. 5 7.5 10 20 30 8 feet 3.7 4.2 4.3 4.6- 4.7 9 3.9 4.4 4.6 4.9 5.0 10 4.2 4.6 4.8 5.1 5.2 12 4.5 4.7 5.2 5.6 5.7 14 4.7 5.2 5.5 6.0 6.1 16 4.9 5.5 5.8, 6.4 6.5 18 5.1 5.8 6.1 6.7 6.9 20 5.3 6.0 6.4 7.1 7.2 22 5.5 6.2 6.6 7.3 7.6 24 5.6 ' 6.4 6.9 7.6 7.9 30 6.0 7.0 7.5 8.4 8.8 40 6.5 7.7 8.4 9.6 10.0 50 6.9 8.2 9.1 10.5 11.1 60 7.2 8.7 9.7 11.4 12.0 70 7.4 9.1 10.2 11.8 12.9 80 7.6 9.4 10.6 12.8 13.6 90 7.8 9.7 11.0 13.4 14.3 100 7.9 10.0 11.4 14.0 15.0 NOTE. The thickness of abutment for a semicircular arch may be taken from the above table by considering it as approximately equal to that for an arch of 120 degrees having the same radius of curvature; therefore by divid- ing the span of the semicircular arch by 1.155 it will give the span of the 120- degree arch requiring the same thickness of abutment. DBA INAGE CULVEETS. 549 TABLE LXXYII. DIMENSIONS, WEIGHT, AND PRICES OF DRAIN-TILE. Inside Diameter. Inches. Area in inches. Weight per foot. Price per 1000 feet.* Curves and Reducers. Each.* No. Feet to Carload. 2 3.141 3 $15.00 $0.20 8000 3 7.068 4| 25.00 0.20 6000 4 12.566 6| 45.00 0.25 4000 5 19.625 9 , 75.00 0.30 3000 6 28.274 12 100.00 0.40 2200 7 38.484 15 110.00 0.50 2000 8 50.265 22 150.00 70 1250 9 63.617 26 200.00 0.75 1000 10 78 539 33 250.00 1.00 850 12 113.09 44 325.00 1.25 750 15 176.71 60 450.00 1 50 500 18 254.46 92 700.00 2.25 350 20 314.16 106 1000.00 3.00 250 21 345.00 110 1250.00 4.00 225 24 452.39 150 1625.00 5.00 200 * Subject to discount. TABLE LXXVIII. DISCHARGING CAPACITY OF CIRCULAR PIPES IN CUBIC FEET PER MINUTE. Diameter f\f Inclination. Inches per 100 feet. or Pipe. 3 6 9 12 24 inches cu. ft. cu. ft. cu. ft. cu. ft. cu. ft. 2 1.71 2.54 3.07 3.61 4.95 3 3.07 4.68 5.34 6.16 8.56 4 6.28 8.82 10.82 12.43 17.51 8 35.42 30.01 61.49 70.72 100.26 9 47.46 67.24 82.48 95.05 161.23 12 97.59 138.10 170.18 196.25 277.54 15 171.37 243.04 297.32 329.41 483.55 18 270.32 383.69 468.98 540.77 749.18 20 327.54 461.23 558.82 649.73 914.43 24 555.08 784.89 962.83 1176.87 1570.05 714a. Concrete Masonry. The cheapness and adaptability of concrete, both plain and reinforced with steel, has within recent years led to its extensive use as a substitute for stone and brick masonry in the construction of culverts, arch bridges, and retain- ing-walls. The methods and rules for designing concrete structures are given in various treatises. Vide Taylor and Thompson's " Con- crete, Plain and Reinforced" (John Wiley & Sons, New York). CHAPTER XV. BRIDGES, RETAINING. WALLS, PROTECTION WORKS, TUNNELS, FENCING. 715. Bridges. The construction of bridges is an important subject, and should not be attempted without the professional ser- vices of. a civil engineer. Neglect of this precaution, and an inad- equate conception by the people of the risks to their own and other persons' lives produced by faulty bridge design, are causes to which may be attributed many of the numerous failures of highway bridges annually recorded. As the subject is so extensive, but a few general remarks will be made in this volume. No one bridge is adapted to every situation; each one must be designed to sustain the amount and character of the load to which it will be subjected. 716. All bridges should be proportioned GO sustain the strains produced by the following loads : (1) The dead load, which is the weight of the structure itself, and in certain cases some extraneous loading. The dead load is taken as uniformly distributed over the bridge. (2) The live load. The live load on a bridge is the moving load passing over it. In calculating the dimensions of the several parts forming the superstructure of a bridge, the heaviest load which is likely to traverse it should be taken. Liiye loads are of varied character; they comprise the weight of loaded vehicles passing either singly or in continuous strings, por- table engineSj agricultural machinery, steam road-rollers, and the weight of a crowd of people densely packed. (3) The wind-pressure, including both direct and indirect effects. (4) Variations of temperature. Valuable information on the subject of highway bridges is to be 550 BRIDGES, RETAINING-WALLS, TUNNELS, ETC. 551 found in the specifications for highway bridges of iron and steel by J. A. Waddell. 717. Nothing improves the appearance and attractiveness of a road so much as a handsome bridge. And it need cost no more to construct than a homely, uncouth structure. 718. Materials for Bridges. Bridges may be either of stone, brick, wood, steel, iron, or iron and wood. For permanence and beauty, stone or stone and brick is preferable. Steel and iron make handsome bridges, but require more attention than stone. Wood is the least permanent, and cheapest in first cost. 719. Timber Bridges. In many localities timber is the only material available for bridges. Therefore a few directions for their construction may be useful. The simplest form of wooden bridge is that of plain stringers laid across the stream and covered with plank. The width of the openings which such beams span should not exceed 16 feet. For greater widths, supports in the form of piles may be introduced, thus dividing the long span into a number of shorter ones; but such supports are obstructions to the stream and liable to damage in time of freshets. It is, therefore, desirable to avoid their use. Other forms of support must therefore be devised for strengthening the beams. This may be effected by supports from below or above. Of supports from below, the sim- plest are shorter timbers (bolsters or corbels) placed under the main ones to which they are firmly bolted, and projecting about one third of the span. Still more effective are oblique braces or struts supporting the middle of the beam, and resting at their lower ends in shoulders formed in the abutments. Similar braces may be applied to the bolsters (Fig. 113); but as the span increases, these braces become so oblique as to lose much of their efficiency. A straining-piece is therefore interposed between them. Openings up to thirty-five feet may thus be spanned. For longer spans, the bolsters, braces, and straining-beams may be combined as in Fig. 114. The principle of this method may be extended to very wide openings. But in many cases supports from below may be objectionable, as exerting too much thrust against the abutments, and being liable to be carried away by freshets, etc. The beams must in such cases be strengthened by supports from above. 552 HIGHWAY CONSTRUCTION. TYPES OF TIMBER BRIDGES, Fig 109. Fig.110. Fig- 117. Fig. 118 Flg^.119. [ Fig- 116. HEAVY LINES WOOD, LIGHT LINES IRON, BKIDGES, RETAIIUNG-WALLS, TUNNELS, ETC. 553 The simplest form of such is shown in Fig. 115, in which the horizontal beam is supported by an upright " king-post" to which it is attached by an iron strap, or by the upright " king-post" being formed of two pieces bolted together, and enclosing the beam be- tween them. The king-post itself is supported by the oblique braces, or struts, which rest against notches in the horizontal beam. Since the king-post acts as a suspending tie, an iron rod may be advantageously substituted for it; the struts may be also stiffened by iron ties, binding them to the main timbers as in Fig. 116. For longer spans, a straining-beam may be introduced between the struts as in Fig. 121, in which the posts are represented as en- closing the beam. The diagrams of simple bridges, Figs. 125 to 132, and Tables LXXIX and LXXX give the spans for which they may be em- ployed and the dimensions of the several parts. Fig. 129 shows the iron washer used at the end of the beam. The latter should be at right angles to the direction of the rod. It is better to have two rods instead of one rod under each beam. This allows the rods to be outside of the beam, as shown in the figure, instead of requiring holes to be bored through it, thereby weakening it. Fig. 130 shows the shoe used at the foot of the post and which holds the rods in place. Figs. 131 and 132 show the same method of construction applied to bridges of greater width and span. Combination structures of wood and iron require constant watchfulness, to repair and replace damages arising from decay or defective material. Iron Bridges. The first cost of iron or steel bridges is greater than that of wood or combination structures ; but where economy of the public funds is desired, the first two materials are to be pre- ferred, because the annual cost of repairs to the wooden structure will in a very few years equal, if not greatly exceed, the additional sum required for the construction of the all-metal bridge. More- over, the metal structure will outlive two if not more timber ones. To ascertain the saving in favor of iron, see Chapter XXIV. 720. The substructures of bridges should be of masonry. Tim- ber should not be used if it can possibly be avoided. Such struc. 554 HIGHWAY CONSTRUCTION. Fig. 125. LONGITUDINAL SECTION, if M 1 M Fig. 126. TRANSVERSE SECTION, TABLE LXXIX. DIMENSIONS FOB, FIGS. 125 AND 126. Span. Feet. Girders. Inches. Floor-beams. Inches. Floor. Inches. Railing. Inches. 5 8X 10 6X6 4 3X4 10 10 X 14 < " 15 12 X 18 20 14 X 22 < Fig. 127. LONGITUDINAL SECTION. BRIDGES, RETAINING-WALLS, TUNNELS, ETC. 555 Fig. 128. TRANSVERSE SECTION. I Fig. 129. DETAIL OF WASHER. Fig. ISO. DETAIL OF SHOE. TABLE LXXX. DIMENSIONS FOR FIGS. 127 TO 182. Span. Girders. Diameter of Rods. Post. Feet. Inches. Inches. Inches. 15 12 X 15 1ft 3 X 12 20 12 X 18 m 3 X 12 25 14 X 18 2 3X 14 30 15 X 20 2& 4 X 15 Fig. 131. LONGITUDINAL SECTION. 556 HIGHWAY CONSTRUCTION tures are unsatisfactory owing to early decay caused by the destroy- ing action of air and water. For directions and specifications for the construction of iron Fig. 132. TRANSVERSE SECTION. and steel highway bridges the excellent specifications of Messrs. G-. Bouscaren, Theodore Cooper, Edwin Thacher, and J. A. Waddell may be. consulted. 721. Retaining-walls. Eetaining-walls are structures of stone laid dry or in mortar, and are employed under various forms to sup- port the sides of roads on hillsides, or places where land for the slopes is not obtainable (see Figs. 133 to 136). 722. Thickness of Walls. Retaining-walls require a certain thickness to enable them to resist being overthrown by the thrust of the material which they sustain. The amount of this thrust depends upon the height of the mass to be supported and upon the quality of the material. 723. Surcharged Walls. A retaining- wall is said to be sur- charged when the bank it retains slopes backwards to a higher level than the top of the wall ; the slope of the bank may be either equal to or less, but cannot be greater, than the angle of repose of the earth of the bank. 724. Proportions of Retaining-walls. In determining the pro- portions of retaining-walls experience, rather than theory, must be our guide. The proportions will depend upon the character of the material to be retained. If the material be stratified rock with in- BRIDGES, RETAINING-WALLS, TUNNELS, ETC. 557 terposed beds of clay, earth, or sand, and if the strata incline toward the wall, it may require to be of far greater thickness than T FIG. 133. FIG. 134. FIG. 135. FIG. 136. any ordinary retaining-wali ; because when the thin seams of earth become softened by infiltrating rain, they act as lubricants, like 558 HIGHWAY CONSTRUCTION. soap or tallow, to facilitate the sliding of the rock strata; and thus bring an enormous pressure against the wall. Or the rock may be set in motion by the action of frost on the clay seams. Even if there be no rock, still if the strata of soil dip toward the wall, there will always be danger of a similar result ; and additional pre- cautions must be adopted, especially when the strata reach to a much greater height than the wall. 725. Form of Retaining-walls. Retaining-walls are built of numerous forms of profile or cross-section, varying from the rect- angular to the triangular. A triangle is that figure which is theoretically the most economical; and the nearer that practical conditions will allow of its being conformed to the better. All other things being equal, the greater the face-batter the greater will be the stability of the wall; but considerations con- nected with the functions of the wall limit the full application of this condition, and walls are usually constructed with only a moderate batter on the face, the diminution towards the top being obtained by a back batter worked out in a series of offsets. Walls so designed contain no more material and present greater resist- ance to overturning than walls with vertical backs. 726. Dry stone retaining-walls are best suited for roads on ac- count of their self-draining properties and their cheapness. If these dry walls are properly filled in behind with stones and chips, they are, if well constructed, seldom injured or overthrown by pressure from behind. If the stone is stratified with a flat cleav- age, the construction of retaining and parapet walls is much facili- tated. If the stone has no natural cleavage, great care is necessary to obtain a proper bond. If walls built of such stone are of coursed rubble, care is required that the masons do not sacrifice the strength of the walls to the face appearance. The practice of building walls with square or rectangular-faced stones, tailing off behind, laid in rows, one course upon the other, the rear portions of the walls being of chips and rough stones, set anyhow, cannot be condemned too strongly. Such a construction, which is very common, has little transverse and no longitudinal strength. Little or no earth should be used for back filling if stone is available. Where earth filling is used, it should only be thrown in and left to settle itself; on no account should it be wetted and rammed. BRIDGES, RETAINING-WALLS, TUNNELS, ETC. 559 The foundation of retaining-walls should be particularly secure; the majority of failures which have occurred in such walls have been due to defective foundations. 727. Failure of Betaining-walls. Retaining-walls generally fail (1) by overturning or by sliding, or (2) by bulging out of the body of the masonry. Sliding may be prevented by inclining tha courses inward. An objection to this inclination of the joints in dry walls is that rain-water, falling on the battered face, is thereby carried inwards to the earth backing, which thus becomes soft and settles. This objection may be overcome by using mortar in the face-joints to the depth of a foot, or by making the face of the wall nearly vertical. 728. Protection of Retaining-walls. The top of the walls should be protected with a coping of large heavy stones laid as headers. Where springs occur behind or below the wall, they must be carried away by piping or otherwise got rid of. The back of the wall should be left as rough as possible, so as to increase the friction of the earth against it. 729. Weep-holes. In masonry walls, weep-holes must be left at frequent intervals, in very wet localities as close as 4 feet, so as to permit the free escape of any water which may find its way to the back of the wall. These holes should be about 2 inches wide and should be backed with some permeable material, such as gravel, broken stone, etc. 730. Formula for calculating Thickness of Retaining-walls. E = weight of earth-work per cubic yard. W= weight of wall. H= height of wall. T = thickness of wall at top. T= II X tabular number (Table LXXXI). 731. Surcharged Walls. In calculating the strength of sur- charged walls substitute Y for H, Y being the perpendicular at the end of a line, L = H measured along the slope to be retained (Fig. 136). Y = 1.71ZT in slopes of 1 : 1 ; = 1.5577 " " " 1| : 1; = 1.35 H " " "2:1; = 1.31# " " "3:1; = I.24H " " " 4 : 1. 560 HIGHWAY CONSTRUCTION". TABLE LXXXI. COEFFICIENTS FOR RETAINING- WALLS. E: W:: 4 :5 E: Wr.l :1 Batter of Wall Clay. Sand. Clay. Sand. Iin4 .083 .029 .115 .054 1 in 5 .122 .065 .155 .092 Iin6 .149 .092 .183 .118 1 in 8 .184 .125 .218 .153 1 in 12 .221 .160 .256 .189 Vertical .300 .239 .336 .267 732. Retaining-walls of dry stone should not be less than 3 feet thick at top, with a face of 1 in 4 and back perpendicular, the courses laid perpendicular to the face-batter. Weep-holes are unnecessary unless the walls are in very wet situations. Retaining-walls of masonry should be at least 2 feet thick at top, back perpendicular and face battered at the rate of 1 in 6. 733. On steep hillside or mountain roads retaining-walls should be built (1) At all re-entering curves. (2) At all culverts and bridges. (3) On the edge of precipitous places, where there is no room for a bank. (4) Where the bank slope and the ground slope are nearly or quite parallel to each other. (5) Where a bank would be of excessive length owing to the angle of the natural ground slope. (6) Where a wall would be cheaper than a bank. Retaining-walls on the edge of dangerous precipices, having to support great weight, should be built of masonry. All others may be of dry stone. 734. Protection of Roads. All roads should be protected, but hillside and mountain roads which are unprotected can only be classed as dangerous. Blocks of stone of not less than 2 to 3 feet in height, and set with not more than 3 feet between them, afford a fair protection on a mountain road not very precipitous BRIDGES, RETAI^ING-WALLS, TTONELS, ETC. 561 at itb outer edge, and there is an advantage attendant upon their use that no outer gutter is necessary, for the drainage passes over the bank in every direction, and after the first year or two but little damage occurs to the banks from this cause. 735. The proper amount of protection required for the danger- ous portions of a mountain road is best obtained by stone parapets a ad earthen mounds. Parapets should not be less than 3 feet o k eight and, if of masonry, 1| feet in thickness. If stone parapets be built dry, they should be at least 2 jeet in thickness, and the coping should be set in mortar ; otherwise they are too easily deranged, and cartmen halting on the road and desiring to block the wheels of their vehicles invariably resort to them for a stone for this purpose. Next in order of protection afforded by the \ise of stone may be mentioned the plan of placing large blocks of : uugh stone and boulders on the edge of the road and touching each other. If of good size and well set, considerable protection is afforded by this method, which is cheap. Dry stone parapet walls should never be employed if masonry walls can be afforded, and should on no account be used on precipitous curves. Parapets should be employed to protect all embankments of a road which have stone- wall revetments, and the outside of all cuttings in rock. They should also be built on each side of the road at all cross-drainage works, and should be adopted at all situations where stone is available from cuttings. Where the embankments are of earth, earthen mounds are to be preferred on the score of economy. These earthen mounds should not be less than 3 feet in height, and they are best formed, both for appearance and for their own preser- vation, by being ^revetted with dry stone inside. Earthen mounds constructed in this manner afford the most secure protection for traffic, as, if well rounded off on the outer side, they do not yield to any concussion, however violent. 736. Wooden railings should never be employed to protect dan- gerous places on a mountain road. They afford no real protection to the traffic, but only give a sense of protection to passing vehisha which do not come into collision with them, and show to unexcite 1 animals that the way is barred in that direction. 737. Besides the protection so necessary for the safety of the travelling public, the roads themselves require protection at their 562 HIGHWAY CONSTRUCTION. edges from passing vehicles. Cart-wheels, if not prevented from hugging the very edge of the road, and from slipping, either from design or accident, into the gutters, do great damage. Curb-stones ge.t forced out of their places, and if one be displaced, others soon follow, to the destruction of the road edge as well as of the gutters then -.selves. These become blocked with loose stones, and when rain falls greater destruction to the road ensues. It is necessary, therefore, to protect the edges of mountain roads where they are likely to be damaged by wheel traffic, which occurs chiefly on the inside of salient and outside of re-entering curves. 738. Guard-stones about 9 inches square and of sufficient length should be placed every 4 or 5 feet apart at the curbs, clear of the t FIG. 137. gutter, on the hill side of salient curves. The re-entering curves must also be protected on the inner curve, which is the outer side of the roadway, by means of similar guard-stones, which, however, in this situation are set up in the gutters themselves. 739. Eoads along the seashore, margin of rivers and lakes, may be constructed according to either of the methods shown in Figs. 137 to 139. In Fig. 137, two rows of piles, spaced about 10 feet centre to centre, are driven, one row along the toe of the slope and another along the crest of the slope, and capped with a 3-inch plank ; be- tween eacli pile and fastened thereto a 4 X 6 inch or heavier stringer is placed. On these stringers a layer of matched tongued and grooved plank 2 or 3 inches thick are laid and spiked. In Fig. 138 a bulkhead is formed as follows: a row of piles, spaced 6 feet centre to centre, is driven to a solid bearing and capped with a heavy stick of timber. To the piles waling-sticks are bolted, one immediately at the head, the other at or below the BRIDGES, RETAINING-WALLS, TUNNELS, ETC. 563 natural surface of the beach; on the land side of the waling-sticks matched sheet -piling is driven and spiked to the upper waling- stick. Anchor-piles are driven on the land side at such distance from the main piles as will form an angle of from 30 to 45 degrees. The main piles may be fastened to the anchor-piles by wrought- iron tie-rods, and bevelled cast-iron washers or timber n^ay be used FIG. 138. for the same purpose. A brace-stick of either round or square timber should be placed in the angle formed between the tie-rod and head of the anchor pile. The face of the main piles at high- water mark should be protected by a chafing-stick. Fender-piles may also be used if the water is navigable for large boats. FIG. 139. In Fig. 139 a masonry wall is shown, built on a timber plat- form. To this class of work the same rules apply as to retaining- walls. . 740. Tunnels. For highways, generally no tunnels can be al- lowed. They are too costly, and can only be employed under 564 HIGHWAY CONSTRUCTION. exceptional circumstances. If a tunnel would shorten the road by a length, the cost of which would equal, or nearly so, the extra cost of the road through the tunnel, the construction of the tunnel would be justified. The saving in tractive energy to the public using the road would, in most cases, be a saving too indirect to be imported into the calculation. 741. Fencing. Fences are usually built by the property-own- ers, but occasionally the road-builder is called upon to include fencing in his work; therefore the following few remarks may be useful. The requirements of a highway fence are somewhat different from those of ordinary farm fences. They must possess sufficient strength to withstand the rough usage to which they are frequently subjected. In northern climates they must be of such construc- tion as will offer the least obstacle to drifting snow and thus pre- vent as much as possible the blocking of the roadway. In all situations they must be durable and present a pleasing appearance. The materials employed for fences are earth in the form of mounds either with or without hedges, stone laid dry or in mortar, wood and metal in a variety of forms. The mound and ditch shown in Fig. 140 is much used in Europe. The material excavated from the ditch is thrown into ..:,. *^^ /r %J FlG. 140. DITCH AND MOUND FENCE. the mound and a quickset hedge planted along the top. After the lapse of some time this makes a good fence; but it requires in the interim a considerable amount of attention and repair. In the construction of fences which depend for their support upon posts set in the ground the same considerations should con- trol as in the construction of any other structure, viz., durability of the material, strength, and stability. BRIDGES, RETAINING WALLS, TUNNELS, ETC. 565 The materials employed for the posts or foundations of fences are stone blocks, wood and metal posts. Stone Posts. The durability of stone depends upon its chemi- cal constitution and physical structure. If the chemical constitu- ents are soluble in water the stone will be short-lived. If the phys- ical structure is porous the stone will absorb water and under the action of frost will be speedily split and disintegrated. The decay of stone is more rapid at the surface of the earth, where it is exposed to the frequent alternations of wet and dry conditions. The horizontal exposed surface should be cut to such form as will readily shed water. Holes bored for the reception of posts, etc., should be filled with lead, sulphur, etc.; if not they will act as receptacles for water, allowing it to penetrate the interior of the stone and thus hasten its destruction. Wood Posts. In the selecting of wood for posts the character of the soil should be considered, as it exercises considerable influ- ence upon the life of the wood. Sand and sandy loam are the least favorable to durability and clay the most favorable. The average life of the woods most commonly used is about as follows: white cedar twelve years; red cedar thirty years; white oak in sand five years, in clay fifteen years; osage orange thirty years; chestnut and tamarac twelve years. Bois d'arc or bodark is very durable; stockades built in Mexico and the Southern States over a hundred years ago are still in a good state of preservation. Well-seasoned timber will last much longer than that which is used while green. Posts obtained from trees which have been subjected to forest fires will absorb water and decay rapidly. Impregnating wood with creosote, chloride of zinc, etc., will about double the life. Metal posts are to be had in a variety of forms. At this time there are about thirty different styles on the market. All the different shapes in which metal can be wrought have been utilized with varying degrees of success. The life of a metal post depends upon the perfectness with which it is protected from rust. Several coatings are in use, such as coal-tar, asphaltum, graphite, etc., but their lasting qualities and the amount of protection they afford to the metal in the presence of the mineral salts in the earth is a subject of much controversy. The dimensions of posts must be sufficient to afford the required 566 HIGHWAY CONSTRUCTION. strength for wood 4 inches square or 5 inches in diameter will usually be sufficient; the length of the posts must be ample to allow of their being placed sufficiently deep in the ground to prevent heaving by frost. The spacing of the posts will depend upon the style of fence and ought not to exceed 16| feet centre to centre. In localities subject to heavy snowfalls the posts should be spaced at short distances so as to afford strength to support the load of snow. In stapling wire fences in such localities the staples may be driven slanting upwards, so that they will pull out under the weight; then after the snow is thawed the fence may be restapled and restored to its former good condition. Steel wire for fencing is to be had in a great variety of shapes, as plain, barbed, braided, woven, twisted, crimped, etc. The object of these various shapes is to prevent sagging and provide for the expansion and contraction of the metal under the variations of temperature. But these shapes are not always advantageous. Short bends or kinks, spirals, and coils are objectionable, as in the process of their formation the fibres of the wire are injured and the structure in which they are used is weak and liable to destruc- tion under sudden shock or strain. With regard to the quality of the wire used it should be "medium" steel; if too soft it will stretch under strain and consequently sag and become unsightly; if too "hard" it will be liable to break under sudden shock. The size of wire used is generally No. 12, and it should have a tensile strength of at least 800 pounds. The wire, in whatever form used, should be protected from oxidation. This is effectually secured by galvanizing, but the wire should not be galvanized before being twisted, barbed, etc., for much of the coating will be cracked and peeled off in the process of shaping, and hence the life of the wire will be lessened. 742. Height of Fences. The height of the fence will depend upon the purpose for which it is erected. If required to act as a barrier against cattle it should not be less than 4 ft. 9 in. ; if as a protection to travellers on the edge of banks, etc., 3 ft. 6 in. will be sufficient; and if for ornamental purpose of such height as may please the fancy. Barbed-wire fences are usually made four feet high; the number of wires used varies from two to five, which are generally spaced as follows : BRIDGES, RETAINING WALLS, TUNNELS, ETC. 567 SPACING OF BARBED WIRES. Inches above Ground. Two Wires. Three Wires. Four Wires. Five Wires. First wire 22 40 15 30 48 16 25 35 48 8 16 25 35 48 Third " Fourth " Fifth " 743. Cost of Fencing. The cost of a plain or barbed wire fence with wood posts and four strands of wire will be from $200 to $250 per mile; a four-strand wire fence with steel posts will cost about $350 per mile. The cost of woven and other forms of wire with metal posts will vary from $350 upwards per mile. Common board fence, posts set 8 feet apart, costs from $350 to $400 per mile. An estimate for a mile of barbed-wire fence would be about as follows: 350 posts, including braces, at 10 cents $35.00 1700 Ibs. barbed wire, at 6 cents . 102.00 40 Ibs. staples, at 6 cents 2.40 Labor , 36.86 Freight, tools, superintendence 3.07 Total $179.33 TABLE SHOWING THE AMOUNT OF No. 12 BARB WIRE REQUIRED TO FENCE VARIOUS DISTANCES. IRod. 10 Rods. 80 Rods or i Mile. 160 Rods or * Mile. 320 Rods or 1 Mile. One Wire Pounds. 1JL Pounds. 1(U Pounds. 85 Pounds. 170 Pounds. 340 Two Wires 2A 21 170 340 680 Three " 8A 81} 255 510 1020 Four " 4? 42 340 680 1360 Five " sX 52i 425 850 1700 "I? CHAPTER XVI. CITY STREETS. 744. THE first work requiring the skill of the engineer is to properly lay out town sites, especially with reference to the future requirements of a large city where any such possibility exists. Few if any of our large cities were so planned. The same principles to a limited extent are applicable to all towns or cities. The topo- graphy of the site should be carefully studied and the street lines adapted to it ; they should be laid out systematically with a view to convenience and comfort, also with reference to economy of con- struction, future sanitary improvements, grades, and drainage. 745. Arrangement of City Streets. Generally straight lines, with frequent and regular intersecting streets, is the best method of laying out streets, especially for business parts of a city. When there is some centrally located structure, such as court- house, city hall, market, or other prominent public building, it is very desirable to have several diagonal streets leading thereto. In the residence portions of cities, especially if on hilly ground, curves may replace straight lines with advantage by affording better grades at less cost of grading, and improving property by avoiding heavy embankments or cuttings. 746. The rectangular arrangement of streets as seen in New York and other cities is being found objectionable and a bar to convenient communication; it therefore becomes necessary to examine what other systems, if any, may be used, and determine their relative merits. The following investigation of this subject by Mr. Lewis M. Haupt, A.M.C.E., Professor of Civil Engineering, University of Pennsylvania, is very interesting, as showing what may be done in the way of opening diagonal streets : " The systems may be divided into two classes : 1st, regular, and 2d, irregular. The first class may be subdivided into rectangular, diagonal, and circular; the second into every possible kind of dis- 568 CITY STREETS. 569 tortion more or less intricate, according to the circumstances at- tending the growth of a city. The latter class is discarded as being unscientific, expensive, inconvenient, and poorly adapted to the requirements of a growing community. " As people move through a city in every conceivable direction, it will be impossible to provide the shortest lines for all; but the case may be met by supposing a greater or less number of centres or points d'appui, to and from which the currents of daily life flow and ebb. " With reference to the subdivision of the first class, it is evident that, the straight line being the shortest distance between two points, the chord will be shorter than its arc, and hence the circular system is defective. The rectangular compels a waste of distance and time, and the diagonal by itself becomes the rectangular, so that no single system fulfils all possible requirements. A combina- tion must therefore be resorted to, and that composed of right-line elements is both the simplest and most direct. A judicious ar- rangement of diagonal streets with the rectangular system will doubtless be found to meet more fully than any other the require- ments of the case ; but it is evident that if the streets be too wide or too numerous, the building areas will be correspondingly decreased and a certain proportion of people forced beyond given limits, thus increasing their distances. On the other hand, the diagonals will in general open new building lines with more than residences enough to provide for all the displaced inhabitants. "To illustrate the utility of such a combination, suppose a portion of a town or city to be laid out in the form of a square whose side is L feet long, and in which the blocks are I feet square and the streets w feet wide. " Let the diagonals of the large square be opened as thorough- fares, and note their effect. The blocks or small squares extend from the middle of one street to that of its parallel, or from the building line of one block to that of the next; hence the length of a side of such a square must be I -\-w (Fig. 141a). " The area of the small square, including the streets, multiplied by the number of such squares will give the area IJ 1 of that portion of the city, and the ratio of street to property area is the same for the small as for the large squares ; but the area of the small squares is (I -f w)* T + Zlw + w 2 , in which I* is the property or build- 570 HIGHWAY CONSTRUCTION. ing area, and 2lw -j- w* is the street area; the ratio being -- - , and the percentage of street to property area, 100. M (A) P n n DC C n ZlD n n D Q FIG. 141. ARRANGEMENT OF CITY STREETS. N For any rectangle with streets of unequal widths, the general formula would be be -4- ad - ac -100, (A 1 ) in which a and c are the sides of the rectangle and b and d the widths of the streets. If these quantities are equal, each to each CITY STREETS. 571 (A 1 ) becomes (A). The number (n ) of blocks in a given square whose area is L? will be U (B) " If now two diagonals, MN and PQ be introduced, it is evident that where they cross the rectangular streets no additional area is taken from the private property of the city, but they will cut out of L JL JL Area I n FIG. 141 a. FIG. 1416. each of the small squares which they cross an area whose length is -- , breadth w, and whose area for one block, Z 2 , is \ w (gee Fig. 1416). For n blocks the total building area consumed from U by both diagonals when n is even will be C V%1* 5-), and the percentage of the building area will be I r TT ) X 100, which reduces to w .8281 -w)WO, (C) the formula for diagonals when n is even. If n be odd, G becomes ^(2.8282)100 = 282.8^ ( C1 ) 572 HIGHWAY CONSTRUCTION. " If diagonals be opened, benefits will accrue both from the short- ening of distance and the additional frontage which will be fur- nished, while but a small proportion of the inhabitants will be displaced. The greatest economy in distance will be in passing from M to (Fig. 141), which by the square system is equal to L t L/V^- 1 4142 70 and by the diagonal LV%, the ratio being ^ = ' = , the numerator indicating the distance (in feet) by the diagonals, the .denominator by the squares. This gives a gain of 30 per cent, which is the greatest amount possible, and from which it diminishes to zero at P. " The total length of frontage on the streets in the square system is 4ln\ The diagonals give an additional length of 4w(4/2/ 2 w), and the percentage of increase is therefore In " The ratio of people displaced is the same as that of the area consumed by diagonals to the entire area U. " To determine these values for any particular case, and so dis- cover whether or not the diagonals will be beneficial, let I = 500 feet, w = 50 feet, and n = 10. " Formula (A) gives 21 as the percentage of large or small squares consumed by streets in the rectangular system. " Formula (C) gives only 2.82 per cent of additional building area consumed by diagonals. " Formula (D) gives 13 per cent as the increase in frontage due to diagonals, and it has been shown that the saving of distance varies from 30 per cent to nothing. " The number of people displaced, which is only 2.82 per cent, will be abundantly provided for by the additional frontage on the diagonals, revenues will be augmented by assessments on the new buildings erected, and a large saving will be effected in time and distance for a majority of the inhabitants by this combination ci systems, which is therefore found to fulfil the requirement? of practice more fully than any other. " Similar applications of the above formula will show to what extent the plans of cities already established or to be built may be CITY STREETS. 573 ULJULJI ll_lUui_r._ DDDD m E7/3C-3 D [ 1 DnnDc^Qnaaa Ra 142. ARRANGEMENT OF STREETS (PART OF WASHINGTON, D. C.) 574 HIGHWAY CONSTRUCTION. improved by the opening of diagonals ; the most economical relation of street to building area, the proper distribution of the street area, and, by extending the analysis, the ratio of pavement to carriageway may also be readily determined. All of these questions have a direct bearing on the convenience, health, and extension of our cities." Fig. 142 shows the system adopted in laying out the streets o* Washington, D. C. 747. Width of Streets.=~The width of streets should be propor- tioned to the character of the traffic that will use them ; but, as a rule, this has not been considered in the laying out of cities, and the width of the commercial thoroughfares is now found insufficient to properly accommodate the traffic. No rule can be laid down by which to determine the best width of streets; but it may be safely said that a street which is likely to become a commercial thoroughfare should have a width of not less than 120 feet between the building lines the carriage-way 80 feet wide, and the sidewalks 20 feet each. In streets occupied entirely by residences a carriage-way 32 feet wide will be ample, but the width between the building lines may be as great as desired. The sidewalks may be any amount over 10 feet which the fancy may dictate. Whatever width is adopted for them, not more of it than 8 feet need be paved, the remainder being occupied with grass and trees. Wide streets add materially to the commercial prosperity of the inhabitants of a city by relieving them of the heavy tax imposed by narrow streets on transportation through constantly recurring blockades. Wide streets afford a good amount of breathing space, and thus add to the general health of the people. Moreover, they contribute to a city an air of spacious comfort and dignified distance, and for all time remove from it the crowded appearance which is too commonly found in all old cities and towns. 748. The maximum and minimum width of streets, with the average width of sidewalks and maximum grade, as at present es- tablished in various cities, are given in Table LXXXIL 749. Street Grades. Following the location of streets, there is the important duty of establishing a comprehensive system of grades. If this could always be done in advance of improvements, CITY STREETS. 575 there would be little difficulty in obtaining the best grades for a city. Unfortunately this is seldom the case, and in adjusting the street grades of villages in process of transformation into towns the engineer encounters one of his most trying duties; he meets much opposition from the property-owners who have made improvements based upon the natural slopes, also from those who object to having a street in excavation where it passes through their lands. Each one is looking to his individual interest, and he must exercise much dis- cretion and endeavor to fix a system of grades harmonious, conven- ient, and economical for the public rather than for individuals. Every town that expects to thrive should at a very early stage in its history establish the grades of its streets to the full extent of the town plot, and in doing so keep in view the probability of future extension. In new towns this ought to be done when the town is laid out, and the grades might be made part of the original record. 750. No rule can be laid down for determining the proper grades for city streets. They will depend upon the topographical features of the site. The necessity of avoiding deep cuttings or high embankments which would seriously affect the value of adjoining property for building purposes often demands steeper grades than are permissible on country roads. There are, however, certain con- ditions which it is important to attain: first, that the longitudinal crown level be uniformly sustained from street to street whenever practicable, so as to avoid undulations; second, that the crown level at all intersections be extended transversely to avoid the necessity of driving over a channel, which is otherwise formed. Table LXXXII shows the maximum grade of streets in several cities. 751. The best arrangement of intersections of streets when either or both have much inclination is a matter requiring much consideration and is one upon which much diversity of opinion exists. $Jo hard or fast rule can be laid down; each will require special adjustment. The best and simplest method is to make the rectangular space aaaaaaaa, Fig. 143, level with a rise of one-half inch in 10 feet from AAAA to B, placing gulleys at AAAA and the catch-basins at cccc. When this method is not practicable, adopt such a grade (but one not exceeding 2 \ per cent) that the rectangle AAAA, Fig. 143, shall appear to be nearly level; but to secure this 576 HIGHWAY CONSTRUCTION. TABLE LXXXII. WIDTH OF CITY STREETS. City of Width of Streets between Building Lines. Maximum. Feet. Minimum. Feet. Maximum Grade. Feet per 100 feet. Average Width of Sidewalks. Feet. New York, N. Y 100 Brooklyn, N.Y 100 Buffalo, N. Y 100 Syracuse, N. Y 120 Elmira, N. Y 100 Scheuectady, N. Y 90 Boston, Mass Lynn, Mass 100 Worcester, Mass 100 Lowell, Mass 70 Cambridge, Mass 102 Chicago, 111 150 Bloomiugton, 111 100 Jersey City, N. J 80 Camdeu, N. J 100 Newark, N. J 132 Trenton, N. J 80 Paterson, N. J 120 Terre Haute, Ind 99 Richmond, Ya 118 Omaha, Neb 120 Nashville, Tenn 104 Parkersburg, W. Va 60 Washington, D. C 160 Wilmington, N. C 99 Seattle, Wash 120 Philadelphia, Pa 120 Pittsburg, Pa 100 Erie, Pa 100 Harrisburg, Pa 120 Providence, R. 1 225 Cumberland, Md 65 Hartford, Conn 70 Waterbury , Conn 1 60 New Haven, Conn 100 Detroit, Mich 120 Grand Rapids, Mich 100 St. Paul, Minn 200 Minneapolis, Minn 120 Bucyrus, Ohio 82 Salt Lake City, Utah 132 Ogden,Utah 132 Burlington, Vt 99 Rutland, Vt 99 Milwaukee, Wis 100 * London, Eng 80 * Birmingham, Eng. 80 60 60 40 33 33 20 50 20 30 26 30 30 30 26 40 30 40 50 30 40 20 40 80 30 60 30 30 50 20 10 20 25 28 40 36 50 50 60 40 50 60 28 49 60 12 15 13 12 7 20 5 8 17.21 20 16 11.66 2.40 4.80 14 3 10 8 17 5 3 15 11 9 16 7 19 10 6 13 12 5 12 15 12.38 10.70 10 9 4 9 15 18 23 14 7 8 17 14 8 25 to 4 15 10 16 to 6 13 17 17 16 to 8 | width of st 20 to 12 width of st. * " " 6to4 6 20 to 8 20 to 6 12 to 4 ' 27 16 20 to 6 16 to 10 12 to 6 25 to 12 15 to 3 8 * Foreign cities for comparison. CITY STREETS. 577' WIDTH OF CITY STREETS Continued. Feet. Berlin : Unter den Linden 196 Leipziger Strasse 72 Konig Strasse 57 Brussels: Le Boulevard Circulaire 220 L0 Boulevard Ansbach 91 Le Rue Royale 65 Paris : Rue de Rivoli 88 Grands Boulevards 114 Avenue des Champs filysees 229 Avenue Bois de Boulogne. . . , 393 Vienna : Ringstrnsse 187 Hauptst rasse . it must actually have a considerable dip in the direction of the slope of the street. If steep grades are continued across intersections, , they introduce side slopes in the streets thus crossed, which are troublesome, if not dangerous, to vehicles turning the corners, es- pecially the upper ones. Such intersections are especially objection- able in rainy weather. The storm water will fall to the lowest point, concentrating a large quantity of water at two receiving-basins, which with a broken grade could be divided between four or more - basins. FIG. 143. ADJUSTMENT OF GRADES AT STREET- INTERSECTIONS. 752. Fig. 144 shows the arrangement of intersections on steep grades proposed by Messrs. Rudolph Hering and Andrew Rose water for the streets of Duluth, Minn. From this it will be seen that at - 578 HIGHWAY CONSTRUCTION. these intersections the grades are flattened to three per cent for the width of the roadway of the intersecting streets, and that the grade of the curbs is flattened to eight per cent for the width of the inter- secting sidewalks. Grades of less amount on roadway or sidewalk are continuous. The elevation of block-corners is found by adding together the curb elevation at the points facing the. block-corner, and also the sum of the widths of the two sidewalks at the corner multiplied by two and one half per cent, and dividing the whole by two. This gives an elevation equal to the average elevation of the curbs opposite the corner plus an average rise of two and one half per cent across the width of the sidewalk. 300 \5Z.22. Lfet 300 300 31.1% o 1 T \ Cvi ztijz : 300 ..... 1r 753. The instructions of the Department of Public Works of York contain the following directions for regulating grades at street-intersections : " In calculating the grades from the centre of the intersection to the circular corners or curb-lines, they will be established as follows : In the avenues when the ascents and descents of the cross CITY STREETS. 579 intersecting streets exceed 1 inch in 10 feet, the grade will be cal- culated at 1 inch in 10 feet to the curb-line from the centre, mak- ing 6 inches difference in the curbs on opposite sides of the avenues, and the slopes up and down the avenues will be calculated accord- ing to the grade of the avenue, let the same be more or less." " Apexes and punch-bowls to be set into the curb-line at the same height as the centre grade." 754. Accommodation summits have to be introduced between street-intersections, first in hilly localities to avoid excessive excava- tion, and second when the intersecting streets are level or nearly so, for the purpose of obtaining the fall necessary for surface- drainage. The elevation and location of these summits may be calculated as follows: Let A be the elevation of the highest corner, B the elevation of the lowest corner, D the distance from corner to corner, and R the rate of the accommodation grade. The elevation of the summit is equal to D . R + A -f B 2 The distance from A or B is found by subtracting the elevation of either A or B from this quotient and dividing the result by the rate of grade. Or the summits may be located mechanically by specially prepared scales. Prepare two scales divided to correspond to the rate of grade that is, if the rate of grade be one foot per hundred feet, then one division of the scale should equal 100 feet on the map scale. These divisions may be subdivided into tenths. One scale should read from right to left, and one from left to right. To use the scales, place them on the map so that their figures correspond with the corner elevations; then as the scales read in opposite directions there is of course some point at which the op- posite readings will be the same : this point is the location of the summits, and the figures read off the scale its elevation. If the dif- ference in elevation of 'the corners is such as not to require an in- termediate summit for drainage, it will be apparent as soon as the scales are placed in position. 755. Sufficient fall for surface drainage may be secured without the aid of accommodation summits, by arranging the grades as shown in Fig. 145. The curb is set level between the corners, a summit is .580 HIGHWAY CONSTRUCTION. formed in the gutter, and receiving-basins are placed at the centre .and each corner. CDRB LEVEL ^ BOTTOR ~OF ""GUTTER"" ^ SHOWING CROWN IN STREET GUTTER. 756. Transverse Grade, In transverse grade the street should be level; that is, the curbs on opposite sides should be at the same level, and the street crown rise equally from each side to the centre. But in hill-side streets this condition cannot always be fulfilled, and opposite sides of the street may differ as much as five feet; in such cases the engineer will have to use his discretion as to whether he will adopt a straight slope inclining to the lower side, thus draining the whole street by the lower gutter, or adopt the three-curb jnethod and sod the slope of the higher side. In the improvement of old streets with the sides at different levels much difficulty will be met, especially where shade-trees have to be sjpared. In such cases recognized methods have to be aban- .doned, and the engineer will have to adopt methods of overcoming the difficulties in accordance with the condition and necessities of >each particular case. As an example of what may be done in such cases the methods adopted by Mr. J. T. Desmond, City Engineer of Haverhill, Mass., may be cited. In Fig. 146 is shown a street 66 feet wide, with one sidewalk Fig. 146. 03 Fig. 147. CITY STREETS. 581 5 feet higher than the other. In order to get a fair cross-section a third line of curbing was put in at the crest of the slope, and the slope between the two curbs sodded. This produces a very pleasing effect. In Fig. 147 the same conditions exist, but only two lines of curb- ing are used, the slope being sodded in the same manner as in the first case. Again, it often happens that two parallel streets are laid out with sharp descending grades, and later on the city is called upon Fig. 148. ARRANGEMENT OF STREETS WITH OPPOSITE SIDES AT DIFFERENT LEVELS. to accept a new street laid out between them. The method shown in Fig. 148 is adopted. 757. Transverse Contour. The most suitable form of transverse contour and proper rise for each kind of pavement are given in Articles 618 and 619, Chapter XII. 758. Sub-foundation Drainage of Streets. The sub-foundation drainage of streets cannot be effected by transverse drains, because of the liability of their disturbance by the introduction of gas, water, and other pipes. Longitudinal drains must be entirely depended upon; they may be constructed of the same materials and in the same manner as road drains. The number of these longitudinal drains must depend upon the character of the soil: if moderately retentive, a single row of tiles or a hollow invert placed under the sewer in the centre of the street will generally be sufficient, or two rows of tiles may be employed, one placed at each curb-line; if the soil be exceedingly wet and the street very wide, four or more lines may be employed. These drains may be permitted to discharge into the sewers . si* 2o New York, N. Y Chicago 111 575 2048 1151 653 1061 408 780 342 486 462 372 625 400 419 235 186 800 508 240 970 756 400 195 438 140 105 251 106 79 100 100 125 130 136 800 82 30 529 340 56 50 80 224 90 140 150 200 125 30 120 358 629 750 375 422 408 459 92 254 69 194 89 147 72 163 48 25 52 72 40 '234 195 60 32 19 147 2 23 31 82 80 33 83 75 17 25 14 9 50 4 35 43 26 5 170 15 27 31 1 45 1419 50 3 40 "106' 190 129' 'm '"Q 138 4 41 72 325 756 16 '220 62.26 30.71 65.16 57.43 39.77 100.00 58.85 26.90 52.26 14. 91 52.15 14.24 36.75 17.18 69.36 25.81 3.13 10.24 30.00 4.12 1200 'iss' 50 14.30 12.75 8.90 24.68 17.29 11.56 27.48 22.12 19.44 18.57 9.53 16.85 19.43 24.65 22.95 10.47 15.48 20.73 15.38 18.86 48.81 39.72 5.73 22.21 18.52 9.4* 29 74 9.68 13.55 23.04 25.32 11.75 8.77 30.77 28.99 12.29 20.41 68.88 11.00 22.31 12.56 7.97 69. 35 20.2'^ 31.75 22. oe 4.2S 15. 2( 25. (X 18.* 16.25 15.94 8.42 32.72 19.65 8.78 34.86 28.91 18.41 23.21 10.47 19.15 20.97 35.01 43.46 11.89 23.46 25.92 14.57 21.44 S3. 95 56.42 5.43 27.76 21.04 8.92 28.16 9.17 12.83 26.18 28.77 11.13 11.76 40.79 32.94 1 11.64 22.42 78.27 16.67 21.13 14.28 7.55 86.69 21.07 42.09 25.0? 3.2C 19. 81 .2 23.51 2,635.31 537.03 909.61 1.234.83 435.80 1,099.21 556.97 874.26 610.92 565.70 687.27 387.26 514.69 487.99 863.74 977.58 205.9^ 276.48 557.90 137.27 141.15 263.59 434.13 185.92 580.70 739.96 303.46 101.87 886.43 583.13 574.58 445.82 409.46 373.21 62.99 544.56 1,454.93 71.96 111.19 650.45 712.74 437.56 147.83 330.09 191.94 174.59 127.24 200.72 830.60 196.53 1300 '306 30 7 "'5' 10 Philadelphia, Pa Brooklyn, N. Y St. Louis, Mo Baltimore, Md San Francisco, Cal. . . Cincinnati, Ohio Cleveland, Ohio Buffalo, N. Y Hew Orleans, La Detroit Mich 100 200 25 '349 230 350 30 360 '230 '466' 10 10 30 15 '26' ... 6 Milwaukee, Wis. .. . Washington, D. C. .. Newark, N. J Minneapolis, Minn.. Omaha, Neb Rochester, N. Y St Paul, Minn 50 28 36 Denver Col Indianapolis, Ind Worcester, Mass Toledo, Ohio New Haven, Conn... Lowell, Mass Nashville, Tenn Fall River, Mass Cambridge, Mass . . . 58.50 100.00 13.70 22 86 234 150 70 234 "25" 6 '"{2 1 "79" "20 50 30 50 52 76 " 3 66 75 43 "'TO' 20 5 79 115 20 110 3 50 18.10 58.57 1.89 29.11 31.00 7.00 65.60 61.54 24.26 10.38 91.46 56.67 4.73 4.12 16.07 100.00 5.00 15.63 47.78 18.57 3.33 85.00 12.00 90.00 25.83 79 50 150 20 50 75 20 91 6 ""9 15 45 49 '"SO '45 30 150 "20 25 60 1 5 "9i" 80 ""is 90 3 12 50 23 85 5 16 20 2 98 20 5 '"l5 12 30 " 2 8 10 4 4 10 6 6 8 r '"5 Trenton, N. J Lynn, Mass Hartford, Conn Evansville, Ind Los Angeles, Cal Lawrence, Mass Hoboken, N. J Dallas, Tex Sioux City, Iowa .... Portland, Me Holyoke, Mass Binghtmton, N. Y... Duluth, Minn Elmira N Y Dav nport, Iowa... Canton. Ohio Tauuton, Mass Lacrosse, Wis Newport. Ky Rockford. Ill CHAPTER XVII. FOOTPATHS, CURBS, GUTTERS. 768. A FOOTPATH or walk is simply a road under another name, a road for pedestrians instead of one for horses and vehicles. The only difference that exists is in the degree of service required; but the conditions of construction that render a road well adapted to- rts object are very much the same as those required for a walk. The effects of heavy loads such as use carriageways are not felt upon footpaths, but the destructive action of water and frost is the same in either case, and the treatment to counteract or resist these elements as far as practicable and produce permanency must, be the controlling idea in each case, and should be carried out upon a common principle. It is not less essential that a walk should be well adapted to its object than that a road should be, and it is annoying to find it impassable or insecure and in want of repair when it is needed for convenience or pleasure. In point, of economy there is the same advantage in constructing a footway skilfully and durably as there is in the case of a road. 769. Width. The width of footwalks (exclusive of the space occupied by projections and shade-trees) should be ample to com- fortably accommodate the number of people using them. In streets devoted entirely to commercial purposes the clear width should be at least one third the width of the carriageway; in residential and suburban streets a very pleasing result may be obtained by making the walks one half the width of the roadway and devoting the greater part to grass and shade trees. The width adopted for sidewalks in several cities is given in- Table LXXXIL 770. Cross-slope. The surface of footpaths must be sloped so< that the surface-water may readily flow to the gutters. This slope 59,5, 596 HIGHWAY CONSTRUCTION. need not be very great; inch per foot will be sufficient. A greater slope with a thin coating of ice upon it becomes dangerous to pedestrians. 771. Foundation. As in the case of roadways so with foot- paths, the foundation is of primary importance. Whatever material may be used for the surface, if the foundation is weak and yielding the surface will settle irregularly and become extremely objection- able, if not dangerous, to pedestrians. 772. Surface. The requirements of a good covering for side- walks are : (1) It must be smooth but not slippery. (2) It must absorb the minimum amount of water, so that it rnay dry rapidly after rain. (3) It must not be easily abraded. (4) It must be of a uniform quality throughout, so that it may wear evenly. (5) It must neither scale nor flake. (6) Its texture must be such that dust will not adhere to it. (7) It must be durable. 773. Materials. The materials used for footpaths are as fol- lows: stone natural and artificial, wood, asphalt, brick, tar con- crete, and gravel. 774. Of the natural stones, sandstone (bluestone) and granite are extensively employed. The bluestone when well laid forms an excellent paving mate- rial. It is of compact texture, absorbs water to a very limited extent, and hence soon dries after rain; it has sufficient hardness to resist abrasion, and wears well without becoming excessively slippery. It can be obtained in flags of almost any size and thickness. As found in the quarries, the layers of stone range from 1 inch to 3 feet in thickness, the top beds being usually the thinner. The size of the blocks in superficial area varies; frequently blocks 60 feet long by 20 feet wide and 10 inches thick are lifted from the bed . The largest slab as yet brought to tide-water was 20 X 24 feet and 10 inches thick, and there are slabs used for flagging in New York 15 by 20 feet by 8 inches. Granite, although exceedingly durable, wears very slippery and its surface has to be frequently roughened. 775. Slabs of whatever stone must be of equal thickness FOOTPATHS, CURBS, GUTTERS. 597 throughout their entire area; the edges must be dressed true to the square for the whole thickness (edges must not be left feathered as FIG. 160. IMPROPER MANNER OF DRESSING THE EDGES OF CROSSING-STONES AND FLAGSTONES. shown in Fig. 160) ; and they must be solidly bedded on the foun- dation and the joints filled with cement-mortar. Badly set or faultily dressed flagstones are very unpleasant to walk over, especially in rainy weather; the unevenness causes pedestrians to stumble, and rocking stones squirt dirty water over their clothes. 776. Specifications for Flagstones, (New York). Flagstones shall be of the best quality of North Eiver bluestone, 4 feet wide, not less thaji 3 inches thick, and to contain not less than 12 super- ficial feet. The edge shall be dressed the whole depth of the stone, so as to lay close joints, and the top shall be cut evenly, so as to leave no depressions. Flagging shall be laid in four inches of sand or clean gritty earth, and the joints closed with cement-mortar. . 777. Wood has been largely used in the form of planks; it is cheap in first cost, but proves very expensive from the fact that it lasts but a comparatively short time and requires constant repair to keep it from becoming dangerous. 778. Asphalt forms an excellent footway pavement; it is dur- able and does not wear slippery. It is largely employed for this purpose in Europe. The proportions of materials employed in Paris are given as follows : Bituminous rock 1456 pounds Bitumen 68 " Sand 784 " This requires about 225 pounds of coal to heat it, and one work- man can prepare 3 tons of material in 12 hours. The following table gives the number of square yards that a ton of prepared rock-asphalt will spread : 598 HIGHWAY CONSTRUCTION. TABLE LXXXIV. With about Without Grit. Square yards. 25 per cent of Grit. Square yards. Thickness. Inches. 63 80 1 51 65 1 32 40 I 26 33 16 20 H m 16 2 A skilled workman properly assisted can lay 140 to 180 square- yards in a day. 779. The life of asphalt footways may be taken at about twelve years under ordinary traffic. The concrete will remain untouched, and what is left of the asphalt may be remelted, so that a renewal is not so costly as the first expense. Compressed-asphalt paths have lasted ten years in some of the busiest thoroughfares of London. In Leicester, uncompressed- asphalt paths have lasted fifteen years under considerable traffic. The thickness of the asphalt should not be less than one inch. 780. Specifications for Sheet-asphalt Footway Pavements (Wash- ington, B.C.) Grading. The space over which the sidewalk is to be Iai3 will be graded to a depth of 3 inches below the finished surface of the pavement. Soft and spongy places not affording a firm foundation will be removed and good, clean gravel substituted therefor. The bed thus prepared will be thoroughly rolled and rammed to the satisfaction of the Engineer or his authorized representative. Tree-spaces. A space of such dimensions as may be directed by the Engineer Commissioner (usually 2 by 4 feet) will be left around each tree. Around the edges of this space will be planted a framework of Georgia pine, 2 inches in thickness and 9 inches in depth. The plank forming the rear of the framework, and which is parallel to the curb, will be firmly nailed to the other two pieces, and will be cut in such a manner that it will bind underneath the pavement to be laid, so that the top edges will be even with the pavement when completed. In the spaces between the framework and the sides of the trench coarse sand will be placed and com- pacted by tamping with narrow rammers especially constructed for FOOTPATHS, CURBS, GUTTERS. 599 this purpose. These spaces will be then filled to the sub-grade of the pavement, and the tree-spaces will be filled with earth and left in a neat and clean condition. Base. On the bed prepared as above specified a layer of clean broken stone, of size not exceeding f inch in largest dimen- sions, will be spread to a depth of 2f inches. This will be com- pressed by rolling arid tamping to a thickness of 2 inches. On this will be poured, at a temperature of about 250 degrees Fahr., the residuum of coal-tar distillation known in the trade as No. 4 Paving Composition. About \ gallon of this composition will be used for each square yard of pavement, and it will be poured on the base of broken stone in such manner as to thoroughly coat the -stones on the surface and fill the interstices thereof. Wearing Surface. The cementing material of the wearing surface will be asphalt paving-cement prepared from the best quality of Trinidad asphalt, obtained from the so-called Pitch or Asphalt Lake in the island of Trinidad, and the residuum of petroleum distillation, mixed in the proportions of about six parts, of refined asphalt and one part of residuum. With tliis paving- cement will be combined the old asphalt pavement from Penn- sylvania Avenue or elsewhere, and crushed granular limestone quartz or other stone of a white color, in the following proportions : Old pavement ... , 69 to 76 per cent Crushed stone 26 to 15 Asphalt cement as above specified . . . . , 5 to 9 " 100 100 per cent The old pavement will be furnished by the District at the property yards near the foot of New Hampshire Avenue ; the other materials will be furnished by the contractor. The crushed stone in the wearing surface will vary in size from J of an inch to dust. The asphalt pavement will be broken into pieces not exceeding 4 inches in their largest dimensions, and will then be mixed with the crushed stone in the proportion of about 4 parts of asphalt pavement to one part of crushed stone. This mixture will then be heated to a temperature of about 300 degrees Fahr. in a suitable apparatus, and thoroughly mixed and made homogeneous by stirring, special care being taken not to overheat the material or 600 HIGHWAY CONSTRUCTION. burn the asphalt. During the progress of mixing, asphalt cement will be added in the proportion of 5 per cent to 9 per cent by weight of the mixture; the exact proportion of asphalt cement thus to be added for the purpose of enriching the old pavement will be determined by the Engineer Commissioner. The material thus prepared will be brought to the work at a temperature of 250 degrees to 275 degrees Fahr., and will be spread on the base above specified by means of hot iron rakes to a thick- ness of H inches, and will then be compressed by rolling and ram- ming to the thickness of 1 inch. A small amount of hydraulic cement will then be spread over the surface, and the rolling will be continued until the pavement is thoroughly compressed. Care shall be taken at all times not to interfere with business or travel more than is absolutely necessary for the faithful performance of the work. During the time that' travel is necessarily closed at any point the contractor shall provide temporary walks, said walk to be at all times in condition for pedestrians, and easy of access from adjoining walks. The contractor shall remove all stone, plank, brick, or other material of value from points where the sidewalks are to be laid, as the work progresses, and shall haul them to the nearest property yards, or otherwise dispose of them, as the Engi- neer Commissioner may desire. Curb. Whenever ordered the curb will be reset. Curb will be redressed by the contractor whenever ordered, for which a fair price, to be fixed by the Engineer Commissioner, will be paid. 781. Extracts from Specifications for Asphalt Footway Pave- ments (Paris). Form and Dimensions of Work. Art. 7. The width of the sidewalks for each locality will be determined by the administra- tion, its slope by the engineer. The curb between the sidewalk and the roadway will not be included in this contract. Art. 16. The mastic pavements will be formed of a layer of pure asphaltic mastic at least T 9 g- inch thick, resting on a bed of hydraulic concrete 4 inches thick which comprises a covering of hydraulic mortar at least f inch thick. Art. 17. The compressed-asphalt pavements will consist of an upper layer of compressed asphalt 1 to 2 inches thick, resting on a foundation of hydraulic lime or cement concrete 4 to 6 inches thick, covered as above with mortar, or upon an old macadam road" FOOTPATHS, CURBS, GUTTERS. 001 way picked over and covered with a thin coat of hydraulic mortar. Art. 2t. The asphaltic mastic employed either for new or re- pairing o!d paving shall be composed of naturally impregnated rock with natural bitumen of good quality, coming exclusively from mineral rocks. The fictitious bitumens extracted by the purification of the heavy oils or schists and by the distillation of coal, also the so- called fatty bitumens, and all other analogous products shall be rigorously proscribed. The rock employed after being reduced to powder will be melted with a sufficient quantity of purified natural bitumen to form a mastic which, when cold, presents a homologous mass slightly elastic and which does not soften under a hot sun. This mastic shall be moulded into blocks. There may also be used blocks of bituminous mastic with a base of slates manufactured by the process of M. Sebille. Art. 22. The contractor shall be bound to employ under the orders of the engineers upon each public way the bituminous mas- tic above described. The mastic shall be formed of a mixture of natural bitumen, in the proportion of one twelfth of its weight at most, and the calca- reous asphalt rocks of Seyssel, Seyssel-Forens, Pyrimont or Vo- lants, of Val de Travers or Lobsan, or others deemed equivalents by the engineers. The mastic having a base of slate of M. Sebille will be formed of a mixture of bitumen described in Art. 23 following, and of powdered red or blue slate of Ardennes, powdered chalk of Men- don or of Nanterre, and of silica from the basin of Paris, in the following proportions by weight : Refined mineral bitumen 30 parts Ground slate 35 " Powdered chalk 10 " Silica, ground and sifted 25 " 100 parts Art. 23. The bitumen shall come as much as possible from the weighings of bituminous sandstone or the asphaltic rock of Maestu, and in their default from the dry pitch of Trinidad, perfectly puri- HIGHWAY CONSTRUCTION. fied. It ought to be viscid at the ordinary temperature, never brittle or liquid ; drawn into threads it should lengthen and only break in very fine points. Art. 24. The rock employed should be calcareous, soft, with fine grain, texture fairly compact, regularly impregnated with bitumen so as not to show black and white spots; it should be of a brown color; heated to 122 to 140 degrees Fahr. it should soften and break on being torn. Care must be taken for the area in asphalt to choose only such pieces as are of the most even grain and richest impregnation. The rock of Lobsan, however, should not be employed alone in the asphalt roadways; it ought to be mixed with other rocks less fat, in proportions which will be de- termined by the engineer according to the composition of the other rocks. It should contain at least 7 per cent of bitumen and at the most 93 per cent of lime; its change into mastic must not require more than 9 per cent of bitumen. Art. 25. The materials entering into the composition of the pavements are the mastics described in Art. 22 ; pure gravel grit and natural bitumen to assist the melting. These materials ought to be generally employed in the following proportions by weight : ( Aspbultic mastic 100 Foot-pavements with a base of asphalt < Bitumen 6 ( Grit 60 C Asphaltic mastic 100 Foot-pavements with a base of slate < Bitumen 7 (Gravel 50 Art. 26. One month before the award of this contract the competitors must deposit at the office of the works in Paris samples of, 1st, a block of the mastic described above; 2d, specimens of the asphaltic rocks and the natural bitumens they intend to use; 3d, a note indicating the elements of the composition of the mastics, and proportions of the various rocks that they intend to employ in the composition of the asphaltic areas. The blocks and specimens of rocks and bitumen to have the trade-marks of the works from whence they came and the signatures of the com- petitors. The necessary certificates to compete for the contract will not be delivered till after the examination and acceptance by the engineers of the specimens deposited. During all the term of this FOOTPATHS, CURBS, GUTTERS. 603 contract the contractor can only use materials exactly similar to the specimens deposited. Art. 27 provides for continuous inspection of the contractor's works, and the right to compel the contractor to manufacture the mastics in the depots belonging to the city. Art. 31. The lime employed is to be hydraulic lime in powder. It must be brought onto the works in sealed bags marked with the name of the maker. Only the lime and cement designated in the specifications for the construction and repair of sewers will be allowed. Art. 32. The broken flint must pass through a ring of 2 J inches and be at least f inch thick. It must be free from all earthy matters and washed clean. Art. 33. The sand shall be dredged from the Seine and well cleansed from all foreign matter; it shall be screened from all grains larger than f inch for the mortars or -fa inch for grit for the mastic pavements. The grit for this last purpose shall be perfectly washed and dried before use. Art. 34. The mortar of hydraulic lime shall be composed of 5 parts of sand and 2 parts of lime, by volume, furnished in powder; the mixture shall be directly reduced to a paste by adding the quantity of water exactly required to reduce it to the consistency of plastic clay. The cement-mortar shall be composed of 1 part of hydraulic cement of Bourgogne or Portland cement of Boulogne and 3 parts of sand; the sand and cement shall be thoroughly mixed before the addition of any water. All mortar which shall have set shall be rejected. Art. 3.";. The beton shall be composed ordinarily of 2 parts in volume of mortar and 3 of stone. The mixture, made either by rake or cylinder, must be perfectly uniform. All beton not used at the time of making shall be rejected. Art. 36. The bed of beton for the foundation of the sidewalks shall be well rammed and compressed, and nrast at least commence to set and dry before receiving mastic or asphalt. The beton shall in addition be covered with a layer of mortar f inch thick. The gravel for foundation shall pass in every direction through a ring 2 inches in diameter. It must be perfectly compressed and .sprinkled with lime-grout. This foundation shall have commenced fiO-t HIGHWAY CONSTRUCTION. to set before the application of the mastic, and shall be covered with a layer of mortar like the beton. Art. 39. The ground upon which the mastic pavement is to be placed shall always be previously rammed, watered, and crowned with care. When it is thus made solid the contractor shall spread over it the foundation layer, formed according to the orders of the engineer either a bed of beton or of sand covered by a layer of mortar, or a bed of sand impregnated with goudron 2f inches thick, or any other foundation prescribed by the engineer. In all cases the pavement shall not be laid till the foundation has attained the firmness desired and becomes quite dry. The contractor must conform to the following orders for the manufacture of the mastic to be used for pavements: The mastic shall be prepared and cast in one or more manufac- tories belonging to the contractor, and which shall always remain open to the inspection of the engineers and their agents. The contractor shall besides establish in the manufacturing depots, both of asphalt and mastic, offices exclusively for the agents of the administration set apart for the inspection of the composition of these materials. These materials shall not be admitted into the works without a carter's delivery note given by the inspector, setting forth that they have been manufactured in accordance with the specifications. There shall only be allowed in the works blocks of mastic con- forming to the samples deposited and accepted before the award, and bearing the trade-mark, or the old mastics from the walks and streets of Paris. All other bituminous matters, resinous or fatty, found in the works by the agents of the administration will subject the contractor to a deduction of $100 for each time they are found. To assure the execution of these conditions the contractor must not have in any manufactory, under the same penalty, any other blocks than those which should be prepared in his works, and the old mastics that have been taken up. The use of the old mastic is authorized in the works of the city in the proportion of one half with the new ; the pieces of the old sidewalks having been perfectly cleaned with great care, and re- generated by the addition of new purified bitumen and ajsufficient FOOTPATHS, CURBS, GUTTERS. 605 quantity of powered asphalt to render the old mastic, when melted, of the aspect and consistence of the blocks in fusion. This mastic shall be melted in hermetically closed boilers, on wheels of a model approved by the administration, and arranged so that the material can be conveyed from the factory to the place to be used, ready to be employed. For melting, the mastic is broken into pieces 4 inches cube, then the bitumen is melted and the mastic added little by little. The grit must not be thrown into the boiler til] the mastic is completely dissolved. During the whole time of the operation the matter must be stirred up almost constantly, so that the combination shall be well made and the mastic not burned. The mastic being well melted and perfectly homogeneous, it shall be run out in bands of about five feet wide, spread with a wooden float, and levelled with a strike, so as to present neither fissure nor joint. The mastic must be perfectly level, and matched exactly with the curbs, etc., against which it is laid. For this pur- pose the parts of the curbs, flags, etc., which will be in contact with the bitumen shall be previously warmed and goudroned. Art. 40. Upon the soil, well shaped and rammed, shall be placed a bed of concrete, covered with a layer of mortar. The asphaltic rock, conforming to article 24, broken down or de- crepitated by heat, shall be raised to a uniform temperature of from 248 to 266 degrees Fahr., and carried to the place of employment in vehicles that will prevent as much as possible the loss of heat. It must be completely freed from the the water it contains. The use of old compressed asphalt, taken from old roads, is authorized for mixture with new asphalt, in the proportion of one quarter of old com- pressed to three quarters of new rock, provided that the old shall be cleansed with great care before grinding and mixing with the new. Asphalt shall not be put on the concrete foundation until it is perfectly set and dry. The powder shall be spread with a thickness about two fifths more than the finished thickness, levelled with great care, and then rammed, at first carefully, then gradually augmenting the force by means of cast-iron pilons heated to the proper temperature in portable furnaces. In specially exceptional cases the compression. 06 HIGHWAY CONSTRUCTION. may also, with the written permission of the engineer, be accom- plished by means of rollers. In every case, after the pilonnage is finished, the surface shall be smoothed by means of a heated iron (lissoir). The road shall not be open to traffic until it is quite cool. Art. 43. In conformity with the contract price, stipulated here- after, diminished by the rebate of the awarded contract, the con- tractor must make the necessary repairs to all asphaltic mastic foot- paths and areas, furnishing the necessary labor and materials, so that they shall be kept in proper condition. He must each year of the duration of the contract completely relay, in new material, at least the fifteenth part of the surfaces of mastic and compressed asphalt. The surfaces in mastic must be properly plane and regular, pre- senting neither hollows nor projections of more than f inch in a circle whose radius is 3J- feet. These surfaces must be free from fissures. Art. 45. As the works in asphalt or mastic are accepted by the engineer they will pass into the charge of the contractor, who will receive for the maintenance the price stipulated, commencing from the first of January next following their acceptance, what- ever may be the date of said acceptance. In the last nine months of the year instalments may be paid on the contract when the engineers recognize that the conditions have been loyally carried out. The accumulated sums of these instal- ments must not exceed four fifths of the amount of the sums which shall be due after the time has expired. The balance of the con- tract price of the year will be paid in the course of the first quarter of the following year. Art. 49. All damages in the bituminous surface, such as fissures or cracks of at least T V inch in width, or parting from the curbs T % inch in width, any lifting up or breaking away of the mastic for at least -f$ inch in depth, depressions in consequence of settlement of at least f inch in depth under a straight-edge, 3 feet long, will subject the contractor to a deduction of 3 francs (58 cents) per day when the repairs shall not have been done within 48 hours after notice given by the engineer. Art. 51. During the continuance of irost, and during the first month after the commencement o*. the thaw, there shall be no re- pairs to the pavements maintained by the contractor, and the in- FOOTPATHS, CURBS, GUTTERS. 607 spection for defects shall be suspended ; but the contractor shall fill with sand and gravel any holes in these pavements within 24 hours after notification by the engineer, under a penalty of 10 francs ($1.93) for each day they remain unfilled. He may be authorized, in exceptional cases, to fill the holes with broken flint or melted bitumen, but must replace the flint or bitumen with asphalt as soon as the weather permits. It must be so arranged that the main re- pairs, intended to re-establish the normal outline of the roadways, are effected from May 1st to November 1st. Art. 65. When a workman leaves one of the districts of the works under the municipal service, he must have a certificate from the contractor showing the cause for which he left. This certificate shall be submitted at once to the engineer, who shall be at liberty to refuse the right of employing the said work- man, without the contractor deriving therefrom any excuse for not furnishing, when requisite, the number of workmen required. In default of a certificate, the workman cannot be admitted, except on the written order of the engineer. 782. Compressed-asphalt Tile-pavement. The success attend- ing the introduction of compressed-asphalt blocks for light-traffic streets has led to the use of the same composition under the name of " compressed-asphalt tiles " for sidewalk pavements. These tiles can be made of any form and thickness required. The dimen- sions found most suitable are 8x8 inches square and 2 \ inches thick. In this form they have been laid in large quantities during the last seven years and appear to have given satisfaction. 78?a. Specifications for Laying Compressed-asphalt-tile Side- walk-pavements. (1) The tiles will be laid on a foundation of gravel and sand thoroughly compacted by ramming and rolling. (2) The space over which the pavement is to be laid shall be ex- cavated to the depth of ten (10) inches below the top surface of the finished pavement. Any perishable or other objectionable material found below this depth must be removed and the space filled with clean gravel or sand ; the surface of the foundation so prepared shall be thoroughly compacted by ramming and rolling. (3) The foundation for the tiles will be formed of a bed of fine bank gravel*four inches in depth when compacted, screened from all pebbles measuring more than one and one-half inches. Upon 608 HIGHWAY CONSTRUCTION. the gravel there shall be laid a bed of fine, sharp sand, washed and dried, four inches in thickness. The foundation of sand and gravel shall then be thoroughly consolidated by ramming and rolling, care being taken to preserve the surface of the sand parallel to the slope required for the finished surface of the pavement. (The hand- rammers shall weigh not less than 25 Ibs., and the rollers not less than 300 Ibs.) (4) The tiles shall be laid at right angles to the street line, and their surface when finished must be even with the top of the curb and shall have the required slope. The tiles shall be laid by the pavers standing or kneeling upon the tiles already laid, and not upon the sand-bed. Each course of tiles must be of uniform width and depth, and so laid that all longitudinal joints shall be broken by a lap of at least two inches. Each course shall be driven against the course preceding it by a maul so as to make tight joints. When thus laid the tiles will be covered with clean, fine, dry sand, free from loam or earthy matter, and screened through a sieve having not less than 20 meshes to the inch. (5) The tiles shall then be carefully rammed by placing a plank over several courses and striking the plank with a rammer weigh- ing not less than 25 Ibs. The ramming shall be continued until the tiles reach a firm, un- yielding bed and present a uniform surface with the required grade. Any lack of uniformity in the surface must be corrected by taking up the tiles and relaying them. When the ramming is completed a thin layer of fine dry sand shall be spread over the surface and swept into the joints. 784. Brick. Brick of suitable quality well and carefully laid on a concrete foundation makes an excellent footway pavement for residential and suburban streets of large cities, and also for the main streets of the smaller towns. The bricks should be a good quality of paving-brick (ordinary building-brick are unsuitable; they soon wear out and are easily broken). The bricks should be laid in parallel rows on their edges, with their length at right angles to the axis of the path. They should be set ill cement- mortar and the joints filled flush and made as close as possible. FOOTPATHS, CURBS, GUTTERS. 609 785. Specifications for Brick Walks (Washington, D. C.). Brick pavements will be laid on a foundation of gravel and sand; and the bricks will be furnished by the District, delivered on the line of the work. The space over which the pavement is to be laid will be excavated to the depth of 10 inches below the top surface of the proposed pavement when thoroughly compacted by rolling or ramming. Any objectionable or unsuitable material below the bed will be removed, and the space filled with clean gravel or sand. Care must be taken in excavating to preserve the proper slope parallel with the surface. Upon the foundation will be laid a bed of fine sandy bank gravel, 4 inches in depth when compacted, screened from all pebbles measuring mo^B than 1J inches in their largest dimensions, and thoroughly rolled or rammed. Upon this will be laid a bed of fine, clean, sharp sand, 4 inches in thickness, to serve as a bed for the bricks, which will be laid directly upon and imbedded in it with close joints. Special care will be observed to make the surface of this bed of sand parallel to the surface of the pavement when finished. The bricks must be laid by the pavers standing or kneeling upon the bricks already laid, and not upon the bed of sand. The bricks are to be laid at right angles with the line of the street, or in herring-bone style, as may be directed by the Engineer Commissioner, and even with the top of the curb when rammed; each course to be of bricks of a uniform width and depth, and so laid that all longitudinal joints shall be broken by a lap of at least 2 inches. When thus laid the bricks will be immediately covered with clean, fine, dry sand, free from loam or earthy matter, and screened through a sieve or screen having not less than 20 meshes to the inch. The bricks will then be carefully rammed by placing a plank over several courses and ramming the plank with a heavy hammer. The ramming will be continued until the bricks reach a firm, unyielding bed and present a uniform surface, with proper grade and slope. Any lack of uniformity in the surface must be cor- rected by taking up and relaying. When the ramming is complete a sufficient amount of fine, dry sand, as above described, will be spread over the surface and swept or raked into the joints. Rectangular spaces, 7 by 3 feet in dimensions, will be left impaved around trees where already planted, and at intervals of 25 feet between centres adjacent to the curb on streets where 610 HIGHWAY CONSTRUCTION. trees have not been planted. When so ordered a continuous tree space of 4 feet wide will be left unpaved adjacent to the curb. Edges of brick pavements when not abutting against the curb will be finished with a continuous row of brick on edge. Quality of Brick. Sidewalk paving-brick to be of dimensions 8^ by 4 by 2^ inches, hard-burned throughout, of dark red color, without flaws or cracks, and square and true on the edges. Specimens required. Arch-bricks to be of dimensions 8J by 4, by 2J inches, hard- burned throughout, sound, and of true and regular shape. All to conform to the samples submitted with the proposals. No swelled brick or silt or salmon brick will be allowed. Specimens required. In relaying brick sidewalks the existing sidewalks will be taken up and the bricks carefully piled and preserved. The bed will then be prepared in the same manner as prescribed for new brick walks. After the bed is prepared the old brick will be cleaned of all adher- ing materials so that they can be relaid with close joints, when they will be laid as prescribed for neAv brick pavements. In Washington the amount of brick walk laid has steadily de- creased from year to year. The first cost of a brick walk is but little less than one of cement, while the advantages of the latter are incomparably greater. It is almost impossible to maintain a smooth brick sidewalk in Washington on account of tree-roots which grow up under the pavement and displace the bricks. The cement walk, however, is not so easily affected, although with some variety of trees notably the Carolina poplar the surface growth of roots is often sufficient to lift even the heavy blocks of cement. 786. Artificial Stone. Artificial stone is being extensively used as a footway-paving material both in Europe and America. Its manufacture is the subject of several patents, and numerous kinds are to be had in the market. When manufactured of first-class materials and laid in a substantial manner, with proper provision against the action of frost, artificial stone forms a durable, agreeable, and inexpensive pavement. The varieties most extensively used in the Unitecf States are known by the names of " granolithic," " monolithic," " ferrolithic/' " kosmocrete," " metalithic," etc. The process of manufacture is practically the same for all kinds, the difference being in the materials employed; the usual ingredi- ents are Portland cement, sand, gravel, and crushed stone. FOOTPATHS, CURBS, GUTTERS. 611 787. Artificial stone for footway pavements is formed in two ways, viz., in blocks manufactured at a factory and brought on the ground and laid in the same manner as natural stone, or the raw materials are brought upon the work, prepared and laid in place, blocks being formed by the use of board moulds. 788. The manner of laying is practically the same for all kinds. The area to be paved is excavated to a minimum depth of 8 inches, and to such greater depths as the nature of the ground may require to secure a solid foundation. The surface of the ground so exposed is well compacted by ramming, and a layer of gravel, ashes, clinker, or other suitable material is spread and consolidated; on this is placed the concrete wearing surface, usually 4 inches thick. As a protection against the lifting effects of frost the concrete is laid in squares, rectangles, or other forms having areas ranging from 6 to 30 square feet, strips of wood being employed to form moulds in which the concrete is placed. After the concrete is set these strips are removed, leaving joints about half an inch wide between the blocks. Under some patents- these joints are filled with cement, under others with tarred paper, and in some cases they are left open. 789. Good artificial stone is far superior to any other material for footway pavements. It is of a uniform temper and homoge- neous throughout, and consequently its wear is more uniform than that of natural stones. It is practically non-absorbent, and conse- quently dries very quickly after rain. 790. The quality of the cement is an important point in the manufacture of artificial stone. A cement of improper quality will cause cracking. The characteristics of good cement are treated of in Chapter IX. New Portland cement when spread and subjected to a process of aeration will increase in bulk at least 5 per cent. If stones are manufactured with such cement they will blow and crack. Cement increases in strength with age, and therefore stone manufactured with it will also increase in the same ratio; and again, Dykerhoff has shown that slow-setting cement had an average expansive power of .0734 per cent, and quick-setting .2019 per cent, over a period of twelve months. 791. The following detailed particulars for the laying of con- crete footway pavements is taken from " Roads, Streets, and Pave- ments," by Q. A. Gillmore : " Concrete footpaths should be laid upon a form of well-corn- 612 HIGHWAY CONSTRUCTION. pacted sand, or fine gravel, or a mixture of sand, gravel, and loam The natural soil, if sufficiently porous to provide thorough sub- drainage, will answer. "It is not usual to attempt to guard entirely against the lifting effects of frost, but to provide for it by laying the concrete in squares or rectangles, each containing from 12 to 16 superficial feet, which will yield to upheaval individually like flagging stones, without breaking and without producing extensive disturbance in the general surface. " When a case arises, however, where it is deemed necessary to prevent any movement whatever, it can be done by underlaying the pavement with a bed of broken stone, or a mixture of broken stone and grave], or with ordinary pit-gravel containing just enough of detritus and loam to bind it together. In high latitudes this bed should be 1 foot and upwards in thickness, and should be so thoroughly subdrained that it will always be free from standing water. It is formed in the usual manner of making broken-stone or gravel roads already described-, and finished off on top with a layer of sand or fine gravel, about one inch in depth, for the con- crete to rest upon. " The concrete should not be less than 3| and need rarely ex* ceed 4 to 4J inches in thickness. The upper surface to the depth of J inch should be composed of hydraulic cement and sand only. Portland cement is best for this top layer. For the rest, any natural American cement of standard quality will answer. The. following proportions are recommended for this bottom layer : Rosendale or other American cement 1 measure Clean, sharp sand 2 Stone and gravel 5 " " It is mixed from time to time as required for use, and is com- pacted with an iron-shod rammer in a single layer to a thickness less by J inch than that of the required pavement. As soon as this is done and before the cement has had time to set, the surface is roughened by scratching, and the top layer, composed of 1 volume of Portland cement and 2 to 2^ volumes of clean, fine sand, is spread over it to a uniform thickness of about 1 inches and then compacted by rather light blows with an iron-shod rammer. By this means its thickness is diminished to \ an inch. It is then smoothed off and polished with a mason's trowel and covered up FOOTPATHS, CURBS, GUTTERS. 613 with hay, grass, or other suitable material to protect it from the rays of the sun and prevent its drying too rapidly. "It should be kept damp and thus protected for at least ten days, and longer if circumstances will permit; and even after it is open for travel a layer of damp sand should be kept upon it for two or three weeks, to prevent wear while tender. " At the end of one month from the date of laying, the Port- land-cement mixture forming the top surface will hav^ attained nearly one half its ultimate strength and hardness, and may then be subjected to use by foot-passengers without injury. " The rammers for compacting the concrete should weigh from 15 to 20 pounds, those used on the surface layer from 10 to 12 pounds;. They are made by attaching rectangular blocks of hard wood shod with iron to wood handles about three feet long, and are plied in an upright position. Certain precautions are necessary in mixing and ramming the materials in order to secure the best results. Especial care should be taken to avoid the use of too much water in the manipulation. The mass of concrete, when ready for use, should appear quite incoherent and not wet and plastic, contain- ing water, however, in such quantities that a thorough ramming with repeated though not hard blows will produce a thin film of moisture upon the surface under the rammer, without causing in the mass a gelatinous or quicksand motion." 791a. The disintegration and disfiguration of cement walks is frequently due to unskilful manipulation. While the surface mix- ture should be thoroughly rammed and well trowelled, yet this treat- ment should not be continued so long as to bring to the surface a considerable quantity of neat cement, thus leaving the layer of mortar next below without sufficient cement to bind it together. If this is done, the thin layer of cement will flake off when set, re- vealing a layer of almost clear sand. A similar result obtains if attempt is made to retrowel a surface once finished and partially set, but afterwards defaced. Sprinkling the surface before the cement has thoroughly set may cause blisters, which mar the work. If the surface of the setting cement is not protected from the direct rays of the sun, cracks will be produced. 792. One cubic yard of concrete laid 3 inches thick will cover 10 square yards of surface. For the wearing surface the cement and sand are mixed in equal parts. f!ni/-/iriTinches high, with a gutter 12 inches wide. It forms a monolith on sach block, weakened, however, by cuts extending partially through it at intervals of about 5 feet, to allow for expansion and disturbance caused by frost or other agent. 816. Specifications for Standard Granite Curb (Washington, B. C.). The curbing must be of good and acceptable texture and color, dressed 12 inches on the face, 3 inches on the back, and chiselled 6 inches deep on the joints, with no projections beyond the chiselled portion of the joint; the joint to be at right angles to the face and top surface; the top surface to be bevelled inch; the face and top to be plane surfaces, without depressions or irregulari- ties. The length must not be less than 6 feet, depth not less than 20 inches nor more than 24 inches in any portion of a piece, and 634 HIGHWAY CONSTRUCTION. thickness 6 inches. The bed of the curb must average not less than 6 inches in width, and no excessive protuberance will be al- lowed on the sides. 817. Special 8 by 8 Inches Granite Curb. The curbing must be of suitable and acceptable color and texture, dressed on top and the full depth on the face, and 3 inches deep on back. The top sur- face will be bevelled j- of an inch. The face and top to be plane surfaces, without bends, twists, depressions, cups, or other irregu- larities. It will be 8 inches thick, not less than 8 inches nor more than 12 inches deep, and no piece less than 6 feet long. The joint will be chiselled throughout. The bed will be rough-dressed to give secure bearing. 818. Specifications for Bluestone Curb (Washington, D. C.). The curbing must be best North Eiver bluestone, dressed 12 inches on the face and 3 inches on back, and chiselled 6 inches deep on FIRE-CLAY CURB. FIG, 162, FIG. 163, FIG, 164. FIG. 165, FIG, 166, FIG. 167, IRON CURB. FOOTPATHS, CURBS. GUTTERS. 635 the joints, with no projection beyond the chiselled portion of the joint; the joints to be at right angles to the face and top surface. The top surface will be bevelled J of an inch; the face and top to be plane surfaces, without bends, twists, depressions, cups, or other irregularities. The length must not be less than 4 feet, depth not less than 20 inches, and not more than 24 inches in any portion of IL piece, and thickness 5 inches. Each piece must have i bed not less in area than the dressed portion of the curb, and no' "excessive protuberance on the sides. 819. Circular Curb. Circular curb will conform in all respects to the specifications for straight curb, except that it will be cut to the required radius. It must be cut to such lengths that three pieces will make a 90-degree curve. 820. Specifications for Curbstones (New York). The curbstones shall be of the best quality of North River bluestone, 5 inches thick, and not less than 4 nor more than 8 feet long, and 20 inches deep, cut and smooth dressed on the front to a depth of 14 inches, bevelled on top to the slope of the sidewalk. Ends shall be accurately squared, so as to make close joints the whole depth. 821. Specifications for Setting Curb (Washington, D. C.). The trench will be dug 24 inches deep and 18 inches wide, to permit a thorough ramming. A bed of gravel 4 inches deep will be laid in the bottom of the trench and thoroughly consolidated. On this bed the curb will be laid to level and grade with close joints and even and continuous surfaces. The ditch will then be filled with gravel, the first filling to be not more than 3 inches deep, be well rammed by rammers or bars so as to give the curb a solid bearing under its entire length. Other layers will then be rammed in the ditch to within 10 inches of the top of the curb ; the layer for each ramming to be not more than 4 inches deep. The special granite curb will be laid on a foundation of hydraulic concrete, as shown in Fig. 168. On the gravel-bed the concrete foundation made as prescribed for the concrete base for standard asphalt-pavements will be laid, This concrete base will be laid of such depth as to permit the granite curb (of which the depth will vary generally from 3 to 12 inches) to be placed upon it and remain at the proper grade. AH spaces remaining between the curb and the concrete foundation will then be carefully rammed completely full with cement mortar 636 HIGHWAY CONSTRUCTION. or fine concrete suitable for the purpose. The necessary concrete will then be added to bring the foundation to the dimensions shown in the cut. The work of setting this curb will be done by competent stone-masons. If so desired, the contractor will be authorized to StSESJ&l FIG. 1 68. GRANITE CURB (WASHINGTON. D, C.). vs *&fA'&-i s><~* -^v " ' ! Vi FIG. 169, BLUESTONE CURB. finish the foundation in front of the curb with a layer of binder, as prescribed for the intermediate course in coal-tar distillate pave- ments, but no extra allowance will be made for such work. 822. Specifications for Artificial Stone Curb and Gutter (Wash- ington, D. C.). A combination curb and gutter of artificial stone FOOTPATHS, CURBS, GUTTERS. 637 on concrete foundation will be laid on streets, as may be ordered by the Engineer Commissioner. The curb, gutter, and foundation will conform with the dimensions given on drawings on file in Engineer Department. The concrete foundation will be composed of the same materials and will be laid in the same manner as pre- scribed for concrete foundations of asphalt pavements. The curb and gutter will consist of fine concrete composed of one part Port- land cement, two parts clean sharp sand, and three parts clean broken stone not more than 1 inch in their largest dimensions. The exposed surfaces of both gutter and curb will be coated 1-J inch thick with a cement composed of three parts granulated granite (the fragments being of such size as to pass through a quarter-inch screen and free from all dust), and two parts of cement. The cement used in the manufacture of the curb and gutter must conform to the current District of Columbia specifications for slow-setting Portland cement. The work will be carried on uni- formly, and the whole curb completed while in a soft and plastic state, so that it will become a homogeneous solid when set. While still plastic the curb and gutter will be saw-cut at intervals of 8 to 10 feet, as may be ordered, to allow for expansion and contraction, and to give the appearance of cut stone. Contractors may use such methods of moulding the curb into shape as they may deem best fitted to the work. The curb and gutter when set must conform with the cross-section shown in drawing. A conduit for electrical conductors, 4 inches wide and 4 inches high, will be left at the base of the curb if so ordered by the Engineer Commissioner. Hand-holes, to give access to this conduit, will be left at intervals of 50 feet, more or less, as may be ordered, all to be as shown on the drawings. Man-holes will be constructed near each cross-street in accordance with plans and specifications on file in Engineer Department. The exact location of each man-hole will be fixed by the Engineer Commissioner. The cost of these man- and hand-holes, and their frames and covers, must be included in the price per linear foot of the "combination curb and gutter" with electrical conduit. The curb and gutter must be properly protected from injury while setting, and the material used for such protection must be removed within twenty-one 'days from the completion of work, if so ordered. 638 HIGHWAY CONSTRUCTION". The contractor is required by law to guarantee all work for the period of five years from the date of the completion of the contract. 823. Specifications for Dressing Old Curb. Old curb will be dressed by the contractors for street improvements whenever ordered by the engineer. Contractors will employ competent stone-cutters to do the work, and will be allowed the actual cost of the labor employed plus 15 per cent, for tools, sharpening same, and supervision. Certified pay-rolls of men employed and amount paid will be required for each street. 824. Re-setting Curbstones. The curbstones along the line of the work shall be readjusted and brought to the grade, and lines given by the engineer, without extra charge therefor. All curb- stones on the line of the work that are cracked or broken, or other- wise damaged, shall be re-dressed so as to conform practically in form, size, and quality to the requirements of the specifications for new curbstones. New stones shall be furnished when necessary, without extra charge therefor. 825. Hollow sidewalk curbs are shown in Figs. 170, 171; they are especially designed as a conduit for electric wires or cables or for pipes. They are the invention of Mr. E. Grey son Banner, of London, England. The principle is shown in Fig. 170 in its simplest form. The block, a, may be of concrete, through which the channels cc are Pig, 170. HOLLOW CURB. Fig.171. moulded, and which are accessible upon the removal of the flag b. This flag may be continuous in the case of pipes, but for wires, etc., it may be so arranged with hand-holes at short intervals. Fig. 171 is a modified section for use where the wires are to be kept at a distance apart, for the sake of greater insulation, each wire having a separate channel. FOOTPATHS, CURBS, GUTTERS. 639 The curb may be formed in place or manufactured at a factory, in which case the blocks, to secure alignment, are made with projec- tions on one end which fit into corresponding recesses on the other. 826. Gutters. In streets covered with broken stone, a stone gutter is necessary. It may be formed of either stone slabs or pav- ing-blocks, the latter being the better. It should be not less than 18 inches wide. If formed of paving-blocks, the blocks should be laid with their length parallel to the curb, bedded on gravel, and well grouted in with bituminous cement. !V|i} <" '..--'i .'.( ll ,1 \i .. ' ''' 'i ' ' 1 ' I! '.,1 i H li i . , i J ' ' '/, ' [>1|J 1 FIG. 172. PLAN SHOWING MANNER OF LAYING GUTTER-STONES. When stone slaos are used, they should be not less than 3 feet long, 6 inches thick, and from 10 to 15 inches in width. They should be laid alternately (see Fig. 172); for if of uniform width, the continuous longitudinal joint between the gutter and the rest of the pavement will quickly wear into long deep ruts or grooves, which causes severe strains upon the running-gear of vehicles when the wheels, having once entered the rut, attempt to leave it. The gutter should have the same slope as the roadway, and the curb should show seven inches or more above it. In streets paved with asphalt granite blocks or bricks the same material is used for the gutters; the blocks being laid with their length parallel to the curb, instead of transversely as in the street itself. 827. Specifications for Laying Cobble Gutters and Crossings. The cobblestone and flagging will be furnished by the along the line of the work. The materials necessary to be removed shall be excavated to a depth of 12 inches below the top line of the proposed gutter or crossing when fully packed. Any objectionable or unsuitable material found below that depth must be removed, and the space filled with clean sand or gravel. 640 HIGHWAY CONSTRUCTION". All holes or inequalities shall be filled to a proper level with sand or gravel well compacted by ramming or rolling. Upon the foundation thus prepared shall be laid a bed of good bank gravel, 5 inches in thickness, thoroughly compacted by rolling or ramming. Upon this shall be spread a layer of clean, sharp sand, to serve as a bed for the paving-stones, of such depth as may be required to bring the work to grade. The cobblestones shall be assorted as they are brought upon the ground, and no stones that are less than 4 or more than 6 inches long, or less than 2 or more than 4 inches wide, shall be used, and the several sizes must be laid so as to make an even surface when rammed. When thus laid the stone shall be immediately covered with clean, fine sand, in proper quantities, and raked until the joints become filled therewith; the stones shall then be thoroughly rammed to a firm, unyielding bed with a uniform surface and proper grade. The foundation for the gutter and crossing-flag shall be pre- pared in the same manner as described for cobble, upon which the flag shall be laid with close joints and settled into place solidify in such a mannsr as not to fracture the flag. When gutters are laid v/ithout curb, selected stones of large size shall be laid to line in the position and at the height that the curb would be if laid. This, course must be laid true to line and grade and with especial care. Gutters will generally be 4 feet wide, with 12-inch flagging in the centre. 828. Specifications for Brick Gutters. Whenever ordered on streets to be paved with asphalt, brick gutters will be laid. The materials necessary to be removed shall be excavated to a depth of 8 inches below the top line of the proposed gutter. Any objectionable or unsuitable material found below that depth must be removed and the space filled with clean sand or gravel. All holes or inequalities shall be filled to a proper level with sand or gravel well compacted by rolling or ramming. Upon the foundation thus prepared there will be placed a layer of hydraulic-cement concrete 4 inches in thickness. This concrete layer shall conform, in all respects ex- cept depth, with the concrete base as specified herein for standard asphalt pavements. Upon the concrete base so prepared paving- bricks shall be placed on edge with their lengths at right angles to the curb and breaking joints in the direction of the curb. The. FOOTPATHS, CURBS, GUTTERS. outer edge of the gutter shall be left with alternately projecting bricks to tooth into the asphalt pavement. The bricks must be so laid that the upper surface will be smooth and at the proper grade. Immediately after the completion of the asphalt pavement ad- jacent to the gutter, hot paving-tar shall be poured into the joints of the bricks until it rises to the surface. The gutter shall then be covered with a sprinkling of sharp dry sand. If so ordered, instead of the hot paving-tar a grouting of Portland cement and sharp sand in equal proportions, mixed with a sufficiency of water to make a thin grouting, will be used. The bricks for this gutter- paving will be furnished by at its property yards, and hauled thence to the site of the work by the contractor for laying them. Bricks for gutters may be furnished by the at the site of the work. A separate bid is requested for the work if bricks be so furnished. 829. Specifications for Gutter-stones. The gutter-stones to be of stone, not less than 4 feet long and 10 to 16 inches wide, and 4 inches thick throughout; to have a smooth surface free from winds, seams, or other imperfections; to be cut and squared so a& to form close joints with each other and with the curb. The stones shall be laid, at the grade furnished, on a bed of sand 2 inches thick. The joints of the stones shall break joint with the^ joints of the curb. The stones shall be laid narrow and wide alter- nately. The joints shall be filled with a bituminous-cement or Portland-cement mortar. 830. Crossing or Bridge-stones. Street-crossings are footways provided for pedestrians; they are formed of two or more rows of stone slabs, usually with one or more rows of paving-blocks between them. The stone used for crossings should not be less than 3 feet long, 10 inches wide, and 6 inches thick, with the top surface hammer- dressed, the ends cut to a bevel of about 15, as shown in Fig. 174, and dressed so as to form a close joint for the full depth of the stone. The reason for bevelling the joints is to cause the traffic to travel across the joint instead of along it, and thus prevent the formation of the ruts which happens with right-angled joints. The bevelled joints must point towards the centre of the intersection, otherwise the desired result will not be obtained, and ruts will be formal. 642 HIGHWAY CONSTRUCTION. FlG. 173, SECTION AT CROSSING, SHOWING GUTTER PAVED WITH STONE BLOCKS. J t FlG. 174. PLAN OF CROSSING, SHOWING BEVELLED JOINTS. FlG. 175. SECTION OF CROSSING SHOWING GUTTER ; PAVED WITH A SINGLE STONE. FOOTPATHS,, CURBS, GUTTERS. 643 Sandstone is superior to granite for this purpose. At street-crossings the bridge-stones should be kept level with the curb so that pedestrians may step off the path onto the crossing without any drop (see Figs. 173 to 176). FIG. 176. COVERED GUTTER. 831. Specifications for Bridge-stones (New York). Bridge* stones to be of bluestone, equal to the best quality of North Eiver bluestone, free from seams and imperfections. Each stone to be not less than 4 nor more than 8 feet long, except in cases where; specially permitted, and 2 feet wide, and of a uniform thickness, which may vary from 6 to 8 inches, and dressed to a fall on top not varying in evenness by more than a quarter of an inch, and on the bottom bedded, with sides square and full, and ends cut to a> bevel of 6 inches in 2 feet, and in special cases to such other bevel as shall be directed by the Commissioner of Public Works. The- stones to be in quality and workmanship equal to the pattern at the office of the Department of Public Works, and to be cut so as to- lay a joint not exceeding one fourth of one inch from top to bot- tom on the ends and one half inch on the sides. The bridge-stones will be carefully inspected after they are brought on the line of the work, and all those which, in quality and dimensions, do not conform strictly to these specifications shall be rejected and must be immediately removed from the line of the work. 832. Relaying Bridge-stones. The bridge-stones now on the street shall be relaid without extra charge therefor. If any are found defective, new stone shall be furnished therefor at the ex- pense of the contractor. The stones so furnished must correspond in quality, dimensions, and workmanship to the pattern at the office of the Department of Public Works. 644 HIGHWAY CONSTRUCTION. 833. Prices. The prices of the materials employed for footway pavements fluctuate widely, not only in different but in the same localities; therefore the following prices simply exhibit the extreme range : Cents. Bluestone flagging 3" thick, per square foot 35 to 95 Granite stone flagging 6" thick, "per square foot 40 Cement concrete " " 12 Artificial stone " " 18^ Brick " " 9 Granite, straight, per linear foot 85 " circular, " " 100 Bluestone curb, straight, per linear foot 35 " circular " " Sandstone curb, straight, " ** " circular, " ' Brick gutters, per square foot Granite " " " Granite bridge-stone per linear foot. Bluestone 45 35 60 20 40 70 60 110 20 30 22* 125 137 91 110 75 100 38 50 234 III 833a. The Wainwright Patent Curb, Fig. 176a ; is composed of Portland cement and broken stone with a galvanized soft steel FIG. 176A. WAINWRIGHT STEEL-BOUND CONCRETE CURB. bar inserted. It is formed in place; the usual dimensions are 6 inches wide and 18 inches deep, with cuts at intervals of about 10 feet to allow for expansion and contraction. Cost in New York about 87 cents per lineal foot. FOOTPATHS, CURBS, GUTTERS. 615 833b. Metalloid Sidewalk Blocks. These blocks, as made by the St. Louis Expanded Metal Fireproofing Co., are composed of concrete reinforced on the lower side with No. 16 gauge 2J-inch- mesh expanded metal, the long diameter of the metal being placed at right angles to the curb line. Xhe blocks are 2J inches thick, the body composed of 1 part Portland cement and 5 parts of lime- stone screenings, or 1 part Portland cement, 2 parts sand, and 5 parts clean cinders. The top surface, one-half inch thick, is com- posed of 1 part Portland cement and 2 parts of sifted granite -dust, floated to a smooth finish. CHAPTER XVIII. RECONSTRUCTION AND IMPROVEMENT OF COUNTRY ROADgr 834. THE improvement of existing roads may be divided into three branches : (1) Rectification of alignment and grades. (2) Drainage. (3) Improvement of the surface. The first of these consists in the application of the princi- ples which have been laid down for the location, etc., of new roads v and will include straightening the course by extinguishing un- necessary curves and bends; improving the grade by either avoid- ing or cutting down hills and embanking valleys; increasing the width where requisite, and rendering it uniform throughout. The second consists in applying the principles laid down for the drainage of new roads, and in constructing the works necessary to give them effect. The third consists in improving the surface in the best possible manner, either by the forming of an artificial pavement or, if suffi- cient funds for this purpose are not available, by adopting such local materials as will make a comparatively fair surface. 835. Improving Clay Roads. Clay soils can only be made into fair wheelways by means of thorough drainage effected by any of the methods described in Chapter XIV. The narrower the roadway the more effective will be the drain- age. If sand, gravel, ashes, coal-dust, furnace-slag, or shells can be obtained, a coating of any one of them, 4 inches thick, well com- pacted by rolling, will form an improvement; if none of these materials can be obtained, the clay itself may be utilized by being first burned, then spread and rolled. 646 RECONSTRUCTION AND IMPROVEMENT OF COUNTRY ROADS. 647 The manner of preparing and using the clay is as follows : In summer weather, or during the hot season, the soil in the proposed road should be cut out to a depth of two feet into large spits and laid roughly one upon the other, and left in that condition for about ten days. By this time the sun's rays will have evaporated the moisture held by soils of this nature. So soon as the spits are dry they are submitted to the action of fire in the following manner : A circle is formed fifteen feet in diameter, surrounded by a wall made of the roughest and largest spits, two feet high. In the in closure thus formed straw or other light combustible ma- terial is laid; fagots or small pieces of wood are placed on these, and over them are placed other spits, so as to form a cone or pyramid, the whole structure to be about 8 feet high. Fire is then applied to several parts at once, due care being taken to see that the spits sink evenly until the whole mass is well alight. After being well banked the mass is left for a day or two, and as soon as it attains a good red appearance is drawn down, the wall broken, the spits are thrown on top, and others added as required from day to day, until all the earth dug has been submitted to the same process. In a length of 100 yards of road 20 feet wide thus served, it would take about six fires to burn the 12,000 cubic feet contained therein. The cost of labor would probably be twenty or twenty- five cents per cubic yard. The burnt earth is then, after cooling, relaid upon the road, and now, being of a thoroughly porous nature, settles into a good, dry, solid layer. Before applying any of the above-mentioned materials to a clay surface all mud and perishable material must be removed. In fact, all the weather-worn clay should be removed to a depth of 18 inches or more, and the surface thus exposed thoroughly con- solidated by rolling. The following method of burning clay or " gumbo " has been successfully practiced at Clarksdale, Miss. The road-bed was planed and crowned for a width of twenty feet. Trenches about 3 feet wide and 12 inches deep were then cut across it at intervals of four feet, the excavated clay being thrown so as to form ridges between the trenches. Cordwood was then placed over the trenches, the ends of the sticks resting on the intervening ridges ; the trenches thus formed flues. Upon the cord wood the gumbo or clay was thrown in a thin layer; on this was placed a second layer of cord- HIGHWAY CONSTRUCTION. wood, the sticks being laid at right angles with the first layer and as close as possible. This layer was covered with small sticks, chips, bark, and brush. On this was placed a layer of clay, partly clods and partly pulverized. Firing was then begun and con- tinued much the same as with a brick kiln. When the clay had cooled it was spread over the surface of the road, smoothed to the required crown, and the road opened to traffic. 836. In the maintenance of clay roads neither sods nor turf .should be used to fill holes or ruts; for, though at first deceptively tough, they soon decay and form the -softest mud. Neither should the ruts be filled with field-stones: they will not wear uniformly with the rest of the road, but will produce hard ridges. Trees and close hedges should not be allowed within 200 feet of a clay road. It requires all the sun and wind possible to keep its surface in a dry and hard condition. 837. Sand Roads. The aim in the improvement of sand roads is to have the wheelway as narrow and well-defined as possible, so as to have all the vehicles run in the same track. An abundant growth of vegetation should be encouraged on each side of the wheelway, for by this means the shearing of the sand is in a great measure avoided. Ditching beyond a slight depth to carry away the rain-water is not desirable, for it tends to hasten the drying of the sands, which is to be avoided. Where possible the roads should be overhung with trees, the leaves and twigs of which catching on the wheelway will serve still further to diminish the effect of the wheels in moving the sands about. If clay can be obtained, a coating 6 inches thick will be found a most effective and economi- cal improvement. A coating of 4 inches of loose straw will in a few days 5 travel grind into the sand and become as hard and firm as a dry clay road. 838. The maintaining of smooth surfaces on all classes of earth roads will be greatly assisted and cheapened by the frequent use of a roller (either steam or horse) and any one of the various forms of road grading and scraping machines. In repairing an earth road the plough should not be used. It breaks up the surface which has been compacted by time and travel. 839. Improper Use of Scraping-machines. The scraping-ma- chine should not be employed to drag the soft mud out of the ditches and place it in the centre of the road. The use of the RECONSTRUCTION AND IMPROVEMENT OF COUNTRY ROADS. 649 scraper is to remove from the road-surface the weather and traffic- worn material which no longer possesses coherence, and which, no matter how well rounded up and rolled, will be converted into mud after the first shower of rain. This material, along with that removed from the side ditches, must be deposited in such places where it cannot be washed back on the road-surface. As it con- sists chiefly of alluvial and vegetable matter mixed with animal excreta, it is useful for fertilizing purposes and may be disposed of to the neighboring farmers; but it must not be left in heaps on the roadside, to be removed by them at their leisure. 840. Cost of Constructing Earth Roads. The following prices are taken from the bids received for the construction of wagon- roads through the Yellowstone National Park. The specifications were : clearing, 30 feet wide ; roadway, 18 feet wide and 6 inches higher at the middle than the edges; on each side a berme of 1 foot, with a ditch on the outer side 5 feet wide at top, 2 feet at bottom, and 18 inches deep. The roadway to be covered with 9 inches of clay or earth. PRICE PER MILE. Highest, $4382. Lowest, $2529. 841. Cost of maintaining earth roads ranges from $50 to $80 per annum per mile. 842. Value of Improvements. The improvement of roads is chiefly an economical question relating to the waste of effort and the saving of expenditure. Good roads reduce the resistance to locomotion, and this means reduction of the effort required to move a given load. Any effort costs something, and so the smallest effort costs the least, and therefore -the smoothest road saves the most money to every man who traverses it with a vehicle. 843. Before undertaking any improvement it is generally re- quired to know the cost of the proposed improvement and the benefits it will produce. In the improvement of roads the amount of money that may be profitably expended for any proposed im- provement may be calculated with sufficient accuracy as follows. First obtain the following data: (1) The quantity and quality of the traffic using the road. (2) The cost of haulage. (3) Plan and profile of the road. (4) Character and cost of the proposed improvement. 650 HIGHWAY CONSTRUCTION. 844. From the data so obtained ascertain the total annual traffic and the total annual cost of hauling it. Next, calculate the annual cost of hauling the given tonnage over the improved road, which may be obtained from the data given in Chapter X. Then the difference between the two costs will represent the annual interest on the sum that may be expended in making the improve- ment. For example, if the annual cost of haulage over the given road is $10,000 and the cost for hauling the same over the im- proved road will be $7000, the difference, $3000, with money at 6# per annum, represents the sum of $50,000 that may be expended in carrying out the improvement. 845. For the purpose of ascertaining the amount of money that may be profitably expended in improvements, each part of a given road must be separately investigated as above directed, because the amount that may be expended varies with the amount of traffic; and as the quantity of traffic using different portions of a road varies, the data obtained close to a town cannot be taken as correct for distant portions, nor the data obtained for distant; por- tions as correct for portions close to towns. 846. The defects of existing roads may be stated as follows : (1) Unnecessary ascents and descents. (2) Unnecessary length. (3) Imperfect surface. The money benefit accruing from the elimination of any one or all of these defects may be approximately calculated as follows : 847. Profit of Eliminating Grades. Take for example the elimination of a 5$ grade 1 mile long from an earth-road. The observations on this grade show that the daily traffic over it is 224 teams, each dragging an average load of 800 pounds, equivalent to- 24,000 tons per annum; that the time occupied in traversing it is half an hour; that the value of a team's labor is 30 cents per hour. Therefore the cost of haulage on this grade is 33^ cents per ton-mile, or $8064 per annum for the total tonnage using it. From an examination of the ground we find that the grade can be reduced to 2$ by constructing a new piece of road 2 miles long, and that the cost of the change will be $18,000. From the resistance to traction opposed by the new road-surface plus the effect of gravity we find that a team will haul a load, on the reduced grade, of 1200 pounds, and that the time occupied in RECONSTRUCTION AND IMPROVEMENT OF COUNTRY ROADS 05 L travelling the two miles will be one hour. Therefore the cost per ton-mile will be 28 cents, or $6720 per annum for the total tonnage. To this add the annual cost of maintaining the extra mile of new road, say $200; this gives $6920 as the cost per annum, which subtracted from the original cost of $8064 leaves $1144; which sum, with money at 6$, represents a capital of $19,066, a sum sufficient to make the proposed change. 848. The money loss caused by grades may be approximately ascertained as follows : Ascertain the cost of hauling a ton on level portions of the same road and on the grade; take the difference and multiply it by the annual tonnage : the product represents the annual loss. For example, the cost per ton-mile on a level is 22.50 cents, on a 5fo grade 33.60 cents; difference 11.10 cents = loss per ton, or an annual loss on a traffic of 30,000 tons of $3330, which is the interest at 6$ on $55,000; which sum the community could borrow for the purpose of reducing the grade to a level, pay the interest and be no worse off financially, and have a good road besides. 849. Profit of Decreasing Length. The Profit arising from the elimination of any unnecessary length may be stated as follows : (1) Saving in time. (2) Reduction in wear and tear of horses and equipment. (3) Saving the cost of maintenance of such unnecessary portion. (4) Reduction in the cost per ton-mile of haulage. (5) Saving by the return of the land previously occupied by the road to other and perhaps more remunerative uses. (6) The decrease in the working time of the horses will permit of a slight increase in the load. The saving in the above items will vary directly as the distance saved. As an example take a level road 5 miles long and, neglecting the saving in time and rental value of the land saved, and increase of load, what will be the effect of decreasing its length one mile ? (1) Saving of the annual maintenance of 1 mile. (2) Reduction of the time required in travelling over the road, thus permitting persons who make several daily trips to make an extra trip per day at the same cost for driver and horse-feed and with no extra fatigue to the horses. 652 HIGHWAY CONSTRUCTION. (3) Saving in wear and tear of horses shoes, harness, and vehicles. (4) Saving in the ton-mile cost for haulage. Assuming observation of the traffic to show that 100 teams drawing average net loads of 2500 pounds use the road daily, and that the cost per ton-mile is 20 cents, therefore the annual tonnage 33,480 tons, and the total annual cost of haulage per ton-mile = 16696. Summing up the items, we have : Saving of maintenance 1 mile $50.00 33,480 ton-miles, at 20 cents $6696.00 6746.00 Which is equivalent to the interest at Qf on $112,433, which sum could be borrowed to make the improvement. 850. Profit of Improving 1 the Surface. The benefits accruing from this improvement are a general reduction in the cost of haulage and wear and tear. The smooth, hard road-surface enables the same power to haul a greater load with the same and even less fatigue than it can on a rough surface. The less the resistance to traction the greater the load, and the greater the load the sooner will the produce be marketed. Besides the wear and tear on a smooth surface is not one third that on a rough surface. Assuming that it is required to know how much may be profit- ably expended in improving the surface of a level earth road one mile long, and that the observations show that it is used by 50 teams per day, each dragging when the road is in good condition a net load of one ton, and when in bad condition a net load of 1200 pounds, and that the cost per ton- mile when the road is in good condition is 18 cents, and when in bad condition. 39 cents; that the road is in good condition for one half the year, and in bad condition for the other half; that the cost of paving and improving the road will be $7500 per mile, then we have : 150 days, at 50 tons = 7500 tons, at 18 cents = $1350.00 150 " "27 " = 4050 " " 39 " . ,.= 1579.50 11,550 " Cost of maintaining the earth road 50.00 $2979.50 RECONSTRUCTION AND IMPROVEMENT OF COUNTRY ROADS. 655 $2979.50 -r- 11,550 25.81 cents, average cost per ton-mile for haulage. On a broken-stone road in its average condition and at all times throughout the year a team of horses will draw a net load of 3 tons at a speed of 3 miles per hour. If the cost of horses' labor, drivers' time, etc., be taken at 30 cents per hour, the cost per ton- mile will be 10 cents, or for the 11,550 tons annual traffic $1155; to which add for annual maintenance of one mile of road $350. The annual cost will therefore be $1605, which deducted from the former cost of $2979.50 leaves $1375, which, with money at f>< is equivalent to the annual interest on $22,916, which sum may be expended in improving the road-surface one mile long. The annual loss occasioned by the waste of motive power on unimproved road-surface is clearly shown by the above calculations. In the best condition of the earth road it required 50 teams to move 50 tons; on the improved surface but 17 teams are required to per- form a like work, and the labor of 'the teams formerly required may be more profitably employed at other work. On the earth road in its worst condition it required two teams to move one ton; on the improved surface but one team is required to move three tons. 851. Any calculations made to ascertain the benefits accruing to a community from improved roads must necessarily fall far short of the truth, since no account can be taken of the saving in wear and tear of horses and vehicles, of the saving in time caused by the increased size of the loads, which thus decrease the number of days on which hauling must be done, thus allowing the time to be more profitably employed, or of the enhancement of the value of the land in consequence of the improved roads, or of the social advantages arising from their improvement. 85 la. Improving Roads with Crude Oil. Crude petroleum has been used for several years to improve the sandy and gravelly roads of California. The results have been generally satisfactory, this being due in a large measure to the peculiar local conditions of a dry climate, suitable porous character of soil, and an oil having an asphaltic base. The oil abates dust, forms a non-absorbent surface which turns off the rain-water and decreases the amount of mud, and furnishes a dark-colored road-surface which is more pleasing to the eye than the ordinary light color. 654 HIGHWAY CONSTRUCTION. The endurance of oiled roads depends upon the character of the road material and its preparation, and on the selection and appli- cation of the oil. Sandy and gravelly soils absorb the oil readily and form hard surfaces. Loamy, friable soils require to be handled with care; they need a large dosage of oil put on in several applications. Clay soils are liable to form with oil a heavy, sticky mud unless a liberal dose of sand is applied. Kind of Oil. Any petroleum oil will lay dust, but for the pur- pose of binding the loose particles of a road-surface together and forming a stratum that will resist the wear and tear of climate and traffic, it is necessary to use an oil having an asphalt base. The crude oil used in California ranges in gravity from 10 to 23 Beaume and contains from 25 to 60 per cent of asphalt. In some cases an oil has been prepared from the residuum remaining after the naphtha, gasoline, and kerosene have been extracted from the crude oil. A simple test to ascertain the percentage of asphalt contained in an oil is given by Mr. De Camp of San Francisco. Mix a given quantity of the crude oil with an equal amount of refined petroleum, then add 2 per cent of sulphuric acid; after mixing the asphalt will be precipitated to the bottom. By making the test in a suitably graduated glass the percentage can be read off directly. Amount of Oil. The amount of oil required depends entirely upon the character of the road-surface and the depth of loose material present; each kind of material has its own requirements, and no universal rule can be given. It is customary to use on the first application all the oil the material will absorb. In California sandy loam receives from 60 to 600 barrels per mile for a width of 12 feet; clay and adobe from 17 to 400 barrels per mile for a width of 12 feet for the first application, for the second about two thirds as much, and from 25 to 30 barrels for the third and subsequent applications. There is no fixed rule as to the interval of time between the first and second applications; it depends largely upon the character of the material composing the road-surface. Ordinarily the second application is not needed until two or three months after the first, and is then more in the nature of a repair to the defective places which develop than a general complete oiling. Cost. The cost at any particular place will be the function of RECONSTRUCTION AND IMPROVEMENT OF COUNTRY ROADS. 655 the cost of the oil, cost of transportation, and cost of application. In California the range of cost is : Oil delivered, from 20 to 90 cents per barrel; Heating the oil, from 3 to 5| cents per barrel; Applying the oil, about 30 cents per mile. The cost of applying will vary according to the character of the soil and condition of the weather. Hot or Cold Oil. A difference of opinion exists regarding the employment of hot or cold oil. In the early days of road-oiling it was considered necessary to heat the oil, and the results were gen- erally satisfactory; recent experiments show that good results are obtained by applying the oil at the normal temperature (spoken of .as "cold oil"), and the cost is about 5 cents per barrel less than for the heated oil. The advocates of hot oil claim that it is more active and is more thoroughly absorbed; the opponents' argument against heating is its cost, as it requires special .apparatus for its preparation and the results show no advantage over those from the use of cold oil. When hot oil is used it is heated to from 180 F. to 212 F. by passing steam through a coil of pipes placed in the storage- tank. During the heating the oil expands about one per centum for each 20 of heat above 60. For. contract work the oil is measured hot, the price being made accordingly; when cold oil is specified the price is higher. Preparation of the Road-surface. The methods practiced for pre- paring the surface of earth roads to receive the oil vary. In some cases it is graded, crowned, and rolled. In others the surface is left undisturbed, but is covered with a coating of screened sand 1 or 2 inches in thickness; the oil is then sprinkled over the sand and mixed with it by harrowing. In other cases the oil is applied directly to the existing road-surface and then covered with a light coating of sand. In cases where the road is only dusty the oil is simply sprinkled and incorporated with the dust. In some cases the road-surface has been plowed and harrowed before applying the oil. Good roads result from each method, depending upon the different conditions and kinds of soil. In the application of oil to any surface, no pains should be spared to secure its equal distribution. Maintenance. The principal work of maintenance is the keeping of ruts and chuck-holes repaired and the applying of oil to dry 656 HIGHWAY CONSTRUCTION. spots. If the crust becomes broken it must be immediately repaired by the application of a mixture of oil and sand. When a hole starts, all the loose dust should be swept out and sufficient oil and sand spread to fill it, care being taken not to use too much oil, otherwise the patch will remain soft and will require constant mend- ing. Ruts should be removed by the road machine, and the entire surface should be reshaped and rerolled once or twice a year,, according to the amount of traffic. In preparing the streets of Los Angeles, Cal., to receive the oil, the surface was brought to a subgrade and covered with a layer 5 inches thick of gravel containing no stones larger than 1\ inches in diameter; this was compacted by sprinkling and rolling. On this was spread a layer 3 inches thick of gravel containing no stones larger than 1 inch in diameter, which was compacted by sprinkling and rolling. The surface so prepared was then loosened by harrow- ing with a fine-toothed harrow to a depth of 2 inches. Oil was then applied at the rate of from one to one and a half gallons to the square yard. In from 12 to 24 hours after applying the oil the surface was again harrowed and a second coat of oil put on, the quantity being apportioned so that the total amount used for the two applications was not less than 2 gallons per square yard of surface. Places where an excess of oil occurred were sprinkled with sufficient sand to absorb it, and the places which appeared too dry received a further light application of oil. Applying the Oil. The oil is applied by sprinkling from tank- wagons furnished with valves for controlling the flow. Several machines for distributing the oil and loosening and tamping the sur- face of the road have been patented. The simplest apparatus is a metal tank or wagon provided with a sprinkler, consisting of a piece of 4-inch pipe from 6 to 12 feet long, perforated with a row of holes i inch in diameter, from which the oil is discharged by gravity. During the operation of preparing the road-surface and applying the oil, it has been found more convenient and satisfactory to exclude traffic by closing one half the roadway at a time. In this way travel is not obstructed and the work on the road can be carried on free from interruption. If during the rolling the surface becomes sticky, or dry and dusty, dry sand or more oil should be added as required. CHAPTER XIX. MAINTENANCE. REPAIRING ; CLEANSING ; WATERING. 852. Maintenance. The maintenance of a roadway is the keeping of it, as nearly as practicable, in the same condition as it was when originally made; the repair of a roadway is the work rendered necessary to bring it up to its original condition after it has become deteriorated by neglect to maintain it. Thus there is a wide distinction between the two operations, and when the com- parison of costs is instituted errors are frequently caused by setting the repairs of one road against the maintenance of an- other or vice versa. 853. Necessity for Maintenance. No matter how well made a structure may be, or how carefully the materials used have been inspected, the use of it will exhibit defects which it is almost im- possible to guard against, such as variableness in the quality of the material and slighting on the part of the workmen. Moreover, every material, whether natural or artificial, is continually under- going a process of deterioration by the action of the elements; this decay is hastened or retarded in proportion to the means employed and care bestowed to arrest it. The materials employed for pave- ments are not only subjected to the destroying action of the elements, but also to abrasion and concussion, which -by themselves are powerful destroying agents. In view of these facts the con- tinual presence of workmen engaged in repairing pavements must not in all cases be considered as evidence of defective construction or improper materials, but as an honest endeavor by those in charge of the highways to preserve the surface in good travelling condition. 854. The essential requisite to the preservation of a good sur- face is eternal vigilance on the part of the roadway keepers. If a depression appears in consequence of settlement, defective material, or other causes, it must be at once eliminated; if not, it will be 657 658 HIGHWAY CONSTRUCTION". quickly deepened and enlarged by each succeeding vehicle, and will thus become an obstacle to safe travelling. 855. Good Maintenance comprises : (1) Constant daily attention to repair the ravages of traffic and the elements. The character and quantity of these repairs will vary with the character of the pavement and the manner of its construc- tion. With granite blocks laid on a concrete foundation they will be the least, with broken stone they will be the greatest; the other materials, as wood, asphalt, and brick, lying between. (2) Cleansing, i.e., removing the detritus caused by wear, horse- droppings, and other refuse finding its way into the streets. (3) Watering to lay the dust. 856. Systems of Maintenance. Three systems of maintaining pavements are in vogue : (1) By contract, at a fixed price per square yard per annum for a fixed period. Under this method asphalt pavements are main- tained in both the United States and Europe. Wood pavements are also maintained under this system in Europe, but rarely in America. The form of contract under which this system is carried out in Europe is given in Articles 214 and 265. The advantage of this system is that of having some one admittedly responsible for the condition of the pavement. Its defects are (a) the difficulty of determining the exact condition the pavement is in at the expira- tion of the contract, (b) It is an extremely costly system. (2) By independent contracts for the labor and materials, the tools and supervision being furnished by the city. (3) By men in the employment of the city, materials, etc., being purchased in the open market. This is the system adopted by the city of Liverpool, and the excellence of that city's pavements needs no comment. 857. Maintenance of Country Roads. When a country high- way is finished and thrown open to traffic, it cannot be left to take care of itself; if it is, it will soon deteriorate and become bad. It is to the thorough appreciation of this fact that the excellence of the European roads is due. Upon its completion a system of main- tenance must be instituted. Three systems are in vogue : (a) By contract with private parties, (b) Personal service by the rural population, (c) By men permanently employed for the purpose by the community. MAINTENANCE. REPAIRING; CLEANSING; WATERING. 659 (a) The contract system is unsatisfactory, from the difficulty of getting a proper observance of the terms of the contract from the contractor or his employers. In Austria during the last century experiments were made with the letting of the maintenance of the state roads to private parties, which experiments proving unsatisfactory, caused the government to take the work in hand, and it has adhered to this practice up to the present day, with a short interruption in the years 1858-1861, during which time the keeping of the roads was again let by con- tract, and again gave unsatisfactory results. (b) The personal-service or labor-tax system is not applicable to the maintenance of improved roads. In fact, it is not applicable to any class of roads; it is unsound in principle, unjust in its opera- tion, wasteful in its practice, and unsatisfactory in its results. (c) By men permanently employed for the purpose by the com- munity. This system has been adopted by France, Germany, and nearly all European countries. Its advantages are many. The men so employed become familiar with the peculiarities of their sections and with the best way to deal with them, and good men soon learn to take an interest in the road which it is their business to keep in order. "It is in vain to expect the same skill or in- dustry from men employed by the job, or having no interest in the goodness of the road, or in making the most of the means at their disposal." In Massachusetts on two of the State roads repairs are made by men employed for the purpose, who devote their entire time to it. These men furnish horses, wagons, and tools, and such material found within the location as is suitable for repairs. The State fur- nishes the broken stone or gravel, teamed from off the location. Under this system the best possible results are obtained and the roads are at all times in good condition. The experience of the Massachusetts Highway Commission has convinced its members that better results are obtained and money is saved by maintaining the roadway in good condition at all times By a system of continuous small repairs, rather than leaving it until it is practically worn out and then thoroughly rebuilding. The Commission is also convinced that a thorough consolidation by a steam-roller in the spring, after the frost is out, but before the sub- grade is dry, is one of the best means of keeping a stone road in. good condition. 660 HIGHWAY CONSTRUCTION. 858. The maintenance or keeping of the road in proper order consists of : (1) The daily removal of the detritus either in the form of dust or mud, the horse-droppings and other rubbish. (2) The filling of ruts or depressions. (3) The cleansing out of the ditches, catch-basins, and water- courses. (4) Watering the surface in dry weather. The disintegrating action of the weather and the friction of the traffic produces dust ; this dust renders the road heavy for traffic and annoys passengers and horses. If rain falls, the dust is con- verted into mud. A well-swept road produces no mud after a rain, at least not for several days. However, if the humidity continues, the road-surface becomes at first sticky and finally is covered with mud. Mud makes the tracks of wheels apparent; other vehicles follow in them, and after a while ruts are formed which injure the road. Thus it is essential that the dust and mud be removed from the road-surface. The dust may be removed by sweeping, the mud by scraping. These sweepings and scrapings should not be left on the sides of the road to be redistributed by the first wind, but should be immediately removed : they might be utilized by the farmers as an adjunct to their manure-pile. (1) The best time for sweeping is early in the morning before the dew has dried ; besides, there is less inconvenience to the traffic at that time. The removal of dust and mud may be effected either by brooms and hand-scrapers or by mechanical sweepers and scrapers drawn by horses. In the rural districts the former will be most suitable, while in the vicinity of towns the latter will be most economical. (2) Daily attention must be given to the making of slight repairs such as filling ruts and depressions; for, however well the materials may be laid and rolled, the traffic will search out the places which are weak or have escaped the full pressure of the roller. (a) All ruts should be at once filled. If there are three parallel, the centre rut should be first filled. The traffic is thus slightly diverted, as a horse will avoid new metal. (b) Depressions or hollows should be filled at once. The sur- face of the road should never be allowed to lose its regular section. (c) If the surface of the road where these patches are to be placed is very hard, it must be loosened up with the pick. MAINTENANCE. REPAIRING; CLEANSING; WATERING. 661 (d) Water lodging in a depression should not be let off by digging a trench with the pick-axe to the side of the roadway. The depression should be filled up. (e) All loose stones should be picked off at once and stored for use in filling hollows. If allowed to remain, they are not only dan- gerous to horses, but are liable to be crushed or to be forced through the skin of the roadway, thus causing damage. (3) At all seasons of the year the gutters should be kept free from mud and rubbish of all sorts, and anything that impedes the free discharge of the rain-water from the road must be removed. The ditches and culverts should be well cleaned out in advance of the spring and fall rains. In northern localities, where snow lies for some time, the outlets of all ditches and culverts should be opened and cleaned out before the spring thaw sets in. In the fall all weeds and grass in the ditches should be cut, and the culverts and water-outlets left in good shape for the winter. All bridges should be examined at least twice a year. All structures such as bridges, culverts, and drains should be numbered, the numbers being legibly painted on some prominent part; and. a book should be kept in which the dates and condition at periodical inspections are entered. Retaining-walls should be examined and repaired at least once a year. Guard-stones should be reset immediately they become displaced. Parapets, mile-stones, and guide-posts should be periodically examined, repaired, and reset. (4) Watering to lay the dust is essential in summer and occa- sionally in winter. In summer, during the dry hot weather, the road-surface becomes extremely brittle and then should be watered, the dust and refuse having been first removed. Sometimes, in winter especially, after frost the road gets very sticky and picks up freely under passing wheels. It should then also be watered and all slush and mud removed. When the dust is regularly removed from a road it does not require so much watering in dry weather as it otherwise would. A road should never be watered unless it really needs it, as too much water is injurious and it increases the wear from traffic. The most common method of watering a road is that of carrying the water in barrels mounted on wheels or vehicles specially con- structed for the purpose and distributing it therefrom through a perforated pipe. 662 HIGHWAY CONSTRUCTION. Ravelling and Rutting are probably the two most serious evils which have to be contended with in maintaining the surface of broken-stone roads in good condition. Ravelling or loosening of the stones usually occurs during a long period of dry weather; its effects are more serious on roads having light travel than on those subjected to continuous and heavy travel. It may be due to several causes, such as the use of improper binding material, insufficient binding material of good quality, insufficient rolling or watering during construction, or, if the road has been properly constructed, to the removal of the binder through the action of wind and rain. Ravelling also occurs in the spring. The tendency to ravel may be overcome by frequent watering; where this is impracticable the smoothness of the surface may be maintained by the frequent application of thin coats (J to J inch) of screenings or loamy gravel during dry weather and sand in wet and winter seasons. In selecting the gravel one containing an excess of clay should be avoided, as during a rain it forms mud and by adhering both to the tires and the stones will loosen and lift the latter. Before applying the screenings or other material the loose stones should be removed from the surface. They are usually worthless for repairs, as they have become rounded, and conse- quently it would be difficult to get them to bond into a compact mass. Rutting occurs during the spring and wet periods. It is due to some extent to the use of a soft binder or soft stones, and to the use of narrow tires under heavier wheel-loads than the road is capable of sustaining, and to a great extent to the habit of teamsters of driving in one track. "The remedy for rutting would be the substitution of wide for narrow tires, the extension of the double trees of heavy wagons so as to bring the center of the single trees on a line with' the wagon- wheels; then, the wheels and horses moving in the same path, the horses would correct the ruts, and the wheels, especially if clothed with wide tires, would press down the stones loosened by the animals' feet." After ruts appear they must be quickly filled up, otherwise they will act as a catchment for rain, which will penetrate the road-bed soften it, and destroy its resistance to the pressure of traffic. MAINTENANCE. REPAIRING; CLEANSING; WATERING. 663 858a. The Errors Commonly Committed in the Maintenance of Broken-stone Eoads are: (1) The Unskilful Application of Materials. This means using more material than is legitimately required, and the applying it in an improper manner. Eoads always wear out in a succession of small round holes or long straight line?. The usual unskilful method of repair is to put a square patch on a round hole. This means that at least a third too much material is used, with a bumpy or uneven surface as the result; or the long lines are filled up too full, and the overplus means so much stone wasted. In coating a large surface it is the aim of an unskilful roadman to spread all the stone he can, "'to make a good show." The result is the material is heaped on, often three stones thick, or else scat- tered about as if sprinkled on the surface. Material thus improp- erly placed will not be consolidated in the position it was origi- nally intended for; it will be rolled about by each passing vehicle; it thus loses its size, its shape, its angles (so necessary for proper consolidation), and annoys every one using the road. The material so wasted makes the cost of maintenance 15 to 20 per cent greater than is necessary. The misapplication of the material also produces an extremely uneven contour, which necessitates a great amount of new material being again applied later to remedy the uneven- ness that could be easily obviated if the material at first had been properly applied. No material should be placed on the road-surface until the latter is properly prepared to receive it. If ruts have formed, only just sufficient stone should be used to fill the ruts to the level of the adjoining road-surface (it is far better to underfill a rut than overfill it). Material can always be added without much expense,, but ruts filled too full not only cause needless inconvenience, but material is used wrongfully, and becomes absorbed where it is not required, adding a large expense. If the road is regularly coated and maintained, there is no reason why ruts should form. If the manual labor is efficient, no ruts will form if directly a road is tracking, which is the real preliminary for ruts, steps are taken to turn the traffic. This is easily done if the surface is kept clean and free from detritus. When a road shows signs of wearing out small holes successively appear, and these should at once be attended to. The correct process is to open the edge of these wearing holes 664 HIGHWAY CONSTRUCTION. about 3 inches over the exact edge by picking up the road-surface with a sharp pickaxe, then fill with fine stone run out to a thin V-point, and cover with sharp sand or road- scrapings. In dry weather the materials should be moistened with water. In coating large surfaces the material should not be applied more than two stones thick at one time; otherwise the bottom layer will not be consolidated, the top layer will be, and when a secondary settling takes place this will collapse and an uneven surface will result. In patching or coating a hill it is practically impossible to make a patch lie firm unless the road is cross-scored. The extra labor for this is but a very minor expense compared with the loss of value of material where it remains kicking about. with- out being consolidated. Where roads are continually in ruts, and there is no special reason for such to show, it will usually be found useless to attempt any remedy other than the taking up of the rutted portion, strengthening the foundation, and relaying the material. This seems expensive, but it will be found to be the most economical, and a lastingly good road will result. (2) Use of Improper Materials. Well-made roads are fre- quently ruined by the use of local materials whose first cost is cheap, but excessively dear in the end, by want of substance and nnsuitability for the purpose required. (3) Neglect of Repairs. By neglecting to make repairs and restore worn-out material the road becomes so "thin" that it collapses under the traffic. The neglect of applying new material is termed " starving" the road. The remedy is a most expensive one, for the whole of the "starving" has to be made good at once, instead of being spread out in proper maintenance over a period of years. (4) Insufficient and Unskilful Manual Labor. Manual labor must of necessity be employed for caring for the road, and upon its efficiency and skill will depend the condition of the road. This, being the easiest portion of road maintenance to abolish for "saving," and the most constant source of apparent expenditure, is generally the first to suffer when "economy" takes the place of efficient and economical management ; but there is no more wasteful system, leading to bad roads, than thus starving roads. Manual labor should be arranged so as to allow each workman to be properly instructed and superintended. Without this, the MAINTENANCE. REPAIRING; CLEANSING; WATERING. 665 manual-labor difficulty will be found to be one long series of annoyance and disappointment. Until a workman thoroughly ap- preciates that lie is responsible fora GOOD road, and not responsible for making a "show," he is no good as a roadman. " Here's a hole, put a shovelful of stones into it," is not road-repairing. The ever-changing "system" of management invariably results in bad roads. No roads can be effectually maintained where the head or personnel is constantly changing. Each change usually has the same unsatisfactory ending; the roads will be surfeited with material, more often bad because it is cheap, or else starved of necessary material or labor because the initial outlay is great or appears so. 859. Amount of Water Required. Mr. E. P. North found the amount of water necessary to keep macadam roads in the vicinity of New York from becoming dusty to be at the rate of 71.3 cubic feet per 1000 square yards applied twice in a day, or say 143 cubic feet per day. In very hot or beeezy weather this was not quite enough. On the'telford roads in New York 25 cubic feet applied four times a day are necessary per 100 square yards, or about 100 cubic feet per day. One water-cart holding 79 cubic feet waters 35,000 square yards four times a day, keeping it free from dust except during windy weather. 860. Cost of Maintenance. The cost of maintenance is very variable, being principally dependent upon the degree of perfection with which the road has been constructed, but largely influenced by the employment of a sufficient number of skilled laborers to maintain the surface in proper condition under skilled supervision. The cost of maintaining the roads of France varies from $60 to $500 per mile, with an average of $150, of which about half is for labor and half for materials. The following table gives the cost per annum per square yard lor the maintenance of macadamized streets in different localities: Cents. Cents. -Bristol, Eng 8 to 24 Manchester, Eng 12 to 40 Charing Cross, London * . . 100 Paris, France 19 " 258 Glasgow, Scotland 17 Toronto, Can 24 Leeds, Eng 20 to 26 Belgium 4" 10 Liverpool, Eng 24" 86 Germany 20" 80 * Now paved. GG(5 HIGHWAY CONSTRUCTION. The annual expenditure necessary to keep a given highway in proper repair may be ascertained very closely by combining the dif- ferent factors of cost. These factors are : I. The average number of cubic yards of stone per mile which will be necessary to keep the road in proper repair, or, in other words, the quantity of stone which will be required to replace the annual wear caused by traffic and the weather, and removed in the form of mud and dust. This quantity depends upon the following subsidiary factors: 1. Width of road. 2. Nature of foundation, drainage, and thickness of crust. 4. Situation of the road. 5. Quality of the stone to be applied. One cubic yard of stone .broken to pass through a 2-inch gauge will cover 30 square yards of road, one stone thick, and will give f inch thickness of consolidated material. The quantity of material required to cover a mile of road is evidently directly proportional to- the width of the road. On a road 16 feet wide, having a sufficient thickness of crust composed of good sound stone, having a good foundation, the road being well drained and freely accessible to sun and wind, the traffic being equal to 100 tons per day not of an ex- traordinary nature, and carried on broad-tired wheels the wear should be about one-eighth of an inch per annum. Such a road would require about 54 cubic yards of good sound broken stone per annum to keep it in repair. II. The cost of the material. If this is procured by contract, its cost will be positive, but if procured by day's labor under the supervision of the authorities, its cost will depend upon the follow- ing subsidiary factors: 1. Cost of quarrying, including labor, supplies, use of tools, -and royalty or interest on cost of quarry. The cost of quarrying varies with the nature of the stone and character of the quarry. An average price, including all items of cost, is about 60 cents. 2. Cost of breaking, including labor, supplies, interest, and de- preciation of plant. The cost of breaking varies with the stone and ranges from 30 to 80 cents per cubic yard. ._. ._ . REPAIRING; CLEANSING; WATERING. <667 3. Cost of hauling from quarry to depots at the roadside. This cost varies with the distance and character of the roads, and ranges between 20 and 50 cents per cubic yard per mile. 4. Cost of stacking at the roadside. This may be taken at 5 cents per cubic yard. 5. Cost of loosening the stones in the heaps (a considerable item in frosty weather or when the stones have lain for some time). 6. Cost of hauling stones from depots to the portion of the road where they are to be used. 7. Cost of preparing the road-surface to receive the stone. 8. Cost of spreading the stone. The combined cost of the items 5, 6, 7, and 8 varies between 20 and 50 cents per cubic yard. As it consists of manual labor performed by the same men it is difficult to affix a specific value to each item. III. The cost of compacting the stone. This item is very vari- able; it includes the wages of roller attendants, two sweepers, team labor for hauling water, coal, oil, brushes, etc., interest and depre- ciation about 20 per cent of the cost of the roller plant. An average is about 28 cents per cubic yard. IV. Cost of cleaning and scraping. This depends upon the width, nature, and situation of the road, the nature of the traffic, and the quality of the stone. Much diversity of opinions exists as to the frequency and methods of cleaning, and scraping, but it is generally conceded that a road should be scraped as soon as the thickness of the mud reaches one-fourth of an inch. But scraping is not the boot or cheapest form of cleaning a road. Mud is but the refuse of a road with water added. If this refuse is removed when the road is dry, and in consequence dusty, a hand or machine broom can remove nearly three times as much dust as can be scraped off in the form of mud, and the surface of the road will not be injured or torn up. One sweeping will generally clean a road perfectly: whereas when a scraper is employed it must be gone over three or four times before the surface is clean; but under certain conditions of the atmosphere the surface of the road is too sticky to allow of 668 HIGHWAY CONSTRUCTION. sweeping, and at such times it is impossible to do without a scraper. Its use should be as limited as possible, for it will permanently damage a road more quickly than any other method by pulling up the compacted stone. . V. TJie cost of cleaning up the sides of the road, ditches, etc., and keeping open watercourses. This depends upon the frequency with which it will have to be done; usually three times a year is sufficient, and an average price is $15 per cleaning per mile. VI. The cost of sprinkling. This depends upon the fre- quency of sprinkling and accessibility of water, and is made up of team labor for hauling the sprinkling-cart, wages of driver, cost of water, interest, and depreciation of the sprinkling-plant. The average number of days on which sprinkling is needed is 180; number of daily sprinklings, once per day per mile; average cost, 70 cents per mile. To these items must be added a certain sum (about $5) per mile for repair and replacing of tools, etc., and about 5 per cent on the total cost to cover the administrative charges. Combining these factors in the following manner will give the probable cost of maintenance per mile of a given road: Let JV = average number of cubic yards of stone spread per mile; A cost per cubic yard of stone in depots; L = cost of preparing road-surface and spreading stone; R = cost per cubic yard of rolling; C= average number of times sides will require clean - . '' in s; c = cost of cleaning sides, etc., per mile; S = average number of times road will require clean- i j ^g; s = cost of cleaning per mile; W = average number of times road will require sprink- ling; MAINTENANCE. REPAIRING; CLEANSING; WATERING. 669 w = cost of sprinkling per mile; D annual depreciation and renewal of hand tools; 1 '= cost of administration, say 5 per cent of total cost; X~ cost of maintenance per mile per annum. Then X = N(A + L + K] + Cc + Ss -f Ww + D + I. If the stone is quarried by day's labor, its cost will be in which q = cost of quarrying; J = cost of breaking; li = cost of hauling; p = cost of stacking. 861. Repair. When the thickness of the broken stone is so re- duced by wear that it is necessary to restore it, it should be done in sections as large as convenient. The periods at which the restor- ing or recoating will be required depend upon the quantity of the traffic, and vary from one to five or more years. The methods practiced for recoating are : (1) the surface is cleaned from mud and dirt and the new stone spread over it, sprinkled and rolled in the same manner as a new construction; (2) the surface is loosened or broken up by picking or plowing, which operation is termed "scarifying," before spreading the new stones. The object of this is to enable the new stones to become more completely in- corporated with the old material. As to its advantage much differ- ence of opinion exists. Some constructors maintain that it is not good to destroy the compact surface for the questionable advantage of securing a better union of the new stone with the old. Others hold strongly to the opinion that hollow places should be completely excavated to a uniform depth, the stones being sorted and cleaned. 70 HIGHWAY CONSTRUCTION. and then relaid with the addition of new material to restore the proper shape to the surface. Others, again, adopt the middle course of picking furrows on the margin of the patches only, in order to prevent the spreading of the new stone beyond the area of the patch. In deciding which of these methods should be adopted it is necessary to consider all the circumstances. A great deal de- pends upon the thickness of the old covering and the character of road-bed. With a thin covering and a weak foundation breaking up should not be resorted to, as the breaking up will probably make the road weaker than it was- before. In the case of a thick covering which is wearing badly, or where the surface is so full of hollows and ruts that patches are out of the question, the whole of the old surface should be loosened or broken up; but in breaking it up it should not be broken through to the road-bed, as in so doing the foundation may be injured. For breaking up the surface of stone roads many mechanical contrivances have been introduced, some of which have been a success. Spikes inserted at intervals around the driving-wheels of the steam-roller have been much used, but are not to be recom- mended. Machines called scarifiers are extensively employed in Europe. One of these machines recently placed on the market in the United States is shown in Fig. 247B. 862. Organization of Road Force. For the proper care of a roadway an adequate amount of skilled laborers permanently employed is necessary. This labor should be employed by trie community, and be under the direct orders and supervision of the ooimty engineer. The force should be arranged as follows : county engineer, inspectors (assistant engineers), chief foreman, foremen, laborers. The number of men required will depend upon the amount of the traffic. With light traffic one laborer will be required to every 4 miles; with heavy traffic and a wide road one man will be required to every mile. In the spring and fall extra help will be required; MAINTENANCE. REPAIRING ; CLEANSING ; WATERING. 671 the extra men should be directed by the permanent roadman on each section, whose knowledge of his section will enable him to employ them to the best advantage. Chief Foreman. There will be required one chief foreman for every 100 miles of road. His dtfties shall be to superintend the entire road management under direct orders from the County Engineer, received either from himself or his assistants. He shall have no power to engage or discharge any foreman without first reporting to the engineer, but shall have full authority over the laborers. He shall set out and direct all work for the fore- men, shall OK the foremen's requisitions for tools, supplies, horse-labor, etc. He shall under no circumstances purchase tools, materials, or employ special labor unless the requisition there- for is signed by the engineer, in cases to avert an accident or to save expense alone excepted. He shall walk the district in his charge as far as practicable, and carefully take and keep notes of work required to be done, inspect all bridges and structures. He shall examine the foremen's book and see that all accounts are properly entered. He shall keep an order and tool account, a material, team, and general expenditure book, also a careful diary of his day's do- ings. He shall work the same hours as the workmen, and do his utmost to skilfully manage and check all extravagance, filling up any spare time in doing necessary work. In the absence of any fore- man he shall take his place and direct the work until new arrange- ments can be made. He will have charge of the steam road-roller and be responsible for the economical working of the same. Foreman. The best men obtainable should be employed for this work. They should have about ten miles of ordinary country road to superintend, varying, of course, very much with the traffic; they should live as near as is practicable to the centre of their sections. They should not be changed from one section to another, but be retained permanently in the same section. Each foreman should be supplied with a blank diary, in which he should write up every day the work he is engaged upon; each page so written to be initialed by the chief foreman. This diary should always be in his possession while on the road, and should always be ready for examination by the inspector *or engineer, who 672 HIGHWAY CONSTRUCTION". will note in it the date of examination. The foreman will also be supplied with a time-book in which to keep his own and his men's time; also with an account-book in which he will note the recep- tion and weight of all material, keep an account of all tools, extra labor, team-hire, blacksmith and all other accounts of his section. The foreman shall take all necessary instructions from the chief foreman, and in his absence all orders from the inspector or engineer must be promptly carried out. They shall work them- selves and see that the work is properly carried out on their section. They shall have no power to discharge or engage any workman without first reporting the matter to the chief foreman. Tools. Every foreman should be supplied with the following tools for the use of the men .under him and himself : shovels, pick- axes, spades, hoes, rakes, rammers, wheelbarrows, brush-hooks, axes, scrapers, brooms, stone-sledges, stone-hammers, straight-edge, level, line. The tools should be repaired by the nearest blacksmith, under contract for a year or more at schedule rates, and before any tools are repaired the foreman shall give a written order to the smith and preserve a duplicate himself. Whether the county shall purchase a stone-crusher or not will depend upon circumstances, whether stone is to be had in the county or not, or whether it can be purchased cheaper. Roller. The proper maintenance of a road cannot be carried out without the employment of a roller. If the extent of the road will not warrant the purchase of a steam-roller, a horse-roller should be secured. Whichever kind of roller is used, its weight should not be less than 4 tons and need not exceed 10 tons; the weight per inch of width is more important than the gross weight of the machine. Team-labor and Materials. All team-labor and materials should be supplied under contract. The chief foreman of the section will keep the time of all horse-labor and give time-checks for the same. If stone is purchased, it should be bought by weight, And each load delivered should be weighed on a public weighing machine, and the 1 weight-check delivered to the foreman receiving MAINTENANCE. REPAIRING ; CLEANSING ; WATERING. 673 the material, who in turn will deliver to the carter a receipt in the form furnished for the purpose. Accounts. Accounts of all kinds should be sent to the County Engineer direct as soon as the work or contract is complete, and no account should under any circumstances be passed unless accompanied by the necessary order for the work being carried out. Requisitions for tools, etc., should be sent in by the foreman at a fixed date in each month, and a date be fixed for their issuance. Snoiv. When snow has fallen heavily or is drifting, the road- guard must shovel it off the road so as to keep a track open. If he is unable to do this with the assistance of hired laborers, he must make requisition for extra help. If, on account of continued drift- ing, the road cannot be kept open, the travel may be temporarily led over the adjoining fields, care being taken to mark the location of the temporary road by poles and wisps of straw or tree- branches. When the weather permits sleighing for some time, loose stones and gravel liable to cause accidents are to be removed, and bare spots are to be covered with snow. When thaw sets in, all snow and ice on the roads must be speedily removed. County Engineer. The County Engineer with the aid of liis assistants will take direct management of all the roads, set out all work and give directions to the chief foreman, and, in general, superintend the carrying out of all work, make plans and prepare estimates for all materials, keep all accounts and perform all in- cidental duties. Storage- and Delivery of Broken Stone. Depois or spaces for the storage of the broken stone should be provided along the sides of the road; these depots should be close enough together for the* roadmen to wheel out the stone to the intervening portions of the road. The contractor should be required to deliver the broken stone at each of t these depots at such times and in such quantities as the engineer may direct. The stone heaped up at the depots should not be allowed to encroach upon the road or interfere with the gutters; one or two cubic yards will be a sufficient quantity to have at each depot. A convenient size for the stone-heaps will be 6 feet long, 3 feet wide, and 1 feet high. Such a heap will contain ^ cubic 674 HIGHWAY CONSTRUCTION. yard, and the quantity so stored can be ascertained by measurement at any time. 863. Records. It is very desirable that those in charge of roads should adopt some form of record, showing plainly the cost of materials, of labor, and of any miscellaneous expenditures connected with the maintenance of roads. Comparisons of the total cost of different roads, and of the proportion of expenditure for materials and labor, and for other things, would be facilitated, and a step would be taken towards gathering statistics relating to road-main- tenance which are at present wanting in both America and Eng- land. 864. Instructions to Roadmen (published by the Eoad Improve- ment Association of No. 57 Basinghall Street, London, E. C.) will be found useful to roadmen, and are therefore submitted in ex- tenso: , (1) Never allow a hollow, a rut, or a puddle to remain on a road, but fill it up at once with chips from the stone-heap. (2) Always use chips for patching, and for all repairs during the summer months. (3) Never put fresh stones on the road if by cross-picking and a thorough use of the rake the surface can be made smooth and kept at the proper strength and section. (4) Remember that the rake is the most useful tool in your collection, and that it should be kept close at hand the whole year Tound. (5) Do not spread large patches of stone over the whole width of the road, but coat the middle or horse track first, and when this has worn in, coat each of the sides in turn. (6) Always arrange that the bulk of the stones may be laid down before Christmas. (7) In moderately dry weather and on hard roads, always pick up the old surface into ridges six inches apart, and remove all large and projecting stones before applying a new coating. (8) Never spread stones more than one stone deep, but add a second layer when the first has worn in, if one coat be not enough. (9) Use a steel-pronged fork to load the barrels at the stone- heap, so that the sif tings may be available for " binding " and for summer repairs. MAINTENANCE. REPAIRING ; CLEANSING J WATERING. 675 (10) Never shoot stones on the road, and crack them where they lie, or a smooth surface will be out of question. (11) Go over the whole of the new coating every day or two with the rake, and never leave the stones in ridges. (12) Eeniove all large stones, blocks of wood, and other obstruc- tions (used for diverting the traffic) at nightfall, or the conse- quences may be serious. (13) Never put a stone upon a road for repairing purposes that will not pass freely in every direction through a 2- inch ring, and remember that still smaller stones should be used for patching and for all slight repairs. (14) Recollect that hard stone should be broken to a finer gauge than soft, but that the 2-inch gauge is the largest that should be employed under any circumstances where no steam roller is em- ployed. (15) Never be without your ring-guage. It should be to the roadman what the compass is to the mariner. (16) If you have no ring-gauge, remember MacAdam's advice that any stone you cannot put easily into your mouth should be broken smaller. (17) Use chips, if possible, for binding newly-laid stones to- gether, and remember that road-sweepings, horse-droppings, sods of grass, and other rubbish, when used for this purpose, will ruin the best road ever constructed. (18) Remember that water-worn or rounded stones should never be used upon steep gradients, or they will fail to bind together. (19) Never allow dust or mud to lie on the surface of the road, for either of these will double the cost of maintenance. (20) Recollect that dust becomes mud at the first shower, and that mud forms a wet blanket which will keep a road in a filthy condition for weeks at a time, instead of allowing it to dry in a few hours. (21) See that all sweepings and scrapings are put into heaps and carted away immediately. (22) Remember that the middle of the road should always be a little higher than the sides, so that the rain may run into the side gutters at once. (23) Never allow the water-tables, gutters, and ditches to clog, up, but keep them clear the whole year through. 676 HIGHWAY CONSTRUCTION. (24) Always be upon your road in wet weather, and at once fill up with " chips " any hollows or ruts where the rain may lie. (25) When the main coatings of stone have worn in, go ovei the whole road, and, gathering together all the loose stones, return them to the stone-heap for use in the winter to follow ; for loose stones are a source of danger and annoyance and should never be- allowed to lie on any road. 865. The French System of Highway Maintenance. The sys- tem of highway maintenance adopted by* the French, whose roads are unexcelled by any is as follows : The roads are divided into national, departmental, military, and vicinal or country cross-roads. The national roads are maintained entirely at the expense of the public treasury; the departments provide for the second class of roads, and also partly for the military roads; the local cross- roads are maintained by the communes, or when of higher impor- tance by the departments. The national roads aggregate upwards of 23,180 miles in length, of which 1632 miles are paved like a street. These roads average in width 16 metres or 52 feet 6 inches, of which 19.68 feet is for the wheelway, 19.68 feet for the sidewalks, and 13.12 feet for the 'ditches and embankment slopes. The department roads are not quite so wide, their average width being 39 feet. The aggregate length of the latter is about 29,167 miles. The military roads number 28, and are about 932 miles long in all. They are chiefly in the west of France, laid out after the last insurrection of Ven- dee. The sum of about $6,800,000 is yearly expended in making new roads or repairing old ones, and $32,000,000 is expended for maintenance and inspection. The cross-roads are managed by a special branch of the depart- ment of the Minister of the Interior, a branch which employs about 3000 inspectors and 42,000 workmen, specially charged with the duty of keeping these roads in repair. In 1872 these cross-roads aggregated 338,273 miles in length and covered a surface of about 915,000 acres. To the very considerable sum which the communes must apply to the extension and repair of these country roads, the government used to add a yearly grant of $2,300,000; but since 1873 this sum has been reduced to $1,150,000 Annually. MAINTENANCE. REPAIRING ; CLEANSING ; WATERING. 677 The care of the national roads is a large part of the duties of the " Engineers of Bridges and Roads " (Ingenieurs des Fonts et Chaussees) and belongs to the portfolio of the Minister of Public Works. In each department there is appointed by the Minister of Public Works an engineer-in-chief, who has the direction and responsibility of the work of maintenance of such portion of the national roads as lie within that department. He is also placed in charge of some other work in that department; either of rail- roads, canal or river improvements, or the care of the seaports, if such lie in that department. Sometimes he is also in charge of the departmental roads, and in a few cases of the county roads as well. Under him are several Engineers-in-ordinary (Ingenieurs ordinaires), who are employed only in a certain section of the department; each one having charge of the work in an arrondissement. There they direct the repairs according to the general plans of their chief, but at the same time they are allowed consider- able latitude to display their ability or originality and follow out their own ideas in the details of the work. Their duties require them to visit carefully at least four times a year, oftener if necessary, every road confided to their care. The next grade below the engineers-in-ordinary is that of Conductor or Assistant Engineer. The conductor has a subdivision comprising a length such that he may be able to inspect it in detail at least twice each month and still have sufficient time to attend to the other require- ments of the service with which the chief is charged, i.e., of bridges, railroads, canals, seaports, etc. The supervision comprises usually from 25 to 50 miles of road, according to the distribution and the complexity of their main- tenance, and of other details connected with them. The con- ductor makes semi-monthly inspections of the roads under his charge, and, further, he makes his tour of inspection on foot. He gives orders to the foremen of the different gangs at work along the roads. He keeps a record of their work, to see that they do a proper amount. If any have been guilty of neglect, he may recommend to his chief that they be punished. Following each regular inspection he forwards a written report 678 HIGHWAY CONSTRUCTION. to the engineer in charge of that division. He keeps the accounts for his division. He is consulted by the engineer in case of the- receipt of any petition or other affairs upon which his accurate knowledge of the division would make him capable of giving information or advice. If any surveys are to be made, he makes them. He also inspects all road material, all of which is furnished by contract, and has immediate charge of the construction of all new work. The engineer can give no order to the laborers without giving it through the conductor. In districts where there is much to do he is aided by a second assistant engineer. This is the grade held by the younger engineers, who have charge of the drafting and clerical work in the chief-engineer's office, and also assist in the outdoor work when there is a press of it. It is from the ranks of these latter that by promotion the corps of assistant engineers or conductors is kept up to the required number. Their promotion is made on their successfully passing examinations for that purpose. Under the conductor comes the road laborer or cantonnier. The road laborers are divided into squads of five or six. Each one is in charge of an overseer, chosen from one of their number. Each of the road laborers has charge of a length of road varying from 1| to 2| miles, depending upon the condition of the road, the amount of circulation, and the method of maintenance, which would depend upon the nature of its construction. When there happens to be much work to be done at once, a few laborers by the day are hired to assist, but they are reduced to the least possible number. If there is to be work that will require extra laborers for a considerable length of time, they organize another road gang, BO that the work will be done by regular hands. 866. Regulations for Cantonniers (Road Laborers). Definition of the Work of Cantonniers. The cantonniers are charged with the manual labor connected with the daily main- tenance of the roads, over a definite length of road, called a canton. They must obey, in everything relating to their work, the engineers, foremen, and other agents of the administration of roads and bridges. MAINTENANCE. REPAIRING; CLEANSING; WATERING. 679 Nomination of Cantonniers. The cantonniers are nominated by the prefect, from a list submitted to the chief engineer, con- taining three times, or at least twice, the number of candidates required to fill the vacancies. They are dismissed by the prefect on the advice of the chief engineer. Conditions of Admission. To be nominated a cantonnier it is necessary (1) to have fulfilled the laws relating to service in the army, and to be not more than 45 years old; (2) not to be subject to any infirmity which may hinder daily and diligent labor; (3) to have worked on the construction or repair of roads; (4) to have a certificate of good conduct from the mayor of the commune or the subprefect of the arrondissement. Candidates who can read and write will be preferred. Chief Cantonnier. The cantons of the roads in a department shall be grouped in districts containing at least six cantons. The six cantonniers will constitute a brigade ; one of them shall be chief cantonnier; he must be able to read and write, and shall be chosen from the cantonniers distinguished for zeal, good conduct, and in- telligence. The chief cantonniers shall have a shorter length than other can- tonniers, so that they may be able to attend to special duties allotted to them. They shall accompany the foremen* in their rounds, and note the orders which may be given by the cantonniers of their brigade, and see that the orders are carried out. They shall accordingly go over the whole extent of their district at least once a week, varying the days and hours of their visits, to satisfy them- selves of the presence of the cantonniers, and to direct them in their work; they shall report to those under whose orders they are more particularly placed, and shall furnish to the engineers all the infor- mation that may be required of them. They may be temporarily employed in superintending and keep- ing account of the works of re-dressing the paved causeways, and in directing itinerant gangs of workmen. Distinctive Marks of Cantonniers. Cantonniers shall wear a blue jacket and a leather hat, round which shall be a band of copper 0.28 m. long and 0.055 m. broad, with the word "cantonnie?^ $ivfc out in it. The chief cantonniers shall wear besides on the left arm an armlet of the prescribed pattern. There shall be given besides to each man a mark consisting of 680 HIGHWAY CONSTRUCTION. a staff 2 metres long, divided in decimetres, shod with iron, and furnished at the top with a strong iron plate 0.24 m. wide and 0.16 m. high, on each side of which shall be shown in letters 0.08 m. high the number of the canton. This mark must always be set up on the road at less than 100 metres from where the cantonnier is at work. The Work of the Cantonniers. The work of the cantonniers consists in maintaining and repairing the roads daily and constantly, so that they may be dry, clean, and smooth, safe in times of hard frost, and of a satisfactory appearance at all seasons. To effect this, they must, subject to the orders and instructions which may be given them in case of need : (1) Insure the flowing off of water by cleansing the gutters, pipes, etc., by making small drains for the purpose wherever they may be necessary, taking care that these drains should never be made in the body of the road. (2) At suitable times open and maintain the ditches, regulate the sides, throwing the surplus earth on the neigh boring, ground, if there is no objection, or putting it together to facilitate its measure- ment or removal. (3) Kemove as soon as possible with a scraper or shovel all liquid or soft mud from the whole breadth of the road, even if there be neither hollows nor ruts, and collect the mud in regular heaps on the sides to be measured, if there is room for it there. (4) Spread the mud, when dry, on the sides which have lost their shape or have a slope of more than 1 in 25 from the road, and throw the surplus on the neighboring fields, if not objected to. (5) At the approach of winter redouble attention to all that is prescribed in the two preceding paragraphs, to prevent lumps of frozen mud. (6) In dry weather remove the dust and deposit it on the sides. (7) Clear away the snow from the whole breadth of the road, or at least from the middle, particularly at places where it accumulates and obstructs the traffic; throw it immediately on the neighboring fields if possible, or collect it in heaps on the sides, so as to show drivers of vehicles where the road is. (8) Break and remove ice from the road, and scatter sand jmd rubble, especially at the sides and at sharp turnings. MAINTENANCE. REPAIRING; CLEANSING; WATERING. G6L (9) Also break the ice in the ditches and remove it where it accumulates, so as to threaten flooding of the road in the thaw. (10) In the time of thaw assist the flowing off of the water and remove pieces of ice, mud, and dirt, so that the effects of the thaw may prejudice the traffic and road as little as possible. (11) Collect, break, and stack in separate heaps and in a par- ticular shape all loose stones, and those projecting or only just showing if too large, and those near in the neighboring fields which can be used for the purposes of the road. Break the materials intended for maintenance, if the breaking is not done by the con- tractor. . (12) Cut or dig up thistles or other weeds, especially before their flowering season. (13) Clear away loose stones for the road and everything which may hinder the traffic. . (14) Clean and clear away earth, plants, and extraneous matters from the plinths, string-courses, and parapets of bridges, etc. (15) Look after the preservation of mile-stones, sign-posts, and bench-marks on the road. (16) Cultivate and look after plantations belonging to the 'State, see to their preservation and to that of plantations of private owners, straighten provisionally all young trees bent by the wind, and do generally all that the welfare of the road demands, con- formable to more particular instructions given by the engineers of the district for carrying out the above general orders. Employment of Materials. On roads in a state of repair the road laborers shall conform to the following rules for employment of materials. The materials shall be made use of as they are required, always choosing damp weather for their employment, avoiding wholesale coating and throwing down stones at random. To proceed regularly, care should be taken to observe in time of rain the hollows and tracks of vehicles, which perceptibly alter che shape of the road. These worn parts should be cleaned and picked, particularly afc the edges, but only to the depth necessary to insure the binding of the materials. The materials arising from the picking should be cleared of earth and broken if necessary before being used. The filling up of the hollows or wheel-tracks should be effected 682 HIGHWAY CONSTRUCTION. with the debris 'and with the necessary quantity of new material received through the engineer. It must be carefully beaten so as to incorporate it with the lower layer, and then made to conform to the contour of the road. The parts thus restored should be main- tained with particular care until they are completely consolidated. With respect to roads which are not in a good state of repair, but which nevertheless are open for traffic, one should endeavor to keep them in as good a condition as possible by employing, with the care which has just been indicated, the materials available. All large or projecting stones should be taken out, as they oause damage, and they should be broken to a proper size before being used again. The coatings more or less extensive to be made on worn roads will be prescribed by the engineer, who will also decide on the materials to be used. The hollows and ruts to be filled up must first be cleared of mud and earth, and their surface then picked to a depth of from 4 to 5 centimetres (1^ to 2 inches). The materials should not be spread except in layers of from 5 to 6 centimeters (2 to 2-$ inches), which should be carefully beaten and consolidated. Task-work to be performed. To stimulate and maintain the activity of the cantonniers, the engineers, inspectors, and foremen shall assign them work to be performed in a given time, whenever local circumstances permit it. A summary of information on these tasks shall be entered in that part of the cantonnier's book re- served for the instructions of the service. Work thus prescribed shall be one of the principal objects of supervision by the immediate head of the cantonniers, as well as by the mayors and road commissioners. Determination of Working Hours. From the 1st of May to- the 1st of September the cantonniers shall be on the roads, with- out quitting them, from 5 o'clock in the morning to 7 o'clock in the evening. The rest of the year they shall be there from sunrise to sunset. They shall take their meals on the road at hours fixed by the chief engineer. The total duration of meals shall not exceed two hours, but during great heat it may be prolonged to three hours. Removal of Cantonniers. Cantonniers may be removed either singly or in brigades, when the needs of the service imperatively MAINTENANCE. REPAIRING ; CLEANSING ; WATERING. G83 require it, to points indicated to them. These displacements shall not take place except under an express order from the engineer. Compulsory Attendance of Cantonniers in time of Rain, Snow, etc. Rain, snow, or other inclemency of the weather shall not be a pretext for the absence of cantonniers; they must in such times redouble their zeal to prevent damage and keep the road in good condition for the whole extent of their cantons. They are, however, authorized to make themselves fixed or portable shelters which shall not interfere with the public way or adjoining prop- erty, but which must be in sight of the road and less than 10 metres off, so that the presence of the workmen can always be as- certained. Gratuitous Assistance to Travellers. Cantonniers must render gratuitous aid and assistance to drivers and travellers, but only in case of accidents. Surveillance over Breaches of Highivay Law. To prevent as much as possible breaches of highway law, the cantonniers shall warn travellers and occupiers of the adjoining lands who may be disposed to commit them. They shall consequently keep an eye on repairs, building, deposits, encroachments, and planting which may take place without leave on the highway. They shall report any such breaches to the surveyor, either when he makes his rounds, or at once by letter or by message through the chief cantonnier. Tools with which Cantonniers must be provided. Every can- tonnier shall be provided, at his own expense, with a wheelbarrow^ an iron shovel, a wooden shovel, a road -pick, an iron road-scraper, a wooden road-scraper, an iron rake, an iron crowbar, an iron sledge-hammer, and a line 20 metres long. The head cantonniers must besides be provided with three bon- ing rods (rods in the form of a T much employed in European countries to range in grades, etc.), with a level graduated to indi- cate gradients, and with a double metre measure. Tools of a Particular Kind to be furnished by the Administra- tion. -Each cantonnier shall be entrusted with an iron ring 6 centimetres (2^ inches) in diameter, so that he may ascertain if the stones which he has to spread on the road have been broken ac- cording to the specifications. Providing Tools in advance to Cantonniers. Cantonniers who have no means of procuring them can have any tools they require HIGHWAY CONSTRUCTION. supplied in advance. The repayment of the cost of these tools will be insured by the administration by stoppages, which, except in cases of dismissal, shall not exceed one sixth of the monthly salary. Keeping Tools in Repair. Cantonniers shall keep their tools in a good state of repair. If they become negligent in this respect, they will be repaired by the administration, and the expenses will. be repaid in the same manner as for new tools. Tools must not be taken to be repaired during working hours. Excuses for absence based upon the necessity of getting tools repaired will never be accepted. Cantonniers' Books. Every cantonnier will be provided with a book suitably ruled and headed, in which he will make notes on the work and conduct of the laborers, any orders and instructions given them, and information of the work which has been assigned to them. It must be presented by them to the agents charged with the super- vision of the road, every time they are required to do so, under penalty of the stoppage of a day's pay for every time they neglect to produce it, or three days' pay in the case of having lost it. Means of Verifying the Absence of Cantonniers. The absence and negligences of cantonniers will be verified by the engineers and the agents of the administration employed under their orders, who will make a note of them in the books just spoken of. Absence can also be verified by gendarmes on their rounds, by mayors of the parishes in which the cantons are situated, and by road commissioners. Leave of Absence at Harvest-time. At harvest-time, when the road is in good condition, cantonniers can obtain leave of absence from the engineer-in-ordinary, when authorized by the engineer-in- chief . They will receive no salary while on leave of absence, at the expiration of which they must return punctually to their posts or they will be immediately superseded. Surrender of Book and of Distinctive Badges on Dismissal of a, Cantonnier. When a cantonnier is dismissed, he must surrender to the engineer his book, his staff, his ring, and the distinctive badges which he wears on his arm and cap. Failing to do this, double the value of these articles will be retained from that which is due to him for salary at the time of his dismissal. Classification and Salary of Cantonniers. Cantonniers of MAINTENANCE. REPAIRING ; CLEANSING ; WATERING. 685 each department will be divided into three classes of equal number, whose salary, for each class, will be fixed by the prefect, on the proposal of the chief engineer. The classification will be made each year by the chief engineer, on the report of the engineer-in-ordinary, and according to the services of the cantonniers during the preceding year. The chief cantonniers will be divided into two classes, likewise of equal number. Their salaries will be fixed, like those of the ordinary canton- niers, by the prefect, on the proposal of the chief engineer. The cantonniers receive from $10 to $20 per month, and the chief cantonniers receive 20$ more. Indemnity for Removal. Cantonniers who leave their cantons by order of the engineer will receive an indemnity of one fifth more than their salary, and three fifths for every day they sleep out. No indemnity for removal will be allowed to head cantonniers except when they go out of the district of their brigade. In this case, the indemnity to which they are entitled will be regulated in the same way as those which are paid to ordinary cantonniers. Annual Gratuities. Every year, on the report of the engineer- in-chief, the prefect may grant to the most deserving cantonnier in each district of the engineer-in-ordinary, a gratuity, which shall not exceed a month's salary. A similar gratuity may also be awarded to that one of the chief cantonniers of the department who shall have rendered the best service. Fines on Account of Absence. Every cantonnier who shall not be found at his post by one of the agents having a right of super- vision on the road, shall be subject to a fine of three days' pay for the first time, of six days in case of a second offence, and be dis- missed the third time. Those who, without being absent, shall not have done enough work during the month, or who have neglected the duty entrusted to them, will be fined enough to pay for repairing any damage resulting from their negligence. A part of these fines may be granted by the engineer-in-chief, on the report of the engineer in ordinary, for the benefit of those cantonniers who by. their zeal and work have deserved encourage- ment. 686 HIGHWAY CONSTRUCTION. 867. The system described above, while employed throughout France for the maintenance of the national roads, is applied to all the other roads m but 27 of the 87 departments. In three departments the engineer-in-chief has, it is true, the direction of the work, but has under him a different corps of engineers or commissioners to superintend the work upon the county or vicinal roads. In 57 of the departments a commissioner appointed by the Minister of the Interior has charge of the county or vicinal roads. His corps comprises commissioners or trustees in the arrondissements ana cantons who are appointed by the prefect of the department. The ordinary vicinal roads are in the charge of the mayors of the communes. The direct agents are inspectors, who are charged with the duty of watching this work, and are responsible for its proper execution. Inspectors. The chief inspector is under the direct authority of the prefect, and he has charge of all the vicinal roads of the department, and all the sub-inspectors are under his orders. He executes the laws and regulations prescribed, and the inspectors of arrondissements have similar power in their own districts. The chief inspector may, when he deems fit, order that certain opera- tions shall be carried out under agents directly under his control. Under the law of 1836, the appointment of inspectors cf all grades lay with the prefect, who might, if he so chose, transfer the control of the roads to the government corps of engineers. This right of option was taken from the prefect by the law of 1866, which included among the duties and privileges of the Council General of the department the right to designate to what parties should be confided the execution of work upon vicinal roads. The laws of 1871 confirmed this right and extended it to departmental roads, so that to-day the nomination, organization, and control of the staff in charge of department roads of all classes is the exclusive right of the prefectural authority, without restriction. The inspectors are divided, ordinarily, into inspector-in-chief, inspectors of arrondissements, and inspectors of cantons. They shall be French citizens and must be at least 21 years of age. The law of 1836 prescribes that in each department there shall be a commissioner whose duty it shall be to examine candidates for the position; and when a vacancy occurs, it is the duty of the pre- MAINTENANCE. REPACKING ; CLEANSING ; WATERING. 687 iect to announce the date of such examinations in his department, and send this notice to the prefects of adjoining departments. The Minister of the Interior is also notified of all such vacancies and changes. The duties of the inspectors employed on the vicinal roads are to study the projects, arrange the plans, estimate the cost, and watch the execution of all road work, under the authority of the prefects and the mayors. Their pay is fixed by the Council Gen- eral; and they are never to be remunerated by a percentage on work performed. The Laborers. The workmen for all main department high- ways and roads common to several communes are appointed by the prefect. The mayors of the communes name those employed on the ordinary vicinal roads; but as this appointment implies a fixed charge upon the commune, his action must be sanctioned by a vote of the municipal council. Day's Work of Proprietors. France has a system of working out road taxes, but it is carried out as follows : For work of this nature two periods are generally fixed in each year, ranging from one month to six weeks in length, each. The mayors of the com- munes fix the dates, and so arrange it that any work commenced can be finished in the specified time. And in connection with the inspector of the canton, the mayor also divides the workmen among the several roads and fixes the hours for beginning and ending work at each place. Five days before the date fixed the mayor sends to each laborer working under this system a notice requiring him to report at a certain day and hour, upon a certain road, for such work as may be there assigned to him. In case of sickness the laborer must make this fact known to the mayor within twenty- four hours after receiving his notice; and while the mayor may postpone the service required, this cannot be extended beyond the current year. As an unnecessary number of workmen at any one place leads to confusion and embarrassment, it is the duty of the mayor to detail at one time and on any one piece of work only a sufficient number of laborers to best accomplish a specified task without loss of time. If this labor is to be expended on a vicinal road of common interest to several communes, the prefect of the department designates the time and location of such work. Each workman under this system carries to the place designated 688 HIGHWAY CONSTRUCTION. such common tools as the mayor's notice may direct. Tools with which the farmers are not ordinarily supplied are furnished by each commune from the fund appropriated to public works. All beasts of burden must be harnessed, and all vehicles must have a driver, and the time of this driver is received as a full acquittance for the time of one man. Farmers may substitute for themselves, or members of their family, other men hired and paid for by them- selves. These substitutes must be able-bodied men not less than 18 nor more than 60 years of age. The length of the day's work is fixed in each department by a general rule issued by the prefect, and it varies according to the seasons of the year. This day's work cannot be divided, but must be furnished entirely by the laborer. In case of legitimate inter- ruption by reason of bad weather, the laborers are bound to com- plete it at the earliest date possible. If the laborer fails to report at the hour indicated, or in any way fails to complete his legal day's work, the lost time must be paid for in money, and this fine can be legally recovered by the municipal receiver of taxes. Works carried out on vicinal roads under the labor-tax system are under the direction and control of the mayor of the commune in which such roads lie. This functionary is assisted by the in- spector in organizing his force and commencing work, and each day's work is preceded by a roll-call, compared with the list fur- nished by the mayor. If any laborer breaks any of the rules fixed for the conduct of the work, comes unprovided with the tools called for in his official notice, or in any way does not conscientiously per- form the duty assigned him, he can be sent from the work, and the value of his services, or the proportionate part thereof, collected in money. At the end of each day's work the superintendent of works credits each laborer upon his official notice with the number of days and class of work done, and at the same time discharges the original requisition for labor. After the work is completed this accredited notice is signed by the mayor, and sent by him to the municipal receiver, and the latter makes the proper entry upon his books or register of prestataires. In case a commune neglects or refuses to vote the number of days' work necessary on its roads in the proper time for perform- ance, and the sub-prefect advises the prefect of this fact, it shall be the duty of the latter official to serve a special notice upon the MAINTENANCE. REPAIRING ; CLEANSING ; WATERING. 689 mayor of the defaulting commune demanding that he execute the required work within the specified time. This same notice also 'notifies the farmers that unless the work is well done in the time fixed, its value will be required from them, in money. This notice must be made public by the mayor; or in case of his refusal by a special agent of the prefect. All work of this character is done under the supervision of an inspector appointed by the prefect or sub-prefect, and the certificate of execution is delivered by the mayor on the certificate of this inspector. If the mayor refuses to do this, the certificate of the inspector himself is valid. Task-work by Proprietors. Task-work has certain advantages over work by the day, for the laborers are free to select their own time, and by more active exertions they can shorten their hours of labor. When the municipal council of a commune has arranged a basis upon which it can convert day's work into task-work, and this schedule has received the approval of the prefect, the mayor of the commune may decide, so far as the smaller roads are concerned, whether work in his commune shall be done by one system or the other, as he may deem best. This decision is binding upon all the prestataires who have declared their intention of working out their taxes. The prefect of the department, may in a similar manner decide as to the execution of work upon the main highways and roads of common interest to several communes. When such task-work is to be done, the requisition states the class and amount of work and the date by which it must be com- pleted. The character of work required is further indicted upon the ground by the inspector of the canton, and it is carried out under his direction. The party assigned to a task is responsible for its proper execution; and upon the receipt of the measurement and certificate of the inspector that it is properly done and within the given time, the mayor accredits the farmer with his task. Work improperly done must be done over again, and within a time fixed by the mayor. Contract Work. The mayors, with the authority of the prefect for vicinal roads, and the prefect for the main highways and smaller roads common to several communes, may let by contract the con- struction and repair of these roads, But under the law of 1836, the proprietors, even when the work is converted into tasks, cannot be credited for taxes with work done under the control and for the 690 HIGHWAY CONSTRUCTION. account of a contractor. Nevertheless, when work on any depart- ment road is let by contract, the conditions of the contract oblige the contractor to receive in return for services the day work or tasks of the proprietors according to a conversion tariff approved by the Council General of the department in the first case, and by the municipal council with the approval of the prefect in the sec- ond case. In cases where the department supplies this labor in lieu of taxes from the laborer and cash paid to the contract or, the de- partment by its agents makes the requisitions and superintends the execution exclusively; the contractors having nothing to do with the disposition of the men. But if the prestataires do not carry out their obligations, the contractors may call upon the mayor or the inspectors to compel the fulfilment of these obligations. Cash Work. In theory all work for which money is paid should foe executed under a public contract. Nevertheless, with the au- thority of the prefect certain work may be le.t by private argree- ment under the following conditions : (1) For work or supplies when the value does not exceed $600. (2) For work when the conditions forbid the delay of a public letting. (3) That which by its nature requires special skill and experi- ence on the part of the contractor. (4) That which cannot be let by contract after two several attempts to do so. Work may also, with the authority of the pre- fect, be economically carried out either directly under the control of the inspectors, or by way of indirect taxes, in cases of urgency or when other methods of execution have been recognized as im- possible or less advantageous. Under these conditions the work should, if possible, be accomplished by the task system. All projects must be approved by the prefect, and all specifi- cations for work must contain the clause that the contracts are subject to the general conditions imposed upon contractors for vicinal roads as annexed to the general instructions issued on December 6, 1870. The provisional or final acceptance of work performed upon main highways or roads common to several communes lies with the inspector of the arrondissement, assisted by the inspector of the canton, and made in the presence of the contractor. The accept- MAINTENANCE. REPAIRING ; CLEANSING ; WATERING. 69 L ance of vicinal roads lies with the mayor in the presence of the inspector of the canton, two members of the municipal council, and the contractor. The contractor is always summoned on these occasions, but his absence is no obstacle to the action of the offi- cials. All difficulties arising from disagreement as to work performed on vicinal roads, or from damage caused by these works, and not arising from a material expropriation of lands, can be adjusted by the council of the prefecture, with appeal to the council of state. Commissioners of Supervision. In some departments, the pre- fects have thought it proper to delegate a portion of the care of inspection required by the many details of work on vicinal road& to a commission appointed by the prefect and made up from members of the General Council, the councils of the arrondisse- ments, the mayors, and certain proprietors particularly interested in the good condition of the roads. Where a road passes through two arrondissements and is too long to be easily watched by one commissioner, it may be divided, and its several parts supervised: by distinct commissioners. Each commission names its own presi- dent and secretary and fixes the day and place of meeting. When, the prefect or sub-prefect attends a meeting, he is the president; for the time being. When, the prefect thinks best, these commissioners may be con- sulted upon projects recommended by the inspectors for new works, and upon a basis of a division of expenses between the; communes. They may also designate several of their number- to> take part in the acceptance of work done by contract. Within thai- first three months of the year, these commissioners send to the sub- prefects their observations upon the state of the roads and point out the localities most urgently needing repair. In this report they also name the workmen who have most faithfully performed their duty, as well as those who have been careless or slow in the performance of their work. The Police of the Roads. No one without previous authority can perform any act upon a road that in any way interferes with its function as a public way or interrupts travel. And it is specially forbidden to make any trenches or openings; to deposit stones, earth,, or rubbish upon it; to take away any sand, gravel, or other material; to spread anything over the road ; to divert water channels so as 092 HIGHWAY CONSTRUCTION. to cause washing of the road; to interrupt in any way the flow of water in the ditches, even temporarily; to construct or repair any building, wall, etc., bordering upon the road ; to open ditches, plant trees or hedges along said road, or to dig wells or cisterns nearer to the road than provided in the regulations. To perform any of these intended acts, authority must first be formally requested. For all vicinal roads this authority is granted by the mayor with the advice of the inspector; and in no case can the mayors give a verbal authorization. For main highways and other more impor- tant roads the authority comes from the prefect, upon the report of the inspectors, or from the subprefect under similar advice. Every authorization expressly reserves the rights of third parties, and stipulates that the roads must be restored to their normal good condition. Ditches and Slopes. In giving to the department commis- sioners or to the Council General the right to give to vicinal roads the necessary width, the law of 1871 accorded them the right to include all the land required for proper ditches and slopes. These ditches must be cleaned as often as necessary, and the expense of so doing is charged to the commune; the ditches being a legal part of the road, and protected against encroachment in the same manner as the road proper. If the authorities have not opened a ditch along the whole length of a road, as sometimes happens, the bordering proprietors may do so by first having the lines and levels given them by the proper parties ; without this authority they are expressly forbidden to touch the ditches. The care of ditches opened for their own protection and convenience lies in the hands of the proprietors. Rural Roads. Outside of the vicinal roads properly so called, there are in all communes a certain number of minor roads or means of communication which, while of little importance, per- haps, must yet be carefully maintained, as they may lead to a public fountain, a watering-place for cattle, or to common pasturage. Such roads are termed rural roads in the law of 1839, but they are really public roads in the sense that their use is open to all, that they cannot be claimed as private property by the owners of adjoining soil, and that they are legally under the care of the pub- lic authorities and are maintained in the same manner as are other roads of the commune. CLEANSING ; WATERING. 693 The method adopted is to map every road and every public path in the commune, and expose this plan for one month at the office of the mayor of the commune. Any objections made to the correct- ness of the plot or claims of private ownership of roads shown are submitted to the municipal council, which is to sift out those having a basis of fact. And this same official body renders an opinion upon the degree of utility of the roads shown, and the possibility of sup- pressing certain ones so that the soil may be sold for the benefit of the commune. The map with the report of the municipal council is then submitted to the prefect of the department, who examines it to see that no vicinal roads have been included under the head of "rural." The opposition to the official dedication of a certain road may be founded upon a claim of property, or upon the fact that it is not public. The property claim is decided in the courts of justice; the second case must be decided by the administrative power, that is, the prefect. When a minor road of this kind is definitely classified as a "rural road " it is public property, and the administrative author- ity itself cannot restrain travel on it except in case of absolute necessity. If a commune wishes to enlarge such a road, it can do so only by an amicable agreement with the owner of the necessary land, unless the prefect officially classes it among the vicinal roads. If a rural road is suppressed, the soil can be sold for the benefit of the commune; but in such case the proprietors bordering on such a road can either demand that the use of it be continued to them, or that the commune provide some other passage or pay them an Indemnity. 868. Street Cleansing. Although circumstances legitimately determine the intervals at which streets shall be cleaned, neverthe- less clean, well-swept streets not only add materially to the pros- perous appearance of a town, but they also have a very marked influence upon the health and morals of its inhabitants; wet and muddy, badly-formed, ill-drained streets cause dampness in the subsoil of the dwelling-houses in the vicinity and a humidity of the atmosphere, both of which tend to produce a low standard of health in their neighborhood, irrespective of the wet surface through which pedestrians have to wade whenever they are obliged to cross such streets. 694 HIGHWAY CONSTRUCTION'. Dusty streets, too, are very injurious from the gritty silicate- loaded air arising from them. Such an atmosphere when inhaled is known to produce disease of the lungs, even when free from the dust arising from horse-droppings or other organic impurities. 869. The dirt-producing causes common to all roadways are : (1) Detritus produced by the attrition of the paving material, horseshoes, wheel-tires, and shoe-leather. This cause cannot be eliminated. (2) The horse-droppings, which add an offensive element to the body of street dirt, are, if collected at once, valuable as manure. This is done by the street orderly boys in London. If properly- cared for, it would undoubtedly afford an income greater than the cost of collecting it. (3) Dirt forced up through the joints of block pavements. Under modern specifications the joints of block pavements are intended to be closed with a water-proof material. This of course would give full protection against this source of dirt, but in the majority of block pavements it is doubtful if this requirement is ever faithfully performed. A few months generally suffices to dis- lodge the imperfect filling, and the material of the substratum quickly shows itself on the surface of the pavement. (4) House and shop refuse carelessly swept into the streets is an ever-present source of street dirt. London imposes and enforces a fine of not less than $25 and not exceeding $200 upon any person sweeping or throwing any refuse, dirt, ashes, dust, decayed fruit, or offensive matters of any kind upon the foot or carriage ways. Also any person refusing to have the dust or ashes removed by the scavengers or obstructing them in the performance of their duties is liable to a penalty not exceeding $25. Again, the method of removing house-refuse is a prolific source of street dirt. The re- ceptacles containing it are brought out and are placed on the 3tl ge of the curb long before the cart makes its appearance or can be rea- sonably expected to do so. 870. The result of these receptacles, filled with heterogeneous collections of house-refuse, being left unprotected in the public streets is that their contents are quickly strewn about the surface of the street, by their being upset accidentally or purposely; and the appearance of the street, which has probably been carefully MAINTENANCE. REPAIRING ; CLEANSING ; WATERING. G95 swept and garnished during the night or early in the morning, quickly assumes, especially in a high wind, a very offensive char- acter, and probably has to be re-swept and cleansed before the ordi- nary traffic of the day commences. 871. With good pavements the amount of refuse to be removed is reduced to a minimum. With pavements the wear of which is practically nothing, the dirt consists principally of manure, which has a ready sale. The reduction in the amount of unsala- ble refuse is an object to be sought for; its collection and dis- posal is an expensive item. This reduction can only be effected by the adoption of impermeable pavements. In Berlin and Liverpool the average quantity of refuse col- lected by sweeping has been continuously decreasing in spite of increased traffic and area, this reduction being due to good pave- ments. 872. Composition of Street Dust. The following analysis of street dust is given by Mr. H. G. Hanks, State Mineralogist of Cali- fornia. The samples, examined under the microscope, contained vegetable fibre, principally horse-manure and the decaying debris of Oregon pine and redwood planking, bits of coke and coal, glass, horse-hair, quartz sand, some blue particles the nature of which could not be determined, and a dark-colored, finely-divided, half- dried mud which was pleasant neither to the sense of sight or smell. A portion mixed with distilled water and placed in a bottle swarmed with life in forty-eight hours. Professor Tyndall has also shown that dusty air is alive with the germs of the bacteria of putrefaction, whilst the pure fresh air which he gathered on a mountain peak in the Alps is devoid of such germs, and is absolutely powerless to produce any organisms. Persons living in streets that are improperly swept or watered are unable to open doors or windows with impunity by reason of the dust. Dr. Letherby, in 1867, analyzed dry mud from the streets of the city of London dried by exposure for many hours to a tempera- ture of from 266 to 300 degrees Fahr. At the same time he ana- lyzed, for comparison, well-dried, fresh horse-dung and common farm-yard dung. The results of the analyses of the mud from stone pavements are given in Table LXXXV. HIGHWAY CONSTRUCTION. TABLE LXXXV. COMPOSITION OP MUD PROM STONE-PAVED STREETS, HORSE-DUNG AND FARM-YARD DUNG. (Dried at 300 degrees Fahr.) Constituents. FreshJIorse- dung. Per cent. Farm-yard Dung. Per cent. Mud from Stone-paved Streets. Maximum organic (dry weather). Per cent. Minimum organic (wet weather). Per cent. Average. Per cent. Organic.. . 82.7 17.3 69.9 30.1 58.2 41.8 20.5 79.5 47.2 52.8 Mineral 100.0 100.0 100.0 100.0 100.0 The higher proportion of mineral matter in wet weather proves that in such weather the abrasion of stone and iron is greatest. Dr. Letherby estimated that the average proportions of stone, iron, and dung in the muds were : Horse-dung 57 per cent Abraded stone 30 Abraded iron 13 100 per cent The mud was so finely comminuted that it floated freely away in a stream of water. In the mud of wood pavements, the proportion of organic matter in the dried mud was larger than in the mud of stone pave- ments. It amounted to about 60 per cent. The amount of moisture in the street mud varied according to the state of the weather. Stone Pavements. Moisture. In the driest weather rarely less than 35 per cent In ordinary weather In wet weather " 70 to 90 873. The detritus of the material of a granite pavement con- stitutes but a very small proportion of the total quantity of mud- MAINTENANCE. REPAIRING ; CLEANSING ; WATERING. 6 1*7 forming dust. Colonel Haywood exemplified this proportion in an interesting manner, taking the instance of the granite pavement of London bridge, 3-inch Aberdeen granite sets, which was re- moved in 1851, after* having been down nine years. The average loss of granite over an area of 3950 square yards, he estimated, was equal to 2 inches of vertical wear. The total volume of granite worn away was therefore about 219^- cubic yards, assuming that the surface was a continuous mass of granite, though there was of course a considerable superficial area of joints. Assuming that the granite worn of! was reduced to the state of fine powder, it was increased in bulk probably one hal I., and its volume had been (219^ X H = )329 cubic yards. Adding 5$ for the loss upon .stones removed and replaced from time to time, the total quantity worn off and reduced to powder and carried away, mixed with the dust of the street and mud, would only have amounted to 345.7 cubic yards for nine years, equivalent to a wear of .105 cubic yard aboufra tenth of a cubic yard per day. Whereas the quantity of dust removed daily in dry calm weather was from 3 to 3J cubic yards over thirty times as much as the granite detritus. So much for horse-droppings and shoe-leather, which must have constituted twenty-nine thirtieths of the total accumulation, independent of the contributions of house-refuse, in the inhabited streets. Table No. LXXXVI shows the number of cubic yards of street-refuse collected in a few cities. TABLE LXXXVI. AMOUNT OP REFUSE COLLECTED PROM CITY STREETS. City. Street Mileage. Refuse removed. Cubic yards. 780 180 000 73 70 499 365 259 398 Buffalo 225 100 000 660 150 000 341 535 709 Philadelphia 700 266 831 125 127 623 440 200 000 698 HIGHWAY CONSTRUCTION. In 1898 data was collected from the cities of the United States which showed the average quantity of street sweepings collected to be 168.9 tons per 1000 population, or approximately three million tons for all the cities of the United States. Regarding the fertilizing value of sweepings the Department of Agriculture has collected data from which it appears that their value is about two thirds that of farm-yard manure. 874. The relative amount of dirt produced by the different pavements, if swept daily, appears to be about as follows : Pavement. Cubic Yards per 1000 Yards of Surface. Asphalt ... . 007 to 04 Wood (impervious joints) 04 ' 07 .07 ' .20 Granite (impervious joints) ... 015 ' 024 .07 ' .25 Macadam ... 10 ' 35 These figures are only approximations and will vary with the amount of traffic, state of the weather, and character of the pave- ment of intersecting streets : if these are productive of dirt, a large quantity will be dragged by the vehicles on to the good pavement, which is thus debited with a large quantity of material which does not rightfully belong to it. The care exercised in the removal of the ashes and garbage by the occupiers of the buildings on the street will also influence the amount of dirt to be removed. 875. Methods employed for Cleansing. (1) By hand during the day. (2) By hand during the night. (3) By hand 1 and machinery during the night, supplemented by a street orderly or patrol system during the day. Of the above methods each locality will have to decide upon the one which is best suited to its requirements. For large cities the third method is the most suitable. 876. Systems of Executing the Work. (1) By contract; the contractor furnishing all the tools and labor. MAINTENANCE. REPAIRING; CLEANSING; WATERING. G99 (2) By contract for the labor only, the city furnishing the tools and machinery. (3) By contract for the horses and removal and disposal of the refuse, the city furnishing the labor and machinery. (4) By the city, with its own staff and machinery. Cleansing by contract has generally proved unsatisfactory, from the difficulty of obtaining a proper observance of the terms of the contract by the contractor and his employes, and it has been found that the work can be more carefully and systematically carried out by the civic authority with its own officers and staff. It is, perhaps, true that the work may be done under the contract system at less actual cost to the taxpayers, but all public work should be done in the best manner possible irrespective of cost, thoroughly, but without extravagance; and the result of such work, especially where it affects the cleanliness and the appearance of a town, soon fully repays any moderate extra cost that may thus have been incurred, irrespective of the enormous benefit that is conferred upon any community by the reduction of disease and the death rate by a proper attention to such necessary sanitary work. The semi-military organization introduced by the late Col. Waring in the street-cleaning department of New York City has proved eminently successful. He employed as superintendents men especially fitted by either military or technical training to carry out the duties assigned to them; he organized the laborers into a brigade of self-respecting and efficient workmen, clothed them with a conspicuous white uniform, which most of them keep surprisingly 'lean in spite of the work they do. The men are in responsiblj charge of work; if they shirk it, the fact is recorded against them, while good work is also noticed and reported. Each sweeper is furnished with a small wheeled iron framework, to which he attaches a bag of coarse cloth, a broom with a scraper on the back, a watering-can, a short shovel, and a scraper when he has asphalt to look after; with these tools he is expected to keep a definite area of pavement clean. The sweepings, instead of being left in heaps along the gutter to be blown about by the wind and scattered by wagon-wheels, are shovelled up and placed in the bag carried on the truck-frame; when one bag is filled it is tied up and '00 HIGHWAY CONSTRUCTION. placed on the curb, and another placed in position on the truck- frame. These bags are collected by wagons. The work is done under the supervision of foremen, inspectors, and other officers, who report how eacji man is doing his duty. In case the men wish to make complaints, they must first state their case to a committee of forty-one drivers and sweepers; if the committee cannot decide the case, it goes to a committee of five drivers and five officers of the department; and in case this committee does not come to a decision, it is settled by the Commissioner of Street Cleaning. 877. Cost of Cleaning. The average cost of cleaning the dif- ferent pavements appears to be as follows : Asphalt 003 cent per square yard per cleaning Stone block 005 " " " " " Wood 007 " " " " " Brick 0034 " " " " " Broken stone 0106 " " " " " The average cost of supervision varies from .011 cent to 34 cents per mile. Table LXXXVI1, compiled from Bulletins Nos. 20 and 50 of the U. S. Census, shows the methods employed for cleaning streets, i.e., by the city or by contract, by hand or machine; the average num- ber of square yards swept each week and the number of persons employed during 1903; the cost of cleaning, sprinkling, and re- moving snow, and the per capita cost of these services during 1904 in the principal cities of the United States. TABLE LXXXVII. COST OF STREET CLEANING IN THE PRINCIPAL CITIES OF THE UNITED STATES, 1904. City. Av. No. Sq. Yds. Swept per Week. No. of Persons Em- ployed. Annual (1904) Cost of Cleaning. Sprin- kling. Snow Removal. Per Capita Akron, Ohio, H 1*... Albany, N.Y.,B 2... Allegheny, Pa., B 2 .. Allentown, Pa.,H2 . Altoona, Pa., B 2 ... Atlanta, Ga., B 2. ... 1,736,973 2,471,338 6,927,840 461,586 420,257 1,710,000 41 92 95 10 17 28 $15,190 56,083 69,258 10,514 4,883 23,705 $5,191 $0.42 0.58 0.41 0.26 0.11 0.26 $1,750 1,760 * Symbols indicate method of cleaning: H = swept by hand. 1 = by contract. . M= " machine. 2= " city. B = " "both. 3 = partly by city and partly by contract. F = flushing machines. MAINTENANCE. REPAIRING; CLEANSING; WATERING. 701 TABLE LXXXVII Continued. City. Av. No. Sq. Yds. Swept per Week. No. of Persons Em- ployed. Annual (1904) Cost of Cleaning. Sprin- kling. Snow Removal. Per Capita Atlantic City,N.J.,H2 Auburn, N.Y.,H 2. . Augusta, Ga., B 2. . . . Baltimore, Md., B 3. . Biiighamton,N.Y.,B2 Birmingham. Ala.,B2 Boston, Mass., B2. . . Bridgeport, Conn., B2 Brockton, Mass., H 2 Buffalo, N. Y., B 3 . . Butte, Mont., M 2 . . . Cambridge, Mass., B 2 Camden, N. J.,B2 .. Canton, Ohio, H 2 .. . Charleston, S. C., B 2. Chattanooga, Tenn., B2 331,090 244,997 205,130 7,092,267 934,095 701,442 614,020 850,000 10,802,859 485,022 725,000 847,072 594,194 901,824 575,844 120,000 175,000 16,512,000 6,500,000 6,674,236 4,300,000 31,728 550,000 849,754 739,981 2,691,801 5,491,200 894,759 65 18 15 285 30 19 711 58 28 200 16 30 29 25 35 22 20 12 450 255 250 125 15 25 70 40 130 21 $37,125 13,927 3,063 237,168 11,077 6,047 524,447 31,999 9,761 144,691 13,873 30,999 28,267 8,170 15,994 6,771 4,999 $7,852 975 2,819 4,984 600 1,155 166,559 11,718 11,246 2,652 21,421 28,000 $1.28 0.50 0.14 0.45 0.36 0.17 1.60 0.55 0.67 0.62 0.89 0.80 0.34 0.25 0.28 0.24 0.54 $1,355 3,640 270,802 283 10,034 79,139 450 17,999 571 8,391 Chelsea, Mass., B2 . . Chester, Pa., B 2 Chicago, 1 11., B 2 Cincinnati, Ohio, B 2. Cleveland, Ohio, B 2.. Columbus, Ohio, B 2 . Council Bluffs, I a., H 2 Covington, Ky., H2 . Dallas, Tex., M 1. . . . Davenport, la., H 2 . Dayton, Ohio, H 2... Denver, Colo., B 2.. . DesMoines,Ia.,B2.. Detroit, Mich 6,591 275,456 240,499 158,999 15,069 3,022 15,919 15,917 23,738 59,638 58,505 21,041 202,788 11,112 10,844 6,401 6,626 76,399 0.18 0.75 0.39 0.50 0.12 0.35 0.32 0.75 0.65 0.72 0.29 0.65 0.34 0.30 0.19 0.13 6'32 0.57 0.58 0.22 0.31 54,017 10,200 5,009 2,397 48,435 942 4,222 2,819 7,432 Dubuque,Ia., B 1 . .. Duluth, Minn.. B2.. . Elmira,N. Y.,B2... Erie, Pa., B 2. . ... 206,000 943,854 543,947 626,000 397,583 896,740 513,013 79,749 493,640 341,410 467,982 875,860 1,717.476 56,026 881,531 1,024,000 133,332 17 30 15 17 2 17 62 21 20 16 6 25 65 .37 50 65 5 272 734 207 1,097 E.St.Loms,Ill.,MlF Evansville, Ind., M 1 Fall River, Mass., B 2 Fitchburg, Mass., B 2 Fort Wayne, Ind., B 2 Galveston,Tex.,H2. Hamilton, Ohio, H 2. Harrisburg, Pa., H 2. Hartford, Conn., B 2 Haverhill, Mass., B 2 Hoboken, N. J.,B2 . Holvoke, Mass., B 2 . Houston, Tex., H 2. . 11,909 29,586 5,754 11,050 10,447 6,803 16,183 5,028 15,535 8,514 36,517 36,759 7,100 10,670 9,305 19,137 0.67 0.81 0.62 0.22 0.63 0.35 24,937 10,702 11,362 5,931 3,653 7,212 14,340 702 HIGHWAY CONSTRUCTION. TABLE LXXX.VII Continued. City. Av. No. Sq. Yds. Swept per Week. No. of Persons Em- ployed. Annual (1904) Cost of Cleaning. Sprin- kling. Snow Removal. Per Capita Indianapolis, Ind.,B 1 Jacksonville, Fla.,B2 Jersey City, N. J.,B 1 Jkhiiistown, Pa., B 2. . Joliet,lll.,H2 Joplin, Mo., H 2 Kansas City, Mo., B 2 Knoxville, Tenn., H 2 LaCrosse, Wis., B2.. Lancaster, Pa., B 2 . . Lawrence, Mass., M2. Lincoln, Neb., B 2. . . Little Rock, Ark., B 2. Los Angeles. Cal.,B 3 Louisville, Kv., B 2. . Lowell, Mass., B 2 .. . Lynn, Mass., B 2 . . .. Maiden, Mass., M 2.. Manchester, N. H.,B2 Memphis, Tenn., B 2. Milwaukee, Wis., B 2. 5,239,260 461,904 1,500,000 277,638 1,340,346 373,788 15,500,000 120,000 407,360 153,842 33,0:7 230,885 71,500 3,228.104 2,932,400 325,000 250,150 13,477 447,084 800,000 175 30 100 45 36 4 125 9 10 13 40 13 10 265 155 60 38 19 45 71 400 389 12 18 68 300 22 10 66 175 52 2890 44 59 $72,499 6,190 65,145 16,264 $38,591 2,925 3,452 SO. 54 0.27 0.35 $1,800 0.52 486 80,530 2,695 5,120 5,241 8,272 11,962 4,308 61,499 78,418 38,858 13,660 4,500 3,113 21 ,426 110,539 59,464 6,492 5,045 15,127 119,647 23,510 4,204 48,899 79,637 22,489 5,790,858 48,231 38,944 39,866 3,617 " 32,76 i 12,819 16,018 1,012,889 313,964 20,452 64,830 58,062 7,623 3,838 0.46 0.25 0.29 0.11 0.23 0.26 0.11 1.86 0.33 1.17 0.69 0.40 0.32 0.38 0.61 0.76 0.15 0.16 0.33 0.49 0.44 0.12 O.C8 0.26 1.29 1.81 0.84 1.19 0.34 0.28 6^29 0.67 0.25 0.76 0.88 0.64 0.64 0.42 0.20 0.50 4,500 2,347 848 8,592 1,156 130,205 62 28000 21,935 8,680 7.432 22,562 61,051 116,860 44,879 16,502 1,800 9,301 17,892 13,731 Minneapolis, Minn. ,B2 Mobile, Ala., B 2 Montgomery, Ala. , B2 Nashville, Tenn. ,.B 2 Newark, N. J., B 2 . . New Bedford, Mass., B2 4,175,946 452,066 1,017,582 1,082,755 2,497,651 176,271 45,000 1,556,535 3,093,363 37,000 224,693,583 2,126,480 811,160 840 12,940 14^803 7,487 900 Newcastle, Pa., B2 .. New Haven, Conn.,B2 New Orleans, La.,H 2 Newton, Mass., B2 .. New York, N. Y., B 3 Norfolk,Va.,B2.... Oakland, Cal.,B 3... Omaha, Neb 29,696 15,402 42,600 46,841 8,523 1,058,528 Oshkosh,Wis.,B2... Passaic, N. J.,H2... Paterson, N. J.,H2 . Pawt ticket, R.I.,H2. Peoria, 111., H2 Philadelphia, Pa., B 1 Pittsburg Pa., B 2 Port land, Me., B 2.. . Port land. Ore., B2.. . Providence, R. I., B 2 Quincv,Hl.,H2. .... Racine, Wis., M 2 . . . 340,000 10,015 269,100 195,137 2,596,756 74,692,412 10,200,000 90,000 1,352,000 725,233 148,977 70.000 19 36 37 31 83 1080 500 39 35 99 7 20 4,747 2,480 231 10,416 ' 34,240 5,068 157 11,055 14,340 2,156 21,136 11,304 311 MAINTENANCE. REPAIRING; CLEANSING; WATERING. 703 TABLE LXXXVII Continued. City. Av. No. Sq. Yds. Swept per Week. No. of Persons Em- ployed. Annual (1904) Cost of Cleaning. Sprin- kling. Snow Removal. Per Capita Read ing, Pa., HI .... Richmond, Va., B 2... Rochester, N. Y., H 3 Rockford, 111., B2.... Sacramento, Cal., H 2 Salem Mass B 2 337,213 717,259 5,050,000 616,086 590,760 335,000 94,416 42 68 315 11 32 20 55 $19,927 66,905 115,707 10,861 14,357 8,177. 26,918 18,131 200,533 19,296 $600 $115 $0.23 0.78 0.94 0.32 1.01 0.69 1.00 0.31 0.60 0.35 40,029 20,455 16,532 6,867 31,116 5,745 13,200 3,500 10,600 Salt LakeCity,U.,B2 San Antonio, Tex San Francisco, Cal., B 1 6,600,000 2,263,189 2,200,000 685,536 1,200,000 646,743 100,000 528,180 31,710 1,544.632 418^00 1,031,492 1 ,262,274 3,000,000 2,454,836 7,750 6,067,728 250,000 43,296 1,060,785 4,825,110 685,092 1,521,313 5,043,486 5,467,636 16,061,670 345,058 404,418 50,100 651,888 1,800,492 1,234,873 24,640 895,747 1,500,000 423,600 673,040 210 25 45 36 32 21 71 34 6 30 30 39 32 550 181 50 135 10 10 50 154 14 70 330 97 314 22 18 15 8 25 40 14 77 50 9 37 Savannah, Ga., B 2.. Schenectady, N. Y., B2 Scranton, Pa.., H 2 . . Seattle, Wash., B 2... Sioux City, la., B 2. . . Somerville, Mass., B 2 So. Bend,Ind.,B2... So. Omaha, Neb., H 2 Spokane, Wash., B 2.. Springfield, 111., B 2.. Springfield, Mass., B 2. Springfield, Ohio, H 3 . St. Joseph, Mo 18,581 30,393 8,111 14,953 0.16 0.31 0.21 0.31 0.35 20,910 11,530 16,130 31,217 17,688 17,246 533,493 60,254 5,365 59,628 7,356 3,549 19,836 42,043 2,250 20,079 109,824 54,820 216,691 7,698 12,546 0.56 0.44 1.10 0:46 0.16 1.14 0.54 0.25 0.75 0.15 0.26 0.51 0.28 0.06 0.24 1.52 0.96 0.78 0.17 28,220 797 19,011 507 St. Louis, Mo., B 3 . . .. St. Paul, Minn., B2. . Superior, Wis.,M 2. . . Syracuse, N. Y., B2. Tacoma, Wash., H 2. . Taunton, Mass., B 2. . Terre Haute, Ind., B 2 Toledo, Ohio, B2 Topeka,Kan.,B2 Trenton, N.J.,B 2.... Troy,N.Y.,B2 Utica N.Y.,B1 180,883 40,029 829 23,089 2,416 2,682 4,509 30 4,597 5,641 5,051 16,540 2,185 Washington, D.C.,B 3 Waterbury, Conn., B 2 West Hoboken, N. J. H 2 Wheeling, W. Va., H 2 Wichita, Kan., B 3. . . Wilkesbarre, Pa., B 3. Wilmington, Del., B 2 WoonHocket,R.I.,H2 Worcester, Mass., B 2. Yonkers,N.Y.,B2... York, Pa., B 2 15,731 7,670 0.49 0.23 13,111 41,281 25,544 382 5,840 42,358 11,460 0.16 0.22 0.86 0.64 1,228 25,701 Youngstown, O., B 2 . . 12,523 6.25 704 HIGHWAY CONSTRUCTION. 878. The method of cleaning employed in Berlin, which is said to be the cleanest city in Europe, is as follows : The men are city employes. The sweeping-machines are city property, but the horses are hired by contract. The removal of sweepings is also done by contract; the con- tractors for this work being obliged to maintain suitable dumping- places, in return for which they receive for their free use the street sweepings. These sweepings are of some value, the con- tractors often realizing over $20,000 per annum from them. The contractors are bound under all circumstances to supply enough wagons to remove each day all street waste. The number of wagons required varies with the weather. In dry weather often hardly half so many wagons are needed as in wet weather. They are required to remove the rubbish as soon as it is swept up, and only in cases of bad weather are the sweepings allowed to stand more than one hour before being carted away. If these regulations are broken, the contractors forfeit a certain amount to the city. The streets are cleaned during the night. The number of men employed by the city is about 600, and the number of sweeping-machines in use in 1889 was 42. The area cleaned in 1889 was 3,361,312 square yards. The average daily amount cleaned by each man was 5716 square yards. The area swept by a machine ranges from 6545 square yards on bad pavements to 10,315 square yards per hour on asphalt pave- ment. The total expenses of the street-cleaning department in 1888 and 1889 were $481,493.48, made up of the following items: Wages $193,261 .44 Uniforms 2,769. 12 Tools, materials, etc 44,819.76 Carting away. . . 182,487. 12 Sprinkling 53,110.56 Depots for supplies 1,221.12 Public closets 1,279.44 Miscellaneous 2,544.48 $481,493.04 MAINTENANCE. REPAIRING ; CLEANSING ; WATERING. 705 Of this sum the street-car companies paid for cleaning and sprinkling the parts of the street occupied by their tracks the sum of $24,135.58. The quantity of refuse removed from the streets was as follows: In 1882-83, 95,493 wagon-loads; in 1888-89, 97,969 wagon-loads. The number of loads, therefore, varied very little in spite of the considerable increase of area cleaned. In fact in the year 1888-89 the number was about 16,000 less than in 1878. when it amounted to 113,994 wagon-loads. This was due to the constant increase of good, impervious pavements. The wages of the laborers employed in the street-cleaning department vary between 36 and 83 cents per day, in addition to which they receive uniforms free. The salaries of inspectors range from $357 to $636 per year; they also receive their uniforms free. New employes after 1 years service are advanced to a higher grade. The men are paid for Sundays and holidays, and in case of sickness receive half -pay. Old workmen are pensioned after 10 to 15 years' service at $100 per year, and for 30 years or more $150. With relative allowance between, the number of pensioners in 1889 was 11. Assistance is also rendered to sick employes. In 1889 about $100 was expended for this purpose. 879. Tn Paris street sweeping is performed by 2200 men, 950 women, and 30 boys. They begin work at 3 A.M. in the summer and at 4 A.M. in the winter and continue without interruption till 11, when the work for women ceases; the men continue for 10 hours and are paid by the day from 65 to 74 cents. The women are paid 6 cents per hour and cannot earn more than 45 cents a day. All are obliged to provide their own brooms. The roadmen in charge of the sweepers are paid from $21 to $25 a month. Those receiving the lower salaries are obliged each month to con- tribute the odd dollar to a reserve fund that is deposited to the credit of each workman until he quits his employment. The plant consists of upwards of 200 mechanical sweepers. The amount of refuse removed daily averages 2300 cubic yards and requires the daily use of 520 carts and 980 horses. The refuse is disposed of by public tender to contractors for a term of four years. 706 HIGHWAY CONSTRUCTION. 880. The cleansing of the city of London is carried out under the department of the commissioners of sewers. The force em- ployed consists of about 500 men, women, and children. The work begins at 8 P.M. and is concluded at 9 A.M. The street orderly boys begin work at 7.30 A.M. They number about 150, and their duty is to remove every particle of dirt, especially horse- droppings, in the area assigned to them before it has been ground by the wheels. Bins at the street curb receive the gatherings. Not only the more important streets, but minor ones, courts and alleys, are looked after by the orderly boys. These boys are lodged and fed by the city, a certain deduction for the purpose being made from their wages. As they reach manhood they are promoted to other positions, and when they attain old age, after faithful service, they are pensioned. The courts and alleys inhabited by the poorer classes are cleaned daily, and from May to October are washed with jet and hose usually twice a week. 881. Baltimore, Md. Population, 443,547. Street mileage cleaned (1891), 780. Total expenses of street-cleaning depart- ment, $283,070.54. Distribution of expenses: Collecting garbage $139,062.16 Cleaning streets and removing dirt 118,423.00 Dumps 4,689.40 Tools , 2,404. 50 Superintendence 9,991.48 Removing garbage from city (contract) 8,500.00 $283,070.54 The equipment consists of 150 garbage carts, 61 street-dirt carts, 13G scrapers and sweepers. Work executed by city employes. The wages paid range from $10 to $18 per week. The sale of street dirt and refuse realized $912.76. 882. Boston. Henry B. Wood, Executive Engineer of the street commissioners of the city of Boston, in a recent communica- tion to the daily press says: That modern hygiene calls for constant attention to the immediate removal of all kinds of street refuse from public highways and places before fermentation takes MAINTENANCE. REPAIRING J CLEANSING ; WATERING. 707 place, or disease-laden gases or dust, particles emanating therefrom can be disseminated. A mere occasional attempt to clear up what street litter we cannot climb over is not sufficient; indeed, the pave- ment must now be swept so clean that it is passable at any point for pedestrians. He continues : " The number of miles of streets cleaned is 7273.24, at an average cost of less than $20 per mile, and the number of loads of street dirt removed is 77,000. The entire force of men employed has been about 300. Some streets have been swept every day, in sweeping weather; some three times a week. Each day's work has been so assigned that the computed area covered per week has been figured up to about 590,000 square yards to a district. " For a paved district of said area a good working gang is com- posed of one foreman, one sub-foreman, two sweeping-machine drivers, two water-cart drivers, sixteen sweepers, six teamsters, six helpers, and one dump inspector, allowing a trifle over one sweeper to a mile of gutter-stroke. Such a force costs about $23,000 for a full year. Eighty-one per cent of the streets are either gravel or macadam, and the cost of cleaning averages about $65 per mile for each cleaning. " The introduction of the push-cart patrol system as an important adjunct to the regular street-sweeping force has found approval in the tidy appearance of the business thoroughfares. It is found that, even after a street has been once thoroughly swept, in less than two hours' time the sweeping of the sidewalks and the throwing away of waste material into the street will so disfigure its surface that it appears as though the street-cleaning force had neglected it in its daily rounds. To obviate this difficulty the push-cart patrol comes in, collecting and removing this refuse matter continually throughout the day." In 1894 the average force employed was 303 men, using 3 three- horse machines, 19 double and 21 single sweeping-machines, 11 water-carts, 90 street-carts, 100 horses, 14 asphalt-scrapers, and about 33 extra teams. The number of cart-loads of sweepings removed was 95,478, of which 30,766 loads were dumped at sea; 10,433 miles of streets were cleaned and 2176 miles of paved gut- ters on macadamized streets. The average cost per mile, including supervision, labor, yard and stable expenses, was $15.61. The gross expenditure divided by the total mileage of streets in the city shows 708 HIGHWAY CONSTRUCTION. that the cost per mile per season was $679. The operation of the push-cart patrol system was considered most satisfactory, and an extension of their routes is thought advisable. They alone took up 50,280 barrel loads during the year. The cost of snow removal during the year was $78,382. 883. Rochester, N. Y., 1901. Asphalt cleaned by day labor cost $37.10 per thousand square yards for 99 cleanings. Brick cleaned 60 times at a cost of $26.91 per thousand square yards. Medina block cleaned 101 times at a cost of $52.71 per thousand square yards. 884. Cleveland, Ohio. During 1901 the cost of sweeping per great square was, by machine sweepers 99 cents; by hand sweeping (patrol), 22 cents. The cost of flushing by machine was 47 cents per great square. 885. Detroit Mich. The streets are cleaned when and as often as necessary. The work is done by day's labor, with the aid of sweeping-machines. This work is principally performed by aged persons who cannot do a full day's labor and cannot obtain work elsewhere. The purpose in employing labor of this character is to preserve the independence of the men and keep them from becom- ing paupers. Eight hours constitutes a day's work, and $1.50 per day is paid. The hours and per diem allowance are fixed by the common council. 886. In New York the street cleaning is executed by the municipal authority under the direction of a special bureau, part of the labor being furnished by men in its employ and part by con- tract ; the carts are also furnished by contract. The total number of men employed ranges from 1500 to 2000, and the number of carts is between 300 and 400. The amount of sweeping collected per annum is about 550,000 cubic yards. The number of sweeping-machines employed is about 60. , The number of miles of street swept each day is about 60, tri-weekly about 200, and bi-weekly about 70. The refuse is deposited at sea, and it costs 18 cents per cubic yard to place it on the scows. The cost of cleaning the above street mileage, equal to an area of about 314,179,328 square yards, is about $1,279,647 per annum. 887. Philadelphia, Pa. Population, 1,046,252. Street mileage cleaned, 756. Work done by contract. Expense of street-cleaning department, $552,000; supervision, $11,920. Ashes are removed MAINTENANCE. REPAIRING ; CLEANSING ; WATERING. 709 weekly, garbage daily. Amount of refuse removed in 1891: garb- age, 84,065 loads; street dirt, 290,680 loads; ashes, 573,999 loads; dead animals, 14,795. Number of men employed, 400; number of machines, 17. The average number of miles cleaned per man was 118. 888. St. Louis, Mo. Streets paved with granite and wood swept by contract at 50 cents per 10,000 square feet per sweep. Asphalt pavements, 39 cents per 10,000 square feet per sweep. The mac- adam and Telford cleaned by hand labor, under the supervision of the street department. 889. St. Paul, Minn., 1901. Asphalt and brick cleaned by hand during the day. Season commenced April 16 and ended November 15. The average number of miles swept per day was fourteen, at an average daily cost of $114.94. Force consisted of 62 men and 5 teams. Working hours from 7 A.M. to 6 P.M. No sweeping on Sundays. Pay of sweepers, $1.50 per day. 890. Washington, D. C. The cleaning of the streets is per- formed partly by contract and partly by the District itself. The area covered by each is about equal in extent and cost. The District equipment consists of 22 horses, 12 wagons, 150 pick-up sweeping-machines, 100 bag-carriers, 200 snow-scrapers, 500 shovels, 100 sprinkling-cans, and 20 sprinkling-wagons, about equally divided between the Austin and Studebaker types. The force of the District is 115 men with hand brooms and 75 with hand sweeping-machines. Each man handling one of these machines is required to sweep 10,000 square yards of pavement, going continuously over the area during the day and depositing the sweepings at stated intervals along the curb. To every two sweepers there is a bag-carrier, equipped with a pick-up machine for gathering the sweepings in bags. The bags when filled are col- lected by wagons and hauled to the public dumps. Each sweeper is furnished with a 5-gallon sprinkling-can, and he is required to sprinkle the area before sweeping. The force is divided into six districts of about equal extent, and is in charge of an inspector provided with a bicycle, whose duty it is to see the work properly done and make a daily report of the men employed, area covered, and number of loads of sweepings removed. 710 HIGHWAY CONSTRUCTION. The total area cleaned during 1905 was 430,216,853 square yards; sweepings removed, 34,312 cubic yards. The average cost during 1905 per mile of 39-foot roadway swept by hand was $1250. The contract price for machine sweeping was 22| cents per square yard. 891. Street Orderly or Patrol System. This system comprises a staff of men or boys usually the latter, equipped with a bag or scoop and a brush. Each boy is assigned to a definite area, from which he removes all horse-droppings and refuse as it falls and before it has time to be ground up by the wheels. The pans are of sheet-iron formed as shown in Fig. 281. The bags are of canvas and are shaped like an old-fashioned carpet-bag; one of the lips is provided with a metal edge over which the refuse is swept. The brush is generally made of a bundle of birch twigs. The refuse so collected is disposed of in different ways. In London cast-iron boxes are fixed at the curb into which the boys empty the scoops when filled; the receptacles are in turn emptied by shovels into carts at stated intervals. The bag is claimed to be better than the scoop; it holds more than the scoop, and therefore requires less running to the re- ceptacles to be emptied, and it covers up the refuse; but the empty- ing process is always troublesome and can hardly be conducted without considerable dirt being scattered in emptying. In Paris the refuse is collected in a similar manner, but instead of sidewalk receptacles they have a light wrought-iron vehicle pro- portioned to carry four full bags, two inside and two suspended from hooks on the outside. This system fills the bags at once, allows them to be stored without offence or dirt anywhere, and the final removal is expeditious and cleanly. Fig. 278 shows the hand- cart used by the street patrol in New York and several American cities. 892. Street cleansing is effected either by hand sweeping and scraping or by mechanical sweepers. As to which is the most economical, much depends upon the value of labor, and also upon the condition of the roads to be dealt with. On pavements covered with ruts and depressions machine brooms are not effective, but in point of time and as a general rule the value of a horse rotary- brush sweeping-machine is undoubted; the only time at which such a machine fails to do effective work is on the occasions when the MAINTENANCE. REPAIRING; CLEANSING; WATERING. 711 mud to be removed (owing to a peculiar condition of the atmos- phere) has attained a semi-solidity, and is of a stiff and sticky con- sistency, when it either adheres to and clogs the brushes of the machine, or is flattened by them onto the road instead of being re- moved. In such a condition of the street the scraping-machine must be employed, but care must be exercised in its use, as there is always danger of injuring the pavement. 893. Cost of Street Sweeping. The cost of street sweeping varies widely not only in different cities but in the same cities at different seasons of the year. From the records kept it is difficult to state the cost per square yard or mile of street swept. As to which is the cheaper, hand or machine sweeping, no accurate records are available it is generally considered that machine sweeping costs about one third of the cost of hand sweeping, but the records of several cities show that hand sweeping is the cheaper. 894. The amount of surface which one man can sweep per hour depends upon the condition of the pavement, dry, wet, or muddy. The following figures are approximate : Asphalt, dry 1200 square yards per hour. wet and muddy 1000 " " " " Granite block, dry ,....1000 " " " " wet and muddy 750 " " " " Macadam, dry 700 " " " " " wetandmuddy 350 " " " " 895. The amount of surface cleaned by a mechanical sweeper will depend upon the width of the machine broom, the power of the horses, gradient, and condition of the surface. The wider the stroke of the broom the less will be the cost of sweeping. As the width of stroke differs in different machines, the area swept by each in a given time will vary with that width. The average speed of the mechanical sweepers is one and a half miles per hour. 896. The cost of operating a machine sweeper is about 50 cents per hour. With a machine having a stroke of 5J feet it will re- quire six strokes of the machine to sweep a 30-foot roadway; there- fore, to clean one mile of roadway 30 feet wide, such a machine must travel six miles, and will require about four hours and, at 50 712 HIGHWAY CONSTRUCTION. cents an hour, cost $2.00. With a machine having a stroke of 8 feet, but four miles' travel of the machine will be required. 897. Brooms. The hand brooms used are made of steel wire, rattan, bass and birch. As the strength and durability of these brooms is of some importance as affecting the ultimate cost of street sweeping, care should be exercised in their selection. Steel wire lasts longer than any other, but is only suitable for block pavements. Bass and birch are weak and speedily wear out. Rattan is most suitable for asphalt and Macadam pavements. Rubber squilgees or mops are most efficient for cleansing asphalt pavements. 898. Carts and Wagons. The carts and wagons employed in the removal of street dirt should be provided with covers. The employment of wooden carts for this work is not economical; the rough usage which they receive renders their life but a short one, and they are constantly requiring repair. Iron or steel should be substituted. Such carts are to be purchased in the market and have many points to recommend them. 899. The methods employed for the final disposing of the street refuse are many and varied. In the seaboard cities and those situ- ated on rivers it is generally placed on barges, carried to sea or other deep water and deposited. In others it is used for filling in low lands (a practice which cannot be too strongly condemned). In a few localities it is destroyed by fire. This is the superior method and quite successful, and is gaining in favor in situations where difficulties are encountered in disposing of the refuse, the only ob- jection raised against it being the offensive odor. This odor is not so bad as people imagine ; it approximates that of burning leather arid can be entirely avoided by suitable devices and chimneys of sufficient height. As a rule, people are prejudiced against crema- tories being located near their residences. The cost of a plant for a town having a population of 100,000 would be about $100,000. The cost of cremating the refuse ranges from 20 to 40 cents per ton, depending upon the amount of com- bustible the refuse contains. 900. Removal of Snow. An important feature in the care of city streets is the removal of snow. Good management implies that it shall be speedily removed and not left to interrupt travel. Provision for the extra assistance required for its removal is usually made by yearly contracts let before winter arrives. MAINTENANCE. REPAIRING; CLEANSING; WATERING. 901. Snow Removal in New York City. Under the prevailing form of contract, the amount of snow to be removed by the con- tractor and to be paid for by the city is to be determined by mul- tiplying the depth of snow in the city, as officially determined by the United States Weather Bureau, by the superficial area of snow actually removed; this area to be ascertained from the area of streets as given in a set of maps prepared for this purpose and which form part of the contract document. On the snow maps the streets in which the different gangs will work are distinguished by different colors, and the area of each block, exclusive of the inter- sections, is printed on the map. The areas of the intersections are also printed in their respective places. No block is paid for until it is completely cleaned. There are 155 miles of streets in the Borough of Manhattan to be cleaned, or over 6,000,000 square yards, and it has been found that for every inch of snowfall there will be 170,000 cubic yards to be removed. When the snowfall is less than 4 inches it is optional with the commissioner whether or not any - at all shall be removed. The average snowfall for the past 18 years is 35.27* inches; the smallest was 8 inches in 1900-1 and the largest 77 inches in 1892-3. The contract price for 1902-3 was 25 cents per cubic yard. 901a. Extracts from the Specifications for the Removal of Snow, New York City. The Borough of Manhattan is divided into eleven districts, maps of which are submitted, as well as schedules show- ing the streets to be cleaned of snow and ice, and the order in which the cleaning is to be done. These maps and schedules herewith submitted form part of the contract. The contractor will have employed and working at least twenty vehicles and drivers and fifty laborers exclusive of officers, in every gang on the subdivision specified in the schedules, within a period of three hours after the work shall be ordered. Such gangs to be kept continuously employed day and night, until stopped by the commissioner, with whom it shall be discretionary to order additional gangs at any time or at any point that may seem to him necessary. The contractor shall remove the snow and ice from the streets and avenues hereinbefore specified, and from such other streets or 714 HIGHWAY CONSTRUCTION. portions thereof as may be designated by the commissioner, and also from such portions of the sidewalks designated. The contractor will secure the use of all necessary dumps and dumping-places and will keep the water in and about the slips, piers, and bulkheads clear from the snow and ice dumped therein, and the commissioner is to co-operate with the contractor in secur- ing said dumps. The contractor will furnish a sufficient amount and numbar of officers, laborers, materials, machines, etc., necessary to prosecute the work with all possible care, efficiency, and speed. The con- tractor will go back over the work, if directed to do so by the com- missioner, and will perform as many additional cleanings as the commissioner shall deem necessary. The contractor will begin all the work at points designated on schedules and follow the schedules day and night without deviation, except by order of the commissioner or snow inspector. The con- tractor will on scheduled streets cause the snow and ice to be piled at least one long block or three short blocks ahead of each and every gang of vehicles or any division thereof. The contractor shall promptly pay all laborers and other persons employed by him, and shall provide and keep on hand necessary funds and facilities for such payments, and shall make such pay- ments at least once in each week. If the commissioner shall deem it necessary to use the regular force of the department of street cleaning, or any part thereof, or any other piersons, materials, etc., for the removal of snow and ice, or if surface or other railroad companies shall clean the snow and ice between their tracks in conformity with any law or ordinance, or from the entire width of any street or streets with the consent of the commissioner, the contractor shall not in any way interfere with or molest such other force, persons, etc., and shall carry on the work on the remainder of the schedule, and shall not ask any com- pensation on account of the work so done by the department of street cleaning or other forces as aforesaid. The contractor may use machines, appliances, etc., for melting the snow and ice, if approved by the commissioner, such melting to be so carried on as not to unnecessarily impede or interrupt traffic. MAINTENANCE. REPAIRING; CLEANSING; WATERING. 715 The amount of work done by the contractor shall be ascertained as follows : The commissioner shall station in each district one or more special inspectors or district superintendents, whose duty it shall be to report in writing to the snow inspector the number of blocks of streets fully cleaned by the contractor during the previous twelve hours ; and from these reports the snow inspector shall com- pute the number of cubic yards of actual snowfall removed by the contractor during the said twelve hours preceding. Only entirely completed blocks shall be considered, and no block only partially cleaned shall be considered in the amount of work for which the con- tractor shall be paid. All computations of work done by the contractor shall be made from measurements of the area of the department of street cleaning districts drawn from the original surveys made by the Sanborn Map Company for the department of street cleaning, a set of which is attached to contract. In all computations for payment the cubic yards of actual snowfall shall fee the basis of calculation, as deter- mined by said maps. The depth of the snow for any given snowfall shall be the depth as officially determined and reported by the United States Weather Bureau located in the city of New York; provided, however, that if the commissioner of street cleaning shall establish his own method and appliance for measuring the depth of the snow, then the depth so measured and determined shall be the depth made use of under the contract. When, from weather or other conditions, the snow and ice shall be reduced to an average depth of four inches or less, it shall be dis- cretionary with the commissioner to suspend the work until the occurrence of another storm. The inspector shall, in all cases, determine the amount of work to be paid for under the contract. The amount to be paid by the contractor for delay in beginning the work within the period of three hours is fixed at $25 for each and every hour of delay at each and every block. The amount to be paid by the contractor in case the drivers or others dump on any public street or place not approved by the commissioner is fixed at five dollars for each and every load so improperly dumped. 716 HIGHWAY CONSTRUCTION. 902. The organization and arrangements for the removal of snow in the cities of Milan and Turin, Italy, are the most complete of any city, and a description of their methods may be interest- ing. The system adopted in Milan is as follows : The city is divided into districts of varying extent according to their importance ; each district is allotted to a contractor, who has to find the carts, horses, and laborers, while the city furnishes the necessary implements, spades, shovels, brooms, scrapers, barrows, etc., with proper stipu- lations as to their care. The contracts are made annually, and gen- erally the same persons are anxious to secure them. The form of the contract is rigid, and the contractors, who are drawn from the trades most affected by winter paviors, bricklayers, masons, quarry- men, etc., are held to a rigid responsibility. Payment is only made for work which is well done; slovenly and careless execution goes for nothing. The supervision of each district is under an en- gineer aided by assistants and the police. Payment is made per inch depth of snow fallen. The average depth of the snowfall in each district is determined from the depth of the snow caught on a number of stone posts fixed in open spaces and clear of shelter from buildings. Each post is capped with a flat slab set horizontally. The depth of the snow on these slabs is meas- ured by the engineer of the district in presence of two of the con- tractors of his section. The average cost of removing the snow per inch of depth per square yard is .006 cent. Ordinarily the removal of the snow from the. more active thoroughfares is finished within ten hours of the cessation of the storm, and from the rest within 24 hours, exclusive of night. The snow is dumped into the navigable canals and water-courses intersecting the city, and latterly into the new sewers in the central portions of the city, which are promptly flushed whenever it snows. The number of men engaged in the removal of snow in addition to the regular street-cleaning force, ranges from 2000 to 3000, according to the severity of the storm. The implements are housed in different storehouses throughout the city. The whole expense of removing and disposing of the snow during the remarkable winter of 1874-75, when more than 40 inches of snow fell, was about MAINTENANCE. REPAIRING; CLEANSING; WATERING. 717 $44,000. In the case of each storm the work of removal was done within 24 hours. 903. In Turin much the same method is practised, work being paid for by the exact measure of snow fallen. The street-car com- panies are obliged to bear their share of the expense, paying for a width of 9 feet 10 inches for single and 18 feet 8 inches for double tracks. 904. Many schemes for the disposal of snow have been experi- mented with, such as dumping it into the sewers, melting it by the application of steam, hot air, etc., as also with salt ; but the only successful scheme so far is by cartage, depositing it in adjacent streams, or where this is objectionable, as in the case of navigable rivers, it may be heaped up in vacant lots or in the squares and parks, provided no damage is done to the grass or paths. 905. Dumping the snow down the manholes into the sewers has been tried in London and other cities, but has generally failed through the snow consolidating. An experiment with this method in the city of Cologne gave the following results. A number of shafts were opened into the crown of the main sewer that empties into the Rhine, each shaft being from 2 to 5 feet square. At one of these places the sewer was of oval section, 6 feet X 4 feet, and the fall was 1 : 600. It was possible to dump the snow directly from the carts, each of which held about two cubic yards, into the sewer without stopping the flow there. At another place where the sewer was 4 feet X 2.3 feet and the same fall prevailed, this process was not possible although a strong stream of water was throAvn on the mass from the water service-pipes. The large mass suddenly thrown into the. sewer acted as a dam and had to be removed. But at this same shaft when the same amount of snow was regu- larly thrown into it by four laborers no stoppages occurred. A few hundred feet below the place all the snow was found to be melted. Several hundred loads of snow were removed through these two shafts alone in a few hours. The cost of melting snow by the application of hot air or steam far exceeds that of shovelling and carting away. 906. In order to grapple with this question of the removal of snow when no provision has been made beforehand, the following suggestions may be of use : " It is useless to attempt to cart it away while falling, but try 718 HIGHWAY CONSTRUCTION. j_. , to make clear crossings for the foot-passengers and to keep the traffic open. If there should be a high wind at the time,, and the snow drifts in consequence, cut through the drifts so as to allow the vehicular traffic to continue. Directly the snow ceases to fall put on all available hands to clear the channel-gutters and street- gratings, in preparation for a sudden thaw, when, if these precau- tions were not taken, serious flooding and great damage to property might ensue; for the same reason cart away all the snow you can at the bottom of the gradients and in the valleys, and also from very narrow streets and passages, etc. In the wider streets use the snow-plough, or with gangs of men (in the snow season there is generally plenty of labor obtainable) shovel the snow into a long narrow heap on each side of the street, taking care to leave the channel gutters and gratings quite clear, and a sufficient space between the heaps for at least two lines of traffic. Passages must also be cut at frequent intervals through the heaps, in order to allow foot-passengers to cross the street, and also to let the water reach the channel-gutters as soon as the snow begins to melt." 907. With regard to the removal of snow from the footpaths, it is highly desirable that this should be effected by the occupiers of the premises adjacent to the street, as otherwise it adds immensely to the work of the local authority. The following interesting re- marks by the superintendent of the scavenging department of Liverpool will be no doubt read with great interest : " The only way to compass the removal of snow from the foot- walks of the principal thoroughfares within a comparatively short time is by sprinkling them with salt such as is commonly used for agricultural purposes. It is certain that, unaided by the salt, a sufficient number of men cannot be procured for the emergency of clearing snow from the footways of the most important thorough- fares. It has been stated by medical authorities that the applica- tion of salt to snow is detrimental to the health of people who have to walk through the ' slush 9 produced by the mixture, and that the excessive cooling of the air surrounding the places where the appli- cation has been made is injurious to delicate persons. It therefore seems that the application of salt to snow should not be undertaken during the daytime, but should be commenced not before 11 P.M., nor continued after 6 A.M., and that only such an area of footwalks should be so treated on any one night as the available staff of men can clear by an early hour the following morning. MAINTENANCE. REPAIRING; CLEANSING ; WATERING. 719 " To sweep snow from the footwalks whilst the fall of snow continues, and especially during business hours, appears to be wasteful and futile, and to apply salt during the same periods may be held to be injurious to health. " That the snow of an ordinary fall can be removed from the footwalks by an application of salt an hour or so before they are scraped is an ascertained fact, except at least when a moderately severe frost has preceded, accompanied, or followed the snowfall, or when the snow has drifted into extensive accumulations. Were it not for the danger to health by excessive cooling of the air, and for the expense attending the operation, all the impervious pave- ments could be cleared of snow (unless the fall was a heavy one) in a comparatively short time by a liberal application of salt and the employment of the horse sweeping-machines as soon as the snow has become sufficiently softened to admit of their use. In Paris the use of salt for melting the snow is carried to a considerable extent. Pure fine salt for this purpose is delivered at the railway stations at about $6 per gross ton the state and city taxes, which amount to $32, being remitted. It was first used on a large scale in 1 880. It produces a dark-colored slush with a tempera- ture of about 10 F., which will not freeze unless the temperature falls below this degree. When it does not interfere too much with traffic in the streets it is often left in place for several days, because it does not freeze and is to a considerable extent a prevention of slipping. If it becomes too thick, it is removed with scrapers or with sweeping-machines. The action of the salt is more rapid the more rapid the traffic; on streets of great travel the snow of the salted surface is reduced to mud in two hours. No account is taken of the effect of the salt and snow mixture on the health of the people. The salt is spread from wheelbarrows by the shovel, and does not need to be very uniform. If the snow (packed) is six or eight inches deep, a surface layer is first melted and removed, and the lower layer is salted in turn. Amount of Salt Required. It is estimated that to melt packed snow to a depth of 1J to 2 inches about 5 ounces of salt are re- quired per square yard. The application of salt on broken-stone roads in winter will not 720 HIGHWAY CONSTRUCTION". prevent the freezing of the ground, but will increase the mud-pro- ducing action of the water formed by the melted snow, thus caus- ing their condition to be much worse than if the snow were allowed to remain in its solid form. In the United States the bad effect upon horses' feet of the cold produced by the use of salt has been the cause of much complaint, and the Society for the Prevention of Cruelty to Animals has taken up the matter of regulating its use. A mixture of salt and snow produces a temperature in the mixture of F. Sea-water sprinkled on snow causes the latter to melt rapidly. It will not freeze except at a temperature many degrees below that required to freeze fresh water. 908. Weight of Snow. Experiments made show that a cubic yard of fresh-fallen snow may weigh as much as 814 pounds or as little as 71, or a range of from 2.63 pounds to 30.14 pounds per cubic foot. " Snow readily compresses under traffic, and when removed in carts and dumped elsewhere it may be assumed that on an average four cubic yards of snow measured as it has fallen is equal to one cubic yard when placed on the apparatus/ 7 This computa- tation, however, does not make any allowance for the snow thrown from off the roofs, etc., and it of course greatly consolidates whilst traveling in the cart. 909. Snow on Roads. In localities subject to heavy falls of snow, the methods employed to keep the roads passable vary. In some places it is removed from the center of the road and formed into long narrow heaps on each side by snow-plows or shovelling by hand; in others it is not disturbed, but compacted by rolling with a wood or metal roller. The rolling should begin after the first fall of snow and be repeated after each storm. This method is more advantageous than the other, as the compacted snow freezes and does not melt as rapidly in the spring as the loose snow on the sides of the road and in the ditches; consequently the latter are ready to take care of the water coming from the melting snow in the center of the road, and this avoids the damage that results from allowing a large volume of water to flow over the surface of the road, as is the case in the first method. MAINTENANCE. REPAIRING; CLEANSING; WATERING. 721 910. Street Washing. Cleansing the pavements by washing them with a stream of water from the fire-hydrants is practised in both Paris and London. In the former city it forms part of the daily routine, but in the latter it is only used periodically, and more especially in the courts and alleys. Disinfectants are also used in Paris in this connection. During 1890 this method was experi- mented with in New York. The results were not satisfactory; the muddy water collected in puddles in the hollows of the pavement, and the amount of mud and silt carried into the sewers threatened to soon choke them up. This method is specially applicable to impervious pavements, such as asphalt and stone blocks and brick with water-proof joints. Wood pavements when they become covered with sticky mud are more easily cleansed by washing. In washing asphalt pavements sufficient water must be used to convert the dust and dirt into a fluid mud; if a quantity insuffi- cient to produce this result is applied, the dirt is converted into a pasty condition, with the result that the surface becomes dangerous for horses. This pasty mud is also difficult to remove either with brooms or other practicable appliances; horse-manure when it dries sticks to the asphalt and cannot be removed in dry weather unless it be previously soaked and scraped off. After washing, the sludge formed should be removed by the use of rubber squilgees; their use will also hasten the drying of the surface. In many cities, especially such as suffer from periodical droughts, objection is raised to the large quantity of water required for street washing. In many German cities this objection is overcome by scraping the asphalt pavements with rubber squilgees while they are covered with the water from the sprinkling-carts; the opera- tion is repeated four or more times a day. The result is considered satisfactory, and a considerable saving in the cost of keeping the catch-basins clean is effected, as well as the saving in the cost of the water. *A machine for street washing or flushing has been recently placed on the market. It consists of a cylindrical steel tank mounted on a truck similar to an ordinary street-sprinkler; it is provided with mechanism for maintaining a pressure of air by means of which the water is forced out of the nozzles under pres- sures ranging from 10 to 100 pounds per square inch. As the 722 HIGHWAY CONSTRUCTION". delivery of the water from these machines is under control, there is more economy in its use than when applied from a hose, and the clumsiness and other disadvantages of the latter are avoided. In St. Louis, Mo., street washing by compressed-air machines has been practiced for some time. Five carts are used in a gang, one behind and a little to one side of the preceding cart, so that the last one washes the refuse on the pavement into the gutter, where it is piled up by four men. Three dirt-carts follow to remove it. One gang can clean about 5 miles of asphalt in eight hours. The carts require one man to drive and operate them. They are used in the residence streets during the day and on the business streets at night. 911. Street Sprinkling. Streets are sprinkled with water for the purpose of laying the dust and cooling the air. Two methods of applying the water are practised : (1) by hose attached to the fire-hydrants, and (2) by specially constructed carts. The carts are preferable to the hose method; with the latter there is less regular distribution of the water, and in some localities there may be pressure enough to cause injury to the pavements. Again, the hydrants are generally located so far apart that long lengths of hose are required, and the constant rubbing soon wears them out. To obviate this metal pipe is employed in Paris; the pipes are usually in lengths of 6 feet, mounted on two-wheeled trucks, and connected by flexible joints. Carts cause less interruption to traffic, require less time and fewer men; moreover, when there is a scarcity of water they may be filled from wells or rivers. 912. Systems. Three systems are practised for carrying out the work of sprinkling: (1) by the municipality, with its own equip- ment and men ; (2) by contract, the contractor furnishing the labor and equipment ; (3) by contract for the labor, the city furnishing the carts. The first system is generally the most satisfactory. 913. Quantity of water required. The quantity of water re- quired will vary greatly, depending upon the character of the pavement and the temperature. The average number of gallons used in the United States per 100 square yards is 250 ; in Paris about 120 gallons per square yard ; in London about 150 gallons. 914. Frequency of Sprinkling. The frequency of sprinkling will depend upon local circumstances. In Berlin all the streets MAINTENANCE. REPAIRING; CLEANSING; WATERING. 723 are sprinkled twice a day from April 1st to October 1st, and the principal thoroughfares and squares are sprinkled three and four times per day in this period. For this work the contractor receives on an average $1.68 per day for each wagon. About 150 sprinkling- carts are used, each holding about 950 gallons. The street-car companies share the expense of sprinkling the streets occupied by their tracks. I In American cities the frequency of sprinkling the streets varies with the locality and the seasons of the year. The general practice appears to be about as follows : Paved streets are sprinkled twice a day during the months of March, April, and November, three times a day during May and October, and four times a day during June, July, August, and Sep- tember. Unpaved, macadamized, and gravelled, streets are sprinkled twice a day during the months of March, April, May, October, and November, and three times a day during June, July, August, and September. It is not usual to sprinkle the streets on Sunday, but in some few localities boulevards and driveways used on thai day are sprinkled once or twice. The manner of sprinkling is as important as its frequency. The water should be applied in a fine spray falling with little velocity, and the spray should leave the nozzle horizontally or at a small angle above the horizontal. Street sprinkling in San Francisco, Cal., presents some unusual problems, due largely to the clouds of dust brought from the Western Addition hills and the smooth bituminous rock pave- ments on some of the streets. The difficulties to be overcome, as related to a single street, are stated by Superintendent King as follows : " One of the main problems to be solved was the best method of sprinkling Market Street from Second to Van Ness Avenue. The difficulties to contend with here are: (1) a smooth pavement which was easily rendered slippery; (2) the strong westerly and northerly winds blowing down the cross streets from the Western Addition strike the buildings on the south side and blow all the dirt from the south side of the street over to the north side; and (3) the winds prevailing in the afternoon are so strong that when the street 724 HIGHWAY CONSTRUCTION. is sprinkled with a fine enough spray to lay the dust and still not make the pavement slippery, the water is so rapidly evaporated that the pavement is dry and dusty before the cart can complete its trip and return. After several days' experimenting, it was found that the proper way to sprinkle this street is to sprinkle heavily between the car-tracks, to sprinkle the north side of the street with a heavy spray next to the gutter and a light spray out- side, and to leave a strip about 10 feet wide next to the outer rail of the car-tracks unsprinkled. The south side of the street is not sprinkled at all. Dust blowing across or down the street is caught and held by the wet pavement and gutter on the north side, and heavily loaded teams have a dry strip outside of the car-tracks upon which they can travel without slipping." 915. Cost of Sprinkling. The cost of sprinkling is variable, de- pending upon the time occupied in travelling to and from the points where the water is obtained and where it is used. The range ap- pears to be from 4 mills to 7 cents per 1000 square yards sprinkled. In Indianapolis the cost ranges from 2 to 3.4 cents per lineal foot of street (30 feet 1 wide) per month for three sprinklings, and the average amount of water used was 0.38 gallon per square foot per month for each sprinkling. In Newark, N. J., for two sprinklings daily the cost was one cent per foot of street per week. In Rochester, N. Y., the average cost per mile on a width of 27 feet was $359 for the season, or 2.27 cents per square yard. In Washington, D. C., the contract price per 1000 square yards for 1906 is 16$ cents. Boston, Mass. (1901) : Cost $174,742.45 Total miles of streets sprinkled 450 Number of carts employed. 234 Hours of labor 8 Estimated amount of water used 483,337,300 gallons Number of stand-pipes 500 Season March 9 TO November 15 Number of miles covered per cart 1.37 to 2.41 Average miles covered per cart 1.94 Payment: Assessment per lineal foot of frontage ranging from 3 to 8 cents, according to the district. MAINTENANCE. EEPAIRING; CLEANSING; WATERING. 725 Distribution of cost: Teaming $142,222.25 Labor 9,691.50 Maintenance. . 22,828.70 $174,742.45 In St. Paul, Minn., sprinkling begins in April and ceases in October or November. The average cost per mile for the season exclusive of the cost of water was, in 1900, $251.00. The cost is assessed on the abutting property, and the rate per foot on asphalt streets was 9.20 cents, and on stone 4.46 to 5.93 cents. The cost on boulevards was 1.42 to 2.12 cents. The number of wagons required to distribute a given quantity of water will depend upon the design of the wagon, the method of sprinkling, whether lightly or drenching, the number necessary to cover the street, and the number of sprinklings per day. 916. Sea-water and deliquescent salts (as the chloride of calcium) have been used for street-sprinkling. The surface is kept moist, but at the expense of the moisture in the air, and it is said that horses' hoofs are injured by the chemicals. In some cities during very hot weather disinfectants are mixed with the water used for sprinkling. The disinfectant usually em- ployed is a mixture of manganate of soda one pound, sulphuric acid half a pint, and water one gallon to every one hundred gal- lons of water used for sprinkling. Experiments with salt water have been made in San Francisco. Mr. L. M. King, who superintended the experiment, says: " Salt water binds the dirt together between the paving-stones, so that when dry there is no loose dirt to be raised by the wind. The salt which is deposited on the street absorbs moisture from the air during the night, so that during the early morning the street is thoroughly moist and has the appearance of having been freshly sprinkled. This effectually prevents dust being raised by the wind or street-sweepers before the regular sprinkling-carts can get over the ground during the morning. It is more healthful than fresh water, for the reason that salt water will destroy many dis- ease-germs now contained in the dirt on our streets." 726 HIGHWAY CONSTRUCTION. It is claimed by those cities which use salt water that one load is equal to three of fresh water. Experiments made at Hastings, Eng., showed that sea-water was very beneficial in laying the dust on macadam roads, but that when a road had been watered for a fortnight or three weeks it was necessary to thoroughly wash and broom it to get off the coat of salt, while a week or so of watering with salt water had the effect of leaving a thin coat of salt on the road, and as soon as a damp day came, not in the shape of rain, but of moisture in the form of fogs, the surface of the roads was picked up by the wheels of the vehicles in a very unsatisfactory manner. Objections to the use of salt water are raised on various grounds, some of which are: injury to the varnish and running gear of vehicles, corrosion of cast-iron street furniture, and damage to goods from dust con- taining salt. 916a. Sanding Pavements. In all European cities sand is used very freely to prevent the slipping of horses on the pavements, especially on asphalt and wood. The spreading the sand and re- moval of the ground-up sand add materially to the work of the cleaning department. Quantity and Manner of Applying Sand. In Birmingham the sand is spread from a cart with a shovel, and the men who do this work are so expert that they can make an effective covering of the whole street (30 to 45 feet wide) with the use of only one load to the mile. On Fifth Avenue, New York, the contractor was- restricted to the use of four loads to the block or eighty loads to the mile. CHAPTER XX. TREES. 917. OPINIONS differ as to the desirability of trees on roads and streets. Some claim that they do more harm than good; that they impede the circulation of the air, and that, as far the shade they afford, people who do not like sunshine have only to keep on the shady side of the way; that they deprive the road-sur- face of the drying action of the sun and air, and that in wet weather the constant dropping of water from their branches keeps the road in a muddy state. Others claim that trees, especially in streets, temper the heat and serve as a protection against dust, that the evaporation from their leaves tends to keep the surrounding air cool and moist; that the perpetual vibration of their foliage and sway- ing of their branches, whilst admitting a sufficient amount of light, serve to protect the eyes from the noonday glare; that they act as disinfectants by drawing up and absorbing the organic matters con- tained in the filth from which the streets of a town are never free and which, infiltrating the ground, are a frequent cause of fevers and infection ; and it is asserted that on soil roads some varieties of trees both drain the road and help to hold its earthen surface to- gether by their root-fibres. " Those who have observed woodland roads closely know they are dry except when below the general grade of the land or actually' swamped with water. At any point of temperature a tree, even in winter and without any leaves upon it, is evaporating moisture from its twigs, branches, and trunk. It must freeze very deep to prevent all root-action, and whatever moisture roadside trees may draw from the roadbed will, by so much, prevent the tendency to muddiness in any loam road well filled with tree-roots." " Beside the draining and drying effect of tree-roots, the fibres 727 728 HIGHWAY CONSTRUCTION. given to the soil by some kinds of trees (well known to ploughmen in all countries) have a most salutary effect in holding the earth to- gether. If the soil be rich, the whole substance of the raised and rounded roadbed may be completely filled with horizontal stitches, as the housewife darns and runs the heels of stockings, thus treb- ling their ability to resist friction. Boots in the surface-soil are better than brush to hold up travel when they are alive and pump- ing water out of the ground. If we are looking for economy, noth- ing can be cheaper than the way a maple, elm, cottonwood, or white pine will fill the surface of an earth road with fibre. The chestnut, hickory, ash, black walnut, and beach may all be thought of in this connection, but only the close student of nature and the variety of trees adapted to different soils and situations will succeed in this branch of road-making. Yet the nation has many thousand miles of muddy highway where no other improvement seems possible." " There is a use for the overhanging branches of trees in winter They shade the road and permit it to freeze or remain solid when, but for the shadow, the road would be softening in the sun. The branches work in this way to prevent and protect the road from being cut in pieces. The traveller and his weary team, swamped in thawed earthen roads, are glad to reach the frozen track on the north side of a bit of woodland. And the man who would cut away roadside shades so as to let all our earth roads thaw out and settle together is very much mistaken." Trees also serve to make the border of the road discernible at night as well as after snowdrifts, thereby warning the travellers against embankments and other dangers along the sides of the road. 918. In France, as far back as the middle of the sixteenth cen- tury, trees were planted along the royal roads. This practice has been more or less continuously followed. During several periods it was stopped by those in authority, they being of the opinion that trees were more of a damage than a benefit. But now trees are planted along all roads having a width greater than 10 metres (32.8 feet). They are placed at distances varying from 5 to 10 metres (16.4 to 32.8 feet), in single rows upon the narrow roads, and in double rows upon the wider. 919. "The roads of Belgium are flanked on either side by two and sometimes four rows of shade-trees, which add much to the beauty of the country through which they run." TREES. 729 920. Financial Value of Trees. Take two streets in all respects alike, except that one has trees well selected, set at suitable dis- tances apart and well cared for, the other with no trees or with trees carelessly set and neglected, as frequently happens. A person wishing to purchase a residence will undoubtedly select the street having the fine trees, although he may have to pay more than many times the cost of the trees. Thus from a financial standpoint trees pay. 921. In Saxony a considerable revenue is derived from fruit- trees planted on the roadsides. The trees are cared for by the roadmen in so far as professional knowledge is not required ; they remove insects, clear the tree-frames of rubbish, and water them. In sections where fruit-trees cannot be cultivated on account of climatic causes, or where they would be liable to wanton damage and plundering of the fruit, forest-trees are planted. The state-road fruit-trees are leased to the highest bidders, and the money received is covered into the state treasury. The lessees of the fruit-trees are held to a strict account for any damage done the trees. Ladders must be used to gather the fruit, and any battering of the trees with clubs or poles to get the fruit down is prohibited and is punishable by fine. 922. Selection of Trees. Trees should be selected with refer- ence to the climate, locality, quality of soil, extent of space, and circumstances of surroundings in general. Large-growing varieties should be selected for places of great extent, smaller varieties for places of less extent. A low compact tree is not suitable for street planting. The qualities necessary in a good street tree are that it must be hardy, must not be affected by a long-continued drought, heat must not wither it nor make it look rusty ; it must be able to withstand dust, smoke, soot, foul air, and the insidious attacks of insects, and be able to recover from any malicious or accidental injury it may receive. The tree must be of rapid growth and develop a straight, clean stem with shady foliage. It must be graceful either in full leaf or when bare, as in winter; its roots must not require too much room, and they must be able to withstand the effects of pollution or rough treatment. 730 HIGHWAY CONSTRUCTION. As to wnat variety to select very little can be said; a large quantity of suitable trees exists from which one may select as local conditions or fancy may dictate. 923. Precautions to be taken in the Selection. Whatever variety of tree is selected, the following precautions should be taken to insure its flourishing: (1) The young tree should have been well nourished in the nursery; it should not be planted on the street until its stem is over 8 feet in height and about 3 inches in diameter. The stem should be clean and straight, and the whole tree symmetrical. (2) The ground where a tree is to be set should be examined to see whether it is suitable for tree-growth. If it is not, the poor material should be removed and good soil substituted. The amount to be removed depends upon circumstances and can be determined by examination. A tree to flourish must have plenty of good ground in which to grow ; it should be good to the depth of at least 3 feet, and an equal distance in all directions from the trunk when practicable. The amount of good soil is of greater importance than the shape it is in. The further the tree is planted from the curb the better, so as not only to give it a larger body of soil, but to lessen the risk of killing the tree by the pollution of the ground with gas from defective pipes and also excess of moisture from the gutters. 924. Distance Apart to plant Trees generally appears to be a matter of choice, but this should not be so. Trees should be placed so far from one another that at maturity they will not meet. Such distances will enable them to develop in their natural beauty. To determine the proper distance apart measure the spread of full- grown trees of the same variety as those to be planted ; it will vary from 30 to 50 feet. The trees should alternate on opposite sides of the street. 925. Trees at Street-intersections. Where streets cross at right angles or nearly so, two trees of large-growing varieties may be placed on each corner, far enough from the corner of the curb not to interfere with the catch-basin when there is one. Each tree should be placed on the tree line of one street and the fence line of the other; this will require eight trees to every intersection. The trees so planted should form a handsome mass of foliage and afford an agreeable shade where most needed. At some intersec- TREES. 731 tions it may not be possible to plant all the eight trees, but as many as can should be placed. 926. Protection of Trees. Each tree should be protected with a light iron railing to prevent mischievous persons from cutting their names on or otherwise injuring the trunk. Where it is necessary that the footpath be entirely paved the space around each tree may be arranged as shown in Fig. 177. A light stone curb is placed around the tree in a circle the diameter of which should be about 4 feet, and the curb should project above the pavement about 3 to 6 inches; this prevents people from walk- ing on the earth, keeps the ground from becoming hard, and permits air and water to enter to the roots. Or a cast-iron grating 4 feet square may be employed for the same purpose. FIG. 177. PROTECTION OF TREES IN WALKS. 927. Specifications for Protection of Trees. The contractor when directed shall protect from injury trees upon the line of the work, and the grading around them must be carefully done. The grass sodding on the sidewalks must also be protected as much as possible. CHAPTER XXI. STAKING OUT THE WORK. 928. THE staking out of the work consists in placing stakes in the ground to direct the workmen and define the limits of the work. The centre line of the proposed road is marked by stakes set (usually) at distances apart of 100 feet on the straight portions, and at 15, 25, or 30 or 50 feet on curves, depending upon their sharpness ; on the stakes the cut or fill at that point is marked. 929. The staking out of straight lines and simple curves of less than 100 feet radius presents no great difficulty; curves of greater radius, compound or reverse, will require to be set out by the same formula and methods as are empleyed for setting out the curves on railroads. For detailed instructions, etc., any one of the many railroad-engineer's pocket-books may be used, such as Henck's, Trautwine's, or Shunk's. 930. Side Slopes. The setting of the slope stakes on ground that is level or nearly so at right angles to the centre line is a sim- ple matter, the position of the stake being found by adding together the half-width of the roadway, and the base of the triangle ob- tained by multiplying the depth by the ratio of the slope. When the natural surface of the ground is inclined, the setting of tho slope stakes is less simple. The ordinary method employed is a tentative process of combined levelling and calculation, which is nothing better than a rule of thumb. The manner of procedure is as follows : Suppose it is desired to set the stakes 1) and E, Fig. 178. The depth of the cutting at C is ascertained, and a point is taken on the surface where it is assumed the slope will cut; its height above AB is obtained; this height is multiplied by the ratio of the slope, and the half-width A C or CB added : if rhis agrees with the distance of the assumed point, that point may be taken as 782 STAKING OUT THE WORK. 733 correct; if not, a second trial must be made. A difference of 6 inches will be of no practical importance. A C B FIG. 178. MANNER OF SETTING SLOPE STAKES. -The guessing may be aided by taking levels at the points F and G, and performing the calculations as outlined above. A more accurate and sometimes a more expeditious method is as f ollows : Take a cross-section book, and on each page plot the cross-sec- tion of the ground at each station, and draw the slope lines; the exact distances can then be obtained at a glance by counting the spaces between the centre line and the point where the side slope intersects the natural surface. Slope stakes are required at every centre stake along the line, and also where the ground is very rough at intermediate distances. 931. Setting out Culverts. The length of a culvert which passes under an embankment is less than the distance between the bottom of the opposite side slopes, and may thus be found : From the height of the embankment H, Fig. 179, take the above ground height of the culvert A; the remainder will be the height, h lf of the embankment : then the required length ab is equal to the top width of the embankment cd, plus the width of the base of the slopes on the top of the culvert. Thus if CD equal 30 feet, and li l equal 5 feet, the ratio of the slopes 1 to 1, the length ab will be 30 + (5 X 3) = 30 + 15 = 45 feet. 734 HIGHWAY CONSTRUCTION. 932. When the natural surface of the ground is horizontal, the length of any structure passing under an embankment will lie FIG. 179. half on each side of the centre line. When the natural surface is inclined, the ends of the structure will be at different distances B Fig from the centre line, according to the slopes of the ground. This is seen in Figs. 180 and 181, the first of which represents the section, and the second the plan, of an embankment. The lines SS STAKING OUT THE WORK. 735 and 00, representing the ends of a culvert passing beneath the embankment, are seen to be at different distances from the centre line. The position of the points S and may be found by first getting from the tables of side width the points A and D, and measuring in from these points the distances liS and DO, de,- pending upon the slopes AB and AD. In the case of the upper end the distance of SS from A will be less than if the natural sur- face was .level; at the lower end the distance from D to will be greater. Having found the distances of SS and 00 from the centre line, we get the position and length of the wing walls of the culvert by drawing a line from S to any desired angle to intersect the slope A A ; and upon the lower side of the embankment we get, in the same manner, the lines DD, OD, the latter being of course longer than the wings upon the upper side AS, AS. 933. Setting out Bridge Work. In laying out the abutments for bridges there are numerous cases to be considered, as whether the bridge is on the square or on the skew, upon a level or a gradient, upon a curve or a straight line, and whether the natural surface is horizontal or inclined; the position and form of abut- ments and wing walls depending so much upon the various condi- tions affecting each particular case, that any attempt to lay down general rules for each work would be of little use. 934. Staking out Drains. The method of setting grade marks for drains is as follows: At every 50 feet along the line of the trench place a board a couple of feet wider than the width of the trench, bed it firmly in the earth and mark the centre line on it; then ascertain the level of the boards, calculate depth of cutting at each one, and mark it plainly on each board. To transfer the grade line to the bottom of the trench, procure a measuring-rod (say 6 feet long), subtract the depth of cutting from the length of the rod, and to the board that straddles the ditch nail a piece of board upright, the height of which above the horizontal board is equal to the difference found. This operation being performed at each board, a line stretched from the upright pieces will be parallel to the grade line, and six feet above the bottom of the trench. 935. Vertical Curves. As stated in Article 610, the apex or meeting point of grades require to be rounded off by vertical curves, thus slightly changing the grade at and near the point of (36 HIGHWAY CONSTRUCTION". intersection. A vertical curve rarely need extend more than 20O feet each way from that point (Fig. 182). , Let AB, BO, be two grades in profile, intersecting at station B, and let A and G be the adjacent stations. It is required to join the grades by a vertical curve extending from A to C. Suppose a 1 I _ _J . zffT-S-- i i i r.rt 1 . 1 J_ - - -i ' 1 i 1 . _1_ **?>*, I . I I ">^ i 1 1 J. - FIG. 182. chord drawn from A to C. The elevation of the middle point of the chord will be a mean of the elevations of grade at A and (7, and one half of the difference between this and the elevation of grade at B will be the middle ordinate of the curve. Hence we have M= j (grade .4+ grade (7 _ in which M equals the correction in grade for the point B. The correction for any other point is proportional to the square of its distance from A or C. Thus the correction at ^4 + 25 is T 1 M\. at A -f- 50 it is \ M\ at A -f- 75 it is -fa M\ and the same for cor- responding points on the other side of B. The corrections in the case shown are subtractive, since M is negative. They are additive when M is positive, and the curve concave upward. 936. Staking out Contour of Street Foundations. In order to insure the proper transverse form of street pavements, stakes should be driven across the street, the tops of which shall cor- respond to the intended contour. The stakes should be placed longitudinally of the street at distances not exceeding 16 feet, and transversely at distances not exceeding 10 feet. After the stakes are placed ridges of concrete may be formed along the street, as shown in Fig. 183. After the ridges or small banks of concrete ara STAKING OUT THE WORK. 737 so placed the filling of the interspaces may be proceeded with, and a straight-edge resting on the ridges will guide the workmen in keeping the concrete to the proper form ; or the stakes may be placed as directed above and a thin slat nailed to their tops, the concrete filled in and made flush with the top of the slat, a straight- edge 17 feet long, its ends resting on the slats, being used for this FIG. 183. MANNER OF FORMING CONTOUR OF STREETS. purpose. After the concrete is thoroughly set the slats may be^. removed and the space they occupied plastered over with cement. 937. Setting Stakes for Curb. Stakes for setting curb should be placed on the front line of the curb, with their tops at the required: grade. Their distance apart saould not exceed 50 feet, and on cir- cular work will require to be closer. At street corners three stakes should be driven, one at the intersection point of the meeting curbs ; and one at each tangent point (Fig. 184). cx . ---? Stake Stake FlG, 184. SHOWING MANNER OF SETTING STAKES FOR CURBS. 938. In placing the stakes for any structure they should be placed so far outside of the work that they will remain undisturbed during the construction of the work. They must be so placed that lines stretched from any two of them wiP define the corner and 738 HIGHWAY CONSTRUCTION". face of the structure (Fig. 185). Stakes for defining the boundaries of an excavation may be placed at the angles thereof. T 1 Stake*-- iSiake ; FIG- 185. MANNER OF SETTING STAKES FOR STRUC- TURES, 939. Two stakes, at a sufficient distance apart upon the Iand 5 will fix any line upon the water; and two sets of stakes, upon different lines upon the shore, will by their intersection fix any point upon the water with accuracy sufficient for many purposes. Tor exact work, however, a transit should be employed to fix a line ; and two angular instruments, in well-chosen positions, will deter- mine any point. 940. Bench Marks. A permanent bench or reference mark for levels should be established with care, in the immediate neighbor- hood of any proposed structure, from which the elevations of the various parts may be obtained. Such bench marks should also be fixed at the commencement of long cuttings, and generally at intervals of from 500 to 1000 feet along the works, a list of such elevations being entered in the engineer's note-book. CHAPTER XXII. SPECIFICATIONS AND CONTRACTS. 941. Specifications. A specification or detailed description of the various works to be carried out is always attached to a contract, and is prepared before estimates are called for. The prominent points in connection with specifications are as follows: (1) Description of the work. (2) Extent of the work. (3) Quality of the materials. (4) Testing of the materials. (5) Delivery of materials. (6) Character of the workmanship. (7) Manner of executing the work. (8) Time of commencement. (9) Time of completion. (10) Manner and times of payment. (11) Penalties for infraction. (12) Such general instructions and stipulations as may be found necessary in each case. Attention to these points and a clear and accurate description of each detail (leaving nothing to be imagined) will not only materially contribute to the rapid and efficient execution of the work, but will avoid all future misunderstandings. 942. Concerning Tests of Materials. While proper tests should always be stipulated, yet if they are carried to an extreme degree, as frequently happens, they defeat their own object. When it be- comes impossible to carry out certain unreasonable demands, tha alternative is to evade them as much as possible; and it must al- ways be borne in mind that the more stringent the demand, the greater the difficulty in enforcing it. 739 740 HIGHWAY CONSTRUCTION. 943. Contracts. A good, clear, and comprehensive contract is a difficult thing to write, but it should be " common-sense " from beginning to end, and should be the joint production of both en- gineering and legal ability, neither sacrificing the one feature to the other. GENERAL SPECIFICATIONS. The following specifications, in conjunction with those given throughout the work, will aid in preparing specifications for the different works connected with highways. 944. Clearing. The land will be cleared to the width of feet on each side of the centre line, and on each section must be entirely completed before grading is commenced. The clearing must be done in such manner that all useful timber may be saved. Trees of large dimensions shall be trimmed and put into the most profitable shape for the market; when so trimmed they shall be piled in such places along the line of the road as the engineer may designate. Brushwood, stumps, tree limbs, etc., must not be cast upon the adjacent land, but shall be formed into piles and burned; stumps and other material that will not burn, must be removed from the work and disposed of by the contractor. All brush or trees acci- dentally or otherwise thrown upon the adjacent lands must be taken off and disposed of as above described. The land when cleared must be left in a clean condition, and the contractor will be held responsible for all damage to crops, fences, fruit-trees, and timber of adjacent owners. 945. Close Cutting. Where embankments are to be formed more than one foot in height, the stumps shall be chopped close to the ground. 946. Grubbing. Where excavations do not exceed 2 feet in depth, or embankments one foot in height, all stumps shall be grubbed out. The catch-water drains, side ditches, and off-take drains shall be grubbed wherever required. 947. Grading. Grading will include all excavations and em- bankments required to form the roadway, all excavations and em- bankments required for altering the level of intersecting roads. Excavations for the foundations of all structures, excavations for all trenches and ditches, excavations required for the altering of SPECIFICATIONS AND CONTRACTS. 741 the channels of streams, etc., and all other excavations and em- bankments that may be required for the full completion of the road. The grading shall be executed in accordance with the lines and grades given by the engineer. The portions which are above grade are to be excavated, and such and so much of the excavated mate- rial as may be suitable for the purpose, and as may be necessary, shall be filled in those parts which are below the grade lines. The material excavated, not so used for filling, shall be placed in spoil- banks at such points as the engineer designates, or it may be re- moved from the line of the work by the contractor for his own use and benefit, if so directed. Where embankments are to be formed of a height less than 3 feet, all top-soil and vegetable matter must be excavated to such depth as the engineer may direct. The material so excavated will be piled up outside of the embankment lines, and afterwards used to cover the slopes of embankments and cuttings; the surplus that remains after completing this work shall be removed and placed in spoil-banks at such places as will be designated by the engineer, or it may be removed by the contractor for his own use and benefit. In places where the embankments exceed 3 feet in height the perishable matter shall be removed, but no excavation done unless specially ordered by the engineer. All sloping ground covered with pasture shall be deeply ploughed over the base of the embankments before the latter are commenced. On slopes which have been covered with timber the slope shall be cut into steps before the embankment is commenced, 948. Formation of Embankments. Embankments of a height less than 3 feet shall be made by horses and carts. Embankments of greater height may be formed by tipping from dump-cars travel- ling on a*track. The embankments will be formed to such height above the sub-grade as the engineer may direct, to provide for shrinkage, compressions, washing, and settlement, and they must be main- tained to the required height, width, and shape until 'accepted. Whenever embankments are made from side ditches, the width of the berm to be left at the foot of the slopes will be given by the engineer. In the formation of embankments no mud, muck, vegetable 742 HIGHWAY CONSTRUCTION. matter, tree stumps, or other materials which the engineer may deem unsuitable, will be allowed to be used. Such material must be removed from the line of the work and disposed of as the engineer may direct. After completion, the slopes of all cuttings and embankments will be covered to a depth of 6 inches with the loam and vegetable soil previously reserved for this purpose, or such shall be obtained from such places as the engineer may direct. The slopes of embankments will generally be 1J to 1, of earth excavations 2 to 1, of rock excavations 1 to 1 ; and no allowance for excavations outside the limits of these slopes will be made unless specially ordered by the engineer. The widths, slopes, and other dimensions may be varied at any time by the engineer to suit circumstances. In the event of slips occurring in excavations, the contractor will remove the debris and reslope the work. If the slips occur through carelessness on the part of the contractor, no allowance for the removal or reshaping will be made; but if they occur through unavoidable causes, he will be paid for it as loose rock or as earth, according to the class to which it may appear to the engineer to belong. Eock shall be excavated to a depth of two feet below the sub- grade level and the space refilled with stone broken to a size not exceeding 2J inches. In the event of work being proceeded with in winter, no snow or ice will be placed in embankments or allowed to be covered up in them, and all frozen earth must be excluded from the heart of the embankment. 949. Earth-work Measurement and Classification. All earth- work shall be measured in excavation, and will be classified under the following heads, viz., earth, loose rock, solid rock. Earth will include clay, sand, gravel, loam, decomposed rock, and slate, stones and bowlders containing less than one cubic foot., and all other matters of an earthy nature, however compact they may be. Loose rock will include all bowlders and detached masses of rock measuring more than one cubic foot and less than one cubic yard; also hardpan, compact gravel, sandstone, and all other materials of a rock natuie (except solid rock) which may be SPECIFICATIONS AND CONTRACTS. loosened with the pick, although blasting may be resorted to in order to expedite the work. Solid rock will include all rock found in place in ledges, and in masses or bowlders measuring more than one cubic yard, and which can only be removed by blasting, which fact will be determined by the engineer. 950. Drains. At such places as may be designated by the engineer, drains will be formed in the following manner: the trenches will be opened to the width and several depths given by the engineer. In the trenches so opened drains of tiles will be constructed, as directed by the engineer. The tiles furnished shall be the best quality of clay or terra- cotta, manufactured expressly for drainage purposes; they shall be in lengths of not less than one foot, and shall be of uniform diameter throughout. A pipe of larger diameter, broken in half, will be used for collars; the pipes will be laid true to grade and the trenches filled in with round field stones. The stones must not be thrown in, but shall be laid in carefully by hand, the largest stones being used to wedge the pipes in place; on top of the stone filling place good sods, with the grass side down. Silt-basins will be constructed of brick, of the forms and dimensions shown on plans, at the points designated by the engineer. 951. Catch- water Ditches. Catch-water ditches will be ex- cavated at the top of the slope of all excavations on the up-hill side only; they shall be excavated not closer than 6 feet to the edge of the slope; they shall be excavated on the lines and to the grades given by the engineer. 952. Off-take Ditches. These ditches will be excavated where- ever directed by the engineer, and will have such form and dimen- sions as he may direct. The contractor shall also excavate and form all other drams and ditches which the engineer may deem necessary for the proper drainage of the road. 953. Eip-rap. In cases where slopes require protection from the action of water, the protection works will be constructed of brush or stones, and will be carefully performed in such manner and of such dimensions as the engineer may direct. 954. Retaining, Breast, Slope, and Parapet Walls. These walls 744 HIGHWAY CONSTRUCTION. be constructed at such places and in such manner as may be directed by the engineer. 955. Culverts formed of earthenware, cast-iron pipe, stone laid dry or in mortar, will be constructed wherever directed by the en- gineer. Their form and dimensions shall correspond with the detailed plans prepared therefor. MASONRY. Stone masonry will be classified as follows : 956. First-class Masonry shall be built of sound stone, of a quality to be approved by the engineer; it will consist of large rectangular stones, with the beds dressed parallel throughout, and the vertical sides hammer-dressed so as to form quarter-inch joints; the stones will be left quarry-faced except when otherwise ordered ; rock-faced stones to have a one-inch chisel-draught cut on all four edges of the face, and no face projection greater than 3 inches. The rise of the courses of first-class masonry will not be less than 12 inches, and may range up to 24 inches, the thinnest courses being invariably placed towards the top of the work ; the stones in adja- cent courses shall break joints by at least one foot. Headers shall be built in every course not further apart than 6 feet ; they will have a length in the face of the wall of not less than 24 inches, and they must run back at least 2J times their height; when they will not allow this proportion, they must pass through from front to back. Stretchers shall have a minimum length in the face of the wall of 30 inches, and their breadth of bed shall be at least H times their height. First-class masonry will be laid in Portland cement mortar, and each course must be thoroughly grouted before the next course is started. Each stone shall be cleaned and dampened before being set. Improperly dressed stones must be recut before placing in the wall, as no hammering will be allowed after the stones are set. First-class masonry will include all dimension stone, such as coping, cap-stones, bridge seats, and parapets, abutments, and piers of large bridges. 957. Second-class Masonry will include retaining-walls, abut- ments, wing walls and parapets of minor bridges, and head walls on box culverts. It will consist of broken range-work, built of such stone as may be approved by the engineer ; the stones shall be dressed SPECIFICATIONS AND CONTRACTS. 745 to horizontal beds and vertical joints ; the face shall be " rock face/' with edges pitched to line, with no face projections exceeding 2 inches. At least one third of the stones must be headers evenly distributed through the wall; the mortar joints shall not exceed one half-inch in thickness. All vertical joints must be broken by at least 6 inches. No stone will be allowed in the face of the wall which has a less area than 72 square inches. Quoin stones shall have a chisel-draught one inch wide cut on each side of the angle. The backing and foundation will be of large sound stones, roughly squared, no stone to measure less than 2 cubic feet. The broadest bed will be laid underneath, and must have a good bearing on the stones below. The stones shall be laid in full mortar beds, well bonded with each other and with the face stone, and with all /spaces filled with small stones and spalls, well grouted. No stone shall be cut on the wall, and stones once bedded shall not be removed unless directed by the engineer. The foundation course shall be of large stones not less than 12 inches in thickness and 8 feet area of bed, and when the wall is 4 feet or less in thickness shall extend from front to back. The mortar employed for second-class masonry will be of Rosen- dale cement, in the proportion of 1 of cement to 2 of sand. Portland cement will be used wherever directed by the engineer. 958. Third-class Masonry. Masonry of this class will generally be used for box culverts, retaining and slope walls, and for back- ing for first-class masonry. It shall consist of sound stones laid on their natural beds, and roughly squared where used for face work. The walls shall be carried up in courses ranging from 15 to 18 inches in height; each course shall be well bonded, having a header at every 3 i'eet. Not more than one third of the stones shall be less than 9 inches thick, or contain less than two cubic feet, and no .stone shall be less than 6 inches thick. The stones shall be laid in Kosendale cement mortar, and each course well grouted. 959. Fourth -class Masonry will consist of stone laid dry, and will be used for box culverts, retaining, slope, breast, and parapet walls, and paving of box and arch culverts. 960. First-class Arch-culverts shall be built in accordance with the specifications for first-class masonry, with the exception of the arch, sheeting and ring-stones. The ring-stones shall be so dressed that when laid their beds will radiate truly from the centre of the circle. The ring-stones and sheeting shall not be of less thickness 740 HIGHWAY CONSTRUCTION. than 10 inches on the soffit, and shall be dressed the full depth of the bed, so as to form joints not exceeding three eighths of an inch; each stone must break joints with its fellow by at least 10 inches. Arch stones to be full bedded in mortar, and each course afterwards thoroughly grouted. The face stones to be rock-face, with a one- inch chisel-draught around the edges. 961. Second-class Arch-culverts. Arch-culverts of 8 feet span and under shall be constructed of suitable flat bedded stones, rang- ing, according to the span, from 16 to 24 inches deep, and with a minimum length of from 16 to 24 inches, and 5 to 6 inches in thickness on the soffit. They must invariably extend through the entire thickness of the arch ; each stone to be well and closely fitted so as to give half-inch joints, and to break joints with its fellow 9 to 7 inches. The whole to be laid in thin cement mortars, and each course well grouted immediately after being laid. The face-stones of the arch to be as nearly uniform in depth as possible, of large size, and neatly incorporated with the perpendicu- lar face of the masonry. The keystones to be 10 or 12 inches on the soffit, to have a chisel-draught around their edges, and to project beyond the face of the wall 2 or 3 inches. The side and wing walls will be of second-class masonry. The extrados of all arches shall be flushed with cement mortar three inches thick, levelled up and rounded to a moderately even and smooth surface. 962. Centring. Centres of arches must in all cases be well formed, of ample strength, securely placed in position, and in every respect conform to the requirements of the engineer. The ribs must not be placed further apart than 3 feet in any case. The lagging shall be 3 inches thick; the supports of centres .shall be substantial and well constructed, and they must be provided with proper wedges for easing centres when required. Centres shall not be struck without permission from the engineer. 963. Wing Walls will generally be of first-class masonry, laid up in steps, each step covered with a hammer-dressed coping. 964. Parapets of masonry structures will be of first-class ma- sonry, covered with hammer-dressed coping. 965. Laying Masonry in Freezing Weather. No masonry is to be built in freezing weather, except by permission of the engineer. If such permission is given the mortar shall be made by either of the following methods : SPECIFICATIONS AND CONTRACTS. 747 Make a mortar of one part of hydraulic lime and three parts of sand, mix thoroughly, and allow it to stand in a heap covered with stable manure until used, to prevent freezing. Mix mortar for use with ordinary cement in the proportions of one to three. Both mortars to be saturated with brine in the final mixing. Or, Dissolve one pound of rock salt in 18 gallons of water when the temperature is at 32 degrees Fahr., and add one ounce of salt for every degree lower of temperature, or enough salt, whatever the temperature may be, to prevent the mortar freezing. No masonry laid in freezing weather to be pointed until spring. 966. Pointing. All outside joints of first- and second-class masonry shall be raked out to a depth of one inch, and neatly pointed with a mortar made of one part Portland cement and ono part of sand. 967. Grouting. Each course of masonry as laid shall be grouted with a mixture of two parts of cement to 3 parts of sand, no more water being used than that necessary to give the required fluidity. 968. Brick Masonry. The bricks used shall be of the best quality, hard-burned entirely through, regular and uniform in shape and size. Soft or underburned bricks will not be allowed in the work. The bricks shall be laid in cement mortar made as directed. Every brick shall be laid in a full bed of mortar on bot- tom, sides, and ends, which for each brick is to be performed at one operation. In no case is the joint to be made by working in mortar after the brick is laid. The joints shall not exceed f of an inch, and none shall be less than of an inch, and shall be neatly struck or flush-pointed. Every sixth course to be headers. No " bats " shall be used except in the backing of walls, where a moderate proportion (to be determined by the engineer) may be used, but nothing smaller than half -bricks will be allowed. The bricks will be inspected and culled on delivery, and those condemned must be at once removed. The bricks must be thoroughly wet just before laying. In forming arches the bricks must be laid in concentric rings, each longitudinal line of bricks breaking joints with the adjoining lines in the same ring and in the ring under it. * 969. Dry Walls. Retaining, slope, parapet, and breast walls of 748 HIGHWAY CONSTRUCTION. dry stone will be constructed where directed. The stones for this class of work must be sound, flat, bedded stones. No round or cobble stones will be allowed. Not more than one third of the stones shall be less than one foot thick, and no stone shall be less than six inches thick or have a bed area of less than four feet. The stones shall be set horizontally on their largest bed, and so well bedded and fitted as to require neither spalls nor wedges to keep them in place. All walls shall be covered with a hammer-dressed coping of the dimensions shown on the plans. 970. Dry Box-culverts. The bottom shall be paved with good sound stone closely set on edge under the walls as well as the water- way. The side walls shall be built of large well-shaped stones well bonded and joints well broken. No stone shall have a less area, of face than one square foot. There shall be one header to every three stretchers, and the header must pass entirely through the wall. The covering-stones must be entirely sound and wide enough to extend at least two thirds across either wall. The end walls of box-culverts shall be laid up in second-class masonry and finished off in accordance with the plans. The coping must be of proper and uniform thickness, neatly hammer-dressed on top and face. 971. Pipe-culverts. Culverts of salt-glazed earthenware or cast-iron pipe shall be constructed at such points as the engineer may designate. The ends of said pipes will be carried by head walls of either brick or stone masonry covered with stone coping. The form and dimensions of these structures shall correspond to the plans prepared therefor. The earthenware pipe shall be of the quality known as culvert- pipe. It shall be sound and well burned throughout, free from cracks, flaws, fire-checks, and other imperfections, and shall be of uniform thickness throughout and shall have not less than the following weights : Internal diameter. Weight per foot. 6 inches 15 pounds 9 " 28 " 12 " . 40 " 15 " 60 " 18 '" 80 " 20 " 90 " 24 " 130 " SPECIFICATIONS AND CONTRACTS. 749 The joints shall be closed with cement-mortar. Cast-iron pipe shall be used wherever directed by the engineer, and shall be obtained from a foundry approved by him. It shall be of the diameters and thickness ordered, will be laid in the same manner as earthenware pipe, and the joints calked with lead if so ordered. 972. Cement. The cement to be used shall be of a well and favorably known brand, acceptable to the engineer, and shall con- form to the following definitions. Portland cement shall be defined as the finely pulverized product resulting from the calcination to incipient fusion of an intimate mixture of properly proportioned argillaceous and calcareous ma- terials, and to which no addition greater than 3 per cent has been made subsequent to calcination. Natural rock cement shall be defined as the finely pulverized prod- uct resulting from the calcination of an argillaceous limestone at a temperature only sufficient to drive off the carbonic acid gas. Under the above definitions neither slag, puzzolana, nor sand cement will be accepted. Packing. The cement shall be packed in well-made barrels lined with paper, or in strong cloth or canvas sacks. Each package shall be plainly marked with the brand and the name of the manu- facturer. The packages must be unbroken and show no signs of having been exposed to moisture. Weight. One barrel of Portland cement shall contain not less than 376 pounds of cement, four sacks of 94 pounds net each being equivalent to one barrel. One barrel of natural rock cement shall contain not less than 282 pounds of cement, three sacks of 94 pounds net each being equiv- alent to one barrel. Protection after Delivery. After delivery the cement must be pro- tected from damage by storing in a tight building or by suitable canvas or other covering. The packages must not be placed upon the ground, but upon a platform of planks raised a few inches above the ground. Acceptable Brands. A list of acceptable brands will be furnishc d bidder. No cement will be placed upon the list of acceptable brands until complete and satisfactory tests, covering a period of at least 750 HIGHWAY CONSTRUCTION. one year, have been made upon it in the city's laboratory, nor will any brand of cement then be placed on this list or accepted unless batisfactory evidence can be furnished to show that it has been used successfully, without signs of deterioration, for a period of at least two years in the construction of important work. The city engineer reserves the right to suspend or cancel the use of any brand that ki his opinion may develop objectionable qualities a c ter~ acceptance. Inspection. All the cement shall be inspected and tested, and must meet the requirements given below before being accepted. The inspection and sampling may be done on the work after delivery or at the place of manufacture or at both, as may be advised by the engineer. If inspected at the work, not more than 150 barrels shall be covered by one set of tests. If inspected at the place of manu- facture, not more than 200 barrels shall be covered by one set of tests. The sampling of the cement shall be done only by the city's representatives. Sampling. When inspected at the work, samples shall be ob- tained by taking equal amounts of cement from 10 per cent of the packages represented, selected at random and amounting in the total to about 12 pounds. The samples shall be thoroughly mixed together when taken, so as to constitute as nearly as possible a fair average sample of the whole lot represented. The samples shall be shipped to the city laboratory in packages secure from moisture; each sample shall be accompanied by a manifest giving complete data of the same. In the case of brands not on the accepted list and which are offered for consideration with the view of placing on the list, samples for the tests shall be taken in the open market from at least 10 packages and mixed to form one sample for the test. Samples submitted by the manufacturers or agents shall also be tested and the results compared with those obtained from the samples taken in the open market, When the cement is inspected at the place of manufacture, samples shall be taken by the city inspector by means of sampling- tubes driven into the cement. The cement shall be stored in bins set apart for the use of the city. When a bin has been accepted and the cement is packed ready for shipment, each package shall be sealed by the city inspector with a leaden seal for identification. The SPECIFICATIONS AND CONTBACTS. 751 cement manufacturer shall afford the inspector all facilties and fur- nish all labor required for taking the samples and sealing the pack- ages. The city will furnish the leaden seals.. The samples will be forwarded to the city laboratory as described above for cement inspected on the work. In the case of cement accepted on tests made on samples taken at the mill, the city reserves the right to resample the packages on delivery and retest the same, and to reject it if it shows any sign of damage from moisture or other cause. In case packages already sealed are rejected, the seals shall be removed by the manufacturer or owner of the cement when notice of rejection has been received by him, and the seals returned to the city engineer. Cement of each brand shall be required to show uniform and characteristic results in the tests. Marked deviations from such results may be considered cause for rejection of any lot of cement, even though the test requirements may otherwise be fulfilled. Any cement that does not show an increase in strength at 28 days above that of 7 days shall be rejected. Cement which has been rejected shall be immediately removed from the site of the work. 973. Cement Tests and Requirements. The tests of the cement shall be in accordance with the methods proposed by the Committee on Uniform Tests of Cement of the American Society of Civil En- gineers, presented to the Society January 21, 1903, and amended January 20, 1904, with all subsequent amendments thereto. 752 HIGHWAY CONSTRUCTION. TESTS. Fineness. On No. 100 sieve of 10,000 meshes per square inch, wire No. 40, Stubbs wire gauge On No. 200 sieve of 40,000 meshes per square inch, wire No. 45, Stubbs wire gauge Setting. Initial set shall develop in not less than REQUIREMENTS FOR FOR NATURAL CEMENTS. PORTLAND CEMENTS. 90% shall pass. 92% shall pass. 70% shall pass. 75% shall pass. Final Set shall develop in not less than Nor more than . 10 minutes from time of adding water. 30 minutes from time of adding water. 3 hours from time of adding water. Soundness. Cold-water Test. Pats of neat cement about 3 inches diameter and | inch thick at centre, tapering to a thin edge, kept in moist air for a period of 24 hours and for the bal- ance of 28 days in water of tempera- ture approximately 70 F Shall not crack, warp, soften, nor disinte- grate. Boiling-water Test. Pats of neat ce- ment as above described kept in moist air for 24 hours, then exposed in an atmosphere of steam above boiling water in a loosely closed vessel for 5 hours Tensile Strength. Briquets one inch square in section of Am. Soc. C. E. standard form conserved in clean fresh water of temperature of about 70 F. stressed gradually at a uniform 30 minutes from time of adding water. 1 hour from time of adding water. 10 hours from time of adding water. Shall not crack,, warp, soften, nor disinte- grate. Shall not crack,, warp, soften,, nor disinte- grate. SPECIFICATIONS AND CONTRACTS. 753 rate of 400 pounds per minute until fractured shall develop the following minimum tensile strength: Neat T^sts.- Briquets of neat cement: 1 day old (24 hours in moist air). . . 75 Ibs. 175 Ibs. " lb, 28 days old { '^in ttef } 25 600 Ibs. Briquets over 28 days old (in water) shall show a strength not less than the one specified for 28 days. Sand Tests. Briquets of sand mortar in proportions by weight of one part cement to three parts of sand of Am. Soc. C. E. standard crushed quartz: old 28 days old . . 120 Ibs. 225 lb s . Briquets over 28 days old (in water) shall show a strength not less than the one specified for 28 days. Portland cement shall not contain more than 1.75% of anhydrous sulphuric acid (SO 3 ), nor more than 4% of magnesia (MGO). Specific Gravity. The specific gravity of Portland cement thoroughly dried at 100 C. shall not be less than 3.10 and of natural cement not less than 2.80. Chemical tests and other special tests may be applied at the discretion of the city engineer, and shall pass the same to his satisfaction. 754 HIGHWAY CONSTKUCTIOX. 974. Sand. The sand used for making mortar shall be sharp, clean, and free from loam and vegetable matter. If sand of the required quality cannot be found in natural beds on the line of the work, it shall be furnished by the contractor. The sand shall be screened and washed if so ordered by the engineer. 975. Water. The water employed for mortar shall be fresh and clean, free from mud or other objectionable matter. Sea-water may be used if permission is given by the engineer. 976. Mortar shall be composed of two parts of sand and one part of cement, mixed thoroughly dry and tempered to the required consistency. When Used. It shall be used as soon as made, and any mortar that may have taken a " set" while unused shall be wasted. Variation in Proportion. No variation from the above propor- tions will be permitted unless to make the mortar richer when j-equired in special cases. Tempering. The thorough mixing and incorporation of the materials will be insisted upon. The dry cement and sand shall be turned over and mixed with shovels by skilled workmen not less than ten (10) times before the water is added; after adding the water, the paste shall be again turned over a d mixed by skilled workmen not less than six (6) times before it is used. Boxes. Tight mortar boxes will be provided, and no mortar ;shall be made except in such boxes. 977. Concrete, how Composed. Concrete shall consist of angular fragments of sound, durable stone or hard-burnt brick, which shall be cleaned and thoroughly freed from dust and dirt, and broken so as to pass in any direction through a ring two (2) inches in diameter, and of hydraulic cement and sand, in the following proportions by volume : Cement 1 part Broken stone 5 parts -Sand ,...2 Mixing. These materials shall be intimately incorporated on the mixing-board or in a mechanical mixer, and after proper tem- pering shall be deposited carefully in place and thoroughly rammed until the surface is floated. Period of Repose. The concrete so laid shall be left without disturbance or shock for at least twenty-four (24) hours. SPECIFICATIONS AND CONTRACTS. 755 Variation in Proportions. The above proportions shall be varied without extra compensation upon the order of the engineer and to his entire satisfaction. Expeditious Operation. The whole operation of mixing and laying each batch of concrete shall be performed as expeditiously as possible, with the use of a sufficient number of skilled men. 978. Foundation Excavation. Foundation-pits shall be ex- cavated to such depths as the engineer may deem proper for the safety and permanence of the structure to be erected. 979. Artificial Foundations. Foundations of piles, timber,., plank, and concrete shall be prepared of such dimensions and in such manner as the engineer may direct, and the materials used shall conform in quality, etc., to the requirements stated for the respective kincL 980. Timber. The timber furnished shall be sound, straight- grained, well seasoned, and free from sap, large knots, shakes, and wanes. Knotty timber will not be allowed in the work where such would impair its strength. 981. Piles. The piles shall be of sound, straight-grained tim- ber from which the bark has been removed; they shall measure not less than 8 inches in diameter at the small end, nor be less, than 28 feet long. They may be driven with any approved form of pile-driver or by the " hydraulic jet " if they are driven by this latter method, they shall be constantly loaded with a weight of 2000 Ibs. They shall be driven, by whichever method adopted, until they do not move more than one-half inch under the blow of. a hammer weighing 2000 Ibs. and falling 30 feet. 982. Cofferdams. Where cofferdams are required for founda- tions, they shall be constructed in the manner directed by the engineer, and all pumping, bailing, and draining shall be performed as required and directed by the engineer. 983. Wrought-iron. All wrought-iron work furnished to be of the specified form and dimensions. The wrought-iron used shall be the best refined iron; it shall be tough, close-grained, highly fibrous, and when broken shall show a blue-gray fracture. It shall bear a high welding heat, and a cold bar must bend through 90 de- grees without sign of fracture; the tensile strength to be not less. than 50,000 Ibs. per square inch of sectional area when tested in large and long lengths. The reduction of breaking area shall average 25- 7 5 B HIGHWAY CONSTRUCTION. per cent, and the elongation of the bar before rupture shall be at least 15 per cent. Iron subjected to compressive strain to have an elastic limit of not less than 25,000 Ibs. per square inch. 984. Cast-iron. All cast-iron work to be of the specified form and dimensions; the iron to be gray iron, of uniform color and structure, with medium grain, sharp bright fracture, tough texture, and a low percentage of graphite. It shall be clean and free from sand, scoria, cold-shuts, blow-holes, blisters, or other injurious de- fects. Sample pieces 1 inch square, cast from the same heat of metal in sand-moulds, shall be capable of sustaining, on a clear span of 4 feet 8 inches, a central load of 500 pounds when tested in a rough bar. A blow from a 4-pound hand hammer shall produce an indentation on a rectangular edge of the casting without flaking the metal. GENERAL STIPULATIONS APPLICABLE TO ALL CONTRACTS. The following stipulations are applicable to all classes of work and should be inserted in all specifications, being varied, of course, to suit each particular case. 985. Interpretation of Specifications. In case of ambiguity of expression in the specifications, or doubt as to the correct interpre- tation of the same, the matter shall be submitted to the engineer, whose decision shall be final. 986. Omissions in Specifications. Any work or materials that may have been accidentally omitted in the description of the work, but which is clearly implied, shall be furnished by the contractor the same as if it had been specifically stated. 987. Engineer defined. Wherever the word " engineer " is used it refers to the chief engineer or his authorized assistants, by whom all explanations and directions necessary for the satisfactory pros- ecution and completion of the work described in these specifica- tions will be given. 988. Contractor defined. Wherever the word "contractor" is used it refers to and means the party or parties who shall have duly entered into contract with the of to perform the work; their duly authorized agents or legal representatives. 989. Notice to Contractor. Any written notice to the contractor which may be requisite under these specifications may be served oil SPECIFICATIONS AND CONTRACTS. 757 said contractor either personally or by mail, or by leaving the saminai return. 1000. Partial Payments. Monthly estimates shall be made during the progress of the work, arid payments to the amount of 80 760 HIGHWAY CONSTRUCTION. per cent thereof will be made, the retained percentage not being due or payable until the final completion of the work. These monthly estimates do not constitute an acceptance of the work,, the final estimate and formal acceptance constituting the only valid acceptance of the whole or any part of the work. 1001. Commencement of the Work. The work to be done under these specifications shall be commenced on such day and at such place or places as the engineer may direct. Failure to so commence without a good and valid reason therefor will be authority for the to declare the contract forfeited, and the said may proceed with the execution of the work in such manner as may be deemed proper. 1002. Time of Completion. The work shall be prosecuted in such manner as to complete it in accordance with the specifications on or before the expiration of working days. Should the execution of the work be delayed in consequence of any act or omission on the part of the , the condition of the weather, or by any circumstances so unusual that they could not be foreseen previous to or avoided during the construction of the work (all of which shall' be determined by the engineer, who shall certify the same in writing), the time during which the work was so suspended shall be excluded, and the time extended by a corresponding number of days. But neither an extension of time for any reason beyond the date fixed for the completion of the work, nor the acceptance of any part of the work comprised in these specifications subsequent to the said date, shall be deemed to be a waiver by the said of the right to abrogate the contract for abandonment or delay in the manner herein provided. 1003. Progress of Work and Forfeiture of Contract. The reserves the right to declare the contract forfeited, if at any time it should appear to the engineer that the work or any part thereof is being unnecessarily delayed, or that the contractor is wilfully violating any of the conditions of the contract, or is exe- cuting the same in bad faith, or if the said work be not fully com- pleted within the time named for its completion; he shall have power to notify the contractor to discontinue all work or any part thereof, by a written notice to be served upon the contractor either personally or by leaving said notice at his residence or with his SPECIFICATIONS AND CONTRACTS. 7* 1 agent in charge of the work. And thereupon the contractor shall discontinue said work or such part thereof, and the engineer shall thereupon have the power to place such and so many persons as he may deem advisable, by contract or otherwise, to complete the work, or such part thereof, and to use such materials as he may find upon the line of said work, and to procure other materials for the com- pletion of the same, and to charge the expense of said labor and materials to the aforesaid contractor; and the expense so charged shall be deducted and paid by the , out of such moneys as may be then due, or may at any time thereafter become due said contractor on account of work performed under these specifica- tions; and in case such expense is less than the sum which would have been payable if the same had been completed by the said con- tractor, he shall forfeit all claim to the difference ; and in case such expense shall exceed said sum, he shall pay the amount of such excess to the 1004. Damages for Non-completion. The contractor shall pay to the , as damages for non-completion of the work within the time stipulated for its completion, the sum of $100 for each and every day which may exceed the said stipulated time for its completion, which said sum of $100 per day is hereby, in view of the difficulty of estimating such damages, agreed upon, fixed, and determined by the contractor and the as the liquidated damages that the will suffer by reason of such default, and not by way of penalty; and the is hereby authorized to de- duct said sum of $100 per day from the moneys which may be due or become due said contractor for work under these specifications. 1005. Evidence of the Payment of Claims. In case of any legal claims being filed with the against the contractor for labor or materials furnished under these specifications, the said shall retain the whole or so much of such moneys as may be due or to become due the contractor as may be considered necessary to meet the lawful claims of such persons, until the liabilities shall be fully discharged and such notice withdrawn. 1006. Protection of Persons and Property. The contractor shall during the progress of the work use all proper precautions by good and sufficient barriers, guards, temporary bridges, etc., for the pre- vention of accidents, and at night he will put up and keep suitable and sufficient lights, and he will indemnify and save harmless the, HIGHWAY CONSTRUCTION. against and from all suits and actions, of every name and description, brought against it, and all costs and damages to which the said may be put for or on account or by reason of any injury or alleged injury to the person or property of another, resulting from negligence or carelessness of the contractor, his agents or employees, in the performance of the work, or in guarding the same, or from any improper materials used in its prosecution, or by or on account of any act or omission of the contractor, his agents or employees; and the shall retain the whole or so much of the moneys due or to become due by reason of the work under these specifications as may be considered necessary, until all such suits or claims for damages as aforesaid shall have been settled and satisfactory evidence to that effect is furnished. 1007. Bond for Faithful Performance of the Work. The con- tractor shall execute with his sufficient sureties a bond in the sum of thousand dollars for the faithful performance of the work in accordance with the requirements of the specifications. 1008. Power to Suspend Work. The prosecution of the work may be suspended for such periods as the engineer may from time to time determine. No claim or demand shall be made by the con- tractor for damages by reason of such suspensions in the work, but the period of such suspensions will be excluded in computing the time limited for the completion of the work. During such sus- pensions all materials delivered upon but not placed in the work shall be neatly piled or removed so as to not obstruct public travel. The wages of watchmen retained for the public protection during the period of suspension will be allowed. 1009. Loss and Damage. All loss and damage arising out of the nature of the work to be done under these specifications, or from any unforeseen obstructions or difficulties which may be en- countered in the prosecution of the same, or from the action of the elements, or from incumbrances on the line of the work, shall be sustained by the contractor. 1010. Miscellaneous Work. If any work or service be required to be done which in the opinion of the engineer does not come within the class of work to be measured under the contract, he shall be at liberty to direct the contractor to perform the same by day's labor, and the contractor when required by him shall furnish such force and materials and perform such work in the manner SPECIFICATIONS AND CONTRACTS. 7 03 directed, and he shall be paid the reasonable and actual wages of the men as ascertained by the timekeeper and the actual value of all materials furnished, together with fifteen per cent of the total amount for the use of tools and profit. The engineer shall be at liberty to discharge any inefficient or unsuitable workmen who may be placed on such work, and the work so performed will be subject to his approval before payment is made therefor. 1011. Cleaning up. All surplus materials, earth, sand, rubbish, and stones, are to be removed from the line of the work as rapidly as the work progresses. At any time within one month after the completion of the work, if so required by the engineer, all material shall be swept into heaps and removed from the line of the work ; and unless this be done by the contractor within forty-eight hours after being notified so to do to the satisfaction of the engineer, the same shall be removed by the , and the amount of the expense thereof shall be deducted out of any moneys due or to become due to the contractor under these specifications. 1012. Personal Attention. The contractor shall give his per- sonal attention to the faithful prosecution of the work, shall not sublet the same or any part thereof without the consent of the , nor will he assign by power of attorney or otherwise any of the moneys payable under these specifications. 1013. Payment of Workmen. The contractor shall punctually pay the workmen who shall be employed on the work comprised in these specifications, in cash current, and not in what is denominated " store " pay. 1014. Prices. The prices stated by the contractor in his tender and stipulated ID the contract must be understood to cover every contingency, the furnishing of all labor, materials, power, and plant which may be required for the performing and completing of the work described in these specifications (and for maintaining the same in good order for a period of six months). 1015. Payments, when Made. The contractor shall not be entitled to demand or receive payment for any portion of the work done or materials furnished under these specifications until the ;a:ne shall be fully completed in the manner set forth, and such completion duly certified by the engineer in charge of the work, and until each and every of the stipulations herein before men- tioned are complied with, and the work completed to the satisfac- 764 HIGHWAY CONSTRUCTION. tion of the and accepted by , whereupon the will pay in cash, on the expiration of days from the time of acceptance, the whole of the moneys accruing to the con- tractor under these specifications, excepting such sum or sums of money as may be retained under any of the provisions, herein contained, and such sums as may have been paid in the form of partial payments upon the monthly estimates of the engineer. FORMS OF SPECIFICATIONS. The following forms of specifications may be of assistance in preparing specifications for different works. 1016. Specifications for the Construction of a Highway from to in the town of , county of The following specifications are intended to cover the methods of construction and the furnishing of all the labor and materials, necessary for the proper and workmanlike completion of the above- named highways in accordance with the plans on file in the office of the engineer, and in accordance with such instructions relating thereto as may from time to time be given by said engineer, or his assistants and inspectors. Description of the Work. The character and approximate amounts of work to be done are as follows : Earth excavation cubic yards Loose rock excavation " " Solid " " Embankment to be furnished from " " Borrow-pits " " Blind stone drains lineal feet Tile drains, 3 inches in diameter " " 6 " " " " " Earthenware pipe-culverts, 12 ' diameter " ' " " " 18" " " " 24" " Dry box-culverts cubic yards " " " , third-class masonry " " Dry retaining-walls " " Rip-rap Catch- and silt-basins, number of Paved gutters lineal feet [Here insert the clauses suitable for each class of work in the schedule.] SPECIFICATIONS AND CONTRACTS. 765 1017. Specifications for Bulkhead (Fig. 138, p. 495). The bulkhead will be formed as follows : The piles will be of sound straight-grained spruce or other approved timber; they shall measure not less than 6 inches in diameter at the small end and not less than 12 inches nor more than 15 inches at the large end when cut off, The piles shall have the bark removed, be accurately pointed, and when required the heads shall be properly banded to prevent splitting or brooming while being driven; if found necessary, the points shall also be pro- tected with wrought-iron shoes. The piles will be spaced 6 feet from center to center, and shall be driven with a batter of If inches per foot. They may be driven by the hydraulic " jet " or by an or- dinary pile-driver; if by the jet, they shall be loaded with a weight of 2000 pounds. By whichever method driven, they shall reach a total penetration into the soil and sand of not less than 15 feet below low-water mark. Piles injured in driving shall be drawn out and replaced by sound ones at the contractor's expense. Piles found too short shall be drawn out and replaced by longer ones. Lengthening. Lengthening by using a follower or blocking will not be allowed. Any pile found too short must be drawn out and a longer one substituted. When the piles shall have reached the required depth, their tops shall be sawed off evenly at the estab-' lished grade. Pile-cap. And thereon a pile-cap of yellow-pine timber ten (10) by twelve (12) inches will be laid, fastened to each pile with one one- (1-) inch drift-bolt eighteen (18) inches long. On the water face and thirty (30) inches below the top of the pile-cap there will be placed a Brace Stick of yellow pine timber five (5) by ten (10) inches, bolted to every second pile with one one- (1-) inch bolt eighteen (18) inches long. On the water face at mean high-water mark there will be placed a Chafing-stick of yellow-pine timber five (5) by ten (10) inches, bolted to every pile with one one- (1-) inch bolt. On the land side of the piles at both mean high- and low- water marks there will be placed longitudinally Wale-sticks of yellow-pine timber five (5) by ten (10) inches, bolted to every pile with one one- (1-) inch bolt. Sheet-piling. On the land side of the wale-sticks sheet-piling 706 HIGHWAY CONSTRUCTION. of tongued and grooved yellow-pine plank, three (3) inches thick and not less than eight (8) inches wide, will be driven to a depth of not less than ten (10) feet below low-water mark. EacjpL plank will be spiked to both wale-sticks with two six- (6-) inch cut spikes; the tops will be sawed off level with the upper wale-stick. Anchor-piles. On the land side and opposite every third pile :i:nd eighteen (18) feet distant therefrom an anchor-pile not less than six (6) inches in diameter and ten (10) feet long will be driven to the angle shown on plan, to a penetration of not less than seven (7) feet. At the back of the anchor-piles there will be placed loosely upon the ground a brace-stick of yellow-pine timber five (5) inches by ten (10) inches. Tension-rods. Tension-rods made from one and one quarter (1) inch iron will extend from front to rear brace-stick, passing through both sticks and piles; the rods will be screwed on both ends and will have under each nut on the water face an iron washer four (4) inches in diameter, cast to the required angle. Bolt-lioles. All bolt-holes will be bored with an augur one eigth (|) of an inch smaller than the diameter of the bolt they are to receive. Fender-piles. Fender-piles eighteen (18) inches in diameter at the butt and 30 feet long will be driven at every twenty (20) feet along the water face. Lengths of Timber. The pile-cap, braces, and chafing-sticks shall be in lengths of not less than eighteen (18) feet; they shall be arranged so as to bring the Joints on a pile. All joints shall be made by a twelve (12) inch half-lap splice fastened with two seven eighths (f) inch by fifteen (15) inch bolts. All bolt-heads in pile-cap will be countersunk flush with the top. Iron washers will be placed under all bolt- heads and nuts. 1018. Specifications for Grading, Macadamizing, Curbing, and Flagging Avenue, from to Grading. The entire width of the avenue is to be regulated and graded to sub-grade, fifteen (15) inches below finished grade, in accordance with the grades and cross-section shown in plans. Such portions as are above the grade lines shall be. excavated, and such as are below shall be filled in. Slopes. Slopes in both embankment and excavation shall be SPECIFICATIONS AND CONTRACTS. 767 one and one half (1-J-) horizontal to one (1) vertical unless otherwise ordered. If the material taken from the excavations is unsuitable or in- sufficient to make the embankments, the deficiency shall be sup- plied by the contractor. The material so furnished shall be good clean earth, sand, gravel, or broken rock and earth. If broken rock is furnished, the proportion of earth and rock shall not be less than 1 to 1, and the materials shall be so distributed that no voids shall be left. Any perishable matter that may be found at sub-grade level shall be removed and the space filled in with good material. The sub-grade surface shall be truly shaped and trimmed to the required cross-section, then rolled with a roller weighing not less than 300 pounds per inch of run. The rolling will be continued until the surface has become firm and hard : in no case shall it be less than 5 hours per 1000 square yards. Such parts as cannot be reached by the roller shall be tamped with hand rammers. Water shall be applied by sprinkling in advance of the roller, but an ex- cess must not be used ; generally 25 gallons per 1000 square yards will be sufficient. On the sub-grade surface prepared as above described a layer of bank gravel will be spread to a depth of nine inches and rolled con- tinuously until the depth is reduced to seven inches; on the foun- dation so prepared the broken stone will be placed. Its finished thickness will be eight inches. The stones will be spread in two layers : the first layer will be spread to a depth of five and a half inches and rolled till the depth is reduced to five inches ; water will be applied in advance of the roller, but not in excess. AVhen the broken stone is so compacted a layer one inch thick of clean sand, or sand contain- ing not more than 15 per cent of loam, will be spread over the sur- face, and the rolling continued until the stones cease to sink or creep in front of the roller, and the thickness of the layer of broken stone is 4 inches or thereabouts. When the first layer has been finished to the satisfaction of the engineer, the second layer will be spread to the same depth and treated in the same manner as the first layer. The rolling, of this surface will be continued until all settlement has leased. In quality the stone must conform to the sample in the office of the engineer. 768 HIGHWAY CONSTRUCTION. In form it shall be as nearly cubical as practicable, and in size- shall not excesd in any dimension two and a half inches, but may range fiom this size down to quarter-inch chips; but the proportion of siones below one and a half inches shall not exceed 20 per cent of the whole quantity. The stone will not be screened, but shall be delivered as it comes from the breakers; care, however, being taken that clay does not become intermixed with the stone. Gutters. For a width of two feet on each side of the carriage- way adjoining the curb a gutter of granite blocks will be laid. Each block shall measure not less than six nor more than nine inches in length, in width not less than three nor more than five inches in depth, not less than seven nor more than eight inches; the blocks to be split and dressed so as to form, when laid, close joints on sides and ends. The blocks will be laid in courses parallel to the curb. Each course shall be formed with blocks of a uniform width and depth, and laid so that all the longitudinal joints shall be broken by a lap of at least two inches. The blocks will be laid on the gravel foundation and set stone to stone, both on sides and ends. When thus laid, their surface shall be covered with a layer of clean sharp sand, which shall be swept with brooms until all the joints are filled. Into the sand joints thus made there will be poured a hot mixture of coal pitch and creosote. The whole surface of the blocks will then be covered with one half-inch of sharp sand, which shall be left undisturbed until ordered removed by the engineer. Curbing. The curbstones shall be of bluestone, equal in quality to the best North River bluestone. The curbstones shall be not less than three feet in length, five inches thick, twenty inches deep, and matched width throughout. -The top of the stone shall be cut to a bevel of one inch; the front shall be cut smooth and to a fair line, to a depth of fourteen inches. The ends from top to bottom shall be truly squared, so as to form close and even joints, and the front so laid as to present a fair and unbroken line. Curbstones shall be back filled, and backed up with at least one foot of clean, gritty earth, free from clay and loam. Circular Corners. The curbstones at the corners of intersect- ing streets shall be cut on a curve, with true and even joints, and SPECIFICATIONS AND CONTRACTS. 769 ; ____ . shall be of the same description as the curb before described, and be laid in the same manner. Flagging. All the nagging to be of blnestone equal in quality to the best North River bluestone, even on its face, and to measure not less than two feet wide, to contain not less than eight superficial feet, and to be in no place less than three inches thick. To b^ laid with close joints, in regular courses of four feet wide. Each slom? shall be chisel-dressed on the four edges a distance of one inch down from the top and square with the face thereof, and free iroin drill-holes. Flagging shall be bedded in four inches of clean, gritty earth or steam ashes, free from clay and loam, and the work brought to an even surface; the joints of the nagging shall be closed up with cement mortar, and be left clean on the surface ; the whole space of the sidewalks to be regulated before laying the flagging. Catch-basins. Catch-basins will be constructed at the points indicated on the plans or wherever the engineer may direct. They will be of brick masonry, built with care, of the form and dimensions shown on the plan. They will be made perfectly water- tight by plastering the interior with neat Portland-cement mortar one half-inch thick. The exterior shall be coated with cement mortar one inch in thickness. Each basin will be connected by a nine-inch cement or earthenware pipe-shoot connected to a twelve-inch cement or earthenware pipe. This pipe will be laid on the lines and grades given by the engineer, and connected to the sewer or other outlet. Each basin will be fitted and furnished with a cast-iron head and grating of the form and dimensions shown on plan. {Here insert such clauses for general specifications and stipula- tions as are suitable.) 1019. Specifications for the Supply of Broken Stone. The stone shall be fully equal to the sample in the engineer's office,, otherwise it will be rejected. It shall be broken in as nearly cubical form as practicable, each cube to have a square face and sharp edges, and shall not exceed in any dimension two inches, but the stones may range from this size down to quarter-inch chips; but the proportion of stones below one and a half inches shall not exceed 20 per cent of the whole quantity. The broken stones shall not be screened, but will be delivered as 770 HIGHWAY CONSTRUCTION. they come from the breakers; care, however, being taken that clay does not become intermixed with them. The stone when delivered must be clean and free from clay or other dirt. The stone shall be supplied on the order of the engineer in such quantities as he may specify, and must be delivered within the time specified in the order. Failure to so deliver the stone without good and sufficient reason will be a valid excuse for the forfeiture of the contract. ADDITIONAL CLAUSES REQUIRED IN SPECIFICATIONS FOR REPAIRING, ETC. 1020. Indemnification for Patent Claims. The contractor shall indemnify and save harmless the against and from all suits and actions of every nature and description arising out of the claim or claims of any person or persons claiming to be patentees of any process connected with the work herein provided for, or of any materials used upon said work. 1021. Indemnity Bond. The contractor shall execute with two sufficient sureties a bond in the sum of thousand dollars, for the indemnification of the against and from all such suits and actions aforesaid. 1022. Right to Construct Sewers, etc. The right to construct sewers or any work in connection therewith, lay water, gas, or other mains and make house connections therewith, in advance of the pavement, is expressly reserved by the ; and the said may suspend the work on the pavement on any part of the line for the purpose above stated, without other compensation to the con- tractor for such suspension than extending the time for completing the work as much as it may, in the opinion of the engineer, have been delayed by such suspension. And the contractor shall not interfere with or place any impediment in the way of any person or persons who may be engaged in the construction of such works. 1023. Old Materials. All old materials which it may become necessary to remove, and where no instructions for their disposal is , previously given, shall be considered as the property of the con- tractor, and the same shall be immediately removed by him from the. line of the work. SPECIFICATIONS AND CONTRACTS. 771 1024. Security retained for Repairs. The shall re- tain out of the moneys payable to the contractor on completion of the work the sum of ten cents per square yard of pavement laid under these specifications, which sum of ten cents with interest shall be paid upon the expiration of the guaranty period; provided that the work at that time is in good order, or as soon thereafter as the work shall have been placed in good order, to the satisfaction of the engineer. During the guaranty period should any part of the work require repairs, the engineer shall notify the contractor to make such re- pairs, and in case of neglect or failure to make said repairs within forty-eight hours after service of notice the shall have the right to purchase such materials as may be deemed necessary, and to employ such persons as may be deemed proper, and to under- take and complete such repairs, and to pay the expense thereof out of the said sum of ten cents per square yard retained for that pur- pose, and such part of said sum as shall remain after the expenses of said repairs have been deducted will be paid in the manner here- inbefore described. 1025. Alteration of Manhole Covers, Stopcock Boxes, etc. All the frames and heads of sewer manholes, stopcock boxes for water and gas, are to be adjusted (either raised or lowered) to the level of the pavement. 1026. Heads of Specifications for Repaying. Specifications for Regulating and Paving ivitli Pave- , ,T ri * street ment the Carnageivay of avenue * rom * (1) Description of the work. (2) Removal of old materials. (3) Excavation. (4) Adjustment of manhole heads, etc. (5) Adjustment of curb. (6) Adjustment of bridge stone. (7) Furnishing new curb. (8) Furnishing new bridge stones. (9) Preparation of roadbed. (10) Foundation, character of. (11) Concrete. (12) Concrete, manufacture and laying. 772 HIGHWAY CONSTRUCTION. (13) Pavement, character and quality. (14) Manner of laying. (15) Cleaning up. (16) Quality of material. (17) Inspectors. (18) Right to construct sewers. (19) Commencement of work. (20) Time of completion. (21) Suspension of work. (22) Extension of time. (23) Damages for non-completion. (24) Personal attention of contractor. (25) Contractor's representatives. (26) Defective work. (27) Improper prosecution of the work. (28) Accidents or damages to persons or property to be paid for by the contractor. (29) Incompetent workmen. (30) Power to annul contract for violation of stipulations. (31) Payment of claims for labor and materials. (32) Measurements. (33) Engineer's estimates. (34) Payments, when made. (35) Percentage retained. (36) Prices. (#) Interpretation of specifications. (38) Engineer defined. (39) Contractor defined. '(40) Preservation of engineer marks, etc. (41) Indemnification of patent claims. (42) Indemnity bond. (43) Security retained for repairs. 1027. Specifications for Street cleaning should Contain the fol- lowing Conditions. The mode of cleaning shall be to first clean the gutters of all solid matter, and then sweep from the sides towards the centre; dirt collections not to be placed within 5 feet of ttu gutters. Whenever the sweeping of streets would cause the dust to rise, they shall be first sprinkled by sprinkling-wagons to be approved SPECIFICATIONS AND CONTRACTS. 773 by the of the of ; and the sprinkling shall be so done that the dust will not be turned into mud. All hand sweeping shall be done with push-brooms, and all sweep- ing by machinery with machines approved by the of All parts of streets covered with sheet asphalt shall be swept by machinery six times each week, between the hours of 10 P.M. and 6 A.M., and a sufficient number of men with bass brooms shall be kept employed to keep them constantly clean between the hours of 7 A.M. and 6 P.M. All accumulations of sweepings, and of mud or rubbish removed from inlets or gutters, shall be removed within three hours from the time such heaps are made, in carts tightly built in such a man- ner that the contents can be removed without spilling or leaking, and the place where they had been collected shall be swept clean. All gutters kept wet by the flow of filthy water or sewage shall be thoroughly scraped, brushed, and flushed at least twice a week from May 1st to November 1st, and for this work each contractor will be required to keep at least 100 feet of hose in each district, and brushes or brooms especially made for work of this kind shall be used in cleaning the gutters. All solid matter must be removed from the gutters and inlets before they are flushed. All street crossings, inlets, gutters approaching the same, and all gutters necessary to drain crossings within 100 feet of inlets, and streets in front of fire-plugs, for a radius of 5 feet, must be kept clean of dirt, mud, ice, and snow. 1028. Instructions to Bidders. Proposals for [insert descrip- tion and location of the work]. In pursuance of the follow- ing ordinance [insert ordinance]. Sealed proposals for the above work, indorsed with the above title, also with the names of the person or persons making the same and the date of presentation, will be received at the office of until o'clock .M., day of , 189 , at which place and hour the bids will be publicly opened by and read, and the award of the contract will be made to the lowest responsible bidder with adequate security as soon thereafter as practicable. The person or persons to whom the contract may be awarded will be required to attend at the office of with the sureties offered by him or them, and execute the contract within 774 HIGHWAY CONSTRUCTION. five days from the date of the service of a notice to the effect that the contract has been so awarded, and that the adequacy and suffi- ciency of the security offered has been approved by the ; in case of failure or neglect so to do, he or they will be con- sidered as having abandoned it, and as in default to the ; and thereupon the work will be readvertised and relet, and so on until the contract be accepted and executed. The work is to be commenced at such time as the engineer may designate. The price must be written in the bid, and also stated in figures, and all proposals will be considered as informal which do not con- tain bids for all the items for which prices are herein called for, or which contain prices for items not called for, or which contain erasures, alterations, or other irregularities. Permission will not be given for the withdrawal of any bid or estimate, and the right is expressly reserved by the to re- ject all bids if it shall be deemed for the public interest so to do. No bid will be accepted from or contract awarded to any person who is in arrears to the upon debt or contract, or who is a defaulter, as surety or otherwise,, upon any obligations to the Bidders are required to state in their estimates, under oath, their names and places of residence, the names of all persons interested with them therein, and if no other person be so interested, they shall distinctly state the fact ; also that it is made without any con- nection with any other person making a bid or estimate for the same work, and that it is in all respects fair and without collusion or fraud ; and also that no member of or other officer of the is directly or indirectly interested therein, or in the sup- plies or work to which it relates, or in any portion of the profits thereof. Where more than one person is interested, it is requisite that the verification be made and subscribed by all the parties inter- ested. Each estimate shall be accompanied by the consent, in writing^ of two householders or freeholders in the , with their re- spective places of residence, tb the effect that if the contract be awarded to the person making the estimate, they will, upon its being so awarded, become bound as his sureties for its faithful perform- ance ; and that if he shall omit or refuse to execute the same, they will pay to the any difference between the sum to which he Tould be entitled upon its completion, and that which the said SPECIFICATIONS AND CONTRACTS. 775 may be obliged to pay to the person to whom the con- tract shall be awarded at any subsequent letting; the amount in each case to be calculated upon the estimated amount of the work by which the bids are tested. The consent above mentioned shall be accompanied by the oath or affirmation, in writing, of each of the persons signing the same, that he is a householder or freeholder in the and is worth the amount of the security required for the completion of the contract and stated in the proposals, over and above all his debts of every nature and over and above his lia- bilities as bail, surety, and otherwise, and that he has offered himself as surety in good faith and with an intention to execute the bond required by law. The adequacy and sufficiency of the security offered will be determined by the . of the In case a proposal is submitted by or in behalf of any corpora- tion it must be signed in the name of such corporation by some duly authorized officer or agent thereof, who shall also subscribe his own name and office. If practicable, the seal of the corporation should also be affixed. The successful bidder will be strictly held to the time bid for completion of the work, and to the conditions of the specifications. The engineer's estimate of the nature and extent of the work to be done and materials to be furnished is as follows : [Insert esti- mate.] As the above quantities, though stated with as much accuracy as is possible in advance, are approximate only, bidders are required to submit their estimate upon the following express conditions, which shall apply to and become part of every estimate received : 1. The items and quantities stated in the above schedule are merely approximate and may be altered in part or wholly changed during the progress of the work. They are intended only to indi- cate the general character of the work and shall not be made a basis of any claim for extra compensation of profits in case the quantities of the final estimate shall vary from them, nor be regarded as having any relation or bearing whatever upon the quantities of the final estimate. 2. Bidders must satisfy themselves by personal examination of the site of the proposed work as to the difficulties to be encountered and such other matters which can in any way influence their esti- mate*, and no information derived from the drawings or specifica- 776 HIGHWAY CONSTRUCTION. tions or from the engineer or any of his assistants will relieve the contractor from any risks or from fulfilling the terms of the specifi- cations and contract. 3. The contractor will be required to complete the entire work to the satisfaction of the and in substantial accordance with the specifications. No estimate will be received or considered unless accompanied by either a certified check upon one of the National or State banks of the drawn to the order of the , or money to the amount of five per centum of the amount of the security re- quired for the faithful performance of the contract. Such check or money must not be inclosed in the sealed envelope containing the es- timate, but must be handed to the officer or clerk of the department who has charge of the estimate box, and no estimate can be de- posited in said box until such check or money has been examined by said officer or clerk and found to be correct. All such deposits, except that of the successful bidder, will be returned to the persons making the same within three days after the contract is awarded. If the successful bidder shall refuse or neglect, within five days after notice that the contract has been awarded to him, to execute the same, the amount of -the deposit made by him shall be forfeited to and retained by the as liquidated damages for such neglect or refusal; but if he shall execute the contract within the time aforesaid, the amount of his deposit will be returned to him. Bidders are particularly cautioned that in no case will they be permitted to use materials either in quantity or quality different from those described in the specifications. [And also, that a pro- vision in the specifications and contract requires the maintenance of the pavement in good condition for the period of from the final completion and acceptance thereof.] The amount of security is thousand dollars for the faithful performance of the contract, and also for the indemnifica- tion of the -for infringement of patents the amount is thousand dollars. The contractor must notify the en- gineer in writing hours before commencing the work. The plans can be seen and blank forms of proposals and further information can be obtained on application at the office of SPECIFICATIONS AND CONTRACTS. 1029. Form of Proposal. NO. BID OK ESTIMATE. For [insert description of work] , made by , resid- ing at , and residing at , and resid- ing at , and residing at , composing the firm of 1. declare that the only person in- terested in this proposal; and no other person other than herein above named ha any interest in this proposal, or in the contract proposed to be taken. 2. further declare that this proposal is made without connection with any other person or persons making a pro- posal for the same purpose, and is in all respects fair, and without collusion or fraud. 3. further declares that no member of the . or other officer is directly or indirectly interested in this proposal, or in the supplies or work to which it relates, or in any portion of the profits thereof. 4. further declares that the names of the persons affixed to the consent hereto annexed were written by said persons respectively, and that said persons are householders or freeholders in the 5. have examined the proposals for estimates for the above work, dated the day of , 189 , and pub- lished in the , and the form of contract for the work (including the plans and specifications for the work), and have also visited and examined the site and location and made the in- vestigations recommended in the instructions to bidders, and will contract to furnish the material and perform and complete the work mentioned in said proposals for estimates and approved form of contract on the following terms, viz. : For clear- ing, grubbing and close cutting, per acre, the sum of . For earth excavations for all classes, per cubic yard, the sum of For loose rock excavation, per cubic yard, the sum of Foi solid rock excavation, per cubic yard, the sum of For 12-inch culvert pipe, per linear foot, the sum of For 24-inch culvert pipe, per linear foot, the sum of For concrete, per cubic yard, the sum of . For each receiving basin, complete, with iron head and grating, the sum of 778 HIGHWAY CONSTRUCTION. For brick masonry, per cubic yard, the sum of For yellow-pine timber, including fastenings, per 1000 feet-board measure, the sum of For spruce and other plank, including fastenings, per 1000 feet board measure, the sum of . For riprap, per cubic yard, the sum of . For dry stone masonry, per cubic yard, the sum of The above prices include the furnishing of all the materials, tools, plant, and labor, and every risk and contingency necessary for the completion of the work in accordance and with specifica- tions and plans. Time within which will complete the whole work ac- cording to specifications days. CITY OF , COUNTY OF , ss. : being duly sworn, say, each for himself, that the several matters stated in the above estimate are in all respects true. Subscribed and sworn to this day of , A.D. 189 , before me, Commissioner of Deeds. 1030. Form of Agreement (to be executed in triplicate). This agreement made and entered into this day of , one thousand eight hundred and , by and between the [in- sert name of city, town, or county] of , hereinafter called the party o'f the first part, and [name of contractor], of the [insert place of residence], hereinafter called the party of the second part, Witnesseth : That the said party of the second part has agreed, and by these presents does for himself, his heirs, executors, admin- istrators, and assigns, covenant, promise, and agree with the said parties of the first part, for the considerations hereinafter mentioned SPECIFICATIONS AND CONTRACTS. 779 and contained, and under the penalty expressed in a bond bearing even date with these presents, and hereunto annexed, that he, the said party of the second part, his heirs, executors, administrators, or assigns, shall and will furnish and provide, at his own or their own cost and expense, all the necessary materials, appliances, tools, plant, and labor which are or may be necessary for the proper and sub stantial construction and completion of the [insert description of work], in accordance with the general plans on file in the office of the said party of the first part, and in strict conformity in every part and particular with the following specifications, and in accord- ance with such detail plans and instructions relating thereto as may from time to time be given by the chief engineer or his duly appointed assistants; and further agrees that the said parties of the first part shall be, and are hereby, authorized by their chief engineer, or such other person or persons, or in such other manner, as they may deem proper, to inspect the material to be furnished and the work to be done under this agreement, and to see that the same correspond with the specifications and conditions hereinafter set forth. The party of the second part admits and agrees that the amounts and quantities of materials to be furnished and work to be done, as stated in the proposals for estimates for the said work, are approxi- mate only; that he is satisfied with the foregoing estimate in de- termining the price according to which he agrees to do the work required by this contract in accordance therewith, and that he shall not and will not dispute or complain of such statement, nor assert that there was any misunderstanding in regard to the nature or amount of the materials to be furnished or work to be done; and he covenants and agrees that he will complete the entire work to the satisfaction of the and in substantial accordance with said specifications and the plan therein mentioned, and that he will not ask, demand, sue for, or recover for the entire work any extra compensation beyond the amount payable for the several classes of work in this contract enumerated, which shall be actually performed, at the price therefor herein agreed upon and fixed. The parties -hereto also declare that this contract is made with reference to the proposals for estimates for the above-described work, hereto annexed, and the estimate of the contractor now on file 780 HIGHWAY CONSTRUCTION. in the , which are to be taken as part and parcel of these presents [here insert specifications and general stipulations]. Commencement. The said party of the second part hereby further agrees to commence the work comprised under this agree- ment on such day and at such place or places as the engineer may designate. Failure to so commence will be authority for the party of the first part to declare this agreement forfeited, and the said party of the first part may proceed with the execution of the work in such manner as they may deem proper. Time of Completion. The party of the second part agrees to prosecute the work in such manner as to complete the same in accordance with this agreement on or before the expiration of two hundred (200) days after the date of commencement, and it is further agreed that in the computation of said time, the length of time (expressed in days and parts of a day) during which the work or any part thereof has been delayed in consequence of the condi- tion of the weather, or by any difficult circumstances so unusual that they could not be foreseen previous to, or avoided during, the construction of the work, or by any act or omission of the parties of the first part (all of which shall be determined by the chief en- gineer, who shall certify to the same in writing), and also Sundays and holidays on which no work is done, and days on which the prosecution of the work is suspended by order of the party of the first part, shall be excluded. But if the construction of said work should require material or work in greater or lesser quantities or amounts than those men- tioned and set forth in the engineer's estimate, then the said time shall be increased' or diminished as much as the said engineer, by a certificate in writing, shall deem just and reasonaole, and fairly proportioned to the amount of said increase or diminution. But neither an extension of time for any reason beyond the date fixed herein for the completion of the work, nor the doing and ac- ceptance of any part of the work called for by this agreement, subsequent to the said date, shall be deemed to be a waiver by the said party of the first part of the right to abrogate this contract for abandonment or delay in the manner provided for in Article 80 of this agreement. Damages for Non-completion. And the said party of the second part hereby further agrees, that the said parties of the first part SPECIFICATIONS AND CONTRACTS. 781 shall be and are hereby authorized to deduct and retain out of the moneys which may be due or become due to the said party of the second part under this agreement, as damages for the non-comple- tion of the work aforesaid within the time hereinbefore stipulated for its completion, the sum of dollars for each and every day which may exceed the said stipulated time for its completion; which said sum of dollars per day is hereby, in view of the difficulty of estimating such damages agreed upon, fixed and determined by the parties hereto as the liquidated damages that the parties of the first part will suffer by reason of such default, and not by . way of penalty. Improper Prosecution of Work. The said party of the second part further agrees that if at any time it should appear to the en- gineer that the works are being delayed, or are not being prosecuted with due diligence, or with such speed as would be necessary for their completion within the time specified, or that the works are being prosecuted in an improper or unworkmanlike manner, the said engineer shall notify the contractor in writing, specifying the causes of complaint, and upon the party of the second part failing to rectify such matters within seven days after the receipt of said aotice, the engineer shall notify the party of the first part of such failure; and it is further agreed, that in the event of such failure vhe party of the first part may, without further notice, suspend the Contractor from all work under this agreement ; and it is further ngreed, that the said party of the second part shall immediately respect said suspension, and shall stop work, and cease to have any rights to possession of the ground ; and the said party of the first part shall thereupon have the power to carry on and complete the work herein described, by contract or otherwise, employing such plant, tools, and materials as may be on the ground, and procuring such others as may be wanting, for the proper completion of the work, and to charge the expense of such labor and materials to the aforesaid party of the second part, and the expense so charged shall be deducted and paid out of such moneys as may be then due, or may at any time thereafter become due, to the said party of the second part under or by virtue of this agreement, or any part thereof; any excess of cost over and above the amount accruing as above stated shall be charged against the party of the second part and his sureties, who will each and severally be held liable there- 782 HIGHWAY CONSTRUCTION. for; and in case the cost of completion shall be less than the sum which would have been payable under this contract if the same had been completed by the party of the second part, he shall be entitled to receive the difference. Engineer's Returns. The said party of the second part further agrees that the return of the engineer shall be the account by which the amount of material furnished and work done in terms of this contract shall be computed; provided, however, that nothing herein contained be construed to affect the right of .the party of the first part to reject and contest any return or certificate of the en- gineer or inspectors having charge of the work, should such return or certificate be in their opinion not in accordance with the facts of the case or the requirements of this agreement, or otherwise improperly given. Damage to Property. And it is hereby further agreed, that in case any damage or injury, shall or may result to buildings, water-pipes, hydrants, gate-boxes, sewer-basins, man-holes, sewers, or other works through or by reason of any negligence, careless- ness, or want of skill on part of said party of the second part, the said party of the second part shall restore the same to their former good condition; failing to do so, said party of the second part shall pay such amount as shall or may be sufficient to cover the expense and damage occasioned by such negligence, carelessness, or unskilfulness. Gas-pipes. And the said party of the second part further agrees to do everything necessary to support and sustain the gas- pipes laid in or across said streets, which may bfr liable to any in- jury from digging the trenches for the work hereinbefore men- tioned, and to have a sufficient quantity of timber and plank con- stantly on the ground, and to use the same as required for bracing and sheet-piling the sides of the excavation. Notice to Gas Companies. And the said party of the second part further agrees to give notice in writing, at least twenty-four hours before breaking ground for the purpose of constructing the work hereinbefore mentioned, to such and all such gas companies as have, or may during the progress of the work have, any gas-pipes Which may be affected by such excavations as may become necessary. And it is further agreed, that the said party of the second part SPECIFICATIONS AND CONTRACTS. 783 shall not cause any hindrance to or interfere with such gas com- pany or companies in protecting their pipes, nor in removing or otherwise protecting and replacing the main and service pipes, lamp-posts and lamps, where necessary; but that the said party of the second part will suffer the said company or companies to take all such measures as may become necessary for the purpose afore- said. Penalty of Damage to Gas-pipes. And it is hereby further agreed, that in case any damage or injury shall or may result to the said pipes, lamp-posts, lamps, or other works of any gas company, through or by reason of any negligence, carelessness, or want of skill on the part of the said party of the second part, his agents or servants, the said party of the second part shall become liable to pay such amount as shall or may be sufficient to cover the expense and damage occasioned by such negligence, carelessness, or unskil- f ulness; and such amount shall be charged against the said party of the second part, and may be deducted from any sum or sums due or to become due or payable to said party of the second part on account of this contract. Water-pipes. The party of the second part hereby further agrees to sustain in their places, without injury, all the main and service water-pipes which may be affected in any manner by the work under this agreement, including any such protective meas- ures as may be required in cold weather to prevent them from freezing; or failing to do so, the said shall be and he is hereby authorized to replace and recalk and repair the same im- mediately in each block, as the work progresses, and the cost there- of shall be charged to the said party of the second part, and the cost so charged to the said party of the second part shall be re- tained and deducted, and the parties of the first part are hereby authorized to retain and deduct said cost out of the moneys which may be due or become due to the said party of the second Dart under this agreement. Transfer of Contract. The party of the second part further agrees not to transfer or sublet any part of the work referred to in this agreement, without the previous written consent of the en- gineer; any such transfer or subletting without said consent will be null and void, and will be sufficient cause for the annulment of 784 HIGHWAY CONSTRUCTION. the contract; nor shall any of the moneys payable under this con- tract be assigned by power o.f attorney or otherwise. Loss or Damage. And it is further agreed that all loss or damage arising out of the nature of the work to be done, or from any unforeseen or unusual obstructions or difficulties which may be encountered in the prosecution of the same, or from the action of the elements, or from injury to persons or property of another, resulting from negligence in the performance and guarding of the same, which must be protected when necessary with barriers, and at night with red lights, or from any improper materials used in prosecution or by or on account of any act or omission of his own, or his agents, will be sustained by the contractor, and he shall save harmless the party of the first part from any and all liabilities and claims for such, and the said party of the first part shall have the right to retain any moneys that may be due or become due, until evidence has been furnished that all such suits or claims for damages as aforesaid have been satisfactorily settled. Public Protection. It is further agreed that the contractor will enclose every opening he may make in the public highway with sufficient barriers, and must maintain red lights, at the same at night, and must take all necessary precautions to guard effectu- ally against accidents to persons, horses, vehicles, or property of any kind, and all work shall be done in such manner and at such times as to interfere as little as possible with public travel and convenience; and the contractor shall conduct his work for this object as the engineer may from time to time direct. Work not Provided for in Contract. The said party of the second part further agrees, that if, before the completion of the work contemplated herein, it shall become necessary to do any other or further work on or about this regulating, etc., than is pro- vided for in this contract, or to construct any sewer or sewers or appurtenances thereof, on the line of this work, the said party of the second part will not in any way interfere with or molest such other person or persons as the may employ to do such work, and will suspend each part of the work herein specified, or will carry on the same in such manner as may be ordered by the said , to afford all reasonable facilities for doing such work, and no other damage or claim by the said party of the second part hereof shall be allowed except such extension of the time specified SPECIFICATIONS AND CONTRACTS. 785 in this contract for the performance thereof as the may deem reasonable. Security to be retained for Repairs. And the said party of the second part hereby further agrees that the said parties of the first part shall be and are hereby authorized to retain, out of the moneys payable to him under this agreement, the certain sum of twenty-five cents per linear foot of the work done under this agree- ment, and to expend the same, in the manner provided for, in mak- ing such repairs to the work done under this agreement as the said may deem necessary, except curbing and flagging, which will be finally accepted upon the completion of the work. And it is further agreed that if, at any time during the period of six months from the date of the acceptance by said of the work under this agreement, the said work or any part thereof (ex- cepting only such part or parts of the work as after the completion thereof may have been disturbed in the construction or repairs of sewers or drains, or in laying or repairing gas or water main or service pipes, or railroad-pier foundations) shall in the opinion of the said require repairs, the said shall notify the said party of the second part to make the repairs so required, the said party of the second part shall immediately commence and complete the same to the satisfaction of said ; and in case of failure or neglect, on his part, to do so within forty-eight hours from the date of the service of the aforesaid notice, then the said shall have the right to purchase such materials as ke shall deem necessary, and to employ such person or persons as he may deem proper, and to undertake and complete the said repairs, and to pay the expense thereof out of the said certain sum retained for that purpose by the said parties of the first part, as before men- tioned. And the parties of the first part hereby agree, upon the expiration of the said period of six months, provided that the said work at that time be in good order, or as soon thereafter as the said work shall have been put in good order to the satisfaction of the said , to pay to the said party of the second part the whole of the sum last aforesaid or such part thereof as may remain after the expense of making such repairs, in the manner aforesaid, shall have been paid therefrom. And it is hereby further agreed, between the parties hereto, that if the termination of the said period of six months after the completion and acceptance of the work done 786 HIGHWAY CONSTRUCTION. under this agreement shall fall within the months of December, January, February, and March, then in that case the said months of December, January, February, and March, or such part thereof as the may determine, shall not be included in the compu- tation of the said period of six months. Prices. And the party of the second part hereby further agrees to receive the prices set forth in the following schedule as full compensation for furnishing all materials and labor, and the dcing of all work, including all loss or damage arising out of the nature of the work, or from the action of the elements, or from any unforeseen obstructions or difficulties, which may be encountered in the prose- cution of the same ; also all expenses incurred by or in consequence of the suspension or discontinuance of said work which may be required in building and constructing, and in all respects complet- ing the aforesaid [insert description of work], including all appur- tenances and accessories, to the satisfaction of the engineer and the hereinbefore mentioned authorities, and in the manner and under the conditions hereinbefore specified, to wit: [insert schedule of prices]. Manner of Payment. And the said party of the second part further agrees that he shall not be entitled to demand or receive payment for any of the aforesaid work or material until the same shall be fully completed in the manner set forth in this agreement, and such completion duly certified by the chief engineer, and until each and every one of the stipulations hereinbefore mentioned are complied with. Whereupon the parties of the first part will pay, and hereby bind themselves and their successors to pay, to the said party of the second part, on account, ninety (90) per cent of the monthly esti- mate of the whole amount of money accruing to the said party of the second part, and the reserved ten (10) per cent upon the formal acceptance of the work by the party of the first part. In witness whereof, the ha hereunto set hand and seal on behalf of the said parties of the first part, and the said party of the second part hath also hereunto set hand and seal , the day and year first above written; and said commissioner and party hereto of the second part hath executed this agreement in triplicate, one part of which is to remain with SPECIFICATIONS AND CONTRACTS. 787 the said , one other to be filed with the , and the third to be delivered to the said party hereto of the second part. Signed and sealed in presence of Contractor. STATE OF , CITY OF , COUNTY OF , ss. : On this day of , 189 , before me personally came to me known, and known to me to be the , the person de- scribed in and who executed the foregoing instrument, and he acknowledged to me that he executed the same as such , for the purposes therein mentioned. Commissioner of Deeds, County, STATE OF , CITY OF , COUNTY OF , ss. : On this day of 189 , before me personally came to me known, and known to me to be the person described in and who executed the foregoing instrument, and he acknowledged to me that he executed the same for the purposes therein men- tioned. Commissioner of Deeds, County. 1031. Form of Bond, Know all men by these presents, that we, of the , are held and firmly bound unto the of the in the sum of thousand dollars lawful money of the United States of America, to be paid to the said , or to their certain attorney, successors, or assigns; for which pay- ment, well and truly to be made, we bind ourselves, and our several and respective heirs, executors, and administrators, jointly and severally, firmly by these presents. 788 HIGHWAY CONSTRUCTION. Sealed with our seals. Dated this day of , ono thousand eight hundred and Whereas, the above bounden by an instrument in writing under hand and seal , bearing even date with these presents, ha contracted with the said to furnish all the materials and labor, and in a good, firm, and substantial manner construct [description of work] : Now, therefore, the condition of the above obligation is such, that if the said above bounden or executors, administrators, or assigns, shall well and truly, in a good, sufficient, and workmanlike manner, perform the work mentioned in the aforesaid agreement, in accordance with the terms and provisions therein stipulated, and in each and every re- spect comply with the conditions and covenants therein contained, then this obligation to be void; otherwise to remain in full force and virtue. Signed and sealed in presence of STATE OF , CITY OF , COUNTY OF , ss. : On this day of , 189 , before me personally came to me personally known, and known to me to be the same persons described in and who executed the foregoing obligation, and sev- erally acknowledged that they executed the same. Commissioner of De'eds, County. STATE OF , CITY OF , COUNTY OF _,ss.: I , of said , being duly sworn, do depose and say, that I am a holder in the of and in SPECIFICATIONS AND CONTRACTS. 789 said , and that I am worth the sum of one thousand dollars over and above all my debts and liabilities, including my liabilities as bail, surety, and otherwise, and over and above all my property which is exempt by law from execution. Subscribed and sworn to this } day of , 189 , before me, f Commissioner of Deeds, County. 1031a. Specifications for Team Labor. Number of Horses and Carts. The contractor shall at all times be prepared to supply after twenty-four hours'" notice given by the county engineer or his representative to the contractor or his representative any num- ber not exceeding horses, carts, trucks, and the necessary attendants. Employment. Whilst the horses, vehicles, and attendants are at work for the county they shall be under the direction and orders of the county engineer or his representative, and may be used for any kind of work in connection with the (construction) (repair) of the roads. Condition, etc., of Horses and Vehicles. If the county engineer is of the opinion that any horse, vehicle, or attendant supplied by the contractor is unfit for the work, and shall so inform him, the contractor shall without delay provide another horse, vehicle, or attendant to the satisfaction of the engineer. Labor. The attendants sent with the horses shall in every case be able-bodied men over eighteen years of age, and when not en- gaged in handling the horses, they shall assist the laborers fill- ing the vehicles. Hours. The horses shall, in all cases, work the same number of hours as the roadmen, not exceeding hours per day. Time for watering, etc., will be allowed, not exceeding twenty minutes in the forenoon and twenty minutes in the afternoon.. One hour will be allowed at mid-day for feeding. Accidents. During the time the horses and vehicles are em- ployed by the the attendants shall under no circumstances leave them. The contractor shall be responsible in 790 HIGHWAY CONSTRUCTION. case of accident owing to neglect, carelessness, or inattention on the part of the attendants. 103 Ib. Specifications for Sprinkling. A mount of Work. The work to be done consists in sprinkling, in the manner prescribed herein, the roadways from curb-line to curb-line of the following- named avenues, streets, and public places of the city of The total length of streets to be sprinkled under these specifica- tions is estimated at mi^B. The number of times and hours of sprinkling shall be as fol- lows : 1. All streets, avenues, public places, and parts thereof shall be sprinkled times a day during the entire season : provided, that only sprinklings during the season shall be required on Sundays. 2. When a street is sprinkled three times a day, the first sprink- ling shall be completed before 8 o'clock A.M., the second sprinkling shall be between 10 o'clock A.M. and 1 o'clock P.M., and the third sprinkling shall be between 2 o'clock P.M. and 6 o'clock P.M. 3. When four sprinklings a day are required, the first sprinkling shall be completed before 8 A.M., the second shall be between 8 A.M. and 11 A.M., the third shall be between 12 noon and 3 P.M., and the fourth shall be between 3 P.M. and 6 P.M. 4. All streets shall be sprinkled in regular rotation. The starting- point in the morning shall be the starting-point for all the follow- ing sprinklings during the day. 5. The quantity of water to be delivered on the street will be determined from time to time >y the Street Commissioner. 6. The sprinkling shall be done with two-horse wagons which carry a tank holding not less than 600 gallons, and shall have attached two sprinklers. The wagons must be provided with springs (fore and aft), and must have tires not less than three inches in width. The wagons must also be numbered consecutively, and have the name of the contractor in letters not less than three inches in height painted on the rear end of the tank. 7. The sprinklers must be so arranged that the spray of water can be readily stopped by the driver on either side of the wagon. The sprinklers shall be constructed so as to deliver and properly spread the water, and be provided with suitable controlling devices SPECIFICATIONS AND CONTRACTS. 791 for regulating the quantity of water discharged, said devices to be so arranged as to be operated by the driver from the seat or foot- board; the spray of water thrown must be uniform throughout its entire width. The sprinklers must be kept in good condition and repair, Wagons with broken or choked sprinklers, defective gear, and leak- ing tanks or valves shall not be used. 8. All wagons shall be periodically inspected, and* any found unfit for use shall be ordered off the street, and sprinkling done by rejected wagons will not be paid for. 9. Sprinkling must be done with judgment and care, and the street-crossings must be kept as nearly dry as possible. 10. If the contractor fails or neglects to sprinkle any street or avenue the number of times required by this contract except in case of rain, or if he should flood the street or avenue, then two- thirtieths of his monthly pay for said street or avenue will be deducted for each day on which such omission or flooding occurs. 11. As to whether the contractor has given the streets the number of sprinklings and the quantity of water required, and as to whether rain has obviated the necessity of sprinkling, shall be determined by the Street Commissioner. 12. The contractor shall use particular care not to waste any water in filling the tanks; and also in closing the hydrants as soon as the tank has been filled. A deduction of two dollars shall be made on the next monthly estimate for every hydrant which is left wholly or partly open when not in use for filling the tank. Any hydrant found damaged or out of order must be immediately re- ported to the Street Commissioner. Hydrants damaged by the contractor shall be repaired by the Water Commissioner, who will report the cost to the Street Commissioner, who will charge it to the contractor and deduct it from his monthly estimate. 1031c. Form of Monthly Certificate. CERTIFICATE No. $ City of , 19 To THIS is TO CERTIFY that under the terms of the contract dated , for work upon 792 -HIGHWAY CONSTKUCTIOtf. Mr. , contractor, is entitled to the following pay- ment, amounting to TTnr Dollars. The above estimate is based on Am't of this cer- tificate $ Previously paid $ Total paid to date $ Engineer in charge. 103 Id. Affidavit of Contractor. State of , City of , ss : , being duly sworn according to law, on his oath saith that he is the contractor mentioned in a certain agreement made with the Mayor and Common Council of for the improving and paving of from to in said city, and that the work thereon has been completed and finished according to the terms and conditions of said agreement in every particular. And deponent further saith that all the laborers and workmen employed by him on said work, and all and every person or persons who have furnished materials, have been paid, and that he does not now owe anything for materials furnished or to any laborers or workmen or other persons for work or labor done or performed by them on said work. And deponent further saith that there has been no damage done or injury sustained by any person or persons either to themselves or their property, which was caused by reason of any act, omission, carelessness, or want of skill on the part of this deponent or his agents in the prosecution of the work aforesaid, and that no notice has been served upon him or any claims or demand has been made upon him for damages thereunder, and deponent knows of no claim or demand that any person or persons have or can have against him or said city for any damage caused or injury done to themselves or their property during the construction of the afore- said work. Sworn and subscribed to before / me this day of ,19 , f ' SPECIFICATIONS AND CONTRACTS. 793 103 le. Certificate of Acceptance. To THE* MAYOR AND COMMON COUNCIL OF THE CITY OF : I do hereby certify that of from to , contractor, has been completed to my satisfaction and in accordance with the specifications and contract. Engineer in charge. 103 If. Certificate of Final Acceptance. To THE MAYOR AND COMMON COUNCIL OF THE CITY OF : ,19 I do hereby certify that the year(s) during which period the pavement of from to , M , contractor, was required to be kept in repair, expired on , 19 As the proper repairs have been made, and the work is now in a condition satisfactory to me and in accordance with the specifi- cations and contract, the ten per cent retained is now due and payable, for which amount I have given a certificate this day. Engineer in charge. 1031g. General Specifications lor Steel Highway Bridges. {American Bridge Co.) Classification. Bridges under these speci- fications are divided into six classes, viz. : Class A, for city traffic. Class B, for suburban or interurban traffic with heavy electric cars. Class C, for country roads with light electric cars or heavy highway traffic. Class D, for country roads with ordinary highway traffic. Class E, , for heavy electric street railways only. Class E a , for light electric street railways only. Material. All structures to be of rolled steel, except the floor- ing and wheel-guards of Classes A, B, C, E, , and E, , and the stringers, flooring, and wheel-guards of Class D, which may be of timber. Cast iron or cast steel will be permitted only in machinery of movable bridges and in special cases for shoes and bearings. 794 HIGHWAY CONSTRUCTION. Type of Bridges. The following types of bridges are recom- mended : For spans up to 25 feet, rolled beams. For spans from 25 to 40 feet, rolled beams or plate girders. For spans from 40 to 80 feet, plate or lattice girders. For spans from 80 to 140 feet, lattice girders. For spans over 140 feet, lattice girders or pin- connected trusses. Spacing of Trusses. The width between centres of trusses shall in no case be less than one-twentieth of the span between centres of end pins or shoes. Floor-beams. All floor-beams in through bridges shall be riveted to the main girders. Stringers. Steel stringers shall preferably be riveted to the web of the floor-beams. Solid Floor. For bridges of Classes A and B a solid floor, consisting of stone, asphalt, etc., on a concrete bed, is recommended. For this case the flooring will consist of buckle-plates or corrugated sections, and the concrete bed shall be at least 3 inches thick for the roadway, and 2 inches thick for the footwalk, over the highest point to be covered, not counting rivet or bolt-heads. Buckle-plates. Buckle-plates shall not be less than T 5 F inch thick for the roadway and i inch thick for the footwalk. Dead Load. In determining the weight of the structure for the purpose of calculating strains, the weight of timber shall be assumed at 4 pounds per foot B. M., the weight of concrete and asphaltum at 130 pounds, of paving brick at 150 pounds, and of granite stone at 160 pounds per cubic foot. The rails, fastenings, splices, and guard timbers of street-railway tracks, resting on cross-ties, shall be assumed as weighing 100 pounds per lineal foot of track. Live Load. The bridges of the different classes shall be designed to carry, in addition to their own weight and that of the floor, a moving load, either uniform or concentrated, or both, as specified below, placed so as to give the greatest strain in each part of the structure. Class A, City Bridges. For the floor and its supports, on each street-car track or any part of the roadway, a concentrated load of 24 tons on two axles 10 feet centres and 5 feet gauge (assumed to occupy a width of 12 feet), and upon the remaining portion of SPECIFICATIONS AND CONTRACTS. 795 the floor, including foot-walks, a load of 100 pounds per square foot. For the trusses, for spans up to 100 feet, 1,800 pounds per lineal foot of each car track (assumed to occupy 12 feet in width), and 100 pounds per square foot for the remaining floor surface; for spans of 200 feet and over, 1,200 pounds for each lineal foot of track and 80 pounds per square foot of floor; proportionally for intermediate spans. Class B, Suburban or Interurfian Bridges. For the floor and its supports, on any part of the roadway, a concentrated load of 12 tons on two axles 10 feet centres and 5 feet gauge (assumed to occupy a width of 12 feet), or on each street-car track a concen- trated load of 24 tons on two axles 10 feet centres; and upon the remaining portion of the floor, including foot-walks, a load of 100 pounds per square foot. For the trusses, for spans up to 100 feet, 1,800 pounds per lineal foot of each cay track and 80 pounds per square foot for the remaining floor surface; for spans of 200 feet and over, 1,200 pounds for each lineal foot of track and 60 pounds per square foot of floor; proportionally for intermediate spans. Class G f Heavy Country Highway Bridges. For the floor and its supports, on any part of the roadway, a concentrated load of 12 tons on two axles 10 feet centres and 5 feet gauge (assumed to occupy a width of 12 feet), or on each street-car track a concen- trated load of 18 tons on two axles 10 feet centres; and upon the remaining portion of the floor, including foot- walks, a load of 100 pounds per square foot. For the trusses, same as for Class B, except load on car tracks for spans up to 100 feet will be 1,200 pounds, and for spans of 200 feet and over, 1,000 pounds. Class D, Ordinary Country Highway Bridges. For the floor and its supports, a load of 80 pounds per square foot of total floor surface, or 6 tons on two axles 10 feet centres and 5 feet gauge. For the trusses a load of 80 pounds per square foot of total floor surface for spans up to 75 feet, and 55 pounds for spans of 200 feet and over; proportionally for intermediate spans. Class E^ , Bridges for Heavy Electric Street Railways Only. For the floor and its supports, on each track a load of 24 tons on two axles 10 feet centres. 796 HIGHWAY CONSTRUCTION. For the trusses, a load of 1,800 pounds per lineal foot of each car track for spans up to 100 feet, and a load of 1,200 pounds for spans of 200 feet and over; proportionally for intermediate spans. Class E^ y Bridges for Light Electric Street Railways Only. For the floor and its supports, on each track a load of 18 tons on two axles 10 feet centres- For the trusses, a load of 1,206 pounds per lineal foot of each car track for spans up to 100 feet, and a load of 1,000 pounds for spans of 200 feet and over; proportionally for intermediate spans. Impact. To compensate for the effect of impact and vibration, 25 per cent of the maximum strains resulting from the above- mentioned live load shall be added thereto. Wind Pressure. The wind pressure shall be assumed acting in either direction horizontally. First, at 30 pounds per square foot on the exposed surface of all trusses and the floor as seen in eleva- tion, in addition to a horizontal live load of 150 pounds per lineal foot of the span moving across the bridge. Second, at 50 pounds per square foot on the exposed surface of all trusses and the floor system. The greatest result shall be assumed in proportioning the parts. Momentum of Street Cars. For longitudinal bracing of struc- tures carrying street railroads, the momentum produced by suddenly stopping the train shall be considered; the coefficient of friction of wheels sliding upon the rails being assumed as 0.2. Centrifugal Force. When the structure carrying a street rail- road is on a curve, the additional effects due to the centrifugal force shall be considered. Permissible Tensile Strains. All parts of the structure shall be so proportioned that the sum of the maximum loads, together with the impact, shall not cause the tensile strain to exceed: On soft steel 15,000 pounds per square inch. On medium steel 17,000 pounds per square inch. Permissible Gompressive Strains. For compression members, these permissible strains of 15,000 and 17,000 pounds per square inch shall be reduced in proportion to the ratio of the length to the least radius of gyration of the section by the following formulas : 15,000 For soft steel, p = l + _^ SPECIFICATIONS AND CONTRACTS. 797 17,000 For medium steel, p = (V + ll,000r*) where p = permissible working strain per square inch in com- pression, 1 = length of pieces in inches, centre to centre of connec- tion, and r = least radius of gyration of the section in inches. No compression member, however, shall have a length exceeding 120 times its least radius of gyration, excepting those for wind- bracing, which may have a length not exceeding 140 times the least radius of gyration, Reversal of Strains. The reversal of strain in members cf bridges of Classes A, B, C, and D need not be considered, but the members shall be proportioned for the strain giving the larger section. For bridges of Classes E : and E, members subject to alternate strains of tension and compression in immediate succession (as counter stresses in web members or chords in continuous trusses) shall be so proportioned that the total sectional area is equal to the sum of areas required for each strain. Combined Strains. In case the maximum strains due to wind, added to the maximum strains due to vertical loading (including impact), shall exceed the following limits: on soft steel, 19,000 pounds per square inch, on medium steel, 21,000 pounds per square inch, properly reduced for compression, addition must be made to such sections until these limits are not exceeded. Shearing and Bearing Strains. The shearing strain on rivets, bolts, or pins, per square inch of section, shall not exceed 11,000 pounds for soft steel, and 12,000 pounds for medium steel; and the pressure upon the bearing surface of the projected semi-intrados (diameter x thickness) of the rivet, bolt, or pin hole, shall not exceed 22,000 pounds per square inch for soft steel, and 24,000 pounds for medium steel. Plate Girders. Plate girders shall be proportioned on the assumption that one-eighth of the gross area of the web is available as flange area. The compressed flange shall have the same sec- tional area as the tension flange; but tne unsupported length of flange shall not exceed twenty times its width. The shearing strain in web plates shall not exceed 9,000 pounds per square inch for soft steel and 10,000 pounds per square inch for medium steel. 798 HIGHWAY CONSTRUCTION. Floor Timber. The fibre strain on floor timber from dead and live load without impact shall not exceed 1,200 pounds per square inch on yellow pine and white oak, and 1,000 pounds per square inch on white pine and spruce. Spacing of Rivets. The distance from the edge of any piece to the centre of a rivet hole must not be less than 1^ times the diameter of the rivet, nor exceed eight times the thickness of the plate; and the distance between centres of rivet holes shall not be less than three diameters of the rivet. Tie Plates. All segments of compression members connected by latticing only, shall have tie plates placed as near the ends as practicable. They shall have a length of not less than the greatest depth or width of the member, and a thickness of not less than one-fiftieth of the distance between the rivets connecting them to the compressed members. Lacing. Single lattice bars shall have a thickness of not less than one-fortieth, and double bars connected by a rivet at the intersection of not less than one-sixtieth of the distance between the rivets connecting them to the member; and their width shall be in accordance with American Bridge Company's standards, generally : For 15-inch channels, or built sections with 3- and 4-inch angles: 2- inches (|-inch rivets). For 12-, 10-, and 9-inch channels, or built sections with 3-inch angles: 2 inches (f-inch rivets). For 8- and 7-inch channels, or built sections with 2-mch angles: 2 inches (f-inch rivets). For 6- and 5-inch channels, or built sections with 2-inch angles: If inches (-|-inch rivets). Planing and Reaming. In medium steel over f inch thick, all sheared edges shall be planed and all holes shall be drilled or reamed to a diameter of -J inch larger than the punched holes, so as to remove all the sheared surface of the metal. Process of Manufacture. All steel must be made oy the open- hearth process, and if by acid process, shall contain not more than 0.08 per cent of phosphorus, and if by basic process, not more than 0.05 per cent of phosphorus, and must be uniform in character for each specified kind. SPECIFICATIONS AND CONTRACTS. 799 Physical Properties. Steel shall be made of three grades : Eivet, soft, and medium. Eivet steel shall have: Ultimate strength, 48,000 to 58,000 pounds per square inch. Elastic limit, not less than one half the ultimate strength. Elongation, 26 per cent. Bending test, 180 degrees flat on itself, without fracture on outside of bent portion. Soft steel shall have : Ultimate strength, 52,000 to 62,000 pounds per square inch. Elastic limit, not less than one half the ultimate strength. Elongation, 25 per cent. Bending test, 180 degrees flat on itself, without fracture on outside of bent portion. Medium steel shall have: Ultimate strength, 60,000 to 70,000 pounds per square inch. Elastic limit, not less than one half the ultimate strength. Elongation, 22 per cent. Bending test, 180 degrees to a diameter equal to thickness of piece tested, without fracture on outside of bent portion. Pins. Pins up to 7 inches diameter shall be rolled. Pins exceeding 7 inches diameter shall be forged under a steel hammer striking a blow of at least 5 tons. The blooms to be used for this purpose shall have at least three times the sectional area of the finished pins. Steel Castings. Steel castings shall be made of open-hearth steel containing from. 0.25 to 0.40 per cent carbon and not over 0.08 per cent of phosphorus, and shall be practically free from blow- holes. Timber. The timber shall be strictly first-class spruce, white pine, Douglas fir, Southern yellow pine, or white oak bridge timber; sawed true and out of wind, full size, free from wind shakes, large or loose knots, decayed or sap wood, worm-holes, or other defects impairing its strength or durability. 1031h. Specifications for Street-sprinkling Trucks (New York). The sprinkling-trucks furnished under this contract shall be of the latest improved type, with platform spring-gear, fitted with shafts and all appurtenances complete, and equipped with brakes of a power sufficient to hold the loaded truck to a standstill on a 10 per cent grade. The truck to. be fitted with the best Concord steel axles and oil- tempered steel springs, and to have Archibald patent wheels or other equally good wheels with tires 3 inches wide. 800 HIGHWAY CONSTRUCTION. The barrel or tank to be of the best quality white pine, clear stock, to be perfectly water-tight, and to be of a capacity of 300 gallons, the tank to be firmly attached to the truck frame with not less than six adjustable iron hoops, and to be fitted with suitable cast-iron manhole cover and frame, having a swivel gooseneck con- nection for attaching filling-hose. A filling-hose, 12J feet in length, to be provided with each sprink- ling-truck, said hose to be of the best quality four-ply rubber hose of 2J inches interior diameter, fitted with a standard coupling " female " of brass, 2J inches interior diameter, the hose to be attached to the gooseneck connection ready for use, and two iron hooks for holding hose when not in use to be attached to the truck, as will be directed. "At the front end of the tank there shall be a suitable driver's seat on springs and a suitable foot-board ; a suitable foot-board also on each side of front end of tank ; also a suitable tool-box, with lock and duplicate keys, at the front end of tank, to contain hydrant wrench and hose-spanner. One of each of said tools shall be furnished with each truck, the hydrant wrench to be of the combined pattern now in use by the department. "The sprinkling-valves to be made of the latest improved pat- tern, rear sprinkling-tips discharging the water through an adjustable slot so arranged as to force the water from the valves at an angle inclined above a horizontal plane, permitting the water to fall upon the roadway and not forcing it directly thereon ; the volume of water discharged must be under control from the driver's seat. "The frame and running-gear of the trucks, also the iron hoops holding the tank in place*, shall be satisfactorily painted with ver- million paint as per sample; the tank, driver's seat, foot-boards, tool-box, manhole frame and cover, and all valves and brake-rods shall be satisfactorily painted with colors as directed, with three coats of paint and one coat of varnish. "On each side of the tank near the front end there shall be painted in white letters 'D. S. C ,' together with such number as shall be designated, and the said number shall likewise be painted upon each end, the letters and the figures to be of such size and to be arranged as directed. SPECIFICATIONS AM CONTRACTS. 801 "The sprinkling-trucks and appurtenances to be fully complete in every respect, ready for immediate use at the time of delivery. "All the materials used to be first-class and thoroughly seasoned, and to be of the best quality of their respective kind, and the work- manship to be first-class in every particular." CHAPTER XXIII. TOOLS AND MACHINERY EMPLOYED IN THE CONSTRUCTION OF HIGHWAYS. THE implements employed in the construction of highways and pavements are many and varied. A brief description of the prin- cipal ones, and the range in price, is given in the following pages. The prices stated are only approximate and will vary, depending upon the quantity required and the condition of the market. 1032. Tools for Clearing and Grubbing. FIG. 186. BUSH-HOOKS. FIG. 187. AXE MATTOCK. FIG. 188. PICK MATTOCK. Axes price per dozen $12.00 to $15.50 Bush-hooks, handled " " ' ' 17,00 Grub-hoes.,. " " " 11.00 to 17.00 Mattocks o. " " " 15.50 " 18.00 Stump-pulling machines each 150.00 " 250.00 Cross-cut saws .per foot 0.68 802 TOOLS AND MACHINERY EMPLOYED. 803 1033. Tools for Grading. PICKS are made of various styles, ac- cording to the class of material in which they are to be used. Fig. 189 shows the form usually employed in street work. Fig. 190 shows the form generally used for clay or gravel excavation. The eye of the pick is generally formed of wrought iron, pointed with steel. The weight of picks ranges from 4 to 9 Ibs., and cost per dozen $8.50 to $25. FIG. 189. GUADING-PICK. FIG. 190. CLAY-PICK. SHOVELS are made in two forms, square- and round -pointed, usually of pressed steel. They cost from $7 to $13 per dozen for the square-pointed and from $7.25 to $13.50 for the round -pointed. FIG. 191. SHOVELS. PLOUGHS are extensively employed in grading, special forms being manufactured for the purpose. They are known as " grading- ploughs," "road-ploughs," "breaking-ploughs," "township-ploughs," etc. They vary in form according to the kind of work they are intended for, viz., loosening earth, gravel, hardpan, and some of the softer rocks. These ploughs are made of great strength, selected white oak, rock elm, wrought steel and iron being generally used in their con- struction. The cost of operating ploughs ranges from 2 to 5 cents per cubic yard, depending upon the compactness of the soil. 804 HIGHWAY CONSTRUCTION. The quantity of material loosened will vary from 2 to 5 cubic yards per hour. Fig. 192 shows the form usually adopted for loosening earth. This plough does not turn the soil, but cuts a furrow about 10 inches FIG. 192. GRADING-PLOUGH. wide and of such a depth as it may be regulated for up to 11 inches. In light soils the ploughs are operated by two or four horses; in heavy soils as many as eight are employed. Grading-ploughs vary in weight from 100 to 325 Ibs., in price from $22 to $65. Fig. 193 illustrates a plough specially designed for tearing up macadam, gravel, or similar material. The point is a straight bar of cast steel drawn down to a point, and can be easily repaired. Price about $40. FIG. 193. HARDPAN-PLOUGH. TOOLS AND MACHINERY EMPLOYED. 805 SCRAPEES are generally used to move the material loosened by ploughing; they are made of either iron or steel, and in a variety of forms, and are known by various names, as "drag," "buck," "pole," and "wheeled." The drag-scrapers are usually employed on short hauls, the wheeled on long hauls. Figs. 194 and 195 illustrate the usual form of drag-scrapers. FIG. 194. DRAG-SCRAPER. Drag-scrapers are made in three sizes. The smallest, for one horse, has a capacity of 3 cubic feet; the others, for two horses, have a capacity of 5 to 7| cubic feet. The smallest weighs about 90 Ibs., and the larger ones from 94 to 102 Ibs. FIG. 195. DRAG- SCRAPER WITH RUNNERS. 806 HIGHWAY CONSTRUCTION. The price is variable, iron being the cheapest and steel the dearest; the range appears to be from $10 to $18. A recent improvement in drag-scrapers is the furnishing them with runners or a double bottom. These devices prolong the life of the scraper. Fig. 195 shows a drag-scraper furnished with steel runners. Buck-scrapers are made in two sizes two-horse, carrying 7-J cubic feet; four-horse, 12 cubic feet. Pole-scraper Fig. 196 is designed for use in making and levell- ing earth roads and for cutting and cleaning ditches; it is also well adapted for moving earth short distances at a minimum cost. PIG. 196 POLE-SCRAPER. SIZE AND PRICE. 48 in. wide, weight 123 Ibs $14 36 " " " 113 " , 13 Wheeled scrapers consist of a metal box, usually steel, mounted on wheels, and furnished with levers for raising, lowering, and dumping. They are operated in the same manner as drag scrapers, except that all the movements are made by means of the levers, and without stopping the team. By their use the excessive resist- ance to traction of the drag-scraper is avoided. Various sizes are made, ranging in capacity from 10 to 17 cubic feet. In weight they range from 350 to 700 Ibs.; in price from $40 to $75. Figs. 197 to 199 show the three positions of the scrapers when in use. TOOLS AND MACHINERY EMPLOYED. 807 FIG. 197. POSITION WHEN LOADING. FIG. 198. POSITION WHEN CARRYING. FIG. 199. POSITION WHEN UNLOADED. 808 HIGHWAY CONSTRUCTION. WHEELBARROWS. The wheelbarrow Fig. 200 is constructed of wood and is the one most commonly employed for earthwork. Its capacity ranges from 2 to 2%. cubic feet. Weight about 50 Ibs. Price about $20 per dozen. The barrow Fig. 201 has a pressed-steel tray, oak frame, and steel wheel, and will be found more durable in the maintenance depart- ment than the all-wood barrow. Capacity from 3 to 5 cubic feet, depending on size of tray. Price from $5.50 to $7.50. The barrow Fig. 202 is constructed with tubular iron frames and steel tray, and is adaptable to the heaviest work, such as moving heavy broken stone, etc., or it may be employed with advantage in the cleaning department. Capacity from 3 to 4 cubic feet. Weight from 70 to 82 Ibs. Price from $10.75 to $13.50. FIG. 200. FIG. 201 FIG. 202. The maximum distance to which earth can be wheeled economi- cally in barrows is about 200 feet. The wheeling should be performed upon planks, whose steepest inclination should not exceed 1 in 12. The power required to move a barrow on a plank is about -^ part of the weight; on hard dry earth, about T ^ part of the weight. The time occupied in loading a barrow will vary with the char- acter of the material and the proportion of wheelers to shovellers. Approximately, a shoveller takes about as long to fill a barrow with earth as a wheeler takes to wheel a full barrow a distance of about TOOLS AND MACHINERY EMPLOYED. 809 100 or 120 feet on a horizontal plank and return with the empty barrow. CARTS. The cart usually employed for hauling earth, etc., is shown in Fig. 203. The average capacity is 22 cubic feet, and the average weight is 800 Ibs. Price about $75. These carts are usually furnished with broad tires, and the body is so balanced that the load is evenly divided above the axle. The time required to load a cart varies with the material. One shoveller will require about as follows : clay, seven minutes ; loam, six minutes ; sand, five minutes. FIG. 203. EARTH-CART. DUMP-CARS. These cars are made to dump in several different ways, viz., single or double side, single or double end, and rotary or universal dumpers. Dump-cars may be operated singly or in trains, as the magni- tude of the work may demand. They may be moved by horses or small locomotives. They are made in various sizes, depending upon the gauge of the track on which they are run. A common gauge is 20 inches, but varies from that up to the standard railroad gauge J! ^ /" 1 i .OO oi oo^ inches. The principal dimensions, capacity, prices, etc., of single-side dumping-cars are given in the following table. Those made by different manufacturers vary, but not materially, from these stated. 810 HIGHWAY CONSTRUCTION, TOOLS AND MACHINERY EMPLOYED. 811 FIG. 205. ROTARY DUMPING-CAB. DIMENSIONS, CAPACITY, PRICES, ETC., OF DUMP-CARS. Dimensions. M h o ^ o Inches. s o "o IS 0) SI > *o i o 1 A 5 cS M PH P Q g ,d ~ H .S K s 02 8 2 x g QQ CO M hH 1 _. 1 M c UDEBA Wheels K i ^ 8 | u "g w i i i d i 2 02 a .S i 1*1 CO a TOOLS AND MACHINERY EMPLOYED. 8L5 where required. They are operated by the driver, and the capacity ranges from 35 to 45 cubic feet. MECHANICAL GRADERS. Within the last few years several machines have been devised for the purpose of handling earth more FIG. 208. ROAD-GRADEH. expeditiously and economically than can be done by hand; they are called by various names, such as "road machines," "graders," "road-hones," etc. Their general form is shown in Figs. 208 to 210. Briefly described, they consist of a large blade made entirely of steel or of iron, or wood shod with steel, which is so arranged by mechanism attached to the frame from which it is suspended that it can be adjusted and fixed in any direction by the operator. In their action they combine the work of excavating and transporting the earth. They have been chiefly employed in the forming and maintenance of earth roads, but may be also advantageously used in preparing the subgrade surface of roads for the reception of broken stone or other improved covering. A large variety of such machines are on the market, and the price ranges from $100 to $300. Besides the above-described machines, there is another known as the "New Era" grader, shown in Fig. 211. This machine ex- cavates the material from side ditches, and automatically places it in the embankment, or it can be used in a cutting, in which situ- 816 HIGHWAY CONSTRUCTION. TOOLS AND MACHINERY EMPLOYED. 817 FIG. 210. ROAD-GRADER. ation it will excavate and automatically load the material into carts or wagons. Fig. 212 shows the machine at work. Briefly described, the machine consists of a plough which loosens and raises the earth, depositing it upon a transverse carry- ing-belt, which conveys it from excavation to embankment. This carrier is built in four sections, bolting together, so it can be used to deliver earth at 14, 17, 19, or 22 feet from the plough. The carrier-belt is of heavy 3-ply rubber 3 feet wide. The plough and carrier are supported by a strong trussed frame- work resting on heavy steel axles and broad wheels. The large rear wheels are ratcheted upon the axle, and connected with strong gearing which propels the carrying-belt at right angles to the direc- tion in which the machine is moving. The wheels and trusses are low and broad, occupying a space 8 feet wide and 14 feet long, exclusive of the side carrier. This en- ables it to work on hillsides where any wheeled implement can be used. Notwithstanding its large size it is so flexible that it may be turned around on a 16-foot embankment. Pilot-wheels and levers enable the operator to raise or lower the plough or carrier at pleasure. As a motive power 12 horses 8 driven in front, 4 abreast, and 4 in the rear on a push-cart are usually employed. When the teams are started, the operator lowers the plough and throws the belting into gear, and as the plough raises and turns the earth to the side the belt receives and delivers it at the distance for which the carrier is adjusted, forming either excavation or embankment. 818 HIGHWAY CONSTRUCTION. When it becomes necessary to deliver the excavated earth be- yond the capacity of the machine (22 feet or 7J feet above the plough), the earth is loaded upon wagons, then conveyed to any FIG. 211. NEW ERA GRADER FIG. 212. NEW ERA GRADER AT WORK. distance. Arranging the carrier at 19 feet, wagons are driven under the carrier and loaded with 1% to 1| yards of earth in from 20 to 30 seconds. When one wagon turns out with its load, an- other drives under the carrier, and the machine thus loads 600 to 800 wagons per day. TOOLS AND MACHINERY EMPLOYED. 819 The makers claim that with six teams and three men it is capa- ble of excavating and placing in embankment from 1000 to 1500 cubic yards of earth in ten hours, or of loading from 600 to 800 wagons in the same time, and that the cost of this handling is from 1J to 2-g- cents per cubic yard. POINTS TO BE CONSIDERED IN SELECTING A EOAD MACHINE. In the selection of a road machine the following points should be carefully considered: (1) Thoroughness and simplicity of its mechanical construction. (2) Material and workmanship used in its construction. (3) Ease of operation. (4) Lightness of draft. (5) Adaptability for doing general road-work, ditching, etc. (6) Safety to the operator. CARE OF EOAD MACHINES. The road machine when not in use should be stored in a dry house and thoroughly cleaned, its blade brushed free from all accumulations of mud, wiped thor- oughly dry, and well covered with grease or crude oil. The axles s journals, and wearing parts should be kept well oiled when in use, and the blade should be kept sharp and in good condition at all times. An extra blade should be kept on hand to avoid stopping the machine while the dulled one is being sharpened. SURFACE-GRADERS. The surface-grader, Fig. 213, is used for removing earth previously loosened by a plough. It is operated by one horse. The load may be retained and carried a considerable FlG. 213. SURFACE-GKADEK. distance, or it may be spread gradually, as the operator desires. It is also employed to level off and trim the surface after scrapers. The blade is of steel, J inch thick, 15 inches wide, and 30 inches long. The beam and other parts are of oak and iron. Weight about 60 Ibs. Price about $9. 820 HIGHWAY CONSTRUCTION. FIG. 214. ROAD-LEVELLER. The road-leveller, Fig. 214, is used for trimming and smoothing the surface of earth roads. It is largely employed in the spring when the frost leaves the ground. The blade is of steel, J inch thick by 4 inches by 72 inches, and is provided with a seat for the driver. It is operated by a team of horses. Weight about 150 Ibs. Price about $12. The King Log Drag, Fig. 214a. This drag, named after its intro- ducer, Mr. D. W. King, is in great favor in Missouri for smoothing clay roads. The drag consists of the two halves of a 12-inch log, 7 to 9 feet long. Instead of the log, 2 X 12-inch plank may be used. The two pieces are spaced about 30 inches apart and are held together FIG. 214a. THE KING LOG DRAG. by cross-bars. In some cases a platform of 2-inch plank is spiked to the upper surface of the logs. The team is attached to a hitching- ring fastened to the front log by chains, the length of which is such that the drag may be pulled at an angle of 45 to the axis of the road. After each rain the drag is driven along one side of the wheel-track hi the road and back on the other side. TOOLS AND MACHINERY EMPLOYED. 821 1034. Draining-tools. The tools employed for digging the ditches and shaping the bottom to fit the drain-tiles are shown in Fig. 215. They are convenient to use, and expedite the work by avoiding unnecessary excavation. For cost of drains, etc., see Art. 688, et seq. No. 2. No. 1. No.1 FIG. 215. DRAINING-TOOLS. The tools are used as follows : Nos. 3, 4, and 5 are used for digging the ditch ; Nos. 6 and 7 for cleaning and rounding the bottom of the ditch for round tile. No. 2 is used for shovelling out loose earth and levelling the bottom of the ditch; No. 1 is used for the same purpose when the ditch is intended for "sole" tile. 822 HIGHWAY CONSTRUCTION. 1035. Tools for Rock Excavation HAND DRILLING. The tools employed for hand drilling are illustrated in Fig. 216, in which Fig. A represents the first or shortest drill, usually eighteen inches in length, with cutting head about one and three quarter inches wide and weight about four pounds. The second drill is shown by Fig. B; it is about twenty-seven inches long, one and eleven sixteenth inches wide on the cutting edge, and weighs about six pounds. ' The third or longest drill is shown at ; it is usually forty inches ' in length, cutting edge one and five eighth inches wide, and weighs about nine pounds. The scraper is shown by Fig. D. It is used to remove the sludge from the bottom of the hole, and consists of an iron rod one half inch in diameter, one end of which is flattened out in a circular form and turned up at right angles to the stem. The other end is made to terminate in a spiral hook or drag-hoist^ the use of which is to withdraw the absorbent material used to dry the hole before inserting the explosive. The bull or claying-iron is shown by Fig. E. It is used for forc- ing clay into seamy rock and thus prevent the entrance of water into the blast-hole. It consists of a round bar of iron, called the stock or shaft, a little smaller in diameter than the bore-hole, and a thicker portion, called the head or poll, terminating in a striking- face. While this tool is not an essential part of a drilling outfit, yet it is a very serviceable one, and should always be at hand in wet ground when loose gunpowder is employed. Fig. F represents the tamping-iron or rammer. It consists of a bar of copper or phosphor bronze, the tamping end of which is grooved to receive the fuse lying against the side of the bore-hole. The use of rammers made of iron is dangerous, as sparks produced by the striking of the iron against silicious substances may cause ignition of the charge. Fig. G represents an auxiliary implement called the beche. It is used for extracting a broken drill. It consists of an iron rod having a diameter slightly less than that of the bore-hole, and is made hollow at one end. The form of the aperture is slightly con- ical, so that it may pass over the broken stock of the drill, and when hammered down may grasp the stock in its higher portion with sufficient firmness to allow of the two being drawn out together. TOOLS AND MACHINERY EMPLOYED. 823 GO bb n IU bib bn FIG. 216. HAND-DRILLING TOOLS. 824 HIGHWAY CONSTRUCTION. Fig. H represents the sledge or striking-hammer; its form and weight are variable, the latter is usually about five pounds. Fig. I represents the hand hammer; its weight varies from two to four pounds. The distinction between a hammer and a sledge is founded on dimensions only; the hammer, being intended for use in one hand, is made comparatively light and is furnished with a short handle, while the sledge, being intended for use in loth hands, is furnished with a much longer handle and is made heavier. Hand drills are used in sets of different lengths. The sets may be intended for use by one man or by two. In the former case the sets are described as " single-hand " sets, and they contain a hammer for striking the drills; in the latter case the sets are called " double-hand/' and they contain a sledge instead of a hammer for striking. It may appear at first sight that there is a waste of power in employing two men, for that two men cannot bore as fast as one. This rate of speed can, however, be obtained, and is due less to the greater effectiveness of the stroke than to the fact that two men can, by repeatedly changing places with each other, keep up almost without intermission a succession of blows for an indefi- nite length of time, whereas with the single set the man is con- tinually obliged to cease for rest. The making and resharpening of the drills is au extremely important part of the blacksmith's labor and requires judgment ' and intelligence. A smith will, with the assistance of a striker, sharpen and temper about thirty single-hand drills of medium size in an hour, or twenty double-hand drills of medium size in the same time. Of course much will depend on the degree of blunt- ness in the cutting edge ; but assuming the drills to be sent up only moderately blunted, this may be taken as a fair average of the work of two men. PRICES OF HAND-DRILLING TOOLS. Drill-steel per pound $0.25 Striking-hammers, 3 to 5 pounds . . . " .36 "5 pounds and over " " .30 Spoons each 2.00 Wedges per pound .12$ Plug and feathers " -30 Crowbars " -10 Stone-sledges - " " -30 Blacksmith outfit from $50 upwards TOOLS AND MACHINERY EMPLOYED. 825 STEAM DRILLING. A steam-drilling outfit comprises a steam .VO *- N O --< N *O vOr^vo-^t s X * * M 8O I vo VO \O a MM VfiO\M ^^Nj*- O ^" O ^t" *O ws **\ f^S'^N ON 1 -O HH ^O O ^ss 888 8 GO * XXX* O O vovo vO >-i O fc CO ** "*^" VO vo CO M " * X XX X " X gviQ'coo 2^ ^o 888 8 05 ^^ COvO ^-*Oi-iOOMw O MM COOO to l-l l-l CO vo O ^0 *! W M t^s^p >^ XXX oo "> * JN^ IO *-O N d -I O Tf I v co v 2 x XXX "fr O Tf i-i i-i ro 888 8 oo CO XXX 2>S>2> 8 O w * ^?co ^ ^ n3 M 00 ^ N< ^ X 0^ M ^ l?lv?S XXX 888 8 H* CO N XXX ^ vrt ^^^ vo o <$ M M Tf Tf CO * M V*\!* to S*H* O O O O vo i^X -VH ^^; vo t^ COCO XXX coco -^ 88887 O NvovOTj-wO M VO M C4TJ-M s ^1 tr^ VO O O vo vo M VO N VO Tj- CO CO vo i-i CO ^r co co , ^ II VpON5 SN * Vv ^?^t'^t < *^ ^ ^ ^^ * MCOOHHtnl fO MM! O vo TJ- i-i M XXX I? 00 ro XXX 8*8 . 8 XX - a 31 M vo ^f * CO co HH M ^ . ^ CO w ' CO [ ^ V ame and number 1 -^il *8g B 5^?^ Ij.II^lJIs'r l^H -lll?l-.s^ S,fl5 sfl^sdSs^i^ ..s^5^ '^^r-'on^ ~~'~'a<3 ^.coOvo g 4T-S Ji: *"af aT 5 -a tJ ^ & j 'f,-g^g|.ss 8.&^ s s ai= i wPiJO^J_,W3Ajf! fi 'C S C S ij^iSaj^j ^M- l iMC3'^ (U i^ifeo^ iIi!Milil!S Hi; 5, llltilllli si Irflll g 5 n5 (-5 P &Q Q S M M "S Q < x S S flipping measurements (outside) Of box for drill alone, in inches Of box for tripod, in inches Of box for six lengths of hose, ir rices: Of drill complete, unmounted . Adj'ble tripod and w'ts, complet Of column 6 feet high . . . Of drill with tripod and weights or column, complete . . . ; S m AH TOOLS AND MACHINERY EMPLOYED. 827 PRICES OF STEAM-DRILLING TOOLS. Steam drill $185.00 to $480.00 Steam boiler $230.00 to Steam hose . 54 to 97 cents per foot Drill-steels, per set $25.00 to $115.00 Blacksmith's swages for dressing drills $15.00 Forge and hand tools $50.00 upward Sand-pumps, each $3.00 Giant blasting- powder, per pound . . 15 to 60 cents Leading-wires, per foot ,1 cent upward Magneto-electro blasting apparatus, each $25.00 to $50.00 Derricks, each , $100.00 upward PORTABLE BOILERS for operating steam drills. Fig. 218 shows a convenient arrangement of a steam boiler for operating rock- FIG. 218. PORTABLE BOILER. drills. A water-tank occupies one end of the frame and fuel can be carried on the other end. Price from $400 upwards. 828 HIGHWAY CONSTRUCTION. 1036. Tools Employed in the Construction of Broken-stone Roads STONE-HAMMERS. The hammers generally used for breaking stone are three, viz. : 5 pounds and over. ... 30 cents per pound Hand hammers, 3 to 5 pounds. , 36 " " " Ito2 " 45 " THE KING-GAUGE, for testing the size of the stone and through which the largest stone should in all positions freely pass. The diameter is usually 2J inches, can be made by any blacksmith at a cost of 25 cents. THE STRAIGHT-EDGE, Fig. 219, is used for obtaining the proper transverse form of roads. It consists of a horizontal bar having in the centre of its length a plummet for ascertaining when the straight- edge is level. Gauges formed of upright pieces of wood marked off in inches are placed at every four feet ; these upright pieces have a slot cut in them so as to allow of their being moved either u'p or down and adjusted to the desired depths below the horizontal line. These upright pieces are secured to the straight-edge, as shown in the section, by a small bolt passing through the slot in the upright and the straight-edge, the bolt being furnished with a thumbscrew, by tightening which the gauges are fixed in place when adjusted to the required depths. FIG. 219. STRAIGHT-EDGE. LINES. Linen, in rolls 100 feet long; price per dozen rolls* $9. KEEL AND STAKE. Price per dozen $6 to $9.50. STONE-FORKS. The broken stone can be more easily and quickly taken up and thrown upon the roadway by the use of forks than by shovels. The price of forks ranges from $18 to $25 per dozen. TOOLS AND MACHINERY EMPLOYED. 829 FlG. 220. ROADBED.ROLLER, KOADBED-ROLLER, Fig. 220. This is a very efficient form of roller for compacting embankments and the subgrade surface of highways. The roller is 5 feet long with nineteen sections, ten FIG. 221. SPRINKLING-CART. 830 HIGHWAY CONSTRUCTION". of 35 inches in diameter and nine of 32 inches in diameter, set alternately. The sections act dependently on the axle. Weight about 2-J- tons. Price $265. SPRINKLING-CARTS. Fig. 221 shows a convenient form of sprinkling-cart for use either on construction or sprinkling subur- ban streets and country roads. Capacity about 150 gallons. Price about $100. RAKES used for spreading the stone should be about twelve inches long and have prongs from two to three inches in length, spaced three quarters of an inch apart, and have handles about six feet long. The price of such rakes is from $12 to $15 per dozen. STONE-CRUSHERS. The leading styles of stone-crushers are illustrated in Figs. 222 to 232. The dimensions, capacity, weights, etc., are given in the tables on pages 831, 832, and 833. The amount of the product in a given time will vary according to the character of the rock to be broken as well as to the size to which it is broken; the smaller the size the less the amount broken and the greater the power required. In getting an engine to drive a stone-crusher it is advisable to provide one of greater power than is stated in the tables, for no close estimate can be made to cover all varieties of rock, and it is more economical to use 10 H. P. from a 12 or 15 H. P. engine than from a 10 H. P. engine. For cost of crushing stone and cost of operating crushing- plants see Art. 365 et seq., and Table XXXIX. PORTABLE CRUSHERS. Any one of the crushers described can be had in portable form. Some are made portable by mounting on low- wheeled trucks, others by attaching travelling-wheels directly to the frame of the machine, and others by attaching a pair of wheels to one end to act as a front truck, using the fly- or balance-wheels of the machine as rear travelling-wheels. When the balance-wheels are used for this purpose, it is necessary to have independent belt-wheels. If the balance-wheels are used for belt-wheels, it will be necessary to have either a metal or wood covering which can be easily placed and removed, for the face of the balance-wheels will become too roughened to be used directly for belting. Fig. 233 shows one of the many forms of portable crushers. TOOLS AND MACHINERY EMPLOYED. 831 BRENNAN CRUSHER. Size or Re- ceiving Capacity Approximate Product per Hour in Tons to Macadam Size. Approximate Weight. Proper Speed. Horse-power Required. Prices, 5 x 8 to 10 7 000 300 8 7x20 12 15 10 000 300 12 to 15 8 x 12 8 10 8 000 280 8 8x95 15 20 13000 280 15 to 20 10 x 25 20 30 16 000 280 20 " 30 12x37 30 40 32 000 260 30 " 40 20x48 60 100 72 000 240 80 GATES CRUSHER. 2x 4 4x10 5x12 6x14 7x15 8x18 10x20 11x24 14x30 18x42 SIS s^s .9>.S SIP *> S n Su 5 2x 12 4x 30 5x 36 6x 42 7x 45 8x 54 10 x 60 11 x 72 14 x 90 18 x 126 r eight of Pounds. 500 3,300 5,600 7,800 13,800 21,500 27,000 40,500 65,800 89,000 2 to 4 8 12 20 30 40 60 125 150 10 15 25 30 50 100 c? ' Space Occupied '> by Breaker. Inches. |. JCB '=!> m 700 500 475 450 425 400 375 350 350 350 24 50 55 61 75 91 101 114 144 156 mete nches. 54J 79! 88 103 120 132 1 to 4 8 W JO 25 M 40 75 100 . 10 15 25 30 40 60 125 150 RELIANCE CRUSHER. FIG. 232. Size of crusher, being the size of opening or receiving capacity of jaws in inches 8X14 9X16 10 X 18 11 X24 12X30 14 X36 Capacity per hour in tons, with jaws closing to 2 inches 1O-15 12-18 16-24 24-40 32-50 45-60 Capacity per hour in tons of com- mercial stone 2 inches and smaller 7-10 9-12 12-16 18-24 24-36 36-48 Weight, including foundation timbers Weight, mounted on four-wheel truck 5,200 j 6,000 7,200 ' 8,200 10,000 11,300 ( 18,000 Not mounted 28,000 Not mounted 40,000 Not mounted Weight, mounted with 16-foot folding elevator j 7,200 9,400 12,500 { Not mounted Not mounted Not mounted Nominal H.P. of engine and boiler required 10-12 12-15 15-20 30-35 40-50 60-75 832 HIGHWAY CONSTRUCTION. FARREL CRUSHER. d 25 Size or Receiving Capacity. Approximate Capacity in Tons, per day of 10 Hours, to Sizes Stated. Extreme Dimensions. Revolutions of Pulley. II %% B Total Weight. 1 3 1 | fi I a 6i 8 *9 *10 *11 *12 *13 15 X 9 16 X 10 20 X 10 24 X 15 30 X 13 30 X 15 36 X20 36X 24 tons. in. 100 to 2J 120 2i 175 3 250 3 300 3 400 4i 800 8 1000 10 tons. in. 80 to 2 100 2 150 2* 200 2i 475 2} 350 3* 600 6 800 8 tons. in. 55 to 1* 75 H 125 " 2 175 " 2 225 " 2 500 to 5* ft. in. 7 7 2 7 8 7 10 8 6 8 6 9 10 9 10 ft. in. 5 3 5 6 5 10 7 2 8 2 8 2 8 8 8 8 ft. in. 5 3 5 8 5 1 5 9 6 4 6 4 6 10 6 10 275 275 275 275 275 "75 275 275 12 15 20 25 30 30 40 40 Ibs. 15,000 16,200 18,300 26.000 37,600 37600 50,000 50,000 $ 750 375 1050 1575 2250 2250 2875 2875 * These sizes have two driving-pulleys. CHAMPION CRUSHER. No. Size or Receiv- ing Capacity of Jaws. Product per Hour in Tons when Machine is Closed to 2 Inches. Weight, Approxi- mated. Speed, Revo- lutions. Driving- Diameter and Face. Horse- power Required. Price. inches. tons. Ibs. inches. 3 7 X 13 7 to 13 5,000 180 44 X 8 12 $ 600 4 9 X 15 12 " 18 8,000 160 50 X 8 15 800 5 11 X 26 24 " 36 16,000 150 60 X 10 25 1500 CLIMAX CRUSHER. No. 1. No. 2. No. 3. No. 4. Size of top opening of jaws in inches Product per hour in tons when machine 7X 13 7 to 12 9X 16 10 to 15 10* X 22 15 to 30 12X28 25 to 40 Weight approximate 5 000 8 500 15 000 20000 Weight, with two-wheeled trucks and ele- vator . 6 000 10 000 Weight, mounted on 4 wheels, with 10-feet elevator 7 200 11 000 Speed, revolutions . 325 300 290 275 Driving pulleys, diameter and face, inches Horse- power required .... .... 28X8 10 32 X 9 12 38 X 10 25 42 X 12 35 5ft. 6ft. 7ft. 8 ft. 1 in. Floor-space required width .... ... 4 ft 4 in. 5 ft. 1 in. 5 ft. 6 in. 6ft, Extreme height of machine 2 ft 7 in 3 ft. 10 in. 4 ft. 7 in. 4 ft. 10 in. Size of elevator best suited No. 1 No. 2 No. 3 No. 3 Diameter of screen best suited, hi inches . . 30 30 86 36 TOOLS AND MACHINERY EMPLOYED. 833 WESTERN CRUSHER. No. Size or Receiv- ing Capacity of Jaws. Product per Hour. Weight, Approxi- mated. Speed. Revo- lutions. Diameter and Face of Driv- ing-pulleys. Horse-power Required. inches. tons. Ibs. inches. 5 7 X 13 10 to 12 5,000 200 40 x e* 8 to 10 10 9 X 15i 12 " 20 8,000 200 44 X 8 10 " 12 15 10 X 22 18 " 25 14,000 200 44 X 10* 15 " 20 AUSTIN CRUSHER. Jaw-ope in Inch 8X 15 10 X 18 1 Her 10 H. P. 15 " 300 300 6000 Ibs. 8000 " ity r. 10 to 14 15 " 20 2* X 7 ft. 3X8" $600.00 900.00 IS. $ 725.00 1050.00 S X - $40.00 50.00 Elevator, 14 ft. long, $175; for each additional foot add $5. Revolving screen, 2-section, $200; 3- section, $250. Each section is 2J ft. long by 2 ft. in diameter, made of steel, and turns on anti-friction rollers. BLAKE CRUSHER. i "S Extreme Dimensions. cjS |. Size or Rec ing Capac Product per Hour in Cubic Yards. Weight of Heaviest Piece. Total Weig Proper Spe Revolutic Horse-powt Required 1 Price, f.o.b Pittsburg. 1 Breadth. 4-> a W) i inches. Ibs. Ibs. ft. in. ft. in. ft. in. 10X 4 3 1,695 4,000 3 11 3 3 3 9 250 4 $ 275 10 X 7 5 4,339 8,000 5 31 3 8 4 5 250 6 450 15 X 9 7 6,500 15,000 6 5 5 5 11 250 9 750 20 X 12 10-12 10,000 21,000 7 5 6 6 3 250 15 1000 20 X 15 j Coarse or Pre- ) 8,450 32,600 8 6 5 6 7 150 12 24 X 18 | liminary Breaker, f 9,425 37,500 9 10 5 1 6 10 125 12 \ 834 HIGHWAY CONSTRUCTION. FIG. 222. THE BRENNAN CRUSHER. EXTERIOR VIEW. 223. THE BRENNAN CRUSHER SECTIONAL VIEW. TOOLS A.ND MACHINERY EMPLOYED. 835 FIG. 224. THE GATES CRUSHER. EXTERIOR VIEW. FIG. 225. THE GATES CRUSHER. SECTIONAL VIEW, 836 HIGHWAY CONSTRUCTION. FIG. 226. THE FARREL CRUSHER. SECTIONAL VIEW. FIG. 227 I'HE CHAMPION CRUSHER. SECTIONAL VIEW. TOOLS AND MACHINERY EMPLOYED. 837 FIG. 228. CLIMAX CKUSHER. SECTIONAL VIEW. FIG. 229. THE WESTERN CRUSHER. SECTIONAL VIEW. 838 HIGHWAY CONSTRUCTION. FIG. 230. THE AUSTIN CRUSHER. SECTIONAL VIEW. FIG.. 231. THE BLAKE CRUSHER. SECTIONAL VIEW. SCREENS. Nearly all specifications for broken stone call for it to be screened, either to separate it into different sizes or to remove the tailings; for either purpose revolving screens made of steel plate perforated with holes of the required size are employed. They can be run in several ways, as shown in Figs. 237 to 241. 840 HIGHWAY CONSTRUCTION. Fig. 234 shows a three-section screen; the first section has holes one inch in diameter, the second section holes one and one half inches in diameter, and the third section holes two and one half inches in diameter. Holes of any other dimensions may be used, depending upon the sizes desired. Dust-jackets are also used in connection with the screens, thus separating the dust from the crushed stone. The following table contains the usual dimensions, weight, price, etc., of steel-plate screens: No. Diam- eter. Length, with three sections. Revolu- tions of Pulley. Size Pulley, Diameter Face. Weight, Lbs. Price for three sections complete. Price for two sections complete. inches. ft. in. inches. 1 24 10 6 90 30X 6J 2200 $275 $225 2 30 12 6 90 36X 8 3550 385 325 3 36 12 6 80 36X 8 3900 450 375 4 4-2 12 6 70 36 X 8i 4500 550 450 5 48 15 6 60 42X 9 5500 700 575 6 54 15 6 60 48x10 .... 950 800 FIG. 234. REVOLVING STONE- SCREEN, TOOLS AND MACHINERY EMPLOYED. 841 FIG. 235. SEMI-PORTABLE ENGINE AND BOILER. ENGINES AND BOILERS FOR DRIVING EOCK-CRUSHERS are usually of the portable or semi-portable type. Fig. 235 shows a compact combination of the semi-portable form, and Fig. 236 shows the portable type. 842 HIGHWAY CONSTRUCTION. FIG. 236. PORTABLE BOILER AND ENGINE. SPECIFICATIONS OF PORTABLE BOILERS AND ENGINES ON WHEELS. FIG. 236. No of size 1 2 3 4 5 6 8 Horse-power 6 8 10 12 15 20 25 30 35 Diam. of cylinder, in . 5 5 6 7 8 8 9 10 10 Length of stroke, in. . Usual no. revolutions. 8 185 8 240 9 190 10 160 10 160 12 170 12 170 12 170 15 150 Diara. of pulleys, in. . Face of pulleys, in... . Diam. of boiler, in 14&32 8i&8 26 14&32 16&36 ^ 20&44 10i&10} 32 20&44 10J&10J 32 30&48 81&12* 34 S2&54 m&m 36 32&54 10}&12i 36 36&60 10| & 14; 40 Length of furnace, in. Height of furnace, in. 34 80 86 32 38 34 38 38 44 38 52 38 52 40 52 40 52 44 Width of furnace, in.. 21 22 24 26 26 28 30 30 34 No. of 3-inch tubes. . . . 17 20 22 26 26 30 34 34 40 Length of tubes, in. . . 54 66 72 72 78 90 90 102 102 Shipping wt. complete Price 4800 $700 5000 $724 5700 $788 6000 $880 7100 $931 8100 $1045 9500 $1085 10,500 $1,277 11.300 $1,351 STONE-CRUSHING PLANTS. Complete crushing-plants include a stone-crusher, engine, boiler, shafting, pulleys, and belting. These plants maybe divided into two classes, viz., stationary and portable. In arranging either class of plant care must be taken to save un- necessary handling of the stone; to this end the crusher must be TOOLS AND MACHINERY EMPLOYED. 843 placed (1) so as to receive the stone directly from the carts or other conveyance used to transport it from the quarry, and (2) so as to deliver the broken stone into the vehicles which are to haul it away without handling. FIG. 237. CRUSHING-PLANT FOR HILLSIDE LOCATION. FIG. 238. CRUSHING-PLANT FOR LEVEL GROUND. In Figs, 237 to 240 a few illustrations are presented showing simple methods of arranging plants. Fig. 237 shows a fixed plant for hillside location, with road graded for delivery of stone to the crusher, and chute for delivery of broken stone to the carts. Fig. 238 shows a fixed plant for location on level ground, with road graded for delivery of stone to crusher, and elevator for rais- ing crushed stone to chute for delivery into carts. 844 HIGHWAY CONSTRUCTION. Fig. 239 shows a plant for temporary use, with platform for re- ceiving the stone to be crushed, three-section screen, and platform FIG. 239. TEMPORARY CRUSHING-PLANT. FIG. 240. PORTABLE CRUSHING-PLANT. for receiving the crushed and screened stone, from which it can be shovelled into the carts or an elevator can be attached. ^ig. 240 shows a portable plant with elevator and screen. TOOLS AND MACHINERY EMPLOYED. 845 Fig. 241 shows a portable plant with crusher elevated sufficiently to allow of a screen being used without the employment of an ele- vator. FIG. 241. CRUSHER MOUNTED ON WHEELS. STONE-DISTRIBUTING CARTS. The cart shown in Fig. 242 is specially designed for distributing broken stone for building or re- pairing roads. The cart is mounted on four wheels, so arranged that it can be turned in a short space. The bottom of the cart slopes downward to the back, and the tail-board is hinged at its upper edge and is furnished with two adjusting chains by which the opening or swing of the lower edge is regulated. Steel wings are attached to the sides of the cart at the tail-board for the purpose of spreading the stone the full width between the wheels. The cart is tilted by a rack and pinion operated by the driver, and may be fixed at any desired angle. As the stone flows from the rear of the cart it is levelled by a scraper attached to the bottom of the tail- board; this scraper is pivoted at the centre and can be adjusted so as to spread the stone to any required thickness and over any de- sired width equal to or less than the gauge of the cart, and thicker on one side than on the other. The carts are built in two sizes, to be hauled by two or three horses, respectively, the horses oeing harnessed abreast. The two- 846 HIGHWAY CONSTRUCTION. horse size is five feet wide and has a capacity of one and one half cubic yards, and weighs empty 2250 pounds. The three-horse size is seven feet six inches wide and has a capacity of two and one half cubic yards, and weighs empty 2750 pounds. The price of the two-horse cart is $175, and of the three-horse size $200. FIG. 242. STONE-DISTRIBUTING CART. HORSE ROLLERS. The following figures show a few selections from the large variety of horse rollers in the market. The principal dimensions, weights, and prices are given on pages 847 and 848. FIG. 243. ENTERPRISE ROLLER. For the advantages of rolling, form of rollers, amount of rolling, etc., see Articles 396, 397, and 400. TOOLS AND MACHINERY EMPLOYED. THE ENTERPRISE KOLLER, Fig. 243. This roller is made in two forms, " reversible " and " non-reversible." Both styles are made in sizes of 3, 4, 5, and 6 tons, the diameter of the rolling cylinders being respectively 54, 56, 58, and 60 inches, and a width of 54 inches, which is common to all weights. The non-reversible roller is equipped with a ballast-box which will hold a weight of 2 tons, so that a 4-ton roller can be increased to 6, and a 6-ton to 8 tons. Price about $100 per ton. Pope's reversible roller, Fig. 244, is made in sizes ranging from 5 to 10 tons. The diameter of the 5-ton roller is 5 feet, and width FIG. 244. POPE'S REVERSIBLE ROLLER. 5 feet. The diameter of the 10-ton roller is 7J- feet, and width 5 feet. Price $100 per ton. The Champion reversible roller, Fig 245, is constructed in two sections which revolve independently on the axle. The diameter of the rolls and width of the rolling face are the same, viz., 5 feet. This roller is made in four weights, viz., 2J, 3J, 4-J-, and 5 tons, and each is supplied with two steel boxes, each of which will hold about a ton of pig iron, thus converting each roller from a light- to a medium- or heavy-weight roller, as desired. Price &J tons $350; for each additional ton add $50. 848 HIGHWAY CONSTRUCTION". The Austin roller, Fig 246, is made in weights of 3 J, 4, and tons. The rolls are 4 feet in diameter, and width 5 feet. FIG. 245. CHAMPION REVERSIBLE ROLLER. FIG. 246. AUSTIN REVERSIBLE ROLLER. STEAM ROLLERS. There is a large variety of steam rollers in the market from which to select. The leading types are shown in Pigs. 247 to 151, and the principal dimensions, etc., are given in the following tables. For the advantages of rolling, cost of maintaining steam rollers, and amount of rolling required, etc., see Articles 396, 398, 403, and 404. TOOLS AND MACHINERY EMPLOYED. 849 THE SPRINGFIELD ROLLER. FIG. 247. 25,000 Ibs. 30,000 Ibs. 35,000 Ibs. 48 inches 48 inches 48 inches 40 inches 44 inches 48 inches Beveled driving-wheels, diameter . . . Beveled driving- wheels widtli . 76 inches 20 inches 76 inches 22 inches 76 inches 24 inches Extreme widtli of machine 70 inches 78 inches 86 inches Compression per square inch 550 pounds 600 pounds 650 pounds 450 pounds 500 pounds 550 pounds Water capacity ... . 280 gallons 315 gallons 850 gallons Maximum grade ascended with 120 pouiids steam on loose metalling. . . 22 per cent. 22 per cent. 22 per cent. THE PITTS ROLLER. FIG. 248. 10-ton. 12J^-ton. 15-ton. F>' >nt roll diameter 44 inches 46 inches 48 inches Front roll, widtb 47 inches 51 inches 52i inches Driving-wheels, diameter.. Driving-wheels, width Extreme width of machine 69 inches 18 inches 78 inches 117 inches 69 inches 20 inches 89 inches 128 inches 72 inches 22 inches 94 inches 133 inches COM] capacity 400 pounds 500 pounds 500 pounds Water capacity 225 gallons 275 gallons 320 gallons Coal consumption per d.-iy varies according to work a'id gr.ides from 400 to 900 Ibs 600 to 1000 Ibs 800 to 1200 Ibs Travelling speed per hour wit h fist gear 2.92 miles per hour 2f to 2f- miles 2f miles Travelling speed per hour with slow gear 2 21 miles per hour 2 miles 1 85 miles THE HARRISBURG ROLLER. FIG. 249. 10-ton. 12-ton. 15-ton. Driving-wheels width. . 18 inches 466 pounds 400 pounds 130 gallons 20 per cti 20 inches 500 pounds 500 pounds 155 gallons 20 per ct. 22 inches 566 pounds 600 pounds 180 gallons 20 per ct. Pressure per inch of width Coal capacity Water capacity Maximum grade ascended with 120 pounds of steam 850 HIGHWAY CONSTRUCTION. THE AVELING & PORTER ROLLER. FIG. 250. 10-ton. 15-ton. 20-ton. 45 inches 48 inches 54 inches Driving-wheels, diameter 66 inches 72 inches 78 inches Extreme width of machine .... Pressure per inch of width 78 inches 450 pounds approx. 400 pounds 87 inches 550 pounds approx. 450 pounds 96 inches 650 pounds approx. 500 pounds 150 gallons 200 gallons 250 gallons Maximum grade ascended with 100 pounds of steam on bin of loose metalling . . 17 per ct 17 per ct 17 per ct THE COLUMBIAN ROLLER. FIG. > 251. 27,000 Ibs. 32,500 Ibs. 38,000 Ibs. Front roll diameter 48 inches 48 inches 52 inches Drivinff wheels diameter".. . 70 inches 72 inches 74 inches Driving-wheels width 20 inches 22 inches 24 inches Extreme width of machine Coal capacity ) 81 inches sufficient 87 inches for 5 95 inches hours Water capacity f ' ' Compression of drivers per 507 pounds 575 pounds 605 pounds 14 to 20 feet per 100 THE RUSSELL ROLLER. FIG. 247a. 10-ton. 12J-ton. 15-ton. 50 inches 52 inches 54 inches Front rolls width 46 inches 48 inches 50 inches Driving-wheels diameter .... 70 inches 72 inches 74 inches Driving-wheels width 20 inches 22 inches 24 inches Extreme width of machine.. . . Coal capacity ... ... 73 inches 450 pounds 79 inches 500 pounds 87 inches 600 pounds 285 gallons 365 gallons 415 gallons THE UNIVERSAL ROLLER. FIG. 251a. Weight of Roller. 5 Tons. 7 Tons. 10 Tons. 18 300 175 12 9 11? 25 400 225 13 10 8 125 40 500 275 16 I0| &i 125 Coal capacity pounds \Vater capacity gallons . . Length over all feet Height with stack swung back "Working steam pressure pounds ... TOOLS AND MACHINERY EMPLOYED. 851 FIG. 247. THE SPIUNGFIELD. FIG. 247a. THE RUSSELL ROLLER. 852 HIGHWAY CONSTRUCTION. PIG. 248 -THE PITTS. 249. THE HARBISBTTKG. TOOLS AND MACHINERY EMPLOYED. 853 PlG. 350. TELE & PORTER. 251. THE COLUMBIAN-. 854 HIGHWAY CONSTRUCTION. TOOLS AND MACHINERY EMPLOYED. 8540 MOTOR ROLLERS. The roller shown in Fig. 2516 has for its motive power gasolene or denaturized alcohol. It is made in four sizes, weighing 7, 10, 12, and 15 tons. FIG. 2516. MOTOR ROLLER. FIG. 251c. TAMPING ROLLER. Tamping Rollers. Fig. 251c shows the tamping roller used in applying oil to earth roads. It weighs about 5000 pounds; its surface is furnished with teeth or spikes 7 inches long, the outer end of which is bent to form a foot or tamper 2X3 ins. TOOLS AND MACHINEKY EMPLOYED. SCARIFIEKS. This is the name given to the tools or mechanical devices used for picking or breaking up of broken-stone roads pre- paratory to the applying of new metal. In England these tools are extensively employed. There are, broadly speaking, two types, the one fashioned on the form of ploughs and harrows, and the other based on the principle of the rock-drill and ore-stamping mill. Each type is arranged to be operated by attaching to the steam-roller or by a traction engine, and is provided with regu- lating devices which adjust the depth of penetration. It is con- sidered that a suitably constructed scarifier will perform the work more expeditiously and thoroughly than it can be performed by hand, and at one-half the cost. Steam-rollers are usually furnished with spikes to fit in sockets on the hind rollers, which are intended to be used for breaking up roads, but they do not usually perform this operation in a satis- factory manner. The scarifiers employed in the United States are generally of the plough type, and are drawn by four to eight horses. The shoe is usually reversible and adjustable, and provided with a sharp and a blunt point. It is found that in some work the sharp point is the better; in other work the blunt one is more suitable. When using scarifiers it is essential to have the road thoroughly soaked with water. FIG. 251d. THE " PORCUPINE" SCARIFIER. 856 HIGHWAY CONSTRUCTION. 1037. The Tools employed for the Maintenance of Broken-stone Koads are : Shovels , per dozen $ 7.00 to $13.50 Picks " " 10.75" 22.50 Spades " " 13.25 " 14.50 Hoes " " 13.50 Rakes " " 14.00 to 16.00 Hand rammers each 1.15 " 12.00 Wheelbarrows per dozen 20.00" 52.50 Brush-hooks " " 17.00 Axes " " 12.00 to 15.50 Scrapers each 8.00" 12.00 Brooms per dozen 8.50" 9.00 Stone-sledges per pound .30 Stone-hammers " " .45 to .30 Grass-shears each 1.63 " 2.63 Turfing-axes " 1.75 Sod-lifters " 2.75 Straight-edges " 12.00 Drain-cleaners per dozen 9.00 to 11.00 Levels " " 48.00 Lines " " 9.00 1038. Tools Employed in the Constrnction of Block Pavements HAND HAMMERS. Cobblestone-hammer, Fig. 252, price $2.50 each. Square-block hammer, Fig. 253, price each $2.50. Brick-hammer, Fig. 254, price each $1.50. "IT FIG. 252. FIG. 253. FIG. 254. Pavers' crowbars, per pound 12 cents. Sand-screens, from $6 to $12 each. Brooms, rattan and wire, $4 to $8 per dozen. HAND RAMMERS. Hand rammers are of different forms, aa shown in Figs. 255 to 259. Fig. 255, used for cobblestones, is of wood, generally locust, banded with iron, weighs about 40 Ibs.; price $4 to $7.50. TOOLS AND MACHINERY EMPLOYED. 857 "Fig. 256, used for Belgian blocks, is of wood and steel, weighs about 45 Ibs. ; price $9. Fig. 257, used for granite blocks, is made of iron, with cast- steel face, locust plug, and hickory handles, weighs from 45 to 55 Ibs. ; price $9 to $12. FIG. 255. FIG. 256. FIG. 257. FIG. 258. FIG. 259. Fig. 258, used for brick, is made of wood, shod with cast iron or steel, weighs about 27 Ibs.; price $3. Fig. 259 is used for miscellaneous work, as tamping in trenches and next to curbs, weighs about 20 Ibs.; price $1.15 to $3. 1039. Machinery and Tools Employed for Asphalt Pavements, The machinery or plant employed for the preparation of the asphalt mixtures may be stationary or portable; several of the latter type are on the market. Both types consist essentially of (a) tanks for melting the asphalt and making the cement. These tanks are heated either by fire or by steam. Fig. 260 shows a tank heated by steam and furnished with pipes through which compressed air is conveyed to agitate the mixture, (b) Sand-dryers, which con- sist of one or more revolving cylinders connected to a furnace. They are made in various sizes; the one shown in Fig. 261 is 15 feet long and 3 feet in diameter and has a capacity of about 5 cubic yards per hour. Price $600. (c) Accessories comprising sand-screens, sand- 858 HIGHWAY CONSTRUCTION. Side View Top View- View FIG. 260. STEAM MELTING-TANK FOR ASPHALT CEMENT. TOOLS AND MACHINERY EMPLOYED. 859 bins, sand-measuring apparatus, oil-storage tanks, oil-pumps, steam boiler and engine, air-compressors, elevators, and conveyors. (d) Mixers for mixing the asphaltic cement and sand and prepar- . 261. SAND-DRYER. ing the binder. In some plants two mixers are used, one for the binder and one for the surface mix. In other plants one machine is used for both purposes ; when so used it is furnished with two shafts having blades of different lengths. The general form of the mixer is shown in Fig. 263. The cut shows an engine attached to the machine, but this can be omitted and the power applied by belting or gearing. The machines are made in various lengths and diameters and with or without steam jackets. A steam-jacketed mixer, 30 inches in diameter and 8 feet long, with a capacity of about 5 cubic yards per hour, costs about $325. Fig. 262 shows a portable plant which may be used for original construction or repairs. These portable plants are made with capacities ranging from 500 to 5000 square yards per day; one having a capacity of 500 square yards weighs about eight tons. Price varies considerably. The tools used on the street in laying the pavement comprise iron rakes, hand rammers, smoothing-irons, hand rollers either with or without a fire-pot and oiling device, and steam rollers either with or without provision for heating the front roll. 860 HIGHWAY CONSTRUCTION. TOOLS AND MACHINERY EMPLOYED. 861 FIG. 263. ASPHALT-MIXING MACHINE. 862 HIGHWAY CONSTRUCTION. The tamping- and smoothing-irons are shown in Fig. 264. They are of cast iron, with wrought-iron pipe handles. They are used hot, being heated in the portable fire-box shown in Fig. 265. The tam- pers are usually 6X8 inches and cost about $2 each. The smoothing- irons are made in two sizes: 10^X6J inches, weight 50 pounds, price about $3 each; and 14X7J inches, weight 65 pounds, price $5 each. FIG. 265. PORTABLE FIKE-BOX. The rake shown in Fig. 264 is stamped from one piece of steel and can be heated without damage; the length is usually 18 inches, "with 14 teeth 4J inches long, steel shank, and ash handle. Price about $25 per dozen. The shovels used for handling the asphalt have the handle and blade all made of steel. Price about $12 per dozen. The sandals shown in Fig. 264 are for the use of the hand-roller pushers. Price per pair $2.20. The cutters shown in Fig. 264 are used for trimming the edge of the asphalt where repairs are to be made; they are made single- and double-eye. The single-eye cutters range in size from 8^X2J to 20JX3 inches; price per dozen about $12. The double-eye cutter is made in the same sizes ; price about $20 per dozen. The curb tongs shown in Fig. 264 is used in setting stone curb. Price per pair $6. The scraper shown in Fig. 264 is commonly called a "pusher." It is used in scraping the debris from the surface of the asphalt pave- TOOLS AKD* MACHINERY EMPLOYED. 863 ment. The blade is made of No. 12 steel; handle 4 feet 6 inches long. Price $3 each. The portable fire-box, Fig. 265, is used for heating the tampers and smoothing-tools. It is made about 4 feet long and 2 feet wide, with and without cross-bars and standards for suspending melting- pots. Price with standards about $165; without standards about $90. Fig. 266 shows a hand roller with fire-pot; it is of cast iron, with a smooth-turned face; it is usually 3 feet in diameter and 3 feet wide. FIG. 266 FIRE-POT ROLLER. FIG. 266a. HAND ROLLER WITH AUTOMATIC GREASER. The weight varies from 400 to 1000 Ibs.; the price is about 10 cents per pound. Fig. 266a shows a plain hand roller with automatic device for greasing the roller to prevent its picking up the asphalt mixture; the material used is generally kerosene and water. The price of the greasing attachment is about $40. The steam rollers used for compressing and smoothing asphalt and plastic pavements are different in construction, appearance, and weight from those employed for compacting broken stone. The difference is due to the different character of the work re- quired: In compacting broken stone the solidification is mechan- ical and is effected by the weight or pressure of the machine; in the case of asphalt and plastic pavements the solidification is effected by chemical action, the roller being only required to bring 864 HIGHWAY COXSTRyCTIOX. the constituents into more intimate contact and to produce a smooth surface. FIG. 2666. ASPHALT-ROLLER. FIG. 266c. ASPHALT-ROLLER. Figs. 2665 and 266c illustrate the form of roller used for asphalt and plastic pavements; the weight is usually five tons, but TOOLS AND MACHINERY EMPLOYED. 865 they are made in sizes ranging from three to fifteen tons; the rear drum or roller is usually made with solid heads, so that it can be filled with water or sand and thus increase its weight. There are several of these rollers on the market to select from; they all agree in the principle of construction, differing only in minor details and dimensions. The principal dimensions of a five-ton roller are as follows : Front roll or steering-wheel 30 to 32 inches diameter Rear roll or driving-wheel 48 " " Width of front roll 40 " " " rear " 40 " Extreme length 14 feet height 7 to 8 feet Water capacity 80 to 100 gallons Coal " 200 pounds The price for a five-ton roller and heavier is about $400 per ton. ASPHALT-MIXERS. The general form of the machines employed for mixing the materials for asphaltic cement pavements is shown in Fig. 263. The cut shows an engine attached to the machine, but this can be omitted and the power applied by belting, using either spur or bevel gearing to suit location. The machines are made in various lengths and diameters and with and without steam-jackets. A steam-jacketed mixer 30 inches diameter and 8 feet long, with a capacity of about 5 cubic yards per hour, costs about $325. SURFACE-HEATER FOR KEPAIRING ASBHALT PAVEMENTS. Fig. 267 shows the Perkins surface-heater for repairing asphalt and mastic pavements. It consists of a metal tank mounted on wheels, and at the rear of this a series of burners surrounded by a wire netting packed with asbestos cement. The tank, which has a capacity of about half a barrel, contains gasoline. An air-pump at the head of the tank is used to force the gasoline to the burners. The purpose of the asbestos packing is to conserve and diffuse the heat. Each burner can be turned on and off at will, and when all are in use the tank will keep them running for about five hours. The machine complete weighs about 700 pounds. The method of operation is to place the heater over the space to be repaired and turn on the heat. In a very short time the 866 HIGHWAY CONSTRUCTION. entire surface of the pavement under the hood is softened, so that the top can be removed with a hoe. Only sufficient of the old material is taken off to secure a clean, fresh surface, which, being hot, the new material welds perfectly with it. FIG. 267. SURFACE-HEATER. FIG. 268. PORTABLE HEATER FOR ASPHALT OR PAVING-CEMENT. TOOLS AND MACHINERY EMPLOYED. 867 HEATING-KETTLES are employed for heating the paving-cement used for filling the joints in block pavements, and for heating the asphalt paving mixture for asphalt pavements when it has to be conveyed long distances from the factory. They are made in various forms and sizes. Circular ones are usually about 3 feet 6 inches in diameter and 3 feet 6 inches high, with the melting- chamber 20 to 24 inches deep, and cost about $60. The rectangular ones range from 4 to 8 feet in length and from 3 to 4 feet in width and from 2 to 4 feet deep at centre of heating-chamber; they range in price from $75 to $500. The most approved form is shown in Fig. 268. It is constructed with double bottom, similar FIG. 268a. STREET KETTLE FOR ASPHALT AND TAR. 868 HIGHWAY CONSTKUCTIOK. to a double boiler, so that the heating-surface extends the full length and well up on the sides. The melting-chamber is made of soft steel. Capacity about 600 gallons; weight with tongue, double- tree, and neck-yoke 3320 Ibs. Fig. 2686 shows Hooke's combined fire-wagon and asphaltic mix- ture heater, designed for use in making small repairs, using either the FIG. 2686. HOOKE'S COMBINED FIRE-WAGON AND ASPHALTIC MIXTURE HEATER. old material or a new paving mixture. The capacity is about 5 square yards of surface to a batch; the price is about $400. The old paving material is used by breaking it into fragments measuring about 3 inches; these are placed in the pan of the heater, covered with water, and boiled until disintegrated ; then the surplus water is removed and residuum-oil added, and the mass mixed until of the required consistency. The use of the old material is said to give satisfactory results. TOOLS AKD MACHINERY EMPLOYED. SQSa 8686 HIGHWAY CONSTRUCTION. The gutter-painters shown in Fig. 269 are made of cast iron with a slot in the bottom, provided with a screen to prevent clogging; made in two sizes. Price, each, small size, 14X12 inches, $14- large size, 14X18 inches, $19 each. The melting- and pouring-pots shown in Fig. 269a are made of galvanized iron. Melting-pots, 12X14 inches, price $6.40 each; pouring-pots, price, each, $4. Among the miscellaneous tools used are the raker's gauge, made of round steel, 12 feet long, with five legs adjustable to height; price, each, $10. Patching hoes, used in making repairs, made of steel, with saw-teeth and iron handle; pri^e, each, $2.80. Grading tees, made of 2 X 1-inch pine, with a 14^-inch head and 48-inch blade ; a set consists of one red, one white and one blue T; price per set $3. FIG. 269a. MELTING- AND POURING-POTS FOR ASPHALT AND TAR. Straight-edges, made of pine, 16 feet long, 6 inches deep at the centre, and 4 inches deep at the ends; price, each, $3. Dippers are made of galvanized iron, varying in capacity from 6 to 9 quarts; price, each, $4.50 and $5. Sand thermometers, price about $30 per dozen. Asphalt tank thermometers, registering to 600 F., made in lengths from 3 to 6 feet; price, each, from $12 to $25. CONCRETE-MIXING MACHINES. Where large quantities cf con- crete are required, as in the foundations of improved pavements, con- crete can be prepared more expeditiously and economically by the ute of mechanical mixers, and the ingredients will be more thoroughly mixed than by hand. Thorough incorporation of the ingredients is an essential element in the quality of a concrete ; when mixed by hand, the incorporation is rarely complete, because it depends upon TOOLS AND MACHINERY EMPLOYED. the proper manipulation of the hoe and shovel. The manipulation, although extremely simple, is rarely properly performed by the or- dinary laborer unless constantly watched by the overseer. Several varieties of concrete-mixing machines are m the market. A con- FIG. 270. CONCRETE-MIXING MACHINE. venient portable type is illustrated in Figs. 270 and 271. The ca- pacity of the mixers ranges from five to twenty cubic yards per hour, depending upon size, regularity with which the materials are supplied, speed, etc. In price they range for machines without engines from 1425 to $600; with engines, from $950 to $1250. For the advantages of concrete, cost, etc., see Articles 457 et seq. SAND-DRYERS. Revolving cylinders connected to a furnace are employed for drying the sand used, for the cushion coat of block pavements, for mixing with asphaltic cement, and for heat- ing the gravel used to fill the joints in block pavements. They are made in various forms and sizes. 870 HIGHWAY CONSTRUCTION. Kevolving cylinders mounted on wheels, 9 feet long and 2 feet in diameter, cost about $250. Rectangular dryers mounted on wheels, 9 feet long, 4 feet wide, and 4 feet deep, cost about $150. Pans 6 feet long, 5 feet wide, and 6 inches deep cost about $20. FIG. 271. CONCRETE-MIXING MACHINE. FIG. 272. SWEEPING MACHINE. TOOLS AND MACHINERY EMPLOYED. 871 1040. Tools for Cleansing HAND TOOLS. Brooms for street sweeping are made of steel wire or rattan; their size is generally 16 inches long by 4 inches wide; wire lasts longer than rattan, but is only suitable for block pavements. Price, steel per dozen $12.00 to f 18.00 " rattan " " 8.50" 9.00 SQUILGEES, or rubber scrapers, are used for cleaning asphalt pavements. Price per dozen $7.50 to $9. MECHANICAL SWEEPERS. A large variety of sweeping machines are on the market, and in various sizes, to be used with one to four Lorses. Price ranges from $300 to $600. Figs. 272 to 276 show a few of the many forms. Some of the characteristics of a well-designed machine are that its draft shall be as light as possible, the balance well arranged, the mechanism for raising and lowering the brushes and for throwing them in and out of gear as accessible to the driver as possible, and placed so that he may manipulate it without losing control of the reins or sight of the traffic adjacent to him; that the working parts shall be protected as much as possible from being splashed with mud; that the moving parts of the machinery shall be covered so that in the event of a collision or other accident the driver shall not be thrown, into the midst of it ; gearing for lowering the brushes as they become worn, and an arrangement whereby the pressure of the brushes on the surface may be regulated. FIG. 273. SWEEPING MACHINE. The sweeper shown in Fig. 272 is known as the "Pride of New York." The broom is 8 feet 6 inches long, and sweeps a track 7 $72 HIGHWAY CONSTRUCTION. feet 10 inches ; it weighs complete 1900 Ibs., and is operated by two horses, and costs about $400. Smaller machines of the type are also manufactured, to be operated by one horse; the one- horse machine sweeps a track 5 feet 6 inches wide, weighs 1400 Ibs., and costs about $300. FIG. 274. SWEEPING MACHINE. Fig. 273 shows the "Austin Sweeper." It is made of steel throughout. The broom is 8 feet in length and is made of tem- pered flat steel wires or rattan, and sweeps 6 feet wide. It is operated by two horses. The sweeper shown in Fig. 274 is known as the "Barnard Castle." It is made in England, and is extensively employed both in that country and in America. It is manufactured in two sizes, viz., to sweep six feet and seven feet six inches, respectively. The smaller machine is made either with shafts for one horse or with a pole for two horses. The larger machine is made only with a pole for two horses. TOOLS AND MACHINERY EMPLOYED. 873 COMBINED SWEEPER AND SPRINKLER, Figs. 275 and 276, is designed for cleansing either stone, wood, or asphalt pavements. FIG. 275. COMBINED SWEEPER AND SPRINKLER. FIG. 276. COMBINED SWEEPER AND SPRINKLER. The machine consists of a circular water-tank with a revolving brush beneath it. A water-pipe or spreader travels in advance of the brush and facilitates its operation. 874 HIGHWAY CONSTRUCTION. FIG. 277. SCRAPING MACHINE. SCRAPING MACHINES. For the removal of stiff mud and snow from pavements scraping machines are extensively employed. They generally consist of a number of steel or iron teeth, three to five inches wide, attached to a frame in such manner that they will rise and pass over any fixed obstacle without suffering injury. Fig. 277 illustrates the Barnard Castle street-scraper. It is drawn by either one or two horses, and delivers the mud or snow on one side in ridges, similar to the sweeping machine. The extent of surface scraped per hour by one of these machines is about 8000 square yards. TOOLS AND MACHINERY EMPLOYED. 875 PATROL OUTFITS. In the sweeping of streets by the "patrol" or block system, it is essential to have an easy and convenient method of transporting the hand tools, and for disposing of the sweepings as soon as collected. With this object several " outfits" have been designed, the principal being the metal box shown in Fig. 278; the Waring bag and bag-carrier, Fig. 279; and the metal can and truck, Fig. 280. FIG. 278. PATROL-CART. FIG. 279. WARING BAG-CARRIER. 876 HIGHWAY CONSTRUCTION. In each of the types the full receptacles are stored at convenient places along the sidewalk and collected periodically by a suitable vehicle and taken to the dump or place of disposal, the receptacle cleansed and returned to the street. In the bag type no delay is occasioned by waiting for empty receptacles, as sufficient empty bags can be carried for a day's work. FIG. 280. PATROL-CART. Fig. 281 shows the hand scoop used by the -street patrol in several cities. FIG. 281. HAND SCOOP. TOOLS AND MACHINERY EMPLOYED. 87? Eig. 282 represents a hand sweeping machine which can be operated by one man. Price $65. PIG. 282. HAND SWEEPER FIG. 282o. THE PEERLESS " PICK-UP" HAND STREET-SWEEPER. 878 HIGHWAY CONSTBUCTION. HAND PICK-UP MACHINES. The hand pick-up machine, Fig. 282a, consists of a circular brush, 30 inches long and 13^ inches in diameter, with a metal box to receive and hold the refuse thrown into it by the revolving brush. The box under ordinary conditions will hold the refuse from an area of 750 to 1000 square yards. Price of machine about $65. DUMP-CARTS. The carts employed for the removal of street refuse must possess certain essential features, among which are the following: The material employed in the construction must not absorb moisture; the form must be such as will permit of easy cleansing; it must be provided with covers to prevent the dust being blown about the streets to the annoyance of the pedestrians; the cover should embrace the whole vehicle. The openings in the cover should be large enough to allow all the various vessels in which the dust is collected to be emptied without spilling the contents; the openings should be so arranged as to command the whole surface of the vehicle, so as to render unnecessary the disturbance or raking of the contents when once deposited in the vehicle; the covers for the openings should not be too heavy, they should be arranged to open and shut quickly and easily; the mechanism for their operation should be simple, durable, and not liable to get out of order. The weight of the vehicle should be as light as is consistent with the strength required to carry the load; the width should not be exces- sive ; for ease of draft the wheels should be large and have wide tires ; the height of the sides of the vehicle should be such as to permit of ease in loading; it must dump and recover easily and quickly^ must be strong and of moderate cost. Figs. 283 and 283a show two forms of steel-tank carts which are made in various sizes 7 ranging in capacity from 37 to 54 cubic feet for the two-wheeled type and 54 to 70 cubic feet for the four-wheeled type. In the two-wheeled type the diameter of the wheels is 4 feet 8 inches, with either 2J or 3J inch tires. The weight of the two- wheeled vehicles ranges from 1300 to 1500 Ibs. The weight of the four-wheeled type is about 2000 Ibs. The two-wheeled cost about $200 and the four-wheeled about $270. Covers and springs cost about $15 each. TOOLS AND MACHINERY EMPLOYED. 879 FIG. 283. DUMP-CART. FIG. 283a. DIJMP-CART. 880 HIGHWAY CONSTRUCTION. COMBINED SWEEPING AND COLLECTING MACHINE. In conse- quence of the increasing use of improved pavements, and with the- view of reducing the amount of manual labor required with the usual form of side-sweeping machines, inventors have sought to devise machines which will, instead of merely sweeping the dirt into windrows, collect and pick it up. Three types of "pick-up" machines are now on the market, viz., the "International," the "Universal," and the "Pneumatic." The International machine (Figs. 284 and 285) consists of an iron collecting-box and a revolving broom. The box has hinged sides and bottom, and is open at the back to receive the dirt brushed up by the broom. The broom is entirely enclosed, and the FIG. 284. SWEEPING AND COLLECTING MACHINE. back part of the casing forms a receptacle for dirt 'carried over b} the broom, and which would otherwise be deposited upon the sur- face already swept. The operation resembles that of an ordinary carpet-sweeper. The machine is made of iron and steel, is mounted on four wheels, and is drawn by two horses. The broom is 5 feet long, and revolves on a stationary spindle running through a tube in the TOOLS AXD MACHINERY EMPLOYED. 881 centre of the broom. Medium-coarse bass is used for the broom, and its life is from 18 to 25 days. The collecting-box has a ca- pacity of one cubic yard, but it cannot be filled to its capacity, as the dirt would fall back upon the broom, and, in fact, the dirt has a tendency to form a ridge near the open end of the box, which prevents the entrance of fresh dirt carried up by the broom, so that the box has to be dumped frequently in order to prevent the dirt from dropping back on the street. FIG. 285. SWEEPING AND COLLECTING MACHINE. The machine weighs about 2500 pounds, sweeps within one foot of the curb, and the driver can regulate the pressure of the broom on the pavement or throw it out of gear. This machine has been successfully used for collecting and pil- ing the dirt swept to the side of the street by an ordinary side- sweeping machine. When used in this way, it is said it saves the cost of three gutter-men, and half the teams for hauling off the sweepings, as the Avagons can be loaded much more quickly on account of the piling of the dirt. The Universal machine (Fig. 286) consists of an iron frame carrying a diagonal revolving broom, 26 inches in diameter, which sweeps the dirt into a windrow. Directly in line with this wind- row, and behind the delivering-end of the long broom, is a short broom, 31 inches in diameter and 2 feet wide, which revolves at two and a half times the speed of the main broom, and drives the 882 HIGHWAY CONSTRUCTION. material of the windrow into a chamber at the base of an endless- belt elevator, the buckets of which carry up the dirt and dump it into a chute, through which it falls into a covered bin mounted on the frame of the machine. This bin is carried by trunnion bear- ings at each end, and when full a dump cart is driven alongside the machine, and the bin is tilted by means of a crank-handle and gearing to discharge its load into the cart. FIG. 286. SWEEPING AND COLLECTING MACHINE. The machine weighs about 4000 pounds, and is drawn by three horses; the capacity of the bin is about one cubic yard. If worked steadily without delays, the machine can sweep about a mile of street an hour. This machine has been successfully tried in New York and Boston, and Mr. H. H. Carter, M. Am. Soc. 0. E., Superintendent of Streets, Boston, states that it has demonstrated its ability to do the work at about 45 per cent of the cost under the former method, by which the dirt was swept into windrows by ordinary side-sweep- ing machines, then swept by hand into piles and shovelled into dump-carts. The Pneumatic machine works by an air-blast. It consists of an iron box 6^ feet wide, 1G feet long, and 7-J- feet from the ground to the top, mounted on four wheels, and equipped with an exhaust fan operated by a 5-horse-power engine, and rectangular brushes or scratchers. It is operated by two men and three horses, and in working order weighs about 6000 pounds. In operation the scratchers drag on the street and loosen the TOOLS AXI) MACH1STEKY EMPLOYED. 883 dirt, which is carried by the air-blast into the dirt-box. The ex- haust steam is used to dampen the dirt, and any dust that may be picked up is carried to the furnace of the boiler. The dirt-box has a capacity of about half a cubic yard, and when full is dumped, leaving the material in convenient piles for shovelling into the dump-carts. SPKINKLING-CARTS are made in various sizes, and of wood, iron, and steel, and with various devices for controlling and spreading the water. The sprinkler shown in Fig. 287 is made in the following sizes: Price. 1000 gallons $550. 00 750 " 475.00 550 " 425.00 350 " 400.00 FIG. 287. STREET-SPRINKLER. Fig. 288 shows a sprinkler made entirely of steel. Three sizes are on the market, viz., 600, 750, and 1000 gallons. The sprinkler shown in Fig. 28Sa is styled the " Contractor's Sprinkler." The gear used is called "Contractor's Gear," and dif- fers from an ordinary farm gear in that the reach is dovetailed 884 HIGHWAY CONSTRUCTION. FIG. 288. STKEET-SFRINKLKK. FIG. 288a. CONTRACTOR'S SPRINKLER. TOOLS AND MACHINERY EMPLOYED. 885 into and firmly bolted and braced to both the front and hind bol- sters, coupling the two gears together rigidly. The bolsters being thus kept in line and immovable as compared to each other, the tank rests firmly on them and the bolster-spring cases are not subject to any lateral strain. The front gear is so constructed that the front wheels cut under until they strike the reach, making it possible to turn very short. The tongue is stiff and is held up firmly by sway bars pressing against the under side of the reach and is heavily ironed its entire length with continuous iron. The axles are of FIG. 288&. STREET SPRINKLER. solid steel, firmly clipped to the wood stocks. The tank is made of wood and rests on double coil-bolster springs in cast-iron cases; it can be lifted off the gear and set to one side, thus allowing the use of the gear in other hauling work. This combination is much in favor with contractors. The sizes and prices are as follows : No. 46. 750 gallons capacity, 2J" front and 2f" hind axles $310.00 No. 47. 600 gallons capacity, 2" front and 2J" hind axles $255.00 Fig. 288b shows the standard platform spring-gear sprinkling: $86 HIGHWAY CONSTRUCTION. wagon which has been adopted by the Street Sprinkling Association, of New York City. It is made in various sizes as follows : No. 28J. 450 gallons capacity $315 . 00 No. 27. 600 gallons capacity 325 . 00 No. 26. 750 gallons capacity 365 . 00 Automobile Sprinklers. An automobile sprinkler has been in use in Paris for some time and has proved quite satisfactory. It consists -of a steam tractor of the De Dion type, having a 35 horse-power boiler and compound engine; the tank holds 1250 gallons of water; the sprinkling-nozzles are arranged to distribute the water in two symmetrical sheets 23 feet wide or 46 feet in all. The sprinkling capacity of the car is about 1700 square yards, which can be covered in 15 minutes. SNOW-PLOUGHS. The ploughs employed for the removal of snow on country highways are usually made of wood. The general form is shown in Figs. 289 and 290. They are loaded with stone. In light falls, say of 6 inches, one horse is sufficient, but in deeper falls two or more are necessary. Fig. 290a shows a snow-plough with which a track from 9 feet to 25 feet wide can be cleared. MACHINES FOR MELTING SNOW have been experimented with in various cities. The results have not been entirely satisfactory the capacity being low and the cost of operating high. A machine using naphtha as fuel was tried in New York City in 1897, for which is claimed a melting-capacity of 60 cubic yards per hour at a cost of $8. TOOLS A^D MACHINERY EMPLOYED, Side View. 88G0 Plan. FIG. 289. SNOW-PLOUGH. Side View. Plan. FIG. 290. SNOW-PLOUGH. Snow-shovels per dozen $4.50 Sidewalk-chisels " $7.00 to $17.00' HIGHWAY CONSTRUCTION. TOOLS AND MACHINERY EMPLOYED. 887 1041. Tools Employed for Artificial Stone Pavements. TAMPERS (Fig. 291). Cast iron, with hickory handle; range from X 8 inches to 8 X 10 inches. Price from $2 to $2.50 each. FIG. 91. FIG. 292. FIG. 295. FIG. 294. FIG. 296. FIG. 297. 888 HIGHWAY CONSTRUCTION. QUARTER-ROUND, Fig. 292, is used for rounding corners and sedge. Made of any desired radius. Price from $1.75 to $3 each. JOINTER, Fig. 293, is used for trimming and finishing the joints. Price from $2 to $3 each. CUTTER, Fig. 294, is used to cut the concrete into blocks. Price $3 each. FIG. 298. CAST-IRON CATCH-BASIN. GUTTER-TOOL, Fig. "295, is used for forming and finishing gutters. Price $2.50 each. IMPRINT-ROLLERS. Figs. 296 and 297 show two designs of rollers for imprinting the surface of artificial stone pavements with grooves, etc. Price ranges from $8 to $15 each. TOOLS AND MACHINERY EMPLOYED. 889 1042. Catch-basins, Sewer Inlets, and Gutter-crossings, Fig. 298 illustrates a catch-basin made of cast iron, which is introduced as a substitute for the brick chambers now generally used. It is easily put together without skilled labor, and each piece or section is light enough to be handled readily. The front opening is 1 foot high and 4-J feet wide, protected by a wrought-iron grating, so formed that floating refuse will not lodge and close the opening. Price, corner inlet $125; side inlet $115. Fig. 299 shows a catch-basin cover and grating for use as a side FIG. 299. SIDE INLET. inlet. The grate-opening is 12 X 24 inches. The lid or cover for removing sediment is 24 inches in diameter. Price $16. FlG. 300. GUTTEE-GBATING. Fig. 300 shows a cast-iron gutter-box designed to fit into the hub of a 10-inch sewer-pipe, and is suitable for use on highways, 890 HIGHWAY CONSTRUCTION. park walks and streets. Dimensions on top, 9 inches long, 6 inches wide, and 3 inches deep; total height, 4J inches; weight about 20 pounds. Price $2.50. Among the appliances invented for the purpose of closing the street inlets to sewers against the escape of gases, etc., may be mentioned the Hitchcock patent sewer inlet-trap (Fig. 301). The FIG. 301. THE HITCHCOCK SEWER INLET- TRAP. FIG. 302. FIG. 303. device explains itself; the purpose is to prevent the escape of gases from the sewer during the cooler seasons, when the air in the sewer is usually warmer than the air in the streets. The lid A opens and permits the discharge of water entering the inlet; but at TOOLS AND MACHINERY EMPLOYED. other times it remains tightly closed by its own weight against the fixed spout D. The trap is made of cast iron, and has been suc- cessfully used in Springfield, Mass., for about fifteen years. The price is about $4.50; including the grate and rim, which is 18 inches in diameter and weighs about 175 pounds, the price is $9. Figs. 302 and 303 show a cast-iron inlet and manner of setting designed for conducting storm-water from the side ditches of im- proved suburban or country roads into the nnder-drains. FIG. 304. GUTTER-CROSSING. FIG. 305. GUTTER-CROSSING PLATE. The inlet-head is of cast iron, with a removable grate of wrought iron, which is placed at an angle of 60 degrees, to correspond with the slope of the bank. It is provided with flanges to rest upon a brick or stone foundation, is circular in form and 18 inches in diameter, and can be reduced to fit any desired size of pipe. Price, without reducer, $6; with reducer, $7. Figs. 304 and 305 show two forms of gutter-crossings. Fig. 302 892 HIGHWAY CONSTRUCTION. is made in widths from 4 to 26 inches, and from 4 to 10 inches in depth, and in lengths from 3 to 6 feet. Price per foot ranges from $1.30 for the smaller sizes to $7.60 for the larger. Fig. 303 is made in sections 30 inches wide and 5 feet long. Price $12 each. FIG. 306. GUTTER-BOXES AND GRATINGS. Pig. 306 shows cast-iron gutter-boxes and gratings for use with catch-basins. They are made in sizes from 4 feet long, 1 foot wide, and 9 inches deep to 15 inches long, 9 inches wide, and 9 inches deep. Prices range from" $25 for the largest size to $3.75 for the smallest. 1042a. Street Name-plates. The custom of using tablets of pottery and stone built into buildings was resorted to by the Romans, both to name streets in large towns, and to direct way- farers from one place to another. Until the early part of the pres- ent century the names of streets and roads were usually painted or carved on boards, and sometimes the names were inscribed on stone, and in one instance on slate. Regarding the durability of the latter, Mr. Francis Smythe, C.E., states that he saw in Wales a direction notice written in slate which was stated to have been in TOOLS AND MACHINERY EMPLOYED. 893 existence for over a century, and it showed but little ill effect from the action of the weather. It was not until about the third or fourth decade of the present century that cast iron was known to be used for this purpose^ having been previously introduced as mile-posts. At the present time in Europe probably more name-plates of this metal are used than any other kind, although many devices have been introduced. Among these may be mentioned enamelled iron plates; plates made of an alloy containing a large proportion of zinc; embossed or raised letters on sheet-iron and zinc plates, or letters cut out of the same metals; china or glass letters fastened on to wood or metal plates; plates made entirely of glass, glazed terra-cotta, or china; metal plates let into the surface of foot-paths; glass slips fastened into the lanterns of public lamps; and metal plates fastened to the lamp- columns or to independent columns. Cast-iron name-plates have hitherto been most in use on account of their cheapness and durability, the objections to them being their brittleness and consequent liability to fracture, scaling of the paint, and corrosion. Enamelled- iron name plates are extensively used. They are neat in appearance, and can be read from quite a distance. The colors generally employed are white for the letters and dark blue for the background. The letters are usually 2 inches in height. Enamelled signs deteriorate when subjected to frequent changes of temperature. The difference in expansion between the enamel and the backing causes the former to crack and scale, and when the backing commences to oxidize the lettering is quickly obliteratedo Many manufacturers claim that their plates are proof against this defect, but, experience shows that all are liable to this fault. Wood is extensively used for name-plates. Oak is preferred. It should be well braced across the grain to prevent warping. With gilt letters on a sanded black surface, wood makes a sign satisfac- tory in appearance and durability, and not very expensive. As a rule street name-plates are made too small and not suffi- ciently prominent. An extra-sized letter (2 to 4 inches) does not add a very large proportion to the cost, as the time of fixing, which is a considerable portion of the expense, would not take any 894 HIGHWAY CONSTRUCTION. longer. A bold moulding round the plate increases its promi- nence. Various methods have been suggested for placing the names in the sidewalk. Among those tried may be mentioned the cutting of the name in the top of the curbstone and coloring the letters black. Where concrete is used for the sidewalk, wooden pattern letters 1 inch deep are bedded in the concrete, which, when the concrete is sufficiently set, are removed and the space filled with colored cement mortar or letters made of brass or composition metal. The streets of St. Louis are posted with enamelled signs having clear white letters on a dark blue ground. The plates for these signs are 4| inches wide, from 16 to 26 inches long, and are made of No. 18 wrought iron, United States standard gauge. At the middle of the sides and ends and three-eighths of an inch from the edge of the plate are the four screw-holes, No. 9 brass screws being used. Where posts are used they are of cypress or cedar, 4x4 inches in section and 12 feet long. The signs are screwed on seven-eighths-inch clear pine kiln-dried lumber, painted with one coat of asphaltic paint. The letters on the signs are half block and three inches high. Numbered streets from First Street to Ninth Street, inclusive, are spelled out in full, but from 10th Street up figures are used, followed by " nd," " rd," or " th," as may be called for. The word " Street " is spelled out in full on the numbered streets. On named streets the abbreviation " St." is used after the name. Avenue is abbreviated to "Av."; Boulevard to"Bl."; Place to "PI."; and "Road" to " Rd." No periods are used except after abbreviations. The enamel of the ground color on the plates is a dark, glossy blue, free from lumps and blisters, and guaranteed not to exude white powder when exposed to the atmosphere. The lettering is a clear white, free from dark spots. The back of the plate is thoroughly coated with enamel, and before acceptance the plates are subjected to an impact and bending test, any sign of flaking or scaling being rejected. The cost was 36 cents each, delivered. 1042b. Direction Indicators should be placed at junctions and crossing of roads for the convenience of travellers. They should be- substantially made of an imperishable material, bold and neat in TOOLS AND MACHINERY EMPLOYED. 895 design, with strong self-bracing bases. The lettering should be bold and legible, the direction arms easily fixed at any angle without the necessity for special castings or complicated fastenings. FIG. 306a. TYPES OF DIRECTION INDICATORS. 1042c. The Viagraph (Fig. 307), invented by Mr. I. Brown, is an instrument for ascertaining and registering the inequalities in road, surfaces, so that any given road may be compared with another, or with itself at different times. In principle the viagraph is a straight- edge applied continuously to the road-surface along which it may be drawn, and conveying an apparatus for, first, recording on paper a profile of the road-surface; and, secondly, indicating a numerical index of the unevenness of the surface. Fig. 307 gives a view of the instrument with the cover removed. The frame is in form like a sled, with straight runners on which are 896 HIGHWAY CONSTRUCTION. FIG. 307. mounted the working parts. The lever T, pivoted to the main frame at H, carries on its free end a toothed wheel, the upper part of which is seen at V. While the main frame in being drawn along the road preserves a sufficiently even line, the road-wheel V rises and falls over all the unevennesses of the surface, carrying with it the lever T, and thereby transmitting its movements by means of the link and lever 8 to the pencil P (raised abnormally in the figure) and recording them on the roll of paper drawn from the stock roll C and wound upon the receiving-drum B. The profile thus made is of full size, vertically, and -J inch in to 1 foot horizon- tally. The second pencil seen below P draws a datum line with which that drawn by pencil P would concide if the road were per- fectly even. The sum of the vertical registration of the pencil P is called " the numerical index of unevenness," and is recorded automatically by the decimal counter W operated by a cord attached to the free end of the lever T and passing once around a double- grooved pulley X. 1042d. Motor Vehicles for Municipal Services. Mechanically propelled vehicles are extensively used in England for such munici- pal services as the collecting of dust and refuse, street sweeping, sprinkling, etc. Most of the vehicles in use are operated by steam; they are generally made with interchangeable bodies, so that the same vehicle may be employed as a dump-wagon, sprinkling-cart, etc. The change from one body to another can be made in about five minutes. The body of the dump- wagon is made of steel, with dde-boards and close-fitting tail-boards, having a capacity of 7 cubic yards and arranged to tip to the rear. By means of a winch and suitable gearing the load can be dumped by one man. The motor is capable of drawing a trailer. The speed is about 5 miles an hour, the price about $3500. TOOLS AXD MACHINERY EMPLOYED. 897 The English specifications under which several successful vehicles have been constructed are as follows: 1. The motor vans must come under the definition of light loco- motives, as defined in the Locomotives on Highways Act, 1896. The requirements of this act are : (1) To weigh less than 3 tons when unladen, without taking into consideration the weight of water, fuel, or accumulators. (2) To emit no smoke or visible vapor. (3) To measure less than 6 feet 6 inches in width between their extreme projecting points. (4) To have flat tires to each wheel, and if the weight exceeds 1 ton the width of the tire is not to be less than 3 inches, and if 2 tons not less than 4 inches. (5) To be capable of travelling either forwards or backwards. (6) To have two independent brakes. 2. The vans are to be four-wheeled vehicles, provided with easily removable covers, and are to be of sufficient capacity to carry 6 cubic yards of sand or other material, of a weight not exceeding 4 tons. The extreme width of the vehicles is not to exceed 6 feet 6 inches, and they are to be capable of going anywhere where a horse-drawn vehicle carrying the same load is ordinarily required to go. Each vehicle is to be completely under the control of one man, both for driving and steering, and is to be capable of being dumped by one man over a dumping-stick 14X14 inches, and held at any angle. 3. The vans will not be required to go at a greater speed than 6 miles an hour, and must be able to carry the load up an incline of 1 in 20 for 100 yards at a speed of 4 miles an hour. 4. Makers are not restricted to any kind of motive power, but must state which they intend to use, and must be prepared to guar- antee that the cost of working, apart from the drivers' wages, shall not exceed a certain sum per mile, to be named in the tender. *5. The tare weight of each vehicle must be given both exclusive of water and fuel, and also in full working order. 6. The body is to be of suitable seasoned wood, but the frame may be of iron or steel. 7. The inside of the platform is to be not more than 3 feet 4 inches above the ground-level when unloaded. 8. All working parts are to be properly encased. 898 HIGHWAY CONSTRUCTION. 9. The surveyor to the vestry shall be at liberty to inspect the vans at any time when being built at the maker's yard. 10. The vans are to be painted as directed, and lettered . . . . , and are to be delivered within .... months of receipt of order. 11. The vans are to be driven/for one week after being delivered, by the maker's drivers, free of expense to the vestry. 12. Payment will be made on the certificate of the surveyor, as follows : 90 per cent within one month of approval, and the balance within three months from the payment of the first instalment. 13. The makers are to enter into an undertaking to maintain the vans against fair wear and tear for a period of two years from the date of approval. 14. Tenders are to be delivered in a sealed envelope, endorsed 15. A drawing or photograph of the vans is to be submitted with the tender. 16. The vestry do not bind themselves to accept the lowest or any tender. CHAPTER XXIV. MISCELLANEOUS NOTES. 1043. Comparison of European and American Methods and Prices. Comparison is frequently made between the methods and cost of constructing and maintaining roads and pavements in the United States and Europe. In making such comparisons it must be remembered (1) that comparisons are of little value unless based upon similar conditions; (2) that the cost of materials and labor in Europe is generally much less than in America; (3) that the- methods and cost will vary very much in different parts of the same country ; (4) that the cost of constructing and maintaining; roads and pavements depends upon many diverse elements, due to local conditions, customs, and habits, as well as upon the quality of the materials, distance of transport, skill of the workmen, charac- ter of the traffic, climatic conditions, etc. Although it is evident that comparisons based upon such vari- able elements as are enumerated above must be imperfect, never- theless intelligent observation and comparison of the methods and cost of construction and maintenance, both at home and abroad, will materially aid in avoiding unnecessary expenditure in experi- ments, and will promote economy and efficiency. Table No. LXXX VIII shows the wages paid in several European, localities. TABLE LXXXVIII. Kind of Labor. London. Berlin. Paris. England. Bel- gium. France. $0.58 $20.001* $1.55 Unskilled $0.00 $1.00 to $2.00 $1.75 $080 $1.50 $2.00 to $2.50 $1.75 $0.48 to $0.70 $0.83 $1.50 $0.71 $1.60 to $1.80 $1.50 $0.80 $0.90 to $1.20 SI.CO $080 $0.90 to $1.10 $1.60 $1.56 to $1.75 $1 00 $080 to $090 $0.80 to $1.44 $1.75 to $2 50 $1.25 $0.06 to $0.07* Foreman Pavers. Sweepers Steam-roller drivers . Horse and cart Masons * Per hour. t Per month. 899 900 HIGHWAY CONSTRUCTION". In European cities 10 hours constitute a day's labor. Wages in the United States range between the following limits, and a day's work varies from 8 to 10 hours : Foremen, $3 to $5. Sub-foremen, $1.75 to $2.50. Unskilled, $1.25 to $1.75. Pavers, $2.50 to $4.50. Masons, $3 to $4.50. Steam-roller drivers, $3 to $4.50. Single horse, cart, and driver, $2.50 to $3.50. Double horse, wagon, and driver, $3 to $6. Drillers, $2 to $3. Sweepers, $1.25 to $2. 1043a. Statistics of Roads in the United States, The following statistics concerning the weight of load for horses, cost of haulage, and length of haul from farms to markets are deduced from the investigation conducted by the office of Koad Inquiry of the De- partment of Agriculture. * AVERAGE WEIGHT OF LOAD FOR TWO HORSES. Eastern states , 2216 pounds Northern states 2136 " Middle Southern states 1869 " Cotton states 1397 " Prairie states , 2409 " Pacific coast states 2197 " Average for the United States 2002 " AVERAGE COST OF HAULAGE PER TON PER MILS; Eastern states 32 cents Northern states 27 " Middle Southern states 31 " Cotton states 25 " Prairie states 22 " Pacific coast states 22 " Average for the United States 25 " MISCELLANEOUS NOTES. 901 AVERAGE LENGTH OF HAUL IN MILES FROM FARMS TO MARKET OR SHIPPING POINTS. Eastern states 5.9 miles Northern states 6.9 " Middle states 8. 8 " Cotton states 12.6 " Prairie states 8.8 " Pacific coast states 23.3 " Average for United States 12.1 " AVERAGE TOTAL COST PER TON FOR THE WHOLE LENGTH OF HAUL. Eastern states , $1.89 Northern states 1.8& Middle Southern states 2.72 Cotton states 3.05 Prairie states 1.94 Pacific coast states 5.12 Average for the United States 3.02 In conquence of the great attention which highway improve- ment is now receiving and the agitation for the construction of' light railways connecting the markets and shipping points with: the farms, accurate and reliable information as to the cost of haul- age over country roads is in demand, and the above figures, if trust- worthy, will be received with much satisfaction. The accurancy of the figures cannot, however, be tested with- out a knowledge of the condition of the roads at the time the observations were made. If they were earth in a dry and hard con- dition, the cost seems high ; but if they were earth covered with mud and ruts or dry sand they are riot excessive. See also Table I, page 3. 1043b. Suppression of Dust. The advent of motor vehicles has raised what is known as the "dust nuisance/' and many experiments have been made both at home and abroad for the purpose of dis- covering a cheap, effective, and readily applied means of suppressing or abating it. It seems to be generally believed that the motor vehicles are the cause of the dust. This belief is erroneous. These vehicles would not produce an objectionable amount of dust if the dust was not already present on the surface of the road. The dust has always been present, but except during windy weather it has not been notice- ; 902 HIGHWAY CONSTRUCTION. able. Motor vehicles, however, because of their construction and the high speed at which they are run, raise more dust than the ordi- nary horse-drawn vehicle. The actual making of the dust, except to a very limited extent and on a surface composed of a very friable material, is not done by the wheels of the motor vehicles; they only put the dust in motion. The high velocity at which the vehicle is moving creates a vacuum into which the air rushes, and meeting the dust already disturbed by the wheels, takes it up and forms a cloud which follows the vehicle and is distributed in all directions, thus causing the nuisance com- plained of by other users of the road and residents along it. The dust is composed of the material used to fill the interstices or joints of the material forming the surface of the road, together with the fine material worn from the road-surface by the attrition of iron-tired wheels, horses' feet, the action of the elements, horse- 'droppings, and the silt and dust washed or blown from adjoining streets, roads, and lands. The amount of dust present on any road-surface depends upon the. character of the material composing it ; the greater the resistance 'offered by it to abrasion and disintegration the less dust will be formed. But the dust due to horse-droppings is independent of the character of the road material, and for equal amounts of traffic will be the same for all materials. The formation of dust and mud cannot be absolutely prevented, because all materials by attrition and the disintegrating action of the elements yield dust when dry and mud when wet. It will also be impossible to avoid the formation of dust and the presence of unsanitary constituents in the debris of streets and roads until mechanical traction is substituted for animals. If the surf ace of the road could be maintained in a moist condi- tion there would be no dust, but moistening with water even in cities, towns, and villages is expensive, and in rural districts the cost is prohibitive and the practice would be impracticable, owing to the absence of water available for the purpose. Hence in dealing with existing road-surfaces a remedy has been sought in more fre- quent cleansing and in the use of some substitute for water which would be cheap, effective, lasting, and easily applied. To meet this demand several "dust-laymg " compositions have been placed on MISCELLANEOUS NOTES. 903 the market. Experiments have been made with some form or other of these compositions, and it has been clearly demonstrated that, with but few exceptions, they have a very temporary effect, and their application must be frequent and systematic. The remedy in the case of new construction is to form the sur- face with a material possessing great resistance to abrasion and dis- integration; the first cost will be great, but the cost of maintenance and the formation of dust and mud will be reduced to a minimum. The methods so far employed for abating dust may be classed under two general heads : (A) those of a temporary or palliative character; (B) those of a more or less permanent character. Under the first head may be included : 1. MOISTENING WITH FRESH WATER. This is the simplest but not always the most practicable nor the cheapest. It can only be applied superficially, and its effects are very transient. The opera- tion must be repeated frequently during dry periods, and requires considerable force and proper equipment. The expense is permis- sible in cities and large towns, but prohibitive in small ones. 2. MOISTENING WITH SEA- WATER. This is a simple remedy but only available in places located on the sea-coast. The salts the sea- water contains are highly antiseptic and hygroscopic; a light sprinkling will keep the dust down for many hours. Its use, how- ever, is objected to for the reason that it injures the varnish and running-gear of vehicles, corrodes cast-iron street furniture, and when the surface on which it has been used has dried the dust then produced, containing salt, injures food and other goods exposed to it. Moreover, after a few weeks' use the mud is converted into a pasty mass which adheres to the wheels and causes the surface of the road to be " picked up." It is also noticed that broken-stone roads on which it has been used during the summer yield more mud in winter than when fresh water had been used. 3. MOISTENING WITH DELIQUESCENT SALTS. Several non- patented and patented solutions of deliquescent salts are on the market and extensively advertised as successful dust-layers. The chief advantage of these solutions is that their effect is more lasting than that of water and they are easily applied by the ordinary sprinkling-cart; but to secure the best results they must be frequently applied, and their cost is against them. Considerable 904 HIGHWAY CONSTRUCTION. difficulty is also encountered in obtaining a solution of constant strength except by constantly agitating the liquid in the distribu- ting-vessel; this is quite a material objection. Among the non-patented solutions may be named Calcium chloride, prepared by dissolving 112 pounds of chloride in 100 gallons of water. For the first application one-half gallon per square yard is used, and for the second one-third gallon. A few of the patented solutions are: Sandisize, which consists of the water used for washing wool. It contains grease, soap fats, and potash; its hygroscopic qualities cause it to keep the dust down for a considerable length of time (used in Scotland with good results). Fitzsimons' Patent Dust-layer, composed of sand, water, and soda, fused in a crucible and dissolved in water. Akonia, invented by Mr. D. de Liebhaber (composition not published), claims: That it does not make the road slippery; that it is non-injurious to health and has no harmful effect on horses' hoofs, vehicles or clothes, and is free from smell. The results of its use showed considerable dust-abating qualities by keeping the road damp when there was sufficient moisture in the atmosphere. The objection expressed was the destructive effect it had on the road, which was similar to that of frost. Hahnite, a saline admixture of oil and water, for which the claims are: That it forms an insoluble and impervious surface free from dust and mud, has no smell, and causes no injury to clothes, varnish, or rubber tires. Lyminite, a patented dust-laying preparation composed of nitrate of soda, sodium chloride, and lime. These ingredients are mixed together and heated. Water is added when the mixture has cooled; the liquid is applied by an ordinary sprinkling-cart. Cost said to be about $20.00 per mile of road 27 feet wide. 4. PAINTING OR COATING THE SURFACE WITH COAL-TAR. The idea of coating broken-stone roads with coal-tar is said to have been originally advanced by an Italian physician, Dr. Gugliel- minetti, practicing at Monte Carlo, and the method was first applied to the roads of Monaco. A French engineer named Chris- tophe also coated a portion of the streets in Sainte-Foy-la-Grande, Gironde, with tar more than twenty years ago, and since 1892: MISCELLANEOUS NOTES. 905 several streets in Saint Gaudens have been treated with it, and later an Italian named Rimini took out a patent for the process of applying it. In 1902, engineers Dreyfus and Andouin, of France, made the first systematic investigations to ascertain the dust-laying qualities of coal-tar. Three roads were selected at Champigny near Paris, one newly made, a second in good condi- tion, and the third in bad repair. The experiments showed that the coal-tar was successful in preventing the formation of dust and mud, that it successfully stood the action of vehicular traffic, rain, frost, and thaw, and that its use would reduce the wear and tear of the road and consequently reduce the cost of maintenance probably from twenty-five to fifty per cent. In England coal-tar has been used in many ways, and is found to effectively retard the formation of dust and to materially increase the life of the road. But after a period, shorter or longer according to local circumstances, certain defects appear. In wet or damp weather the tar produces a greasy, slimy mud, ruinous to clothes and productive of " side-slip " in vehicles, and though visible dust is obviated, an invisible dust is produced which is even more injurious than ordinary dust, because it blackens the articles on which it falls. Prior to applying the coal-tar the surface of the road must be prepared by removing the loose dust, stones, and other material. This should be done by sweeping and, if necessary, washing with water and scraping ; the hollows should be filled with new stone and the surface brought to a suitable contour. The success attending the coating with coal-tar will be propor- tional to the character of the road covering, its foundation, state of repair, cleanliness (in every case where the tar has been applied to a dirty surface it has been lifted or picked up by the traffic), quality of the tar, and the care exercised in heating and applying it. The coal-tar must not be overheated. A proper temperature seems to be about 140 F., and the best results will be obtained by heating it in small quantities (about 50 gallons) and applying it as rapidly as possible from hand-sprinkling cans of about 5 gallons capacity. In France an automatic heating and spreading machine, known as the "Laissailly " machine, is much used. The tar is heated by steam and automatically spread in a thin layer by four mechanic- ally operated brooms. 906 HIGHWAY CONSTRUCTION. The coating must be applied during dry weather, and the surface must be dry. Failure will follow its application to a wet or even damp surface. If it is necessary that the road be opened to traffic immediately after the application of the coal-tar, it is advisable to sprinkle the surface of the tar with fine grit or sand and roll it with a light roller, in order to prevent the surface from becoming slippery as well as to produce a dull surface, so that horses will not shy at the reflection of the sun. The sand, however, is a source of dust, and the avoidance of its use would be of considerable advantage; therefore if the road can be kept closed for a sufficient time to allow the tar to be thor- oughly absorbed by the road material, sanding will not be necessary. The amount of coal-tar required varies from one quart to five pints per square yard of surface. Coal-tar at Jackson, Tenn. In May, 1905, after fifteen years of use, it became necessary to repair the macadam streets of Jackson, Tenn. The material originally employed in the construction of these streets was the hard, almost non-absorbent, siliceous rock known as novaculite. The method followed in their restoration, as described by }.lr. S. C. Lancaster, city engineer, was as follows : The old surface was cleansed by sweeping with a horse-sweeper; the road material was next loosened by picks placed in the wheels of a 10-ton horse-roller; the street was then reshaped and new stone added where required; it was then sprinkled with water and rolled until a hard, compact, and even surface was formed; it was then allowed to dry thoroughly. Then coal-tar heated to about 210 F. was applied through a 1^-inch rubber hose, furnished with a 1-inch iron-pipe nozzle slightly flat- tened to produce a broad stream. When the tar was absorbed, which occurred in from a few hours to several days, the surface was covered with a light layer of clean sand or stone screenings and rolled with a steam roller. The surface resulting from this treatment is hard and smooth and resembles asphalt, except that it is more gritty. The tar penetrates the interstices of the stone to a depth ranging from 1 to 2 inches. The tarred surface is dustless in the same sense that an asphalt surface is dustless; a fine sandy powder wears off as in the case of asphalt, which can be removed by sweeping or washing. The tar used was that produced in the manufacture of coke ; the MISCELLANEOUS NOTES. 907 amount used per square yard was approximately 0.45 gallon. The cost of labor per square yard ranged from $0.0056 to $0.0095 (Circu- lar No. 47, Office Pub. Rds., U. S. Dept. of AgrL). 5. MOISTENING WITH SOLUTIONS OF COAL-TAR AND PETROLEUM. Several patented preparations of coal-tar and petroleum are on the market for the purpose of suppressing dust. The principle of all is practically the same, namely, the solution of the tar or oil in water by a volatile agent which on evaporation leaves a more or less insoluble coating on the surface of the road. A few of these solu- tions are: Tarvia, a preparation of coal-tar manufactured by the Barrett Manufacturing Company of New York, has been tried on broken- stone roads with very satisfactory results. As in applying coal-tar, the road-surface must be dry and thoroughly cleansed from dust and dirt. The tarvia is applied hot, being spread from a metal tank mounted on wheels, through a slotted sprinkler, at the rate of about one- quarter gallon per square yard. After coating the road is kept closed to traffic for a few hours to allow the composition to be absorbed. The surface is then covered with a thin layer of stone screenings and then rolled with a steam roller. The cost is stated to be less than one cent per square yard for the labor of sweeping, applying the composition, spreading screen- ings, and rolling. Adding the cost of screenings, the total cost varies from three to four cents per square yard, or about $400 a mile of road 16 feet wide. Westruritc, invented by a German chemist named Von Wes- trum, is composed of petroleum and ammonia; it has been ex- tensively used in Germany and England. The claims are that it is an effective and permanent dust-layer and a reliable disin- fectant; that but one application of a 10 per cent solution (90 parts water to 10 parts westrumite) is sufficient to render dustless an ordinary macadam road for a period varying from 2 to 4 weeks, according to the weather and the amount of traffic. The price of the composition is stated to be $50 per ton, and the cost of treating one mile of road 35 feet wide $90. Subsequent applications are made with a 5 per cent solution and cost about $50 per mile. It is claimed that the effect of frequent applica- 908 HIGHWAY CONSTRUCTION. tions is cumulative and the road improves considerably under the treatment; that bad weather has no effect on the preparation after it has been down for a short time. No special machinery is required, ordinary sprinkling-carts being used to apply it. The objections raised against westrumite in Chicago are : The cost, which is about 45 per cent greater than the cost of sprinkling with water; the disagreeable odor, which, however, disappears in about two days; the slipperiness it causes, although this is less than on sheet asphalt or wood blocks. It appears to cause disintegration of the limestone used for the macadam. When first applied it makes the driveway objectionable to pedestrians, although not more so than by heavy water sprinkling. In Liverpool, Eng., westrumite was tried on wood and granite block pavements. While it was effective in laying the dust, it was found that the pavements became too slippery for safe travel, and the cost was against it. Dustroyd, a liquid preparation of coal-tar, is insoluble in water, and is applied to the surface of the road in a fine spray under air pressure at the rate of about 3 tons per mile of road 24 feet wide for the first application, 1J tons for the second, and for the third application 1 ton or less. About 5? tons per annum per mile are required, at a cost of about $100. It has been noticed in France that the dust arising from roads on which some patented preparations of oil and tar had been used proved irritating to the skin and caused a painful inflammation of the eyes. This is attributed to the alkaline salts used to render the oil and tar soluble in water. 6. MOISTENING WITH CRUDE PETROLEUM AND RESIDUUM-OIL. Crude petroleum and residuum-oil have been extensively em- ployed both at home and abroad for the purpose of allaying dust. The results have been variable: in California, where it was first used, it has been uniformly successful; where failure has occurred it was probably due to unsuitable oil, improper methods em- ployed in its application, or unsuitable condition of the road- surface. The oil maybe applied either hot or cold; the hot oil, being more fluid, will under some conditions give better results. In applying the oil it must be thoroughly mixed with the dust. MISCELLANEOUS NOTES. 909 If it is merely sprinkled on the surface, only the top layer of dust will be impregnated; the wheels of vehicles and horses' feet will break up the cake so formed, exposing the dust below, and the road will be more disagreeable than before. If the surface is damp when the oil is applied, the mixture of oil and dust will become very sticky and will be removed in spots by adhering to the wheels. The presence of trees which make a dense shade seems to be detrimental to the oiled surface; the shade causes it to remain soft and muddy after a rain. In the oiling of broken-stone roads it is not desirable to loosen up the crust; the surface should be thoroughly cleansed by sweeping, and the minimum amount of oil applied by sprinkling when the surface is heated by the sun. after which it should be covered to a depth of about one-half inch with fine road material sand or fine gravel and then thoroughly rolled. After this coating has hardened the surface may be again oiled and the sanding and rolling repeated. The use of oil is objected to on account of the unpleasant odor and the damage it causes to the rubber tires and varnish of vehicles. Oiling Macadam at Jackson, Tenn. The oil used varied from a light crude oil to a heavy, viscous residue from the refineries. The surface of the macadam received no preparation beyond the removal of manure. The crude oils were used cold, distributed from an ordinary sprinkling-cart. The lighter oil soaked into the road-sur- face very quickly and left no coating on top. It caused the light covering of sand which was applied to pack down and gave the road a dark color. The amount of oil used per square yard was approximately 0.38 gallon, and the cost of labor averaged $0.0033 per square yard. The light crude oil produced little if any permanent results. The roads where it was appplied are but slightly changed, and some dust arises on them from traffic. The heavy residual oils, with one exception, were applied hot, because they were too thick to flow readily when cold. The experi- ence with the application of cold, heavy oil was that it formed a thick, sticky mass on top of the road, that rolled about under pres- sure and seemed to have an unlimited capacity for absorbing the 910 HIGHWAY CONSTRUCTION. sand which was spread upon it. The greater part of this mass of sand and oil had to be removed from the street. The heated oil was allowed to flow directly from the outlet of the tank onto the road, where it was spread over the surface by men with brooms. Twenty-four hours after the oil was spread it was covered with either sand or limestone screenings, and in four days it was firm enough to bear traffic without showing any wheel-tracks. It shed water well during a violent rain-storm. The amount of residual oil used per square yard was about 0.71 gallon, and the cost for labor was $0.0078 per square yard. The experiments indicate that excellent results can be secured by the use of heavy residual oil if it can be applied to the road-sur- face at a temperature approaching the boiling-point. The heavier oils produce a comparatively noiseless and dustless surface, which can be readily cleansed by sweeping. A medium-grade oil from Texas, classed by the refiners as " steamer oil," was tried. The road-surface was prepared by re- moving the heavy matter. The oil was heated by steam, but was cool when it reached the road; it was applied with a street-sprinkler. It mixed with the dust and formed a thin, compact crust, which pro- tects the stone from wear and produces a practically noiseless surface, free from the grinding noise and vibration experienced on the un- treated novaculite surface. 7. MOISTENING WITH OIL-TAR AND CREOSOTE. Oil-tar is the residual liquid from the manufacture of carburetted water-gas. It has the same odor and appearance as the tar produced from coal in the manufacture of gas, and is of such a nature that it can be dis- tributed over the road from ordinary watering-carts. From experiments made in England it appears that oil-tar is an effective, economical, and easily applied dust-preventative. The results of the experiment are stated as follows: The road- surface was treated in May and remained in good condition until the end of October. The oil-tar can be applied to the road without in- terrupting traffic; the liquid sinks rapidly into the road crust, so that vehicles can pass over it without inconvenience almost immediately after being applied. There was no tendency to "pick up " at any time, either when freshly put on or after rain. The application can be more expeditiously made than with coal-tar. The cost for the MISCELLANEOUS NOTES. 911 first application was about one cent per square yard, and each suc- ceeding application cost less, owing to the greater area covered per hour and per gallon of liquid. No " watering " was necessary, and scavenging, other than picking up horse-droppings, was very materi- ally reduced. No sand or grit was spread on the treated surface. The mode of applying the oil-tar is very similar to that practiced in the application of coal-tar. The surface of the road was prepared by thoroughly removing loose dust and horse-droppings. The oil-tar was heated in a suitable heater, run into hand-sprinkling cans pro- vided with coarse rose nozzles, and applied as rapidly as possible, and was brushed into the interstices of the surface with stiff tar brushes. The coatings were repeated until the interstices seemed well filled and the surface assumed an asphalt-like appearance. Creosote alone and mixed with rosin and tallow has been tried at Liverpool, England. The mixture of creosote and rosin was found to be the most effective; the odor of the creosote was objectionable, but was probably compensated for by the disappearance of flies. The application was made at intervals of three weeks, and the cost varied from one-half to one cent per square yard. The wood pavements in Liverpool were sprinkled with creosote; the dust was satisfactorily kept down, but the surface became slip- pery, and sanding had to be resorted to as a preventative. Under the head of more or less permanent methods are included the renewing of the road-surface with broken stone, gravel, slag, etc., cemented with a bituminous .cement, as coal-tar, asphalt, or other adhesive material. For this purpose several patented processes are on the market, among which may be mentioned Warren's Bitulithic (Art. 4500, Tur-macadam (Art. 450e), Whinery's Asphalt Macadam (Art. 450s), Massam's Macadam (Art. 450v), Wadsworth's Macadam (Art. 450w). In the use of the bituminous binders three methods are prac- ticed: (1) The existing LAFAYETTE s.e M OAKLAND 12.9 M ELEV.96ft NO. 1. ARRANGEMENT OF WORDING ON GUIDE BOARD. of good metallic or other suitable paint. The exposeds urface of the boards shall be 15 X 24 inches in size, each, except at the entrance to local roads, which may have but a single projecting arm 6 X 15 inches in size and affixed to a 4 X 4 inch post ; in all other particulars to be of similar construction to the larger size ; the wording and lettering to conform to the general plan indicated by the design accompanying this ordinance, and made a part thereof. All of the lettering upon the guide-boards, except the second line, which is in letters smaller than the others, and a section of eighteen inches of the two faces of the guide-post directly under the guide-board, shall be painted with luminous paint. SEC. 17. Upon all guide-posts the following notice shall be conspic- uously painted or stencilled : A PENALTY FOR DEFACING OR POSTING. SEC. 18. Whenever the provisions of Section 13 have been complied with as to road or roads, and guide-boards have been erected, the super- visors shall also cause a printed notice to be served upon the occupants of every residence upon such road r roads outside the limits of incor. 936 APPENDIX. porated towns, left at such residence, or, where the residence is distant a mile or more from the public or named roads, mailed to their address accompanied by a copy of this ordinance or abstract thereof. Such notice shall also be delivered or mailed to one of the officers of each school district and church of which the building is located upon said measured road. These notices shall have a blank form, to be properly filled with the exact location and correct number of the entrance to the house, with instructions as to the house number to be posted and maintained. SEC. 19. Every householder upon such measured road, residing outside the limits of incorporated towns, shall within thirty days after the service of the notice required in Section 18, post, and thereafter per- manently maintain in legible condition, upon the road or at the entrance or right of way from the road, the correct house number of his residence as given in said notice. It shall be placed in such a conspicuous posi- tion as to be easily seen and read from the centre or opposite side of the road. ^The figures shall be well proportioned, and of a size not less than three inches in height, nor more than four inches, except in town or vil- lage settlements, where the numbers may be one inch less in height and may be maintained upon the doorway or at the gate. The numbers must be neatly made, and in the style and manner that a professional sign-writer would use. SEC. 20. Any owner or occupant of any dwelling in the county which is reached by a private road or right of way is hereby permitted to post and maintain his house number upon the public highway at the entrance to such private road or right of way, or upon such private road or right of way, and he or she may place therewith his or her own name and business, provided such sign is made in a neat and tasteful manner, and conforms to the provisions of this ordinance. SEC. 21. Whenever the occupant of any dwelling upon a measured and numbered road shall fail for the* term of thirty days to maintain the proper house number at the entrance thereto, and having been noti- fied by the road officer to comply with the law shall fail to do so, he shall be deemed guilty of a misdemeanor. SEC. 22. Whenever any house upon a measured and numbered road now vacant shall be occupied, or any new dwelling-house shall be erected upon such road, it shall be the duty of the occupant within thirty days to properly post and thereafter permanently maintain, at the entrance thereto, the correct house number of the same as provided in this ordi- nance, and such residence shall thereafter come under the provisions of this ordinance the same as dwelling now occupied. APPENDIX. 937 SEC. 23. There shall be prepared for county use a book of records for the roads of the county, in which shall appear, arranged in proper order, under the name of each road, an index of all ordinances or other official action relating to that road, making such road record an official history of all the roads of the county. SEC. 24. A copy of all the field notes of the survey measurements, elevations, and other records, with the block and house numbers as provided for, shall be carefully preserved in the office of the county clerk, and open to the inspection of citizens as are other county records. SEC. 25. The execution of the work required by this ordinance shall be subject to the inspection and be made to conform to the requirements of a road committee to serve without pay, and to consist of three mem- bers, one to be appointed by the Board of Supervisors, one to be named by the road-naming committee who have prepared this plan, and the third to be chosen by the two thus appointed, and all to be confirmed by the Board of Supervisors; and any work of measurement, erecting guide-boards, or affixing numbers, shall not be held to be complete until approved by a majority of this committee. SEC. 26. It shall be the duty of the road officials to thoroughly inspect the roads within their respective districts and to make reports to the CONTRA COSTA HIGHWAY >ALAMO S.ZM DANVILLE 6.3M SANRAMON io.7M DUBLIN I3.4M LlVERMORE 19.6 M PACHECO 5.7M MARTINEZ IO.BM ELEV. 96ft NO. 2. GUIDE BOARD AT RIGHT ANGLES TO NO 1. Board of Supervisors at least as often as at the close of each six months of their terms of office, as to the condition of such roads, and any failure to comply with the provision of this ordinance. They shall also see that guide-boards are preserved in a legible condition and house numbers 938 APPENDIX. properly maintained, notifying residents of any neglect in this respect. It shall be their duty to report any person charged with violating the provisions of this ordinance, and to enter complaint against them in such case; they shall also have full authority to arrest any person or persons found defacing or removing block or house numbers, or muti- lating any guide-board, or posting any notice upon the post or boards, or in any way violating the provisions of this ordinance. SEC. 27. If any person or persons shall mutilate, deface, destroy, or remove any guide-board or guide-post, any block or house number, any name, sign, or advertisement which may be lawfully posted at or upon the entrance to the residence or dwelling of any person to whom such notice belongs, whether such entrance be public or private or through right of way, or shall mar, deface, or injure, by shooting, stoning, or otherwise, any guide-post or board, or shall fasten, or paint, or stencil any notice or advertisement to such posts or boards, save such as are required by this ordinance, the person or persons so offending shall be deemed guilty of misdemeanor, punishable, upon due conviction, by a fine of $50, one half of which shall go to the informer, or by imprisonment, or both. SEC. 28. The roads of the county, as enumerated in Section 29, are listed according to the following rule: Commence on the east side of a line extending due north from the county seat and work around in a circle to the east, southwest, and back again to the north, always facing outward and working from the county seat outward, and always from the left to the right. List first those roads touching the county seat; next the first left-hand branch roads, and any left-hand branches of these. Continue with the right-hand branches, follow with the remain- ing trunk roads and- their branches, left-hand branches first, right-hand branches next; omitting nothing on the left until the entire circuit has been made and the roads of the county are all listed. Under this rule the roads leading from Martinez, five of them are first listed; then the first of the five which have branches, No. 2, and then continued in the order explained above. SEC. 29. The following are the names of several public highways and private or local roads of the county, respectively hereby authorized and established. [List of 130 roads, among which are : Alpha Way, from Martinez to Bull's Head; Contra Costa Highway, from Martinez to County line via Pacheco, Walnut Creek, and San Ramon Valley; Alhambra Way, from Martinez to Pinole; Granville Way, from Contra Costa Highway, near Walnut Creek, to Vista Ignacio, Franklin APPENDIX. 939 Road; Teal Local; Tule Road, Pacheco Exit, Vine Hill Way; Locust Way, Plover Connex; Willow Pass Road; Flunaveg (River Road), Black Diamond Way; Empire Road; Paso Corto; Camino Diablo, Carbon Way; Arbor Connex; Lone Tree Road, Almond Way; Summer Road, Dry Creek Local; Zigzag Way, Sunol Local; Concord Lateral; Pomono Road; Ferndale Local; Golden Gate Way; Vaca Crescent; Verdel Circuit; Acorn Local, Highland Drive ; and Forest Road.] SEC. 30. This ordinance shall take effect and be in force on the 16th day after its passage. Passed March 8, 1892. 940 APPENDIX. II. METHODS OF ASSESSING THE COST OF STREET-PAVING. THE following summary shows the different methods employed for assessing the cost of street-paving. I. THE WHOLE COST BORNE BY THE ABUTTING PROPERTY; e.g., Albany, Brooklyn, Buffalo, New York, Rochester, Syracuse, Troy, N. Y. ; Boston, Mass.; Newark, Paterson, N. J. ; Philadelphia, Harrisburg, Scranton, Pa.; Baltimore, Md. ; Dayton, Ohio; Indianapolis, Ind.; Peoria, 111.; Milwaukee, Wis. ; St. Paul, Minn. ; San Francisco, Cal. ; Kansas City, Mo. II. THE WHOLE COST BORNE BY THE CITY AT LARGE J e.g., Portland, Me.; Manchester, N. H. ; Springfield, Mass.; Wilmington, Del.; Rich- mond, Va. ; Charleston, S. C. ; Nashville, Tenn. III. THE COST DIVIDED EQUALLY BETWEEN THE ABUTTING PROPERTY AND THE CITY; e.g., Washington, D. C.; Augusta, Ga.; Montgomery, Ala. IV. THE COST DIVIDED IN PROPORTION OF TWO-THIRDS ON THE ABUT- TING PROPERTY AND ONE-THIRD ON THE CITY,' e.g., OsWCgO, N. Y. J Hart- ford, Conn. ; Atlanta, Ga. ; Jacksonville, Fla. V. THE ABUTTING PROPERTY PAYS FOR ITS FRONTAGE, AND THE CITY PAYS FOR INTERSECTIONS; e.g., Allegheny, Pa.; Sioux Falls, S. Dak. VI. THE ABUTTING PROPERTY PAYS FOR THE GRADING, THE CITY PAYS FOR THE PAVING; e.g., Lowell, Worcester, Mass.; Providence, R. I. VII. THE CITY PAYS FOR THE GRADING AND ONE-THIRD OF THE PAV- ING, THE PROPERTY PAYS THE REMAINING ' TWO-THIRDS J e.g., Hartford, New Haven, Conn. ; Atlanta, Ga. VIII. THE CITY PAYS ONE-HALF COST OF GRADING AND ALL COST OF INTERSECTIONS, THE PROPERTY PAYS THE REMAINDER,' e.g., Salt Lake City, Utah. IX. THE CITY PAYS FOR ONE-HALF THE GRADING, THE ABUTTING PROPERTY THE OTHER HALF AND THE WHOLE COST OF THE PAVING,* C.g.J Omaha, Neb. X. THE CITY PAYS ONE-FOURTH OF THE WHOLE COST, AND THE PROP- ERTY THREE-FOURTHS; e.g., New Orleans, La. APPENDIX. 941 XI. ClTY PAYS FOR GRADING AND FOR THE PAVING OF STREET AND ALLEY INTERSECTIONS; e.g., Detroit, Mich. XII. THE COST DIVIDED BETWEEN THE CITY AND THE PROPERTY IN DIFFERENT PROPORTION; e.g., Cincinnati, Ohio, city pays 2%, prop- erty 98%; Cleveland, O., city pays -fa and intersections, property f$. XIII. THE CITY PAYS FOR GRADING; COST OF PAVING ASSESSED UPON ABUTTING PROPERTY IN PROPORTION TO BENEFIT, DETERMINED BY APPRAISERS SPECIALLY APPOINTED; e.g., Topeka, Kan. XIV. THE WHOLE COST PAID BY THE ABUTTING PROPERTY IN PRO- PORTION TO ITS VALUE; e.g., Little Rock, Ark. When the assessment is by improvement districts, all land, including street areas, between termini of the improvements and within a fixed distance (usually one-half the depth of the block) of the street line on each side of the street improved constitutes an improvement district, except that when a cross-street has already been improved its area is excluded. The area on each side of the street-lines is divided into zones by lines drawn parallel to the street-line. The number of the zones may be three, four, or more. When four are used the total cost is levied on the area within the zones in the proportion of 40 per cent on the one immediately adjoining the street, and on the other at the rate of 25, 20, and 15 on the most remote. In some cases the centre line of the street to be improved is taken as the base for the zones; in this case the city at large pays the assessment charged to the street area. In all cases where the assessment is made by frontage, the location or value of the property is not taken into account. In cases where the cost is borne by the city at large it is paid either from the general tax or by the emission of bonds or improvements cer- tificates. The practice of assessing corner lots varies. In Louisville, Ky., they pay 25 per cent more than inside lots. In Portland, Ore., the corner lot is assessed f and the one adjoining f . The street-railway companies are assessed in various ways : 1. Directly for the area occupied by them. 2. Are required to do the paving and maintain the space between their rails and from 1^ to 2 feet outside the rails. 3. They are required to maintain the pavement from curb to curb, as in Philadelphia. 942 APPENDIX. 4. A certain proportion of the cost is assessed against them, as in Brooklyn. Renewals and Repairing are paid for either by the property or the city. The following are examples : City pays: Albany, N. Y., ; Brooklyn; N. Y.; in special cases; New York; Paterson, N. J.; Scranton, Pa., ; Dayton; 0.; Detroit, Mich. Property pays: Albany, N. Y., ; Syracuse, N. Y.] Newark, N. J.; Scranton, Pa.J . APPENDIX. 943 III. ORDINANCE REGULATING THE WIDTH OF WAGON-TIRES 1. The owner, driver, or person for the time being employing or having the care or control of any wagon, truck, cart, or carriage drawn by animal power shall not cause or suffer such vehicle to be used on any road or highway in contravention of any such of the following regula- tions as may be applicable to such vehicle, that is to say : 2. No wagon, truck, cart, or carriage shall be used on any road of which the felloes or tires at the bottom or soles of the wheels are not of the width in proportion to the gross weight as hereinafter mentioned, such gross weight including not only the persons, load, or things carried by such vehicle, but also the weight of the vehicle itself. The tires must be neither concave nor convex. Description of Vehicle. Gross Weight, Pounds. Two Wheels. Four Wheels. Without Springs. With Springs. Without Springs. With Springs. Width of Tire. Width of Tire. Inches. Inches. Inches. Inches. Less than 2,000. . . 2,000 and less than 3,000. . . 3,000 U i " 4,000... 4,000 U ( " 6,000... 6,000 U ( " 8,000... 8,000 U ( " 10,000... 10,000 U I " 12,000... For the transportation of loads exceeding 6 tons special permits must be obtained 3. The owner, driver, or person for the time being employing or having the care or control of any wagon, truck, cart, or carriage drawn by animal power on any road or highway shall not cause or suffer the 944 APPENDIX. wheel of such vehicle to be locked when descending a hill, except the hill be in a slippery condition from ice or snow, unless there be placed at the bottom of such wheel, during the whole time of its being locked, a skid-pan, slipper, or shoe, in such manner as to prevent the road from being destroyed or injured from the locking of such wheel. No vehicle shall, when descending a hill, have both hind wheels locked. 4. No vehicle shall have any nail or bolt on the tire of any wheel which shall not be countersunk so as not to project beyond one-quarter of an inch above any part of the surface of the tire of such wheel. 5. The driver or other person having for the time being the care or control of any wagon, truck, cart, or carriage shall, upon demand made to him by the county engineer, or any of his assistants, or by any officer duly appointed, empowered, or instructed in that behalf by the county authority of the county of or by any police officer, stop such vehicle, and permit the person so demanding to examine for a reason- able time the wheels thereof, or the nature and amount of the loading thereof, with the view of ascertaining whether all or any of the regula- tions aforesaid are then being contravened. 6. The driver or other person having for the time being the control or care of any wagon, truck, cart, or carriage shall, upon demand made to him by any such person as aforesaid, cause such vehicle, together with the loading thereof, to be driven to any weighing-machine for the purpose of being, and shall cause or suffer the same to be, weighed thereby on or thereon, provided that such driver or person shall not be required to drive or cause to be driven such vehicle, together with the loading thereof, to such weighing-machine if at the time when such demand as aforesaid shall be made, such vehicle shall be at a greater distance than half a mile from such weighing-machine. 7. Every person who shall break any of the regulations of this ordi- nance shall be deemed guilty of a misdemeanor, punishable, upon due conviction, by a fine of $10, or by imprisonment, or both. 8. This ordinance shall take effect and be in force on the day of , 18 APPENDIX. 945 IV. CYCLE-PATHS Cycle-paths through the country may be constructed according to the most elaborate specifications for broken-stone road construction, or consist simply of a bed of gravel or cinders slightly raised above the adjoining surface. In city streets, strips of asphalt or brick pavement are the most suitable. Location. In the country the paths should be placed at one side of the roadway and so protected that wagons cannot use them. In city streets the best location seems to be adjoining the curb, and there should be a path on each side of the street so the cyclists can move in the same direction as the traffic. Width. Six feet is the minimum width to allow wheelmen to meet and pass without danger of accident. Single paths at the side of streets should be 3 feet wide. Crown. Paths 3 feet wide should have a crown of 1 inches. ii a (i (( ii it it tt tt o t( o (I 1Q <( It It It tt tt tt A It tt -10 it a (i tt tt tt it a u Grades should be as flat as possible. Drainage. In paths through the country attention must be paid to the drainage. Construction. Gravel or cinders should have a thickness of 3 inches and should be well rolled. The gravel should pass through a inch screen. If a foundation is required, it may consist of cinders 4 inches thick, thoroughly rolled and covered with a layer of loamy clay inch thick, moistened and rolled. A mixture of sand and loamy clay in suffi- cient quantity to bind the sand has given good results. Broken Stone (Brooklyn, N. Y.). Foundation consists of gravel covered with a layer of broken stone 3 inches thick, rolled with a steam- roller and covered with stone screenings from i to ^ inch in size. INDEX. ARTICLE PAGE 87?. Abrasion of artificial stone (Table XIV 3 ) 52 870. asphalt (Table XIV 3 ) 52 870. basalt (Tabl ei XIV 3 ) 52 87g. Bauschinger machine for testing 50 870. Dorrey machine for testing 49 870. granite (Table XIV 3 ) 52 870. limestone (Table XIV 3 ) 52 870. Maryland Geological Survey for testing 50 870. paving-brick (Table XIV 3 ) 52 870. quartz (Table XIV 3 ) 52 870. resistance to 48 87r. Deval machine for testing 53 87r. impact 52 870. sandstone (Table XIV 3 ) 52 870, 355. tests of 48, 300 Absorptive power of bricks (Table XXI) 115 cement (Table XLIV) 400 granite (Table XIV 2 ) 48 limestones (Table XIV 2 ) 48 87p. method of testing 47 119. paving-bricks (Table XXI) 115 sandstones (Table XIV 2 ) 48 stones, etc. (Table XIV 2 ) 48 121. wood (Table XXII) . 121 706. Abutments for pipe-culverts 537 714. thickness of (Table LXXVI) 548 22. Accidents to horses 10 754. Accommodation summits 579 862. Accounts 673 872. Acids, resistance to 61 947 948 INDEX. ARTICLE PAGE 617. Acres, number of, required per mile, for different widths of roads (Table LXIII) 486 410. Action of the weather 333 482. Activity of cement 398 486. tests for 400 9. Adaptability of pavements 4 641. Adhesion of earth 494 500. Adhesive strength of mortar (Table XLV) 408, 409 751. Adjustment of grades at street-intersections 575 221. Advantage of asphalt pavements 197 281. and coal-tar pavements 241 103o. bitumen . 91 305. brick pavements 258 346. broken-stone pavements 290 281. coal-tar and asphalt pavements 241 188. creosoting wood 164 142. granite-block pavements 132 511. mixing concrete by machinery 422 511. mixing mortar by machinery 422 396. rolling broken-stone pavements 320 13. smooth pavements 6 153. sorting granite blocks at the quarry 137 398. steam-rollers ' 321 439. stone trackways 356 550. wheels 451 177. wood pavements 156 485. Age, effect of, on cement 400 505. strength of mortar 414 61. Agencies causing destruction of paving materials 24 1030. Agreement, form of 778 63a. Air, effect of, on paving materials 25 Albany, early pavements in xxxix 584. Alignment of roads 465 1025. Alteration of manhole heads, etc 771 92a. American asphaltum 65 99e. bituminous rock 75 300. cost of construction 250 303. pavement, specifications for 250 297. pavements 249 473. natural cements, colors of 392 473. specific gravity of 392 103a. Ammonia, action on bitumen 91 256. Amount of asphaltic cement made by one ton of refined asphaltum. . 222 388. . binding material required for broken-stone pavements. . . . 314 103a. bitumen in asphaltic paving-cement 89 INDEX. 949 ARTICLE PAGE Amount of bluestone used for street purposes (Table XI) 38 874. dirt produced by different pavements 698 25. removed from streets 10, 697 70. granite used for street purposes (Table VII) 32 limestone used for street purposes (Table XIII) 40 412. material required to replace wear on broken-stone pave- ments 339 414. material used to replace wear on broken-stone pavements in England 339 414. material used to replace wear on broken-stone pavements in France 339 $1 at compound interest for a term of years (Table LXXXIX) . . 915 256. paving-cement manufacured from one ton of refined asphaltum . 222 699. rainfall 532 refuse collected from city streets (Table LXXXVT) 697 404. rolling 324 sandstone used for street purposes (Table X) 38 366. stone broken by hand 307 618. transverse rise required for different pavements (Table LXIV) 488 859. water required for sprinkling broken-stone roads 665 913. required for street sprinkling 722 Sip. Amphibolite, water absorbed by (Table XIV 2 ) '. 48 102. Analysis of asphalt, Barbadoes (Manjak) 67 101, 265a. Bermudez asphalt 66, 85, 234 Buena Vista 86 California (Alcatraz) (Table XIVo) 66 asphalts 86 Bakersfield 85 Kern Co 86 fe ^ is. Patera (Table XlVa) 66 Santa Barbara Co 86 Ventura Co 86 Waldorf (Table XlVa) 66 Cuba, Bejucal (Table XlVa) 66, 87 European (Table XV) 76 Forens (Table XV) 76 Indian Territory, Ardmore (Table (XlVa) 66 Chickasaw (Table XlVa) 66 Kentucky (Table XlVa) 66 Lobsan (Table XV) 76 Maestu (Table XV) 76 Manjak 67 950 INDEX. ARTICLE PAGE Analysis of asphalt, Pittsburg asphaltic flux 70 Port Neches, Texas 87 Seyssel (Table XV) '. 76 Sicilian (Table XVj 76 Texas, Uvalde (Table XlVa) 66 Trinidad (Table XVI) 66, 79 Utah, gilsonite (Table XlVa) 66 liquid 70 Val de Travers (Table XV) 76 99/. bituminous limestones, Hthocarbon 76 Utah 77 102. sandstones, California, Ventura Co 86 Kentucky 77 Utah 77 116. clay (Table XX) 110 granite (Table V) ' . . . 31 345. macadam pavement 290 sandstone (Table VIII) 36 shale 107 131. Tompkins Cove gravel 126 103a. and tests of asphalt 88 Sip. Andesite, water absorbed by (Table XIV 2 ) 48 596. Angle of repose 472 645. of earths 495 Angles of slopes (Table LXVI) 495 Annual cost per capita for street maintenance in the United States (Table LXXXVII) 700 43. Annual cost of pavements 16 1045. structures . j 912 wood pavements in London (Table XXXI) 169 103a. Apparatus for penetration tests of bitumen 88 89a. Appearance of asphaltum 62 405. broken-stone pavements after being rolled 325 267. European bituminous limestone 235 IQOd. Trinidad asphaltum 79 Appian Way xxxii 712. Arch-culverts ' 544 960. specifications for 745 713. thickness of (Table LXXV) 544-546 878, 895. Area cleaned by machine-brooms 704 878. Area cleaned by one man 704 793. covered by a barrel of Portland cement 614 375. cubic yard of broken stone 309 792. concrete 61? 256. prepared asphalt ~~ INDEX. 951 ARTICLE PAGE 171. Area covered by a ton of granite blocks (Table XXVI) 149 302, 778. prepared rock-asphalt (Table LXXXIV), 250, 597 of tile-drains (Table LXXVII) - 549 99. water-way of culverts 532 404. rolled by steam-roller per day 324 895. swept by machine-brooms 711 894. one man . 711 674. Areas, sectional, of earthwork, formula for calculating 517 745. Arrangement of city streets 568 751. street-intersections 575 streets with opposite sides at different levels 581 979. Artificial foundation, specifications for 755 443. granite blocks 358 450p. paving stone 377 475, 4500. Portland cement 370, 393 815. stone curb 632 822. and gutter, specifications for 636 786. footpaths 610 796. specifications for 616 825. hollow curb 638 450/. pavements 369 794. wear of 614 Asphalt, Alcatraz, composition of (Table XIVo) , 66 96d. liquid 69 amount produced in the United States (Table XVIII) 102 analysis of (Table XIVo) 66 103a. methods of 88 450r. and broken stone 377 279. coal-tar 240 281. pavements, advantages of 241 285. cost of maintaining 242 282. defects of 241 291. specifications for 243 106. paving pitch 105 89a. appearance of 62 Arkansas, amount produced in (Table XVIII) 102 provided in (Table XVIII) 102 value of production (Table XVIII) 102 . 92a, 936. asphalte 65, 66 103, 267. comprim6 88 103. coule 88 90. asphaltene 63 90a. color of 64 90a. composition of 64 45Qq. asphaltina, composition of 377 952 INDEX. ARTICLE PAGE 88a. Asphalt, asphaltum, definition of 62 105. uses of 103 Barbadoes, analysis of 67 Bermudez, asphaltene in 85 10L bitumen in 85 101, 102c, 265a. characteristics of 84, 87, 234 102c. compared with Cuban 87 composition of (Table XlVa) 66 101. deposit of 84 103a. ductility of ' 99 flowing-point of 85 imports to the United States (Table XIX) 103 101, 265a. manufacture of paving-cement 84, 234 101, 265a. melting temperature 84, 234 101. mineral matter in 84, 85 101, 265a. organic matter in , 84, 85 paving-cement, properties of (Table XVIa) 87 265a. paving mixture, composition of 234 265a. laying of 234 petrolene in 85 101. refining, process of . 84, 85 retine in 85 softening point of 85 101. specific gravity 84, 85 265a. thickness of cushion coat for 234 265ot. wearing surface 234 102c. value of imported (Table XIX) 103 265a. water, action of, on 234 265a. weight per square yard 234 986, 996. bituminous limestone 73, 75 102. sandstone 86 102a. Buena Vista, composition of 86 99?. calcareous sandstone 77 252. calcium carbonate, action of, on 217 252. oxide, action of, on 217 California, amount produced (Table XVIII) . 102 analysis of Alcatraz (Table XlVa) 66 asphalts 86 Bakersfield 85 Kern Co 86 Patera (Table XlVa) 66 Santa Barbara Co 86 Ventura Co 86 Waldorf (Table XTVa) 66 value of production (Table XVIII) 102 INDEX. 953 ARTICLE PAGB 252. Asphalt, cement, ageing of bitumen, effect of j. 91 103a. ammonia, effect of, on 91 103a. amount in paving mixture 89 103a. made from one ton of asphalt 211 102c. Bermudez and Cuban, compared 87 235, 235a. composition of 234 103a. Bowen's penetration apparatus 92 102a. Buena Vista 86 102. California 86 252. carbon, action of, on 217 103a. changes in, due to temperature 90, 92 lOOo. consistency of 83 102c. Cuban, used in Washington 88 96. denned 68 103a. Dow's penetration apparatus 93 103a. ductility of 99 method of determining 99 various 99 97. endurance, essentials to 70 97. manufacture of 68 243. pavement, composition of 213 103a. penetration tests 92 Bowen's apparatus for 92 District of Columbia standard 96 Dow's apparatus for 93 103a. softness, methods of determining 92 262, 2646. specifications for 224, 230 103a. stability of the bitumen 90 103a. tensile strength of . . 97 253. Trinidad, composition of 220 1CKH', 103a. water, effect of 81,91 89a. Chapapota 62 95c. coking, effect of 68 103a. comparative qualities of 100 102c. Cuban, analysis of 87 102c. composition of bitumen (Table XlVa) 66 88. definition ot 62 99/. deposits in the United States 75 89a. earthy variety 62 896. elastic . , 62 European, amount imported to the United States(Table XIX). 103 analysis of (Table XIV) 76 value of imports (Table XIX) 103 303a. expansion, coefficient of 251 319. fillers for joints 267 954 INDEX. ARTICLE PAGE 96a. Asphalt, flux for 69 96rf. Alcatraz liquid 69, 70 98. Maltha 72 97a. petroleum residuum 70 97a, 98. considered injurious 70, 72 976. examination of 71 97c. preparation of 71 96d. quantity required 72 97d. specifications for 72 96d Pittsburg 69, 70 96o. requirements of 69 96d. Utah liquid 70 966. fluxing, process of 69 257. temperature of 222 778. footpaths 596 781. European rock 600 780. 781. foundation for 598, 600 779. life of 598 778, 781. proportions of materials 597-600 781. specifications for Paris 600 780. Washington, D. C 598 782. tile for . '. 607 782a. specifications for 607 780. Trinidad, cement for 598 450. granite 377 88a, 89c. hard 62 274. heat, a bad conductor of 238 imports to the United States (Table XIX) 103 Indian Territory, amount produced (Table XVIII) 102 analysis of (Table XlVa) 66 value of production (Table XVIII) 102 Kentucky, amount produced (Table XVIII) 102 analysis of (Table XlVa) 66 preparation of 77 specifications for 77 value of production (Table XVIII) 102 99e. limestone, American 75 analysis of European (Table XV) 76 996, 266. bitumen, amount in 75 996. characteristics of 75 996. color of 75 996. composition of 75 99c. European 75 93c. lithocarbon 76 Lobsan (Table XV) 76 INDEX. 955 ARTICLE PAGE 99e. Asphalt, limestone, location of deposits 75 99/, 266. preparation of for paving 75, 235 996. softening temperature 75 996. specific gravity 75 268. test for 235 93d. liquid 66 434, 435. macadam, in England 351, 352 434. Paris 351 434. preparation of 351 450Z. Warren's patent. : 379 450s. Whinery's patent 378 Maestu, analysis of (Table XV) 76 88a, 91, 91a, 93d, 94. Asphalt, Maltha 62, 64, 66 Manjak 67 89c. melting-point of 62 896. mineral caoutchouc 62 103. Asphalt mastic, asphalte coule 88 103. described 88 781. footpaths, composition 600 781 laying 600 781. maintenance 600 781. Paris 600 781 preparation 600 103 manufacture of. 88 103. use of. 88 93. mineral pitch 66 88a, 94. tar 67 Missouri, amount produced in (Table XVIII) 102 value of production (Table XVIII) 102 88a, 91. naphtha 62, 64 93. native pitch 65 252. natural changes in 218 93. nomenclature 65 92. occurrence of 64 89a, 89c. odor of . 62 oil, amount produced in United States (Table XVIIIa) 102 value of production (Table XVIIIa) 102 966. oiling of 69 91. origin of 64 292. pavement (block) 246 293. advantages of 247 292. composition of 246 294. cost of construction 247 295. maintenance . 248 292, defects of . . . 247 956 INDEX. ARTICLE PAGE Asphalt pavement (block), extent and cost in various cities (Table XXXVI) 248 292. manufacture of 246 296. specifications for 248 217. (sheet) 195 abrasion, resistance to (Table XIV S ) 52 225. adjoining car-tracks 201 221. advantages of 197 245. aggregate for 214 246. quality of 214 218. American 195 222. less slippery than European 198 874. amount of dirt produced by 698 19. and rain 9 894. area cleaned by one man 711 218-243. artificial and natural 195 251. binder, composition of 215 251. course 215 251. object of 215 251. omitted 215 262, 263, 2646 specification for 225, 229, 231 224. brick gutter for 199 244. cement, amount in 213 243. defined 213 247. 250. Portland, use of 214, 215 243. composition of 213 250. compressing 215 262. specifications for 225, 226 303d. condition at end of guarantee 255 877, 889. cost of cleaning 700 232. construction 206 233. maintenance 206 618. crown for (Table LXIV) 488 251. cushion coat 215 262. specifications for 225 227. durability of 204 222. defects of 197 218. difference between American and Euro- pean 195 303&. disintegration of 253 222. effect of cold on 198 222. neat on 198 ^22. moisture 198 266. European 235 259. in Washington, D. C 223 INDEX. 957 3036. Asphalt pavement (sheet), expansion joint in 252 303a. of 251 extent of in United States (Table XXXV) 208 252. failure, causes of 216 252. asphalt unsuitable 216 252. binder defective 220 3036. cement, excess of 251 252. insufficient 217 252. chilled mixture 218 coal-tar 219 252. compression insufficient . . 218 252. concrete damp 216 252, 3036. defective bond 216, 220 252, 3036. disintegration by gas .216, 220 252, 3036. oil. .216, 220 252, 3036. water . . 219 252. flux unsuitable 216 252. foundation damp 217 252. weak 218 252. ingredients, insufficient mixing of 217 252. limestone dust 217 252. natural causes 218 oil unsuitable 219 252. sand unsuitable 216 252. temperature improper working 216 252. weak foundation 218 252. wet foundation 217 17. falls of horses on 8 225. fire, injured by 202 240. foundations for 212 241. bituminous concrete 212 241. cement concrete 213 240. old pavement 212 259. French, in Washington, D. C 223 222. grade, maximum 198 224, 250. gutter brick 199, 215 250. granite 215 250. waterproofing 215 222, 1049a. heat, effect of 212, 922 250. hydraulic cement in rolling 215 226. injured by gas 202 229. in London 205 266. Paris ... .235 958 INDEX. ARTICLE PAGE 230. Asphalt pavement (sheet) in St. Louis 205 258. Washington 222 217. introduced 195 3036. irregular cracks in 251 239. items comparing cost of 212 249. laying of 214 250. rolling 215 250. smoothing-irons 215 262. specifications for 225 251. spreading-rakes 215 250. tamping-irons 215 27. life of 11 247. limestone dust 214 247. proportions of . . 214 248. quality 214 247. size 214 536. load hauled by horse on (Table LVII) 444 1039. machinery employed for 856 265. maintenance, by contract 232 233. cost of (Table XXXVa).206, 211 244. matrix, proportion of 213 601. maximum grade for 473 256. memoranda 222 256. mixture, area covered by cubic yards 222 249. preparation of 214 257. reheating of 222 257. use of cold 222 256. weight of 222 222. moisture, effect of 198 natural rock 77 247, 250. Portland cement, use of 214, 215 249. preparation of 214 262, 263, 264. specifications for 224, 229, 230 257. reheating surface mixture 222 303/. reinforced with steel 257 3036. repairing, cost of (Table XXXVa) 211 3036. cracks 251 disintegration 253 3036. methods of 251 222. necessity for quick , . . . 198 3036. Perkin's heater for 253 303e. recording methods of 256 3036. rolls 252 3036. skimming process 253 303c. specification for 253 INDEX. 959 ARTICLE PAGE 250. Asphalt pavement (sheet), rollers for, price of 863 type of 215 250. weight of 215 250. rolling, amount of . 215 21, 223. sand, cure for slipperiness 10, 198 246, 252. quality for wearing surface 214, 216 224. temperature for 222 224. sea water, effect of, on 220 19. slipperiness, conditions causing 9 223. remedy for 198 262, 263, 264, 264a, 2646. specifications for 224, 229, 230, 231 249, 251. spreading 214, 215 262. specifications for 226 257. temperature for 222 247. stone-dust for 214 225. street-car rails, effect of 201 1049. temperature of 922 249, 251. thickness of 214, 215 1039. tools employed for 856 traction resistance to (Table L) 437 228. traffic sustained by 205 253. Trinidad, described 220 262. specifications for 224 901. washing of 721 224, 252. water, effect of, on 198, 219 224. methods to reduce 199 231. wear of 206 Pennsylvania, amount produced in (Table XVIII) 102 value of production (Table XVIII) 102 90, 90a. petrolene 53 color of . 63 composition of 63 percentage required for paving 63 91. petroleum 64 97a. residuum 79 79c. preparation of 71 97d. specification for 72 Pittsburg asphaltic flux, analysis of 70 1026. Port Neches, Tex., analysis of 87 104. prices of (Table XVII) ; ./.......... " 101 production in the United States (Table XVII) 102 95. refined, definition of 67 95. refining, Bermudez 67 956. calcareous 68 95-100e. process of 67-79 960 INDEX. ARTICLE PAGE 956. Asphalt refining, silicious 68 95a, 257. temperature of. 67, 222 95c. effect of high 68 95c. low 68 95. Trinidad 65 90a. retine 64 90a. color 64 90a. composition 64 996. rock 75 297. pavement, American ; 249 303. amount of bitumen in 250 300. cost of construction 250 301. maintenance 250 299. durability of 249 303. laying of 250 990, 298. preparation of 249 303. specifications for 77, 250 218. European 197 analysis of (Table XV) 76 92o, 936. asphalte 65, 66 267. comprime 235 266. coule 235 cost of maintenance (Table XXXVa) 211 268. Delano's test for 235 227. durability of 204 259, 277, experience with, in Washington, D. C 223, 239 217. first laid 195 778. footpaths 597 275. laying ." 238 99c. location of mines 75 269. mining the rock 236 272. preparing the rock 237 231. wear 206 100*'. salts, removing from 81 94, 990. sandstone 66, 74 analysis of 66 9906. composition of 76 956. extraction of bitumen 68 Kentucky 66 preparation of 77 990. specifications for 77 Seyssel, analysis of (Table XV) 76 Sicilian, analysis of (Table XV) 76 INDEX. 961 ARTICLE PAGE 252. Asphalt, silicic oxide, action of, on 217 89c. solubility of 62 89c. solvents for 62 219. sources of supply 196 89c. specific gravity 62 96d. standard liquid 69 lOOe. tanks for refining 80 966. tempering of . '. 69 103a. tensile strength of 97 100*. test for action of water 81 103a. testing 88 100. Texas, amount produced (Table XVIII) 102 composition of (Table XlVa) 66 value of production (Table XVIII) 102 tons imported to the United States (Table XIX) 103 100. Trinidad 78 100;. acids in 82 analysis, lake (Table XVI) 79 land (Table XVI) 79 lOOn. bitumen in (Table XVI) 79, 83 lOOn. cement 82 lOOa. cheese pitch 78 WOd. color of crude 79 lOOn. refined 82 composition of bitumen (Table XlVa) 66 lOOd, lOOw. crude 79, 83 100. deposit described 78 103a. ductility of 99 lOOc. epuree 78 100-9. Europe, use in 84 lOOd, lOOw. flowing-point of (Table XVI) 79, 83 1005. Goudron compose 84 imports to the United States (Table XIX) 103 lOOd, lOOn. inorganic matter in (Table XVI) 79, 83 1006. iron pitch 78 lOOr. lake and land, difference between 84 OOp. relative quality of 83 100. lake pitch 78 lOOa. land pitch 78 lOOn. manufacture of cement 82 lOOd, 100m, lOOn. organic matter in (Table XVI) 79, 82, 83 lOOa. overflow pitch 78 253. pavement, composition of 220 1 OOo, lOOn. paving cement 82, 83 lOOn. refined, characteristics of 82 962 INDEX. ARTICLE PAGE 1 OOe. Asphalt, Trinidad, refining process 79 l\)0p. relative qualities, lake and land 83 ICO*, salts in ' 81 100*. removing by washing 81 100*. specification for removing . . . 81 lOOw. softening temperature (Table XVI) 79, 83 lOOn. specific gravity 79, 83 value of imported (Table XIX) 103 lOOi, lOOp. water, action of, on 81, 83 Utah, amount produced (Table XVIII) 102 analysis of (Table XlVa) 66 96d:. liquid 70 QQq. calcareous sandstone 77 value of production (Table XVIII) 102 Val de Travers, analysis of (Table XV) 76 value of imports to the United States (Table XIX) 103 production in the United States (Table X Villa) 102 varieties produced in the United States (Table XVIIIa) 102 weight of (Table XXIV) 127 Assessing the cost of street-paving, methods fftr 940 1012. Assignment of contract 763 153. Assorting granite blocks at the quarry, advantage of 137 410. Atmospheric changes, effect of, on pavements 333 216c. Australian wood pavement 188 418. Austria, amount of material used in, to replace wear on broken-stone pavements 341 1036. Aveling & Porter steam-roller 850 Average width of sidewalks in various cities (Table LXXXII) 57ft B. 629. Balancing transverse of earthwork 491 881. Baltimore, street- cleaning in 706 86. Basalt, description of 41 resistance to crushing of (Table XXIV) 127 specific gravity of (Table XXIV) 127 weight of (Table XXIV) 127 897. Bass brooms 712 136. Belgian block pavement 131 172. cost of construction (Table XXVIII) 151 137. defects of 131 172. extent of (Table XXVIII) 151 138. specifications for 131 traction resistance to (Table L) 437 INDEX. 963 ARTICLE PAGE 418. Belgium, cost of maintaining broken-stone pavements in 341 572, 940. Bench-marks 456, 738 32. Benefit, economic, of good pavements 13 162. Berea sandstone , 141 101, 265a. Bermudez asphalt 84, 234 745. Best arrangement of city streets 568 459. Beton 385 1029. Bid, form of 777 1028. Bidders, instruction to 773 391. Binding, effect of 318 388. using large quantities 314 386. for broken stone 313 390. necessity of 317 430. power of clay 350 389. proportions adopted by the French engineers 314 388. quantity of 314 897. Birch brooms 712 450. Bitulithic pavement, Warren's 379 100s. Bitume compose 84 1005. rafine 84 88, 94. Bitumen 62, 66 103a. action of water and ammonia on 91 103a. ageing of 91 103a. amount in asphaltic paving-cement 88 103a. to determine 89 Trinidad asphalt (Table XVII) 79 103a. Bowen's penetration apparatus 92 103o. change of, due to age 91 composition of (Table XlVa) 66 88. definition of 62 103a. Dow's penetration apparatus 93 89a. earthy '62 896. elastic 62 1005. English refined 84 103a. essential characteristics of 101 1005. Goudron 84 98c. hard 62 in refined Trinidad asphalt 83 93d. liquid 66 89c. specific gravity of (Table XXIV) 127 weight of (Table XXIV) 127 91. origin of 64 103a. penetration tests of 92 103a. softness of 92 89c. solubility of 63 964 INDEX. ARTICLB PAGE 89c. Bitumen, specific gravity of 62 103a. stability at high temperatures 90 103a. susceptibility to change of temperature 92 450e. to determine amount in coal-tar 367 103a. viscosity of 92 96, 160. Bituminous cement, composition of 68, 139 161. cost of 140 160. for filling joints 139 161. manner of using 140 242, 263. concrete 213, 229 99/. deposits in the United States 75 limestone, amount produced in the United States (Table XVIIIa) , 102 996. characteristics of 75 996. composition of 75 99c, 268. European 75, 236 990. German 77 259. pavements, experience with, in Washing- ton 223 277. in the United States 239 specific gravity of (Table XXIV) 127 268. test for 235 value of production in the United States (Table XVIIIa) 102 990. Vorwhole 77 94, 986, 996. limestones 66, 73, 75 268. appearance of European 236 99/. how used 75 270. preparation of 237 434. macadam * 351 450/. Warren's 379 '297. rock, American 249 302. pavement, area covered by a ton of rock 250 300, cost of construction 250 301. maintenance 250 303. pavements, specifications for 250 104. production of, in the United States (Table XVIII) 102 99^. rocks, analyses of European (Table XV) 76 986, 990. sandstone 73, 76 amount produced in the United States (Table XVIIIa) 102 102. California 86 990. Kentucky 77 99,7. Utah . . 77 INDEX, 965 ARTICLE. PAGE Bituminous sandstone, value of production in the United States (Table XVIIIa) 102 99.7. where found 76 102. sandstones, analyses of 86 99gr. in America 76 99^. Europe 76 99gr. preparation of 76 456. Blast-furnace slag for foundations of pavements 384 330. used for bricks 273 450a. paving 361 663. Blasting 511 292. Block pavement of asphalt 246 182. Blocks, sapless cedar 161 81. Bluestone, amount used for street purposes (Table XI) 38 831. bridge-stones, specifications for 643 818. curb 634 818. specifications for 634 78. description of 35 776, 1018. flagging, specifications for 597, 769 774. for footpaths 596 resistance to crushing (Table IX) 37 specific gravity of (Table IX) 37 77. uses of 35 value of, used for street-paving (Table XI) 38 weight of (Table IX) 37 658. Bogs, embankments across 505 1007. Bond for faithful performance of work 762 1031. form of 787 1021. indemnity 770 866. Books kept by cantonniers 678 632. Borrow-pits 492 636. form of 492 637. staking out 493 133. Boston, cobblestone pavements in 129 early pavements in xxxviii 882. street cleaning in 706 103a. Bowen's penetration apparatus 92 711. Box-culverts 542 711. dimensions of (Table LXXIV) 544 597. Brakes, effect of 472 87y. Brard's test for resistance to freezing 61 866. Breaches of highway law 678 362. Breaking stone by hand 307 365. cost of 307 364. machinery 307 966 INDEX. ARTICLE PAGE 367. Breaking stone by machinery, cost of 307 954. Breast- walls, specifications for 743 Brennan's stone-crusher 834 107. Brick * 105 330. blast-furnace slag 273 common hard, resistance to crushing of (Table XXIV) 127 specific gravity of (Table XXIV) 127 weight of (Table XXIV) 127 with tar 273 450m. copper slag 372 688. drains 527 784. footpaths 608 785. specifications for 609 224. gutters for asphalt pavements 198 828. specifications for 640 329. iron 273 masonry, specific gravity of (Table XXIV) 127 968. specifications for 747 weight of (Table XXIV) 127 324. McReynold's patent 272 877. pavement, cost of cleaning 703 transverse rise for (Table LXIV) 488 322. variety of systems 271 304. pavements 258 305. advantages of 258 326. Charleston plan 272 320. cost of 268 318. courses, direction of 263 {518. crown, amount of (Table LXIV) 488 306. defects of 258 disruption of 923 307. durability of 260 318. expansion joints in 263 334/. of 285 308. experience with 260 321. extent of, in the United States (Table XXXVII). ... 269 309. failures of 260 334d. for country roads 283 316. foundation for 262 601. grade, maximum for 473 321. guarantee of 270 325. Hale method ... 272 1049a. heat, effect of 923 304. history 258 328. in Buda Pesth . 272 INDEX. 967 ARTICLE PAGB 304. Brick pavements in Charleston 258 311. Holland 260 312. Rotterdam . 260 319. joint-filling, asphaltic 268 319. cement 266 319. cost of. 265 319. for 265 318. laying at intersections 263 318. the brick 263 27. life of 11 321a. maintenance of . 270 601. maximum grade for 473 334c. number of brick per square yard 283 314. quality of the brick , t 262 318. ramming of the brick 263 318. rolling of the brick 263 3346. rumbling in 282 317a. sand cushion 262 319. sanding of 267 318. soft brick, to detect 263 331. specifications for 273 traction, resistance to (Table L) 437 327. Wheeling plan 272 118a. paving, absorption test for 112 119. absorptive power of (Table XXI) 115 117. characteristics of good 110 113. color of 107 118a. cross-breaking, test for 113 118a. crushing, test for 113 313. edges, square and round 261 334/. expansion, coefficient of 285 313. form of 261 114. grades of ^ 109 313. grooved * 261 323. Halwood block 271 hammer 856 114. manufacture of 107 116. analysis of the clay (Table XX) 109 114. burning the brick 108 114. drying the brick 108 1 14. moulding the brick 108 114. preparation of the clay 107 107, 111. quality of the clay 108 1 14. tempering of the clay 108 USa. National Brick Manufacturers' Assoc., standard tests. . Ill 968 INDEX. ARTICLE PAGE 334c. Brick, paving, number per square yard 283 119. Orion's tests of (Table XXIa) 114, 115 334. price of, per thousand 285 313. projections on 261 314. quality of 262 111. clay for 108 118a. rattler test for Ill 115. repressed. 109 119. resistance to crushing of (Tables XXIa, XXIV).. . 127,716 313. shape of 261 313. size of. 261 114. sorting of 109 119. specific gravity of (Table XXI and Table XXIV). 115, 127 118a. standard test for N. B. M. A , Ill 322. the Hayden 271 117, 119. weight of (Table XXI and Table XXIV) 115, 127 pressed, resistance to crushing of (Table XXIV) 127 specific gravity of (Table XXIV) 127 weight of (Table XXIV) 127 soft inferior, resistance to crushing of (Table XXIV).. . . , 127 specific gravity of (Table XXIV) 127 standard test for 110 weight of (Table XXIV) 127 Stourbridge fire, resistance to crushing of (Table XXIV) 127 specific gravity of (Table XXIV) 127 weight of (Table XXIV) 114, 127, 283 118. . tests of HO Brickwork in cement- mortar, resistance to crushing (Table XXIV). . . 127 575. Bridge sites, selection of 459 specifications for 55& 830. stones 641 831. specifications for 643 720. substructure of 553 421. Bridgeport, Conn., broken-stone paVements in 342 715. Bridges . , 550 858. examination of 661 iron 553 716. live loads on 550 718. materials for 551 716 proportioning of 550 933. setting out 550 719. timber 551 87r. Broken stone abrasion and impact, Deval machine for testing 53 87 r . resistance to 52 87(/. machine for testing 48 INDEX. 969 87g. Broken stone abrasion machine, Bauschinger's 50 87tf. results 51 87<7- Dorrey's 49 656, 87?. resistance to 26, 48 356a. tests for 302 87z. acids, resistance to 61 435. and old asphalt 352 375. area covered by a cubic yard 309 376. ton 310 365. breaking, cost of 307 methods of 307 87w, 356a, 3566. cementation tests 57, 302, 303 354. characteristics of stones 299 354. chert 299 68/u diorite 30 354. feldspar 295 534. fieldstone 299 68/, 354. gneiss 30, 298 68, 354. granite 29, 297 82, 354. limestone 39, 298 354. quartz 298 354. quartzites 299 74, 354. sandstone 35, 295 86, 354. trap 41, 296 371. crushing, cost of 308 367. plant, cost of 307 types of crushers 832 373. determination of voids in 309 87r. durability of 45 87n-. methods of testing 47 87a, 351. essential properties of 42 87&, 356a. binding or cementing 45, 303 SI iv. Page's machine for testing 57 876. hardness 42 87#. Dorrey's machine for testing 49 S7e. toughness 43 875. test for 54 Deval's machine for 53 Page's machine for. 55 3566. wear, resistance to 304 355, 3566. coefficients of (Tables XIV 4 , XXXVIII 55, 301, 304 335. pavement 268 410 action of weather on 333 346. advantages of 290 970 INDEX. ARTICLE PAGE 874. Broken-stone pavement, amount of dirt produced by 698 894. area cleaned by one man 711 386. binder for 314 388. effect of an excess 314 391a. experiments with 318 390. necessity for . . 317 3916. oil 319 386. proportion of 314 389a. quality of 314 421. Bridgeport, Conn., method of construction .... 342 894. cleaning, area swept by one man 711 860, 877. cost of 667, 700 417a. climate, effect of 340 393, 397, 398. compacting the stone, methods of. ... 319, 320, 321 407. construction, cost of 328 408. Europe 332 407a. Massachusetts 331 419, 420, 421. methods of 341, 342, 343, 348 422. specifications for 343 618. crown, amount of (Table LXIV) 488 347. defects of 290 411. disintegration of ' . 336 41jl. disruption by shrinkage 337 354. durability of 294 10436. dust, suppression of 901 410. effect of horses's hoofs on 333 389dL motor vehicles on 316 412. mud on 339 411. rain ; 333 410. wheels on 333 350. erroneous methods of construction 292 349. essentials to good construction 291 extent in the United States (Table XLII) 329 380. failure of 311 15. foothold on 7 3806. foundation for 311 411. frost, effect of 335 601. grade, maximum for 473 411. gravity, effect of 337 1049o. neat, effect of,. 922 411. horses' feet, effect of 333 379. in Bridgeport, Conn 31 ] 380o. Massachusetts 311 356. load drawn by a horse on (Table LVII) 444 340. Macadam's method 233 INDEX. 971 ARTICLE 345. Broken-stone pavement, 857. 418, 860. 860. 860. * 858a. 860. 865. 601. 342. 354. 389a. 351. 355. 3566. 356a. 87r. 411. 417. 861. 866. 864. 401, 415, 86L 397. 400. 398. 399. 400. 400. 403. 405. 400. 402. 400. 398. 404. 406. 405. 405. Macadam's method, defects of 290 maintenance of 658 costof 340,665 in England 665 France 665 Massachusetts 659 errors in 663 factors in estimating cost of. . 666 French system 676 maximum grade for 473 modern Telford 289 most efficient stones for 296 motor vehicles, effect of, on 316 quality of the stone 293 coefficients of 301 French (Table XXXVIII) 301 Maryland Geol. Survey . . 304 Mass. Highway Com 305 U. S. Road Material Lab- oratory (Table XIV 4 ). . 55 rain, effect of, on 333 ravelling, cause and cure 662 recoating 340 repair of 669 Massachusetts method 659 road laborers, regulations for 678 roadmen, instructions to 674 rollers, for breaking up roads . 322, 339, 670 horse 320 form of 321 price of 847 steam 321 advantages of 321 form of 321 grade ascended by 322 maintenance, cost of 323 manner of applying 325 speed of 322 work performed by 322 weight of 322 rolling, advantages of 320 amount required 328 cost of 324 manner of performing 325 rules for . 326 972 INDEX. ARTICLE PAGE Broken-stone pavement, rutting, remedy for. 662 381. sand core for 312 scarifiers 855 860. scraping, cost of 667 862, 909. snow, removal from 673, 720 422, 423. specifications for ' 343, 347 383. spreading the stone 313 859. sprinkling, amount of water for 665 860. cost of 668 423a. State aid, methods of construction 348 382. stone, quantity required per mile 313 372, 375. shrinkage in rolling 308, 309 357. size of 306 1019. specification for supply of 769 87a. tests for 42 378. thickness of 310 384. layers 313 336. Telford and Macadam 285 339. Telford's method 287 344. defects of 289 1049. temperature of 922 411. effect of changes of 337 thickness, annual loss of 338 415. restoring of 339 380. thin vs. thick 311 1036. tools employed in construction and maintenance 828 traction resistance to (Table L) 437 338. Tresaguet's method 286 392. watering during rolling 319 409, 412. wear of 333, 339 Massachusetts roads 338 411. wind, effect of 335 quarrying, cost of 308 387. screening of . 314 screens for 838 372. voids in 308 373. determination of 309 372, 375. reduction of, by rolling 308, 309 354. wearing value of different stones 299 374. weight of 309 897. Brooms, bass 712 897. birch 712 1040. prices of 871 897. rattan . 712 897. steel- wire . . 712 INDEX. 973 ARTICLE PAGE 102a. Buena Vista asphalt 86 1017. Bulkhead, specifications for a 765 C. 674. Calculating amount of earthwork 517 676. the half widths and areas of earthwork 518 102. California asphalt 85 102. bituminous rock, analysis of 101 104. price of 85 866. Cantonniers, absence, fines for 678 annual gratuities 685 appointment of 679 books 684 chief 679 classification of 685 compulsory attendance of 683 distinctive mark 679 duties of 680 fines on account of absence 685 gratuitous assistance to travellers by 683 868. indemnity for removal of 685 leave of absence 684 means of verifying absence of 684 regulations for 678 salary of 684 surrender of books and distinctive marks on dismissal of a. 684 surveillance over breaches of the highway law 683 tools furnished by the . 683 to the 683 keeping in repair by 684 working hours of 682 Capacity of drill-holes (Table LXVIII) 512 1033. scrapers SOG sprinkling-carts .... % 884 1036. stone- crushers 830 39. Care of pavements 14 1033. Carts, capacity of 809 earth 839 898. for street dirt 712 sprinkling, capacity of 884 price of , 884 1042. Cast-iron gutter-crossings 891 specific gravity of (Table XXIV) 127 984. specifications for 756 974 INDEX. ARTICLE PAGE 1Q42. Catch-basin covers 889 761. Catch-basins 582 1018. specifications for 769 704. Catch-pools, use of 536 696. Catch-water ditches 531 951. specifications for 743 858, 869. Causes producing dirt . 659, 694 208, 2166. Cedar-block pavement 174, 188 208. pavements 174 216. specifications for 185 482. Cement, activity of 398 485. age, effect of 400 American natural, requirements for 392 473. specification 392 amount of water absorbed by (Table XLIVJ 400 475. artificial Portland 393 ' 96, 102. asphalt 68, 86 98d. specifications for 73 160. bituminous, composition of, for joint-filling 139 161. cost of 139 manner of using 139 450e. coal-tar 367 473, 479. color of American natural 392, 397 450gr. concrete pavement 370 510. data for estimates 422 485. effect of age on 400 483. variations of temperature on 398 475. English Portland, specific gravity of (Table XXIV) .... 127, 394 476. weight of (Table XXIV) 127, 395 790. expansion of 6J 1 786. footpaths 610 786. ingredients for 610 787. manner of laying 611 795. specifications for 615 794. wear of 614 French Portland, weight of (Table XXIV) 127 473. hydraulic 392 247, 250. in asphalt paving 214, 215 490. measuring fineness of 403 494. -mortar, composition of 406 474. natural Portland 393 706. pipe for culverts 537 707. cost of..... 541 dimensions of 541 161. Portland, and iron slags for filling joints 140 INDEX. 975 ARTICLE PAGE 476. Cement, Portland, characteristics of 395 972. definition of 749 475. effect of sand on 395 509. English specifications for 421 476. 489. fineness of 395, 402, 752 477. . necessity of testing 396 476. specific gravity of . . . 396 476, 973. tensile strength of 396, 752 973. tests for, Am. Soc. C. E 396, 751 476, 510, 972. weight of 395, 422, 749 482. quick- and slow-setting, definition of 398 Roman, specific gravity of (Table XXIV) 127 weight of (Table XXIV) 127 973. Rosendale, tests for, Am. Soc. C. E J52 473. specific gravity of American natural 392 972. specifications for 749 473. strength of American natural 392 492. testing machine 404 477. . necessity of . . 396 477. tests 396 972. specifications for 751 473, 510. weight of American natural (Table XXIV) 127, 393, 422 87 k, 356a. Cementation test, description of 45, 301 Cementing value of rocks (Table XIV 5 ) 60 45. Census, traffic 17 48. form of 19 962. Centring, specifications for 746 450z. Ceramocrystal pavement 371 1031e. Certificate of acceptance 793 1031/. final acceptance 793 1031c. Certificates, form of monthly 791 Chalk, resistance to crushing of (Table XXIV) 127 specific gravity of (Table XXIV) 127 weight of (Table XXIV) 127 89a. Chapapota 62 457. Character of concrete for pavement foundations. 385 453. natural soils 383 543. vehicles 447 473. Characteristics of American natural cements 392 89. asphalt 62 lOOrf. crude Trinidad asphalt 79 268. European bituminous limestone 235 117. good paving-brick 110 476. Portland cement 395 lOOw. refined Trinidad asphalt 82 976 INDEX. ARTICL3 PAGE 448. Charcoal roads 360 326. Charleston plan of brick pavements 272 29. Cheapest pavement . . 11 lOOa. Cheese pitch 78 87;'. Chemical durability of stone 45 122, 188. treatment of wood 121, 164 132a, 354, 450c. Chert 126, 299, 363 87p. water absorbed by (Table XIV 2 ) 48 420. Chicago, broken-stone pavements in 342 819. Circular curb 635 pipes, discharging capacity of (Table LXXVIII) 549 31. City ownership of street-car tracks 13 744. streets 568 accommodation summits in 579 754. rule for 579 873. amount of refuse collected from (Table LXXXVI) 696 745. arrangement of 568 868. cleansing of 693 757. contour, transverse 581 757. crown for 581 758. drainage, subfoundation 581 759. surface 582 762. at intersections 588 751. grade, adjustment of, at intersections 575 749. grades for 574 749. maximum in various cities (Table LXXXII) 576 756. transverse 580 760. gutters 582 755. summits in 579 756. hill-side, adjusting 580 766. increasing width at intersections 593 763. lines, establishing of 588 763, 764. monuments for _ 588, 590 765. plans, scale for 591 765. profile, information on 591 765. scale for 591 766. refuges at intersections , , 593 767 statistics of (Table LXXXIII) 594 755. summit in gutters 579 747. width of 574 748. in various cities (Table LXXXII) 576 766. increasing the, at intersections 593 1005. Claims, payment of 761 949. Classification of earthwork 742 107. Clay 105 INDEX. 977 ARTICLE PAGE 116. Clay, analyses of (Table XX) 10 3896. binder 316 430. binding power of 350 113. color of 107 108. composition of 105 450d. Florida 363 111. for paving-bricks 106 426. proportion of, to gravel 349 835. roads, improving of 646 836. maintenance of 648 traction resistance to (Table L) 437 836. trees on 648 639. shrinkage of 493 686. soils, drainage of 525 specific gravity of (Table XXIV) 127 weight of (Table XXIV) 127 with gravel, specific gravity of , . 127 weight of 127 127. sand for concrete 124 40. Cleaning of pavements 15 101 1. up, specifications for 763 126. Cleanness of sand, to test 124 868. Cleansing of streets 693 877. cost of 700 875. methods employed 698 1027. specifications for ' 772 1040. tools employed for 871 944. Clearing, specifications for 740 1032. tools for 802 884. Cleveland, Ohio, street cleaning in 708 417a. Climate, effect of, on roads 340 450/&. Clinkers 370 945. Close cutting, specifications for % 740 279. Coal-tar and asphalt 240 281. pavements, advantages of 241 284. cost of maintaining 242 282. defects of 241 283. in Washington, D. C 242 291. specifications for 243 450e. cement 367 450e. composition of 367 10436. for abating dust 904 278. pavements 239 advantages and disadvantages 365 composition of 239 978 INDEX. ARTICLE PAGE 278. Coal-tar pavements, experience with 240 450e. failure of 366 450e. maintenance of 365 450e. quality of the stone 366 450e. tar 367 450p. paving-blocks 377 106. paving-pitch 104 450e. to determine amount of bitumen in 367 827. Cobblestone gutters, specifications for laying 57 L 134. pavement 129 172. extent (Table XXX) 152 hammer 856 134. merits and defects of 129 166. on steep grades 143 rammer 857 135. specifications for 129 traction resistance to 437 Coefficients for retaining- walls (Table LXXXI) 560 352. of quality of stones for broken-stone pavements (Table XXXVIII) 301 982. Cofferdams, specifications for 756 687. Collars for tiles 525 1001. Commencement of work 760 79. Commercial names of sandstones 36 Common hard brick, resistance to crushing of (Table XXIV) 127 specific gravity of 127 weight of 127 393. Compacting the broken stone 319 104. Comparative prices of asphaltum (Table XVII) 101 rank of pavements (Table IV) 21 15. safety of pavements 7 1002. Completion, time of 760 90. Composition of asphaltum (Table XlVa) 66 160. bituminous cement 139 494. cement-mortar 406 108. clay 105 450e. coal-tar 367 459. concrete , 385 872. mud (Table LXXXV) 696 872. street dust 695 782a. Compressed-asphalt-tile footway-pavement 607 623. Concave cross-section for street:; 490 466. Concrete, amount of ramming required 388 470. and furnace-slag 391 242. bituminous ... 213 INDEX. 979 ARTICLE 460. Concrete, character of, for pavement foundations 386 459. composition of 385 468. compressive strength of 389 469. cost of 390 459. definition of 385 459. essentials necessary to the manufacture of good. 385 787. footpaths 611 795. specifications for 615 460. for pavement foundations 386 470. formed with asphaltic cement 391 154. foundations, thickness of 138 466. laying of. 388 436. macadam .352 714a. masonry 549 mixing-machine, price of 869 465. mixing of 388 471. mortar for 391 450gr. pavements . 370 450^. where used 370 461. 462. proportions of ingredients % 386 459. quality of stone for 385 464. quantity of materials required for one cubic yard 387 463. water required for 387 466. ramming of 1 388 127. sand for 124 459. size of stone for 386 460. specific gravity of (Table XXIV) 127, 386 512-516, 977. specifications for 423-426, 754 460, 468. strength of 386, 389 458. thickness of 385 467. transverse strength of 389 461. usual proportions of ingredients 386 457. weight of (Table XXIV) 127,385 791. rammers for 613 42. Consequential damages , 15 28. Considerations concerning cost of pavements 11 942. tests of materials 739 555. governing location of roads 453 444. Construction of plank roads 358 593. profile 470 739. roads along the seashore or margins of rivers 562 560. Contour lines 454 618. transverse of roadway 488 625. on hillside roads 490 756. streets . .580 980 INDEX. 476. Contraction of Portland Cement 396 943. Contracts 740 1030. agreement, form of 778 1025. alteration of street furniture 771 1029. bid, form of 777 1028. bidders, instructions to 773 1007. bond for faithful performance of 762 949. bowlder, measurement of 742 999. bridge 759 1031, 1031/. certificate, form for final 793 1031c. monthly 791 1031e. of acceptance, form of 793 1011. cleaning up 763 999. clearing and grubbing 758 1001. commencement of work 760 999. concrete, measurement of 759 1031d. contractor's affidavit, form of 792 1031. bond * , 787 988. defined 756 1012. personal attention 763 999. curbing, measurement of 759 1004. damages for non- completion 761 998. defective work 758 995. deviations from plans 757 999. drain, measurement of 759 949. earthwork, classification of 742 measurement of 742 987. engineer, defined 756 990. marks, preservation of 757 1031e. engineer's final certificate, form of 793 1031c. monthly 791 999. excavation, measurement of 758 1010. extra work 762 1003. forfeiture of 760 1030. improper prosecution of work 781 991. incompetent persons, dismissal of 757 1020. indemnification for patent claims 770 1021. indemnity bond , 770 997. inspector's, appointment of "758 985. interpretation of specifications 756 1009. loss and damage 762 999. masonry, measurement of 759 993. materials, quality of 757 994. samples of 757 1010. miscellaneous work 762 INDEX. 981 ARTICLE PAGfi 1031c. Contracts, monthly certificate, form of 791 1000. estimate 759 989. notice to contractor 756 1023. old material, disposal of 770 986. omissions in specifications 756 999. overhaul, measurement of 758 999. pavements, measurement of 759 1005. payment of claims, evidence of 761 1013. workmen 763 1000. payments, partial 753 1015. when made 763 999. piles, measurement of 759 995. plans, deviation from 757 IOCS. power to suspend work 762 943. preparation of 740 1014. prices, what they cover 763 1003. progress of work 760 1029. proposal, form of 777 1006. protection of persons 761 1006. property 761 1000. retained percentage 760 996. right to alter details 757 1022. construct sewers 770 949. rock, loose, measurement of . 742 1024. security for repairs 771 995. specifications, deviation from 757 992. spirituous liquors, prohibited 757 999. timber, measurement of 759 1002. time of completion 760 1030. transfer of contract 783 999. work, how measured 758 621. Convexity, excessive, objections to 488 450m. Copper-slag brick 372 447. Corduroy roads 360 450Z. Cork pavement 372 43. Cost, annual, of pavements \Q 1047. formula for 921 1045. structures , . .......... 912 wood pavements in London (Table XXXI) 169 per head of population for street maintenance in the United States (Table LXXXVII) 700 33. first, of pavements 13 method of assessing. 940 44. gross, of pavements 16 161. of bituminous cement 140 982 INDEX. ARTICLE PAGE 363. Cost of breaking stone by hand 307 320. brick pavements 268 877. cleaning pavements 700 469. concrete 390 300. construction of American bituminous-rock pavements 250 294 asphalt-block pavements (Table XXXVI) 248 232. asphalt pavements (Table XXXV) 207 172. Belgian block pavements (Table XXVIII) 151 407. broken-stone pavements (Table XLII) 329 172. granite-block pavements 149 432. gravel pavements (Table XLIII) 351 172. sandstone pavements (Table XXIX) 151 205. wood pavements 172 899. crematories 712 188. creosoting wood 165 710. different forms of culverts 542 688. drains 527 drain-tiles (Table LXXVII) 549 840. earth roads 649 706. earthenware culvert-pipe '. 537 672. earthwork 515 668. excavating rock 513 743. fencing 567 709. iron pipe-culverts (Table LXXIII) 542 233. maintaining asphalt 206 418, 860. broken-stone pavements . 341, 665 g41. earth roads 649 169. granite-block pavements 146 403. steam-rollers 323 193, 206. wood pavements (Tables XXXI and XXXIV) 169, 174 905. melting snow 717 886. operating machine- brooms 708 1033. ploughs 803 368. stone-crushers 308 28. pavements, considerations concerning 11 446. plank roads 360 707. Portland-cement pipe (Table LXXII) 541 220. preparing the different varieties of asphalt 196 371. quarrying stone (Table XXX) 308 900. removing snow (Table LXXXVII) 700, 712 406. rolling 328 164. sandstone pavements 141 41. service of pavements 1C 367, 1036. stone-crushers 307 INDEX. 983 ARTICLE PAGE 371. Cost of stone crushing (Table XXXIX) 309 877, 893. ' street cleaning 700, 711 315. sprinkling 724 .893. sweeping 711 439. trackways 536 707. vitrified pipe-culverts (Table LXXI) 541 5, 1043a. wagon transportation (Table I) 2, 900 '878. per capita for street maintenance (Table LXXXVII) 700 216e. Cottonwood blocks 189 555. Country roads, location of 453 862. County engineer 673 650. Covering of slopes 498 1042. Covers for catch-basins. 889 899. Crematories, cost of 712 216/i. Creo-resinate process for preserving wood 190 122, 188. Creosoting wood 121, 165 .588. Crookedness, objections to 469 830. Crossing-stones 641 .830. dressing of 641 .830. quality of 641 :832. relaying 643 831. specifications for 643 573. Cross-levels 456 677. Cross-section of earthwork 518 770. Cross-slope of footpaths 595 619. Crowns for different pavements 488 755. in gutters 579 94. Crude asphaltum 44 1043&. petroleum for sprinkling roads 901 369, 370. Crushers, capacity of 308, 832 369, 370. stone, cost of 308 367. operating 307 horse-power required for 308, 832 369. size of 308, 832 368. wear of 307 132a. Crushing, resistance to, of basalt (Table XXIV) 127 brick (Table XXIV) 127 cast iron (Table XXIV) 127 chalk (Table XXIV) 127 132a. common hard brick (Table XXIV) 127 69. granite (Table VI) 31 132.... 899 266. European asphalt pavements 235 259. experience with, in America 223 268. bituminous limestone, appearance of t .. ........ 235 268. characteristics of 235 rocks, analyses of (Table XIV) 76 1005. Evidence of the payment of claims 761 858. Examination of bridges 662 577. Examples in location 460 639. Excavated material, shrinkage of 493 662. Excavating rock 511 978. Excavation, foundation, specifications for 755 31, 57. Excavations in streets 13, 23 INDEX. 991 ARTICLE PAGE 621. Excessive convexity, objections to 488 392. watering, effect of 319 303a. Expansion of asphalt 251 334/. brick pavements 285 476, 790. cement 396, 611 190. wood-paving blocks 166 662. Explosives, quantity required (Table LXVII) 512 232. Extent of asphalt pavements (Table XXXV) 207 Belgian-block pavements (Table XXVIII) 151 brick pavements (Table XXXVII) 269 cobblestone pavements (Table XXX) . 152 granite (Table XXVII) 150 gravel * ' (Table XLIII) 351 macadam " (Table XIII) 329 sandstone " (Table XXIX) 151 wood " (Table XXXIII) 173 F. 252. Failures of asphalt pavements 216 309. brick pavements 260 641. earthwork 494 727. retaining- walls 559 380. thin broken-stone pavements . . .'. 311 186. wood pavements 162 1007. Faithful performance of work, bond for 762 691. Fall of drains 529 22. Falls of horses, kinds and causes of 10 1036. Farrell stone-crusher 832 354. Feldspar, description of 295 specific gravity of (Table XXIV) 127 weight of (Table XXIV) 127 741. Fencing , 564 743. cost of 567 741. specifications for 564 354. Fieldstone 299 280. Filbert vulcanite pavement 240 160, 192, 319. Filling for joints in pavements 139, 168, 265 592. Final location 470 576. selection of route 460 920. Financial value of trees 729 476, 489. Fineness of Portland cement 395, 402, 752 504. sand for mortar 411 815. Fire-clay curb 632 33. First cost of pavements 13 992 INDEX. ARTICLE PAGE 956. First-class masonry 744 1018. Flagging, specifications for 766 776. Flagstone, specifications for 5.17 Flint, specific gravity of (Table XXIV) 127 weight of (Table XXIV) 127 450d. Florida clay 363 96a. Flux for asphalt 69 14, 524. Foothold, influence of 7, 437 786. Footpaths, artificial stone for T . 610 796. specifications for 616 794. wear of 614 778. asphalt for 597 778. rock, in Paris 597 781. Paris, specifications for 600 780. sheet, specifications for 598 774. bluestone 596 776. specifications for 597 784. brick. 608 785. specifications for 609 793. cement, covering capacity of 613 801. Central Park, New York 620 782. compressed asphalt-tile 607 792. concrete, covering capacity of , . . . 613 791. for 612 791a. precautions in use of 613 795. specifications for 615 770. cross-slope of 595 768. definition of 595 775. dressing of stones for . . * , 597 771. foundation of , 596 774. granite for 596 800. gravel 620 introduction of xxxix 796a. kosmocrete 619 779. life of asphalt 598 773. materials employed for 596 833. price of 644 833&. metalloid blocks 645 812. construction of 628 772. qualities required ,.,.,. .... 596 907. removal of snow from 718 797, 798. tar concrete 619, 620 797. specifications for 619 769. width of (Table LXXXII) 595 777. wood for 597 INDEX. 993 ARTICLE PAGE 527. Force required to sustain a vehicle upon an inclined road 441 1003. Forfeiture of contract 760 452. Foundation, drainage of 383 452. essentials necessary to the forming of good 383 978. excavation, specifications for 755 240. for asphalt pavements 212 316. brick pavements ,. . 262 3806. broken-stone pavements 311 771. footpaths 596 451. pavements ; ' 383 154. stone pavements 133 456. of blast-furnace slag 384 457. concrete 385 458. thickness of 385 726. retaining- walls 559 186. sand and plank, defects of 162 455. manner of forming 384 185. used for wood pavements 162 414. France, amount of material used to replace wear of broken-stone pave- ments 339 867. contract work on roads 689 418, 865. cost of maintaining roads in 340, 676 early roads in xxxv 355. methods of testing the qualities of broken stone 300 865. national roads of 676 road commissioners in 691 road police in 691 87y. Freezing, resistance to 61 865. French system of highway maintenance, regulations for cantonniers (road laborers ) 676 914. Frequency of street sprinkling 722 521. Friction, resistance of .................. 436 411. Frost, effect of, on roads 333 .507. upon mortars , . . , 415 921. Fruit-trees and roads in Saxony . . , 729 .330. Furnace slag for bricks , , , > . . 273 470. concrete , , , , 1 . .' J91 450a. paving 36J, G. 226. Gas, injurious effects of, on asphalt. 202 106. tar _ 103 1036. Gates crusher 831 153. Gauging of granite blocks 4 o 138 994 INDEX. ARTICLE PAGE General stipulations applicable to all contracts 756 91a. Gilsonite 64 45(H'. Glass pavement 371 specific gravity of (Table XXIV) 127 weight of (Table XXIV) 127 68/, 354. Gneiss 30, 298 specific gravity of (Table XXIV) 127 weight of (Table XXIV) 127 1005. Goudron 84 605. Grade on mountain roads . 478 1033. Grader, New Era 817 671, 1033. Graders, mechanical 514, 817 222, 261. Grades, and asphalt pavements 198, 224 400. steam-rollers 322 595. tractive power of horses 472 596. angles of (Table LXII) 472-480 751. at street-intersections, adjustment of 575 594. definition of 470 595. determination of 472 537. effect of, upon the load drawn 465 542. equivalent length of level (Table LIX) 447 609. establishing the 481 532. loads drawn by horses on 441 848. loss caused by 651 599. maximum . . 473 599. for roads 473 601. suitable for different paving materials 473 604. to determine 474 608. methods of designating (Table LXII) 480 606. minimum 479 745. of city streets (Table LXXXII) 568, 576 586. on curves 465 847. profit of eliminating 650 608. rise in feet per hundred 480 608. mile 480 540, 541. steep, objections to 446 166. pavements on 143 542. tractive power on (Table LIX) 447 752. transverse of street 577 607. undulating 479 947. Grading, definition of 740 947, 1018. specifications for 740, 766 1033. tools for 803 Granite, abrasion of (Table XIV 3 ) 52 absorptive power of (Table XIV,) 48 INDEX. 995 ARTICLE PAGE Granite, amount used for street purposes (Table VII) 32 443. block, artificial 358 140. pavement 132 142. advantages of. , 132 874. amount of dirt produced by 698 894. area cleaned by one man 711 160. bituminous cement for filling joints 139 877. cost of cleaning 700 172. construction 149 169. maintaining 146 155. cushion coat for 138 143. defects of 132 extent of (Table XXVII) 150 159. filler for joints 139 161. applying the 140 160. European formula for 139 New York formula for 139 steel 141 161. tar and gravel 140 Washington formula for 139 149. form of blocks 135 154. foundation for 138 151. gutter, manner of forming 135 1049a. heat, effect of, on 923 170. manner of paying for 146 155. sand for foundation 138 size of blocks 134 in various cities 137 146. shape of blocks 134 173. specifications for 152 161. steel joint-filler 141 tar and gravel filler 140 1049. temperature of 922 traction, resistance to (Table L) 437 147. width of blocks 134 171. blocks, area covered by one ton (Table XXVI) 149 152. assorting, at the quarry 138 color of 29 composition of (Table V) 31 816. curb, specifications for 633 68. . description of 29 774. for footpaths 596 27. life of 11 masonry, weight of (Table XXIV) 127 686, 354. most durable variety 29, 297 996 INDEX. ARTICLE PAGE 153. Granite paving-blocks, depth of 137 167. durability of 145 153. gauging of 137 156. laying of 138 152. at intersections 135 148. length of 135 73. manufacture of 33 171. number of, to a square yard 117 157. ramming of 139 168. wear of 145 144. quality of 134 69. resistance to crushing of (Table VI) 31 19. slipperine^s of 9 69. specific gravity of (Table VI) 31 72. uses of 33 70, 71. value of, used for street purposes (Table VII) 32, 33 69. weight of (Table VI) 31 650. Grass on slopes 498 1042. Gratings for catch-basins 892 Gratuitous assistance to travellers 683 131. Gravel 125 639. and sand, shrinkage of 493 425. character of, for pavements 349 430. clay binder for 350 381. core for broken-stone pavements 312 613. crown for (Table LXIV) 488 131. definition of 125 161. filling for joints in block paving 140 800. footpaths 620 428. laying of 350 131. Paducah 125 424. pavements 349 32. cost of construction (Table XLIII) 351 431. repair of . 350 428. sprinkling of 350 transverse rise for (Table LXIV) 488 427. preparation of, for paving purposes 349 , 638. shrinkage of 493 ,427. size of, for paving 349 131. Tomkins Cove 125 131. analyses of 126 traction, resistance to (Table L) 437 131. varieties of 125 812. walks, directions for their construction 628 801. in Central Park, New York 620 INDEX. 997 ARTICLE PAGE 433. Gravel, weight of 351 with clay, specific gravity of (Table XXIV) 127 weight of (Table XXIV) 127 525. Gravity, effect of (Table LII) 439 Greenstone, specific gravity of (Table XXIV) 127 44. Gross cost of pavements 16 967. Grouting, specifications for 747 946. Grubbing, specifications for 740 1032. tools for 802 50. Guaranteeing pavements 21 738. Guard stones 562 216c. Gum wood blocks 188 Gunpowder, specific gravity of (Table XXIV) 127 weight of (Table XXIV) 127 1042. Gutter-crossings of cast-iron 889 760, 826. Gutters 582, 639 828. brick, specifications for 640 827. cobblestone, specifications for 639 755. crown in 579 811. in Central Park, New York 626 694. on inclines, protection of 530 1018. specifications for 766 151. stone block 135 829. Gutter-stones, specifications for 641 H, 325. Hale pavement 272 676. Half- widths, calculating the 518 583. Halting-places 465 323. Halwood paving-block 271 362, 1036. Hammers for breaking stone 307 361. Hand-broken stone 306 897, 1040. Hand-brooms, kinds of 712 1040. Hand-cart used by street patrol 874 465. Hand-made concrete 388 1038. Hand-rammers, price of 857 892. Hand sweeping 710 65c, 87?, 352. Hardness of stones 26, 48, 293 1036. Harrisburg roller 849 450v. Hassam pavement 382 673. Haul 515 322. Hayden paving-block 271 1049a. Heat, effect of, on pavements 922 636. paving materials 25 998 INDEX. ARTICLE PAGE Heater for asphalt g66 Hookes' 868 211. Henson wood pavement 175 1016. Highway, specifications for construction of a . 764 625 H Lside roads, form of transverse contour 490 659. Hillsides, embankments on 506 659. retaining- walls on 506 825. Hollow curbs of artificial stone 638 1036. Horse-power required for stone-crushers 832 397. Horse rollers, defects of 320 1036. dimensions of 846 1036. price of 846 work of, at different rates of speed (Table LVI) 443 532. Horses, draught of 441 22. falls of, kinds and causes 10 410, 1044. feet, effect of, on pavements 333 536. loads drawn by, on grades (Table LVII) 443 maximum velocity unloaded (Table LIV) 442 11, 12. number required to move one ton on different pavements (Table II) 6 tractive power of, at different velocities (Table LIII) 442 534. work done by 442 1044. Horseshoes and pavements 912 78. Hudson River bluestone 35 473. Hydraulic cement 392 472. lime 391 L 63c. Ice, effect of, on paving materials 25 specific gravity of (Table XXIV) 127 weight of (Table XXIV) 127 Sir. Impact and abrasion 52 Deval machine 53 87s. Page machine 55 65&, 87-5. resistance to 26, 54 104. Imports of asphalt into the United States (Table XIX) 101, 103 212. Improved wood pavements 176 834. Improvement of roads 646 842. Improvements, value of 649 835. Improving clay roads 646 851a. roads with oil 653 837. sand roads 648 850. the surface, profit of 652 648. Inclinations given to side-slopes in different materials 497 INDEX. 999 ARTICLE PAGE 699. Inclinations of culverts 532 691. drains 529 527. Inclines, force required to sustain vehicles on 441 536. loss of tractive power on 443 power required to haul one ton up different (Table LIX) .... 447 528. pressure of vehicles on 441 694. protection of gutters on 530 597. tractive power required in descending 472 991. Incompetent workmen, dismissal of 757 790. Increase in bulk of cement 611 639. of excavated rock 493 766. Increasing width of carriageway at street-intersections 593 1020. Indemnification for patent claims 770 1021. Indemnity bond 770 4500. India-rubber pavement 377 461-464. Ingredients for concrete, proportions of 386 1042. Inlet-traps for sewers 889 997. Inspectors 758 765. Instructions regarding street profiles 592 1028. to bidders . . . 773 864. roadmen 674 566. Instruments employed in reconnoitring. 455 3. Interests affected in the selection of pavements 2 578. Intermediate towns 462 985. Interpretation of specifications 756 152. Intersection, paving at street 135 450. Iron and wood, combinations of 561 cast, crushing resistance of (Table XXIV) 127 specific gravity of (Table XXIV) 127 984. specifications for 756 weight of (Table XXIV) 127 815. curb 632 450. pavements 561 329. paving-bricks , 273 pipe, weight of (Table LXXIII) 542 708. pipe-culverts 541 1006. pitch 78 161. slag, and Portland cement for joint-filling 140 wrought, crushing resistance of (Table XXIV) 127 specific gravity of (Table XXIV) 127 983. specifications for 755 weight of (Table XXIV) 127 438. Italian trackways 356 1000 INDEX. J. ARTICLE PAGE 442. Jasperite 357 319. Joint-filling for pavements 265 asphaltic 267 advantages of 268 Cimmerian 267 coal-tar 265 advantages of 265 and creosote 154 defects of 265 manner of using 267 cost of 268 hydrolene 267 Pioneer 267 160. bituminous cement 139 319. cost of 268 160. European, formula for 139 161, 319. Murphy's grout 140, 265 New York 139 object of 265 160. paving pitch 103, 140 manner of applying 192 319. Portland cement 265 161. and iron slag 140 manner of using 266 preparation of 266 quality of 265 sand 265 161. steel 141 161. tar and gravel 140 173. specifications for 154 Washington 139 319. for brick pavement 265, 275 159. granite block 140, 15i 163. sandstone 141, 143 192. wood 168, 180 441. Junctions of trackways 357 152. paving at street 135 K. 216c. Karri wood pavement 188 Keeping tools in repair 684 99 tar and slag macadam 382 450w. tarmac 382 450e. tar-macadam 364 336. Telford's method 286 1049. temperature of 922 280. vulcanite 240 450w. Wadsworth's patent 382 450/. Warren's patent 379 56. waste of money in opening 23 450s. Whinery's patent 378 174. wood 156 216/&. creoresinate method 190 152. Paving at street- junctions 135 66. material, methods of testing 27 58. selection of 24 106. pitch 104 1005. Payment of claims 761 1013. workmen 763 1000. Payments, partial 759 1015. when made 763 Peat, weight of (Table XXIV) 127 103a. Penetration tests of bitumen 92 90, 90a. Petrolene 63 88a, 91. Petroleum 62, 64 976. residuum 71 97d. specification for 72 97a, 976. test for 71 specific gravity of (Table XXIV) 72, 127 weight of (Table XXIV) 127 1010 INDEX. ARTICLE PAGE Philadelphia, early pavements in xxxvii 887. street-cleaning in 708 415. Picks on steam-rollers, objectionable 339 981. Piles, specifications for 755 216d. Pine wood paving-blocks 189 706. Pipe-culverts 537 971. specifications for 748 Pipe, iron, dimensions, weight, and price of (Table LXXIII) 542 707. vitrified, dimensions, weight, and price of (Table LXXI) 541 Pipes, discharging capacity of (Table LXXVIII) 549 88a, 93. Pitch, mineral 62, 66 106. paving 105 specific gravity of (Table XXIV) 127 weight of 127 433. Pit-gravel, weight of 351 656. Plains, embankments over 503 186. Plank- and-sand foundation, defects of 162 444. Plank roads , 358 445. construction of 35g 446. cost of 360 446. life of 360 traction, resistance to (Table L) 437 995. Plans and specifications, deviations from 757 1033. Ploughs, cost of operating 803 1033. for grading, price of 804 1033. quantity of material loosened with 804 966. Pointing, specifications for 747 87o. Porosity of paving materials 47 Porphyry, specific gravity of (Table XXIV) 127 weight of (Table XXIV) 127 1035. Portable boilers, price of . 827 1036. engines, price of 841, 842 475. Portland cement 393 972. American, specifications for 749 476. characteristics of 395 476. contraction of 395 509. English, specifications for 421 476, 790. expansion of 395, 611 973. fineness of 752 973. specific gravity of 753 973. tensile strength of 752 973. tests for, Am. Soc. C. E 751 973. weight of 749 518. Power required to draw wheels over obstacles 430 haul one ton up different inclines (Table LIX) 447 INDEX. 1011 ARTICLE PAGB 1008. Power to suspend work 762 990. Preservation of engineer's marks '. 757 188. wood 164 Pressed brick, resistance to crushing of (Table XXIV) 127 specific gravity of 127 weight of 127 397. Pressure of rollers 321 528. vehicles on inclines 441 1014. Prices in contract 763 104. of asphalt 101 833. footwalk materials 644 69. granite blocks 32 1033. mechanical graders 803 334e. paving-brick 285 129. sand 124 367. stone- crushers 831 tools for asphalt pavement 856 brick pavement 856 1040. cleaning 871 1032. clearing 802 1033. grading 803 1032. grubbing 832 1036. macadamizing 828 1037. maintenance 856 stone-block pavement 856 675. Prismoidal formula 517 574. Profile 459 593. construction 470 765. Profiles, street 591 849. Profit of decreasing the length 651 847. eliminating unnecessary grades 650 850. improving the surface 652 1003. Progress of work ; . . 676, 760 1029. Proposal, form of 777 689. Protection of drain-outlets 527 694, gutters on inclines 530 1006. persons and property , 761 734. roads 560 927. trees 731 31. Public bodies and economy. . . . c 12 Q. 314. Quality of bricks 262 830. cross-stones 641 776. flagstones 597 1012 INDEX. ARTICLE PAGE 144. Quality of granite 134 425. gravel for roads 349 993. materials 757 459. for concrete 385 495. mortar 406 126. sand 124 252. for asphalt pavement 216 155. cushion-coat 138 351. stone for broken-stone pavements 293 459. concrete 385 497. water for mortar 407 187. wood for paving 163 2. Qualities of good pavements 1 772. required in footpaths 596 382. Quantity of broken stone required per mile for different widths (Table LX) 313 1033. material loosened with ploughs 804 464. materials .required for one cubic yard of concrete 387 128. sand required for bedding-blocks 124 366. stone broken by hand 307 367, 1036. machines 307, 830 463. water required for concrete 387 498. mortar 407 913. street sprinkling 722 371. Quarrying stone, cost of (Table XXXIX) 309 354. Quartz, specific gravity of (Table XXIV) 127 weight of (Table XXIV) 127, 298 354. Quartzite 299 487. Quick- and slow-setting cements, definition of 401 R. 1033. Rails, weight of 804 19. Rain and asphalt pavement 9 411. effect of, on roads 333 699. Rainfall, amount of 532 466. Rammejrs for concrete, dimensions of 388 1038. hand, price of 857 1038. weight of 857 466. Ramming, amount required for concrete 388 466. concrete 388 158. granite blocks 139 897. Rattan brooms 712 118a. Rattler tests HI Raveling of broken-stone roads 662 INDEX. 1013 417. Recoating broken-stone pavements, when it should be done 340 558. Reconnoissance 453 834. Reconstruction of roads 646 863. Records 674 766. Refuges at street-intersections 593 873. Refuse, amount collected from streets (Table LXXXV1) 696 899. disposal of 712 866. Regulations for cantonniers 678 34. Relative economies of pavements 14 832. Relaying bridge-stones, specifications for 643 900. Removal of snow 712 907. from footpaths 718 902. in Milan 716 901. New York 713 303a. Repair of asphalt pavements 251 861. broken-stone pavements 669 431. gravel pavements 350 1024. Repairs, security retained for 771 1026. Repaving, specifications for 771 862. Requisitions for tools, etc 673 521. Resistance of friction 436 525. gravity (Table LII) 439 519. penetration .*...... 431 Slq. to abrasion 48 652> and impact ; 26 crushing of basalt (Table XXIV) 127 bluestone (Table IX) 37 bricks (Table XXIV) 127 cast iron (Table XXIV) 127 chalk (Table XXIV) . 127 common hard brick (Table XXIV) 127 concrete (Table XXIV) 127 69. granite (Table VI) 127 656. impact and abrasion 26 lead (Table XXIV) 127 85- Ligonier "granite" 41 limestones (Table XII) 40 119. paving-bricks 115, 127 65a. paving materials 26 pressed bricks (Table XXIV) 127 81. sandstones (Table IX) 37 soft brick (Table XXIV) 127 steel (Table XXIV) 127 Stourbridge brick (Table XXIV) 127 87. trap-rocks (Table XIV) 41 1014 INDEX. ARTICLE PAGE Resistance to crushing of wood (Table XXIII) 122 wrought-iron (Table XXIV) 127 517. traction 430 on different road surfaces (Table L) 437 65. Resisting properties of paving materials 26 721. Retaining-walls 556 728. and springs 559 726. dry-stone 558 727. failure of 559 725. form of 558 730. formula for thickness of 559 726. foundation of 559 730. minimum thickness of 559 659. on hillsides 508 724. proportions of 556 954. specifications for 743 733. where they should be built 560 90, 90o. Retine 63, 64 1036. Revolving stone screens, price of 840 996. Right reserved to alter details > 757 1036. Ring gauge 828 953. Rip-rap, specifications for , 743 Rise, amount of transverse (Table LXIV) 488 739. River-banks, roads along 532 862. Road force, organization of , . , 670 1033. machines, price of 803 1033. Road-leveller, price of 803 1033. use of 803 Road-surface, resistance to traction on different (Table L) 437 1036. Roadbed roller, form of 829 1036. price of 829 1036. weight of 829 516. specifications for preparation of 426 .864. Roadmen, instructions to 674 862. number required 670 Roads, acres, number required per mile (Table LXIII) 487 658. across bogs 505 657. marshes 503 1051. adapted to modern traffic 923 584. alignment of 465 739. along river-banks , 532 739. the seashore 562 450J. bitulithic 379 434. bituminous macadam 351 brick for.. . 283 INDEX. 1015 ARTICLE PAGE 575. Roads, bridge sites 459 354. broken stone for 296 $35. burned clay 647 448. charcoal 360 450c. chert 363 835. clay, improving ; 646 450e coal-tar macadam 364 436. concrete 352 555. Considerations governing the location of 453 623. contour, concave form of 490 625. for hillside 490 625. mountain 490 619. form of 488 624. manner of obtaining 490 619. parabolic form 488 622. straight lines objectionable 490 447. corduroy 360 555. country, location of 453 >621. crown, effect of excessive 488 618. for 488 588. curves, grade on 465 587. increasing width on 467, 624 radius of 465, 624 types of 466 : 588, 590. curving and straight, difference between 469 846. defects of existing 650 derivation of the word , xxxi 869. dirt, causes producing 694 ^682. drainage of 525 dust 901 suppression of 901 840. earth, cost of construction 649 834. improvement of 646 741. fencing for. 564 865. French, maintenance' of 676 450a. furnace slag 361 610. geological considerations in location of 482 604&. grade, cost of steep 478 594. denned 470 595. determination of 472 609. establishing the 481 848. loss caused by 651 599. maximum 473 604. to determine 474 06. minimum ; 479 1016 INDEX. ARTICLE PAGE 604. Roads, grade, most advantageous 475 585. on curves 455 847. profit of eliminating 650 6046. reducing, amount which may be spent in 478 607. undulating 479 1033. grading machinery and tools 803 424. gravel, construction of 349 582. halting- places on 465 734. hillside, protection of , . . . . 560 843, 845. improvement, estimating benefit of 649, 650 842. value of 649 851a. improving with oil 653 laws, early, in England xxxiv 849. length, profit of decreasing 651 608. level stretches on 480 555. location of 453 447. log 360 1033. machinery for 803 852. maintenance, defined 506 858a. errors in 663 European, methods of . 659 857. Massachusetts, methods of 659 857. systems of 658 570. map of 456 605. mountain grade for 478 579. location of 456 865. national, of France 676 851a. oil for the improvement of 653 659. on hillsides 506 660. rock slopes 508 656. over plains 503 Peru, early roads in xxxiii 444. plank 358 593. profile, construction 470 734. protection of 560 raveling of broken-stone 662 558. reconnoissance for 453 834. reconstruction of 646 576. Roman, construction of xxxii 576. route, final selection of 460 most satisfactory 462 rutting of broken-stone 662 837. sand, improvement of 648 909. snow 720 removal of 720 INDEX. 1017 ARTICLE PAGE 1050. Roads, State aid to the construction of 923 423a. methods of construction 348 850. surface, profit of improving 652 568. survey, preliminary 454 450e. tar-macadam 3 34 traction, resistance to, on (Table L) 437 604. transportation on, factors governing cost of 476 618. transverse contours 488 rise 485 919. trees on 728 740. tunnels on 563 582. water on 465 614. wide vs. narrow 485 587. widening wheelway on curves 467, 924 613. width, minimum 485 611. required 485 617. of mountain 486 616. right of way 486 613. wheelway 485 591. zigzags on, objections to 469 661. Rock cliffs, manner of forming roads along 509 662. Rock excavations 511 664. cost of 512 1035. tools for 822 639. increase in bulk of 493 662. quantity of, loosened by blasting 511 660. Rock slopes, roadways on 508 Rocks, absorptive power of (Table XI V 3 ) 48 87/. alteration of, defined 43 cementing property of (Table XIV S ) 60 decomposition of 43 fresh, defined 43 68. granite, described 29 82. limestone 39 recementing value of (Table XIV 5 ) 60 74. sandstone described 35 86. trap 41 67. varieties used for paving 28 397. Rollers, horse, defects of 320 1036. dimensions of 846 1036. price of 846 396. steam, advantages of 320 402. area rolled per day 323 1036. dimensions of , 849 405. manner of applying 325 1018 INDEX. 400. Rollers, steam, speed of 322 404. Rolling, amount required for broken-stone pavements 324 250. asphalt pavements 215 318. brick pavements 263 395. broken-stone pavements 319 406. cost of 328 653. embankments 502 453. foundations 383 428. gravel pavements 350 520. resistance of wheels 435 Roman cement, specific gravity of (Table XXIV) 127 weight of (Table XXIV) 127 473. Rosendale cement 392 973. specifications for 751 tests for 752 weight of 749 26. Roughness and durability 11 450o. Rubber pavement 377 ^Rutting of broken-stone roads 662 S. 15. Safety of pavements v 7 907. Salt used for the removal of snow 718 100L Salts in asphalt 81 994. Samples of materials 757 123. Sand 123 639. and gravel, shrinkage of 493 1326. artificial 126 454. as a foundation for pavements '. 384 252. character of, for asphalt pavement 216 127. concrete 124 126. paving : 124 126. cleanness of 124 381. core for broken-stone pavements 312 223, 916a. cure for slipperiness 198, 726 126, 155, 317a. Sand cushion 126, 138, 262 185. Sand, defects of 162 123. definition of 123 504. effect of size of grain on strength of mortar (Table XLVHI) .... 414 127. for concrete 124 155. cushion-coat of stone blocks 138 504. mortar, fineness of 411 453. foundations, defects of 383 454. manner of forming 384 INDEX. 1019 ARTICLE PAGE 496. Sand, in mortar 406 223. injurious effects of, on asphalt pavement 198 129. price of 124 126. quality of 124 road, load drawn by a horse on (Table LVII) 444 837. roads, improving of 648 traction on, resistance to (Table L) 437 837. trees of 648 125. sharpness of , 124 123. size of, for paving purposes 123 604. sieves for sifting (Table XLIX) 414 specific gravity of (Table XXIV) 127 173, 262, 974. Sand, specifications for 153, 225, 754 916a. Sand, to prevent slipping 726 126. test 124 124. use of , 123 127. 462. voids in 124, 386 130. weight of (Table XXIV) 124, 127 127. with clay 124 87p. Sandstone, absorptive power of (Table XIV L ) 48 79. amount produced for street purposes 38 analysis of (Table VIII) 36 102. bituminous, analysis of (Table XV) 76 986, 990, 102. in America 73, 77, 86 99gr. Europe 76 99^'. preparation of .". i ...'. ;VC. 77 162, 164, 172. block pavements 141 cost of construction 141 cementing value of (Table XIV 5 ) 60 79. commercial names of 36 74, 354. description of , , 35, 295 172. extent in the United States (Table XXIX) , . , 151 163. filling for joints . . . . 141 163. foundation for tt 141 27. pavements, life of . . , 11 recementing value of (Table XIV S ) * . . . 60 81. resistance to crushing of (Table IX) 87 81. specific gravity of (Table IX) 37 164a. specifications for 141 79. value of, used for street purposes (Table X] 38 weight of (Table IX) 37 1036. Scarifiers 855 1040. Scoop used by street patrol 876 450&. Scoria blocks 362 070, 1033. Scrapers 514, 805 1020 INDEX. 1033. Scrapers, capacity of 805 1033. cost of 805 1040. Scraping- machines . 816 839. improper use of 648 839. on earth roads 648 Screens for broken stone 838 739. Seashore, roads along t 562 916. water for street sprinkling 725 10436. suppressing dust 903 1024. Security retained for repairs 771 575. Selection of bridge sites 459 3. pavements, interests affected in the 2 58. paving material 24 922. trees 729 Serpentine, specific gravity of (Table XXIV) 127 weight of (Table XXIV) 127 41. Service of pavements, cost of 15 66a. tests of paving materials -, 27 14. Serviceability of pavements 7 821. Setting curb, specifications for 635 476. of Portland cement 396 937. stakes for curb 737 640. Settlement of earth 493 1042. Sewer inlet-traps 890 1022. Sewers, right to construct 770 112. Shales, composition of 107 for paving-brick >,.,,...,,,, 106 specific gravity of (Table XXIV) , , 127 weight of (Table XXIV) ., 127 132. Shingle 126 specific gravity of (Table XXIV) .... 127 weight of (Table XXIV) 127 670, 1033. Shovels , , . , 514, 803 375. Shrinkage of broken stone in rolling 310 639. clay 493 639. earth 493 639. gravel 493 639. and sand 493 639. loam 493 639. vegetable soil 493 692. Side ditches 529 649. Side-slopes, form of 497 648, 650. inclination of 497, 498 654. of embankments 502 930. staking out 732 INDEX. 1021 ARTICLE PAGE Sidewalks, average width of in various cities (Table LXXXII) 576 construction of, see Footpaths. 504. Sieves, size of, for sifting sand (Table XLIX) 414 686. Silicious soils, drainage of 525 687- Silt basins 526 Sinking fund that with compound interest will amount to $1 at the end of a term of years (Table XC) 915 1046. Sinking funds .* 921 313. Size of bricks 261 131. gravel for paving 125 123. sand for paving purposes 123 504. sieves for testing sand (Table XLIX) 414 stone-crushers 832 357. stone for broken-stone pavements 306 459. concrete 386 146. paving-blo.cks 134 549. wheels 451 182. wood paving-blocks 161 4506. Slag-blocks 362 450.C. Slag-tarred 382 Slate, specific gravity of (Table XXIV) 127 weight of (Table XXIV) 127 19. Slipperiness of asphalt 9 21, 916a. and wood, cure for 10, 726 19. granite 9 19. wood 9 916a. use of sand to prevent 726 651. Slips , 498 645. Slope, angles and length of (Table LXVl) 495 770. of footpaths 595 954. Slope-walls, specifications for 743 650. Slopes, covering of 498 ' 651. drainage of 498 natural, of earth (Table LXV) 495 654. of embankments 502 946. Sloping ground, specifications for preparation of 740 13. Smoothness, economy of 6 906. Snow, disposal of 717 904. by dumping in sewers 717 watercourses 717 melting 717, 886 902. removal in Milan 716 901. New York 713 903. Turin 717 900. of... .712 1022 INDEX. ARTICLE PAGE Snow, removal of, cost of (Table LXXXVII) 701 907. from footpaths 718 907. salt for 718 909. roads 720 901a. specifications for 713 909. roads, formation and maintenance of 720 traction on, resistance to (Table L). 437 908. weight of (Table XXIV) 127, 720 Snow-ploughs, form of 886 Soapstone, specific gravity of (Table XXIV) 127 weight of (Table XXIV) 127 Soft inferior brick, resistance to crushing of (Table XXIV) 127 specific gravity of (Table XXIV) 127 weight of (Table XXIV) 127 453. Soils, natural character of 383 Spain, early pavements in xxxvii 870, Specific gravity, determination of 47 89c. of asphalt 63, 127 basalt (Table XXIV) 127 bluestone (Table XI) 37 brick masonry (Table XXIV) 127 cast iron (Table XXIV) 127 chalk (Table XXIV) 127 clay {Table XXIV) ^ 127 with gravel (Table XXIV) * 127 common hard brick (Table XXIV) 127 460. concrete (Table XXIV) 127, 386 crude asphaltum 63 earth (Table XXIV) 127 English Portland cement (Table XXIV) 127 feldspar (Table XXIV) 127 flint (Table XXIV) 127 glass (Table XXIV) '. . 127 gneiss (Table XXIV) 127 69. granite (Table VI) , 31 gravel with clay (Table XXIV) 127 greenstone (Table XXIV) 127 gunpowder (Table XXIV) 127 ice (Table XXIV) 127 lead (Table XXIV) 127 lime (Table XXIV) 127 limestone (Table XII) 40 liquid bitumen (Table XXIV) 127 mica (Table XXIV) 127 mortar (Table XXIV) , 127 INDEX. 1023 ARTICLE PAGE Specific gravity of mud (Table XXIV) 127 naphtha (Table XXIV) 127 119. paving-brick (Table XXIV) 115, 127 petroleum (Table XXIV) 127 pitch (Table XXIV) 127 porphyry (Table XXIV) 127 476. Portland cement (Table XXIV) 127, 332 pressed brick (Table XXIV) 127 quartz (Table XXIV) . . . .* 127 lOOn. refined Trinidad asphaltum. . . .- 83 Roman cement (Table XXIV) 127 sand (Table XXIV) 127 81. sandstones (Table IX) 37 serpentine (Table XXIV) 127 shales (Table XXIV) 127 shingle (Table XXIV) 127 81. slate (Table XXIV) 127 soapstone (Table XXIV) 127 soft inferior brick (Table XXIV) 127 steel (Table XXIV) 127 Stourbridge fire-brick (Table XXIV) 127 trap-rock (Table XIV). 41 water (Table XXIV) 127 wood (Table XXIII) 122 wrought iron (Table XXIV) 127 941. Specifications, definition of 739 995. deviation from 757 987. engineer, defined 756 1017. for a bulkhead 765 960, 961. arch-culverts 745, 746 822. artificial curb and gutter 636 979. foundations 755 796. stone footpaths 616 450gr. pavements 370 296. asphalt-block pavements 248 780, 781. asphalt footpaths 598, 600 263. pavement on bituminous base 229 264. hydraulic concrete base 230 138. Belgian-block pavements 131 450. bitulithic macadam 379 303. bituminous-rock pavements 250 818. bluestone curb 634 954. breast- walls 743 784. brick footpaths 608 828. gutters 640 1024 INDEX. ARTICLE 968. Specifications 331-334. 830-831. 715, 10310. 423. 984. 951. 1018. 972. 962. 1011. 944. 945. 291. 450e. 135. 982. 782. 795. 512, 977. 303d. 830. 955, 960. 1018. 950. 823. 970. 969. 948. 741. 1018. 776. 978. 947, 1018. 816. 173. 967. 946. 829. 82S, 1018. 450gr. 827. 965. 1018. for brick masonry 747 pavements 273-281 bridge-stones 641-643 bridges 793 broken-stone pavements 343 cast iron 755 catch water-ditches 743 catch-basins 769 cement 749 centring 746 cleaning up 763 clearing 740 close cutting . , 740 coal-tar and asphalt pavements 243 macadam 368 cobblestone pavements 129 cofferdams 755 compressed-asphalt-tile footway pavement 607 concrete footpaths 615 concretes 423, 754 condition of asphalt pavements at end of guarantee period 255 crossing-stones 641 culverts 744, 745 curbing 768 drains 743 dressing old curb 638 dry box-culverts 748 walls 747 embankments 741 fencing 564 flagging 769 flagstones 597 foundation excavation 755 grading 740, 766 gra i e-block curb 633 pavements 152 grouting 747 grubbing 740 gutter-stones 641 gutters 640, 768 hydraulic-cement pavement 370 laying cobblestone gutters 639 masonry in freezing weather 746 macadamizing 767 INDEX. 1025 ARTICLE 956. Specifications for masonry 1010. 976. 952. PAGE 744 miscellaneous work 762 mortars 754 ofE-take ditches 743 954, 964. parapets 743, 746 97( . petroleum residuum 72 981. piles 755 971. pipe-culverts 748 966. pointing 747 516. preparation of roadbed 426 948. sloping ground 741 927. protection of trees 731 993. quality of materials 757 832. relaying crossing-stones 643 303c. repair of asphalt pavements 253 1026. repaving 771 824. resetting curb 638 954. retaining-walls 743 953. rip-rap 743 974. sand . . . 754 821. setting curb 635 954. slope walls 743 1031&. sprinkling 790 1031&. sprinkling-trucks 739 1027. street cleaning 772 797. tar-concrete footpaths 619 450e. tar macadam 368 1031a. team labor 789 339, 422. Telford's pavement 287, 344 1016. the construction of a highway 764 1019. the supply of broken stone 769 980. timber 755 338. Tresaguet's pavement 286 975. water 754 963. wing-walls 746 213, 216. wood-block pavements 178, 185 983. wrought iron 755 985. interpretation of 756 986. omissions in 756 941. preparation of 739 973. requirements for American natural cements 751 973. Portland cements 751 996. right to alter details in 757 895. Speed of machine-brooms 711 404. steam-rollers .324 1026 INLEX ARTICLE PAGE 401. Spikes in steam-rollers, defects of 322 1033. number of, per mile of track 812 1033. size of 812 992. Spirituous liquors 757 1033. Splice- joints, number of, per mile 812 633. Spoil-banks ! 492 636. form of 492 728. Springs behind or below retaining-walls 559 554. on vehicles, effect of 452 859, 913. Sprinkling, amount of water required 665 859. broken-stone pavements, amount of water required for 665, 722 911. Sprinkling of streets 722 915. cost of 724 914. frequency of 722 916. sea- water for 725 912. systems of 722 10306. specifications for 790 1036, 1040. Sprinkling-carts, capacity of 882 1036, 1040. prices of 884 103U. specifications for 754 897. Squilgees for asphalt 712 prices of 871 644, 646. Stability of earth 495 451. pavements 383 637. Staking out borrow-pits 493 933. bridges 735 931. culverts 733 938. curbing . 737 929. curves 732 934. drains 735 930. side-slopes 732 936. street contours 736 938. structures 737 935. vertical curves 735 928. work 732 1050. State aid to road construction 923 Statistics of streets in the largest cities in the United States (Table LXXXIII) 594, 927 Steam-drills, price of 825 402. Steam-rollers and grades 323 404. area rolled per day 324 403. cost of maintaining 323 dimensions of. 849 405. manner of applying 325 INDEX. 1027 ARTICLE PAGS 415. Steam-rollers, picks on, objectionable 339 404. speed of 324 161. Steel for filling joints 141 resistance to crushing of (Table XXIV) 127 specific gravity of (Table XXIV) 127 weight of (Table XXIV) 127 897. wire brooms 712 450^. trackways 372 in Germany 374 New York 375 Spain 373 Gibbon's patent 376 rail, form of 374 traction on, resistance to 376 541. Steep grades, objections to 446 166. pavements on 143 Slq, 356a. Stone, abrasion tests of 48, 302 64. absorptive power of (Table XIV 2 ) 48 412. amount of, worn away annually from broken-stone pave- ments t 339 450p. artificial 377 877. Stone-block pavement, cost of cleaning 700 618. crown for (Table LXIV) 488 133. described 123 601. grade for, maximum . . 473 159. joint-filling for 139 load drawn by a horse on (Table LVII) 444 166. on steep grades 143 1038. tools used in the construction of 856 transverse rise for (Table LXIV) 488 382. Stone, broken, quantity required per mile of different widths 313 87w, 356a. cementing property of 57, 303 355. coefficients of quality for broken-stone pavements (Tables XIV 4 and XXXVIII) 54, 304 1036. crushers, capacity of 832 1036. cost of 832 367. operating 307 1036. horse- power required for 832 1036. price of 832 1036. size of 832 368. wear of 307 1036. weight of 832 371. crushing, cost of (Table XXX) 308 Sli. durability of 45 87a. essential properties of 42 1028 INDEX. ARTICLE PAGE 1036. Stone forks, price of 828 151. gutters 135 1036. hammers, price of 828 876. hardness of 42 87w. methods of testing 47 133. pavements 129 152. paving-blocks at street- junctions 135 153. culling of 137 149. dressing of 135 351. quality of, for broken-stone pavements. ....... 293 459. concrete 386 371. quarrying, cost of (Table XXXIX ) 303 1036. rakes, price of 830 81w. recementing property of .' 60 Six. resistance to weathering 61 87^. rough surface under traffic 44 359. shape of, for broken-stone pavements 306 357. size of, for broken-stone pavements 306 438. trackways 356 87e. toughness of 43 437. trackways 353 870. uniformity of wear 44 362. Stones, breaking by hand . . 307 862. Storage and delivery of broken stone 673 Stourbridge fire-brick, crushing of (Table XXIV) 127 resistance to (Table XXIV) 127 specific gravity of (Table XXIV) 127 weight of (Table XXIV) 127 1036. Straight-edge, use of 828 225. Street-car rails and asphalt 201 31. tracks, city ownership of 13 868. Street-cleansing 693 898. carts and wagons 712, 877 877. 893. cost of 700, 711 897. hand-brooms for 712 881. in Baltimore 706 878. Berlin 704 882. Boston , 706 384. Cleveland 708 885. Detroit 710 880. London 706 886. New York 708 879. Paris 705 887. Philadelphia 708 883. Rochester .708 INDEX. 1029 ARTICLE PAGE 888. Street-cleansing in St. Louis 708 889. St. Paul 709 890. Washington, DC 709 1027. specifications for 772 876. systems of 698 899. dirt, disposal of '. 712 872. dust, composition of 695 749. grades 574 in various cities (Table LXXXII) 576 751. intersections, arrangement of .'. 575 766. carriageway at 593 766. increasing width of 593 925. trees at 730 152. junctions, paving with stone blocks 105 763. lines and monuments 588 maintenance, annual cost per head of population in several cities of the United States (Table LXXXVII) 700 875. methods of cleansing 698 872. mud, composition of (Table LXXXV) 695 1042a. name plates 892 891. orderly system 710 878. patrol in Berlin 704 765. profiles 591 911. sprinkling . 722 915. cost of 724 914. frequency of 722 913 quantity of water required 722 916. sea-water for 725 912. systems of 722 767. statistics for each, of fifty of the largest cities in the United States (Table LXXXIII) 593 745. Streets, city 568 57. excavations in 23 758. subfoundation, drainage of 581 759. surface-drainage of 582 893. sweeping, cost of 711 756. transverse contour of 580 752. grade of 577 917. trees on 727 910. washing 721 747. width of 574 in various cities (Table LXXXII J 576 468. Strength, compressive, of concrete 390 973. of cements 753 460-468. concrete.. . 386-390 1030 INDEX. ARTICLE PAGE 491, 499. Strength of mortar 403, 408 1045. Structures, annual cost of 912 938. setting stakes for 737 516. Sub-grade, preparation of 426 1012. Subletting contract 763 720. Substructure of bridges 553 723. Surcharged walls 556 731. formula for 559 850. Surface, profit of improving the 652 377. to find area of that which can be covered by a cubic yard of broken stone 310 693. Surface-drainage 529 759. of streets 582 1033. Surface-grader, price of 816 1033. use of 815 1008. Suspend work, power to 762 1040. Sweepers, mechanical 871 893. Sweeping, streets, cost of 711 858. time for C60 680. Syenite 30 876. Systems of street cleaning 698 856. maintenance 658 911. sprinkling 722 T. 797. Tar-concrete footpaths, specifications for 619 797. for footpaths 619 106. Tar-gas 74 450e. Tar-macadam, advantages of 365 cement for 367 consistency of 368 composition of 366 construction, cost of 364 disadvantages of 365 experience with ; 364, 369 failure of 366 maintenance, cost of 365 repair of 365 specifications for 368 stone, quality of 366 tar mixture, preparation of 367 quality of 367 quantity required 368 .-88a. Tar-mineral 62 INDEX. 1031 .ARTICLE PAGE 450;r. Tarred slag 382 862. Team-labor and materials 672 1031a. specifications for 789 422. Telford pavements, specifications for 344 342. Telford's method of broken-stone pavements 289 .344. defects of 289 483. Temperature, effect of variations on cement 398 257. for working asphalt paving cement 222 1049. of pavements 922 261. variation in, and asphalt pavements 223 103a. Tensile strength of asphalt 97 503. mortar (Table XLVII) 411 973. Portland cement 751 66. Testing materials 27 103a. asphalt . . . . . 88 H8a. brick , Ill 973. cement ....,...- 751 87n. stone . ., 47 122. . wood 120 1026. Texas asphalt 87 amount produced (Table XVIII) 102 413. Thickness, loss of, on broken-stone pavements 339 415. manner of restoring, on broken-stone pavements 339 722. minimum, of retaining-walls 556 714. of abutments 546 for arches (Table LXXVI) 548 713. arch stones 544 arch stone; (Table LXXV) 549 378. broken-stone pavements , . . , 310 154. foundation concrete 138 429. grave} 350 384. the layers .....' 313 689. Tile-drains 527 688. Tiles, diameter of 527 689. form of 527 689. length of 527 Timber bridges, dimensions for (Tables LXXIX and LXXX) '. . 554 980. specifications for , 755 858. Time for sweeping - , 660 1002. of completion , ; . . 760 544. Tires, effect of narrow 448 545. regulations governing width of 448 545. width of 448 527. To find the force required to sustain a vehicle upon an inclined road. . 441 528. pressure of a vehicle against the surface of an inclined road 441 1032 INDEX. ARTICLE PAGE Toll-roads in the United States xxxix 131. Tomkins Cove gravel 125 131. analyses of 126 1039. Tools employed for asphalt pavements 857 1038. block pavements 856 73. in the manufacture of granite paving-blocks 33 1040. for cleaning, price of 871 1033. grading 803 1032. grubbing, prices of 802 1036. macadamizing 828 1037. maintenance of broken-stone roads 856 1035. rock excavation 822 866. furnished by the administration 683 569. Topography , fc 455 87e, 65d. Toughness, denned 27, 43 Sis. test for 54 439. Trackways, cost of 337, 373 450n. Gibbon's patent 376 450n. steel 379 437. stone 353 517, 520. Traction, resistance to (Table L) 430, 437 597. Tractive force required in descending inclines 472 to move a load of one ton on different pave- ments in Europe (Table LI) 439 to move a load of one ton on different road- surfaces (Table LI) 437 531. power and gradients 44 536. loss on inclines 443 532, 533. of horses 442, 443 at different velocities (Table LIII) 442 45. Traffic census 17 393. defects of compacting the broken stone by the 319 228. sustained by asphalt , 205 670. Transport of earth 514 5. Transportation-wagon, cost of 2 604. factors governing c6st of 476 629. Transverse balancing 491 608. contour of roadways 488 757. streets 488 936. staking out 736 625. on hillside roads 490 756. grade of streets 580 467. strength of concrete 389 86, 354. Trap-rocks 41, 296 cementing value of (Table XIV 5 ) 60 INDEX. 1033 ARTICLE PAGE 86. Trap-rocks, color of 41 recementing value of (Table XIV 5 ) 60 87. resistance to crushing of (Table XIV) 41 87. specific gravity of (Table XIV) 41 value used for street purposes (Table XIVJ 42 87. weight of (Table XIV) 41 925. Trees at street- intersections 730 924. distance apart to plant 730 920. financial value of 729 919. on Belgian road 728 836. clay roads : 648 917. roads 727 837. sand roads 648 917. streets 727 918. the French roads 728 927. protection of . , 731 922. qualities of 729 922. selection of 729 927. specifications for protection of 731 917. use of 727 338. Tresaguet's system of broken-stone pavements 286 100. Trinidad asphalt 78 lOOrf. analyses of (Tables XlVa and XVI) 66, 79 lOOe. preparation of 79 104. price of 101 100. source of 78 740. Tunnels 563 Types of timber bridges 552 U. 91a. Uintahite 64 607. Undulating grades 479 847. Unnecessary grades, profit of eliminating 650 704. Use of catch-pools 536 124. sand 123 105. Uses of asphaltum 103 72. granite 33 9, 83. limestone 4, 39 464. Usual proportions for concrete 387 990. Utah asphalt (Table XIV a) 66, 77 V. Value of asphalt imported to the United States (Table XIX] 103 produced in the United States (Table XVlUa) 102 bluestone used for street purposes (Table XI) 38 1034 INDEX. ARTICLE PAGE 70. Value of granite used for street purposes (Table VII) 32 842. improvements 649 limestone used for street purposes (Table XIII) 40 sandstone used for street purposes (Table X) 38 Variations of temperature, effect of, on asphalt pavements 223 482. cement 398 483. mortar 398 120. Varieties of wood used for paving 120 638. Vegetable soil, shrinkage of 493 543. Vehicles, character of 447 543. effect of, on roads 447 543. narrow tires 448 400. loaded pressure of 321 527. power required to sustain, on inclines 441 529. pressure of, on inclines 441 554a. springs, effect of 452 543. tire, best width of 448 544. effect of narrow 448 548. width on load 449 545. regulations governing width of 448 550. wheels, advantage of 451 554. best diameter for 452 553. effect of two and four, on roads 452 520. resistance to rolling 435 549. size of 451 610. Vertical curves 481 935. staking out 736 Vitrified pipe, cost of (Table LXXI) 541 weight of (Table LXXI) 541 461. Voids, determination of 309 372, 461. in broken stone 308, 386 373. to determine ' 309 372, 461. gravel 308, 386 127, 462. sand 124, 386 280. Vulcanite pavement 240 W. 450w. Wadsworth's macadam 382 881. Wages, in Baltimore 706 882. Boston 707 1043. Europe 200 879. Paris 705 73. of paving-block makers 34 range of 900 INDEX. 1035 ARTICLE PAGE 5. Wagon-transportation, cost of 2, 900 670. Wagons, dump 514 450. Warren's bitulithic macadam 379 910. Washing, street 721 890. Washington, D. C., cleaning streets in.' 709 56. Waste of money in opening pavements 23 103a. Water, action of, on bitumen . 91 WQi. test for 81 484. amount of, absorbed by cements (Table XLIV) 400 rocks (Table XIV 2 ). 48 wood (Table XXII) 121 484. required for mortars 400 859. sprinkling, broken-stone pavements 665 695. breaks, objections to 530 497. for mortar, quality of 407 224. injurious to asphalt 198 582. on mountain roads 465 484. quantity of, for mortar 399 463. required for concrete 387 913. street-sprinkling 722 specific gravity of (Table XXIV) 127 975. specifications for 754 weight of (Table XXIV) 127 392. Watering broken-stone pavements 319 392. effect of excessive 319 794. Wear of artificial stones 614 666. asphalt blocks 27 231. pavements 206 666. brick 27 666, 4C9. broken-stone pavements 27, 333 666, 168. granite pavements 27, 145 666, 202. wood pavements 27, 171 729. Weep-holes 559 256. Weight of a cubic yard of asphalt paving- cement 222 American natural cement (Table XXIV) 127 asphaltum (Table XXIV) 127 basalt (Table XXIV) 127 bitumen (Table XXIV) 127 256. bituminous limestones (Table XXIV) 127 bluestone (Table IX) 37 brick (Table XXI) 115 masonry (Table XXIV) 127 374. broken stone 309 cast iron (Table XXIV) 127 972. cement 749 1036 INDEX. ARTICLE PAGE Weight of cement, English Portland (Table XXIV) 127 707. pipe (Table LXXII) 541 Rosendale (Table XXIV) 127 chalk (Table XXIV) 127 clay (Table XXIV) 127 with gravel (Table XXIV) 127 common hard brick (Table XXIV) 127 460. concrete (Table XXIV) 127, 386 culvert-pipe (Tables LXXI, LXXVII) 541, 549 drain-tiles (Table LXXVII) 549 earths (Table XXIV) 127 feldspar (Table XXIV) 127 flint (Table XXIV) 127 French Portland cement (Table XXIV) 127 glass (Table XXIV) 127 gneiss (Table XXIV) 127 69. granite (Table VI) 31 gravel with clay (Table XXIV) 127 gunpowder (Table XXIV) 127 1038. hand-rammers . . 856 ice (Table XXIV) 127 709. iron pipes (Table LXXIII) 542 lead (Table XXIV) 127 lime 127 84. limestone (Table XII) 127 liquid bitumen (Table XXIV) 127 masonry (Table XXIV) 127 mica (Table XXIV) 127 mortar (Table XXIV) 127 mud (Table XXIV) 127 naphtha (Table XXIV) 127 paving-bricks (Tables XXI, XXIa, XXIV) ... 88, 115, 116, 127 peat (Table XXIV) 127 petroleum (Table XXIV) 127 1033. picks 711 pitch (Table XXIV) 127 433. pit-gravel 351 porphyry (Table XXIV) 127 972. Portland cement (Table XXIV) 127, 749 pressed brick (Table XXIV) 127 quartz (Table XXIV) 127 rails 812 791. rammers for concrete 612 road rollers 849 Roman cement (Table XXIV) 127 INDEX. 1037 A.RTICLE PAGE Weight of Rosendale cement (Table XXIV) . 127 130. sand (Table XXIV) 124, 127 81. sandstones (Table IX) 37 scrapers 806 serpentine (Table XXIV) 127 shales (Table XXIV) . . . 127 shingle (Table XXIV) 127 slate (Table XXIV) 127 snow (Table XXIV) 127, 720 soapstone (Table XXIV) 127 soft inferior brick (Table XXIV) 127 steel (Table XXIV) 127 1036. stone-crushers 832 Stourbridge fire-brick (Table XXIV) 127 87. trap-rocks (Table XIV) 41 707. vitrified pipe (Table LXXI) 541 " water (Table XXIV) 127 wood (Tables XXII, XXIV) 127 wrought iron (Table XXIV) 127 1038. Wheelbarrows 808 327. Wheeling, plan of brick pavements 272 550. Wheels, advantages of 451 410. effect on, on pavements 333, 452 518. power required to draw, over obstacles . 430 520. rolling, resistance of 435 549. size of 451 613. Wheelway, minimum width of 485 334d. Wheelways, brick 283 450n. steel 372 437. stone 353 611. Wide roads 485 747. Width of carriageway, increasing of, at street-intersections 574 747. city streets 574 769. footpaths 595 191. joints in wood pavements 168 616. land appropriated in various localities for roads 486 617. mountain roads 487 147. paving-blocks 134 611. roads 485 587. roadways on curves 466 sidewalks in various cities (Table LXXXII) 576 587. streets in various cities (Table LXXXII) ; 576 545. tires 443 548. in Austria 449 547. Bavaria 449 1038 INDEX. ARTICLE PAGE 546. Width of tires in France 448 ordinance regulating 943 411. Wind, effect of, on roads 335 963. Wing-walls, specifications for 746 742. Wire fence, cost of 567 1038. screens, price of ...... 839 120. Wood 120 122. absorptive power of (Table XXII) 121 450. and iron, combination of 361 183. blocks, number per square yard . 161 188. chemical treatment of 164 122. creosoting, advantage of 121 188. cost of 164 777. for footpath: 597 177. pavements, advantages of 156 874. amount of dirt produced by 698 181. and death rate 159 210. asphalt- wood in England 175 216c. Australian wood in England 188 216e. New York 188 201, 208, 2166. cedar blocks 174, 188 186. chief cause of the failure of 162 877. cost of cleaning 700 205. construction (Table XXXIII) 172 206. maintenance 172 216e. cottonwood blocks 189 216k. cracking of 193 216A. creo-resinate process 190 618. crown, amount of (Table LXIV) 488 190a. cushion for 167 27, 193. durability of 11, 168 184. essentials necessary to successful construction 162 175. European 156 190. expansion of 166 expansion-joint for 167 205. extent in the United States (Table XXXIII) 173 192. filling for joints 168 first used in Russia 156 185. foundations used for 162 216e. gum blocks 189 1049a. heat, effect of 923 21 1. Henson system 175 174. history 156 212. improved system, Paris 176 2160. Jetley's patent 190 INDEX. 1039 ARTICLE PAGE 216e. Wood pavements, Karri wood 188 216*. kreodone blocks '. . 193 1906. laying the blocks 167 27. life of 11 214. maintenance by contract 181 206. cost of 172 599, 601 maximum grade for 473 209. mesquite block 175 216a. microbes in 187 179. objections to 156 216d. pine blocks 189 187. quality of wood for 163 216/. redwood block 189 19, 2l6h. slipperiness of 9, 192 213, 216. specifications for 178, 185 1049. temperature of 922 traction on, resistance to (Table L) 437 transverse rise for (Table LXIV) 488 182. variety of systems 161 202. wear of 171 191. width of joints 168 189. paving-blocks, dimensions of 166 depth 166 length 165 width 165 190. expansion of 166 216;. experiment with different 193 number per square yard 161 188. preservation of 164 216/L creo-resinate process 190 creosoting 164 specifications for 164 216t. kreodone 193 182. rectangular, preparation of 161 round 160 182. shape of 161 121, 187. quality of the wood 120, 163 188. preservation of 164 122. resistance to abrasion , 121 crushing of (Table XXIII) 122 122c. test for 121 122e. expansion 123 I22d, impact, test for 122 specific gravity of (Table XXIII) 122 120. varieties used for paving 120 1040 INDEX. ARTICLE PAGE Wood, weight of (Table XXIII) 122 719. Wooden bridges 553 dimensions of (Tables LXXIX and LXXX) 554 736. railings for road protection 561 188. Woods best adapted to chemical treatment 164 1001. Work, commencement of 760 998. defective 758 534. done by horses 442 1007. faithful performance of, bond for 762 999. how measured 758 1010. miscellaneous 762 1008. power to suspend 762 1003. progress of 762 1013. Workmen, payment of 763 983. Wrought iron, specifications for 755 91a. Wurtzilite 64 Z. 680. Zero-point, to ascertain, by calculation 524 591. Zigzags, objections to 469 SHORT-TITLE CATALOGUE OP THE PUBLICATIONS JOHN WILEY & SONS, NEW YORK. LONDON: CHAPMAN & HALL, LIMITED. ARRANGED UNDER SUBJECTS. Descriptive circulars sent on application. Books marked with an asterisk (*) are sold at net prices only. All books are bound in cloth unless otherwise stated. AGRICULTURE. Armsby's Manual of Cattle-feeding i2mo, $i 75 Principles of Animal Nutrition 8vo, 4 oo Budd and Hansen's American Horticultural Manual: Part I. Propagation, Culture, and Improvement i2mo, i 50 Part II. Systematic Pomology izmo, i 50 Downing's Fruits and Fruit-trees of America 8vo, 5 oo Elliott's Engineering for Land Drainage i2mo, i 50 Practical Farm Drainage i2mo, i oo Graves's Forest Mensuration 8vo, 4 oo Green's Principles of American Forestry i2mo, i 50 Grotenfelt's Principles of Modern Dairy Practice. (Wo 11.) i2mo, 2 oo Herrick's Denatured or Industrial Alcohol 8vo, 4 oo Kemp's Landscape Gardening lamo, 2 50 Maynard's Landscape Gardening as Applied to Home Decoration i2mo, i 50 * McKay and Larsen's Principles and Practice of Butter-making 8vo, i 50 Sanderson's Insects Injurious to Staple Crops i2mo, i 50 *Schwarz's Longleaf Pine in Virgin Forest 12010, i 25 Stockbridge's Rocks and Soils 8vo, 2 50 Winton's Microscopy of Vegetable Foods 8vo, 7 50 Woll's Handbook for Farmers and Dairymen i6mo, i 50 ARCHITECTURE. Baldwin's Steam Heating for Buildings I2mo, 255 Bashore's Sanitation of a Country House i2mo, i oo Berg's Buildings and Structures of American Railroads 4to, 5 oo Birkmire's Planning and Construction of American Theatres 8vo, 3 oo Architectural Iron and Steel 8vo, 3 50 Compound Riveted Girders as Applied in Buildings 8vo, 2 oo Planning and Construction of High Office Buildings 8vo, 3 50 Skeleton Construction in Buildings. 8vo, 3 oo Brigg's Modern American School Buildings 8vo, 4 oo 1 Carpenter's Heating and Ventilating of Buildings 8vo s 4 oo Freitag's Architectural Engineering 8vo, 3 50 Fireproofing of Steel Buildings 8vo, 2 50 French and Ives's Stereotomy 8vo, 2 50 Gerhard's Guide to Sanitary House-inspection i6mo, i oo Theatre Fires and Panics I2mo, i 50 *Greene's Structural Mechanics 8vo, 2 50 Holly's Carpenters' and Joiners' Handbook. i8mo, 75 Johnson's Statics by Algebraic and Graphic Methods 8vo, 2 oo Kidder's Architects' and Builders' Pocket-book. Rewritten Edition. i6mo,mor., 5 oo Merrill's Stones for Building and Decoration 8vo, 5 oo Non-metallic Minerals: Their Occurrence and Uses 8vo, 4 oo Monckton's Stair-building 4to, 4 oo Patton's Practical Treatise on Foundations 8vo, 5 oo Peabody's Naval Architecture 8vo, 7 50 Rice's Concrete-block Manufacture .- 8vo, 2 oo Richey's Handbook for Superintendents of Construction i6mo, mor., 4 oo * Building Mechanics' Ready Reference Book. Carpenters' and Wood- workers' Edition i6mo, morocco, i 50 Sabin's Industrial and Artistic Technology of Paints and Varnish 8vo, 3 oo Siebert and Biggin's Modern Stone-cutting, and Masonry 8vo, i 50 Snow's Principal Species of Wood 8vo, 3 50 Sondericker's Graphic Statics with Applications to Trusses, Beams, and Arches. 8vo, 2 oo Towne's Locks and Builders' Hardware i8mo, morocco, 3 oo Wait's Engineering and Architectural Jurisprudence 8vo, 6 oo Sheep, 6 50 Law of Operations Preliminary to Construction in Engineering and Archi- tecture 8vo, 5 oo Sheep, 5 50 Law of Contracts 8vo, 3 oo Wood's Rustless Coatings: Corrosion and Electrolysis of Iron and Steel. .8vo, 4 oo Worcester and Atkinson's Small Hospitals, Establishment and Maintenance, Suggestions for Hospital Architecture, with Plans for a Small Hospital. i2mo, i 25 The World's Columbian Exposition of 1893 Large 4to, i oo ARMY AND NAVY. Bernadou's Smokeless Powder, Nitro-cellulose, and the Theory of the Cellulose Molecule i2mo, 2 50 Chase's Screw Propellers and Marine Propulsion 8vo, 3 oo Cloke's Gunner's Examiner 8vo, i 50 Craig's Azimuth 4to, 3 50 Crehore and Squier's Polarizing Photo-chronograph 8vo, 3 oo * Davis's Elements of Law 8vo, 2 50 * Treatise on the Military Law of United States 8vo, 7 oo Sheep, 7 50 De Brack's Cavalry Outposts Duties. (Carr.) 241110, morocco, 2 oo Dietz's Soldier's First Aid Handbook i6mo, morocco, i 25 * Dudley's Military Law and the Procedure of Courts-martial. . . Large xarno, 2 50 Durand's Resistance and Propulsion of Ships 8vo, 5 oo * Dyer's Handbook of Light Artillery i2mo, 3 oo Eissler's Modern High Explosives 8vo, 4 oo * Fiebeger's Text-book on Field Fortification Small 8vo, 2 oo Hamilton's The Gunner's Catechism i8mo, i oo * HofTs Elementary Naval Tactics 8vo, i 50 2 Ingalls's Handbook of Problems in Direct Fire 8vo, 4 oo * Ballistic Tables ". 8vo, i 50 * Lyons's Treatise on Electromagnetic Phenomena. Vols. I. and II. .8vo, each, 6 oo * Mahan's Permanent Fortifications. (Mercur.) 8vo, half morocco, 7 50 Manual for Courts-martial i6mo, morocco, i 50 * Mercur's Attack of Fortified Places xamo, 2 oo * Elements of the Art of War 8vo, 4 oo Metcalf's Cost of Manufactures And the Administration of Workshops. .8vo, 5 oo * Ordnance and Gunnery. 2 vols i2mo, 5 oo Murray's Infantry Drill Regulations i8mo, paper, 10 Nixon's Adjutants' Manual 24mo, i oo Peabody's Naval Architecture 8vo, 7 50 * Phelps's Practical Marine Surveying 8vo, 2 50 Powell's Army Officer's Examiner I2mo, 4 oo Sharpe's Art of Subsisting Armies in War i8mo, morocco, i 50 * Tupes and Poole's Manual of Bayonet Exercises and Musketry Fencing. 24mo, leather, 50 * Walke's Lectures on Explosives 8vo, 4 oo Weaver's Military Explosives 8vo, 3 oo * Wheeler's Siege Operations and Military Mining 8vo, 2 oo Winthrop's Abridgment of Military Law I2mo, 2 50 Woodhull's Notes on Military Hygiene i6mo, i 50 Young's Simple Elements of Navigation i6mo, morocco, 2 oo ASSAYING. Fletcher's Practical Instructions in Quantitative Assaying with the Blowpipe. 12010, morocco, i 50 Furman's Manual of Practical Assaying 8vo, 3 oo Lodge's Notes on Assaying and Metallurgical Laboratory Experiments. . . .8vo, 3 oo Low's Technical Methods of Ore Analysis 8vo, 3 oo Miller's Manual of Assaying i2mo, i oo Cyanide Process I2mo, i oo Minet's Production of Aluminum and its Industrial Use. (Waldo.) i2mo, 2 50 O'Driscoll's Notes on the Treatment of Gold Ores 8vo, 2 oo Ricketts and Miller's Notes on Assaying 8vo, 3 oo Robine and Lenglen's Cyanide Industry. (Le Clerc.) 8vo, 4 oo Ulke's Modern Electrolytic Copper Refining 8vo, 3 oo Wilson's Cyanide Processes i2mo, i 50 Chlorination Process I2mo, i 50 ASTRONOMY. Comstock's Field Astronomy for Engineers 8vo, 2 50 Craig's Azimuth 4 t o , 3 50 Crandall's Text-book on Geodesy and Least Squares 8vo, 3 oo Doolittle's Treatise on Practical Astronomy 8vo, 4 oo Gore's Elements of Geodesy 8vo, 2 50 Hayford's Text-book of Geodetic Astronomy 8vo, 3 oo Merriman's Elements of Precise Surveying and Geodesy 8vo, 2 50 * Michie and Harlow's Practical Astronomy 8vo, 3 oo * White's Elements of Theoretical and Descriptive Astronomy i2mo oo BOTANY. Davenport's Statistical Me'h:>ds, with Special Reference to Biological Variation. i6mo, morocco, i 25 Thorns and Bennett's Structural and Physiological Botany i6mo, 2 25 Westermaier's Compendium of General Botany. (Schneider.) 8vo, 2 oo 3 CHEMISTRY. * Abegg's Theory of Electrolytic Dissociation. (Von Ende.) i2mt>, i 25 Adriance's Laboratory Calculations and Specific Gravity Tables i2mo. i 25 Alexeyeff 's General Principles of Organic Synthesis. (Matthews.) 8vo, 3 oo Allen's Tables for Iron Analysis 8vo, 3 oo Arnold's Compendium of Chemistry. (Mandel.) Small 8vo, 3 50 Austen's Notes for Chemical Students i2mo, i 50 Bernadou's Smokeless Powder. Nitro-cellulose, and Theory of the Cellulose Molecule i2mo, 2 50 * Browning's Introduction to the Rarer Elements 8vo, i 50 Brush and Penfield's Manual of Determinative Mineralogy .8vo, 4 oo * Claassen's Beet-sugar Manufacture. (Hall and Rolfe.) 8vo, 3 oo Classen's Quantitative Chemical Analysis by Electrolysis. (Boltwood.). .8vo, 3 oo Conn's Indicators and Test-papers i2mo, 2 oo Tests and Reagents 8vo, 3 oo Crafts's Short Course in Qualitative Chemical Analysis. (Schaeffer.). . .i2mo, i 50 * Danneel's Electrochemistry. (Merriam.) i2mo, i 25 Dolezalek's Theory of the Lead Accumulator (Storage Battery). (Von Ende.) i2mo, 2 50 Drechsel's Chemical Reactions. (Merrill.) i2mo, i 25 Duhem's Thermodynamics and Chemistry. (Burgess.) 8vo, 4 oo Eissler's Modern High Explosives 8vo, 4 oo Effront's Enzymes and their Applications. (Prescott.) 8vo, 3 oo Erdmann's Introduction to Chemical Preparations. (Dunlap.) i2mo, i 25 Fletcher's Practical Instructions in Quantitative Assaying with the Blowpipe. i2mo, morocco, i 50 Fowler's Sewage Works Analyses i2mo, 2 oo Fresenius's Manual of Qualitative Chemical Analysis. (Wells.) 8vo, 5 oo Manual of Qualitative Chemical Analysis. Part I. Descriptive. (Wells.) 8vo, 3 oo Quantitative Chemical Analysis. (Cohn.) 2 vols 8vo, 12 50 Fuertes's Water and Public Health i2mo, i 50 Furman's Manual of Practical Assaying 8vo, 3 oo * Getman's Exercises in Physical Chemistry i2mo, 2 oo Gill's Gas and Fuel Analysis for Engineers i2mo, i 25 * Gooch and Browning's Outlines of Qualitative Chemical Analysis. Small 8vo, i 25 Grotenfelt's Principles of Modern Dairy Practice. (Woll.) i2mo, 2 oo Groth's Introduction to Chemical Crystallography (Marshall) I2mo, i 25 Hammarsten's Text-book of Physiological Chemistry. (Mandel.) 8vo, 4 oo Helm's Principles of Mathematical Chemistry. (Morgan.) i2mo, i 50 Bering's Ready Reference Tables (Conversion Factors) i6mo, morocco, 2 50 Herrick's Denatured or Industrial Alcohol. ?vo, 4 oo Hind's Inorganic Chemistry 8vo, 3 oo * Laboratory Manual for Students i2mo, i oo Holleman's Text-book of Inorganic Chemistry. (Cooper.) 8vo, 2 50 Text-book of Organic Chemistry. (Walker and Mott.) 8vo, 2 50 * Laboratory Manual of Organic Chemistry. (Walker.) i2mo, i oo Hopkins's Oil-chemists' Handbook 8vo, 3 oo Iddings's Rock Minerals 8vo, 5 oo Jackson's Directions for Laboratory Work in Physiological Chemistry. .8vo, i 25 Keep's Cast Iron 8vo, 2 50 Ladd's Manual of Quantitative Chemical Analysis i2mo, i oo Landauer's Spectrum Analysis. (Tingle.) 8vo, 3 oo * Langworthy and Austen. The Occurrence of Aluminium in Vegetable Products, Animal Products, and Natural Waters 8vo, 2 oo Lassar-Cohn's Application of Some General Reactions to Investigations in Organic Chemistry. (TingleO i2mo, i oo Leach's The Inspection and Analysis of Food with Special Reference to State Control 8vo, 7 50 Lob's Electrochemistry of Organic Compounds. (Lorenz.) 8vo, 3 oo 4 Lodge's Notes on Assaying and Metallurgical Laboratory Experiments. .. .8vo, 3 oo Low's Technical Method of Ore Analysis 8vo, 3 oo Lunge's Techno-chemical Analysis. (Cohn.) 12010 I oo * McKay and Larsen's Principles and Practice of Butter-making 8vo, i 50' Mandel's Handbook for Bio-chemical Laboratory izmo, i 50 * Martin's Laboratory Guide to Qualitative Analysis with the Blowpipe . . i2mo, 60 Mason's Water-supply. (Considered Principally from a Sanitary Standpoint.) 3d Edition, Rewritten 8vo, 4 oo Examination of Water. (Chemical and Bacteriological.) I2mo, i 2<> Matthew's The Textile Fibres. 2d Edition, Rewritten 8vo, 400 Meyer's Determination of Radicles in Carbon Compounds. (Tingle.). .i2mo, oo Miller's Manual of Assaying I2mo, oo- Cyanide Process : I2mo, oo Minet's Production of Aluminum and its Industrial Use. (Waldo.). . . . i2mo, 50 Mixter's Elementary Text-book of Chemistry I2mo, 50- Morgan's An Outline of the Theory of Solutions and its Results i2mo, oo> Elements of Physical Chemistry i2mo f 3 00 * Physical Chemistry for Electrical Engineers I2mo, 5~oo Morse's Calculations used in Cane-sugar Factories i6mo, morocco, i 50 * Muir's History of Chemical Theories and Laws 8vo, 4 oo Mulliken's General Method for the Identification of Pure Organic Compounds. Vol. I Large 8vo, 5 oo O'Brine's Laboratory Guide in Chemical Analysis 8vo, 2 oo O'Driscoll's Notes on the Treatment of Gold Ores 8vo, 2 oo Ostwald's Conversations on Chemistry. Part One. (Ramsey.) J2mo, i 50 " " " " Part Two. (Turnbull.) i2mo, 200 * Pauli's Physical Chemistry in the Service of Medicine. (Fischer.) . . . . i2mo, i 25 * Penfield's Notes on Determinative Mineralogy and Record of Mineral Tests. 8vo, paper ; 50 Pictet's The Alkaloids and their Chemical Constitution. (Biddle.) 8vo, 5 oo Pinner's Introduction to Organic Chemistry. (Austen.) I2mo. i 50 Poole's Calorific Power of Fuels 8vo, 3 oo Prescott and Winslow's Elements of Water Bacteriology, with Special Refer- ence to Sanitary Water Analysis I2mo, i 25 * Reisig's Guide to Piece-dyeing 8vo, 25 oo Richards and Woodman's Air, Water, and Food from a Sanitary Standpoint.. 8vo, 2 oo Ricketts and Russell's Skeleton Notes upon Inorganic Chemistry. (Part I. Non-metallic Elements.) 8vo, morocco, 75 Ricketts and Miller's Notes on Assaying 8vo, 3 oo Rideal's Sewage and the Bacterial Purification of Sewage 8vo, 4 oo Disinfection and the Preservation of Food 8vo, 4 oo Riggs's Elementary Manual for the Chemical Laboratory 8vo, i 25 Robine and Lenglen's Cyanide Industry. (Le Clerc.) 8vo, 4 oo Ruddiman's Incompatibilities in Prescriptions 8vo, 2 oo * Whys in Pharmacy i2mo, i oo Sabin's Industrial and Artistic Technology of Paints and Varnish 8vo, 3 oo Salkowski's Physiological and Pathological Chemistry. (Orndorff.) 8vo, 2 50 Schimpf's Text-book of Volumetric Analysis i2mo, 2 50 Essentials of Volumetric Analysis I2mo, i 25 * Qualitative Chemical Analysis 8vo, i 25 Smith's Lecture Notes on Chemistry for Dental Students 8vo, 2 .50 Spencer's Handbook for Chemists of Beet-sugar Houses i6mo, moroeco, 3 oo Handbook for Cane Sugar Manufacturers i6mo, morocco, 3 oo Stockbridge's Rocks and Soils 8vo, 2 50 * Tillman's Elementary Lessons in Heat 8vo, i 50 * Descriptive General Chemistry 8vo, 3 oo Treadwell's Qualitative Analysis. (Hall.) 8vo, 3 oo Quantitative Analysis. (Hall.) 8vo, 4 oo Turneaure and Russell's Public Water-supplies 8vo, 5 oo- 5 Van Deventer's Physical Chemistry for Beginners. (Boltwood.) i2mo, i 50 * Walke's Lectures on Explosives < 8vo, 4 oo Ware's Beet-sugar Manufacture and Refining. Vol. I Small 8vo, 4 oo Vol.11 SmallSvo, 500 Washington's Manual of the Chemical Analysis of Rocks 8vo, 2 oo Weaver's Military Explosives 8vo, 3 oo Wehrenfennig's Analysis and Softening of Boiler Feed- Water 8vo, 4 oo Wells's Laboratory Guide in Qualitative Chemical Analysis 8vo, i 50 Short Course in Inorganic Qualitative Chemical Analysis for Engineering Students i2mo, i 50 Text-book of Chemical Arithmetic i2mo, i 25 Whipple's Microscopy of Drinking-water 8vo, 3 50 Wilson's Cyanide Processes I2mo, i 50 Chlorination Process .. i2mo, i 50 Winton's Microscopy of Vegetable Foods 8vo, 7 50 Wulling's Elementary Course in Inorganic, Pharmaceutical, and Medical Chemistry , I2mo, 2 oo CIVIL ENGINEERING. BRIDGES AND ROOFS, HYDRAULICS. MATERIALS OF ENGINEERING. RAILWAY ENGINEERING. Baker's Engineers' Surveying Instruments i2mo, 3 oo Bixby's Graphical Computing Table Paper 19^X24! inches. 25 Breed and Hosmer's Principles and Practice of Surveying 8vo, 3 oo * Burr's Ancient and Modern Engineering and the Isthmian Canal 8vo, 3 50 Comstock's Field Astronomy for Engineers 8vo, 2 50 Crandall's Text-book on Geodesy and Least Squares 8vo, 3 oo Davis's Elevation and Stadia Tables 8vo, i oo Elliott's Engineering for Land Drainage I2mo, i 50 Practical Farm Drainage i2mo, i oo *Fiebeger's Treatise on Civil Engineering 8vo, 5 oo Flemer's Phototopographic Methods and Instruments 8vo, 5 oo Folwell's Sewerage. (Designing and Maintenance.) 8vo, 3 oo Freitag's Architectural Engineering. 2d Edition, Rewritten 8vo, 3 50 French and Ives's Stereotomy 8vo, 2 50 Goodhue's Municipal Improvements I2mo, i 50 Gore's Elements of Geodesy 8vo, 2 50 Hayford's Text-book of Geodetic Astronomy 8vo, 3 oo Bering's Ready Reference Tables (Conversion Factors) i6mo, morocco, 2 50 Howe's Retaining Walls for Earth 12010, i 25 * Ives's Adjustments of the Engineer's Transit and Level i6mo, Bds. 25 Ives and Hilts's Problems in Surveying i6mo, morocco, i 50 Johnson's (J. B.) Theory and Practice of Surveying Small 8vo, 4 oo Johnson's (L. J.) Statics by Algebraic and Graphic Methods 8vo, 2 oo Laplace's Philosophical Essay on Probabilities. (Truscott and Emory.). i2mo, 2 oo Mahan's Treatise on Civil Engineering. (1873.) (Wood.) 8vo, 5 oo * Descriptive Geometry 8vo, i 50 Merriman's Elements of Precise Surveying and Geodesy 8vo, 2 50 Merriman and Brooks's Handbook for Surveyors i6mo, morocco, 2 oo Nugent's Plane Surveying 8vo, 3 50 Ogden's Sewer Design i2mo, 2 oo Parsons's Disposal of Municipal Refuse 8vo, 2 oo Patton's Treatise on Civil Engineering 8vo half leather, 7 50 Reed's Topographical Drawing and Sketching 4to, 5 oo Rideal's Sewage and the Bacterial Purification of Sewage 8vo, 4 oo Siebert and Biggin's Modern Stone-cutting and Masonry 8vo, i 50 6 Smith's Manual 01 Topographical Drawing. (McMillan.) 8vo, 2 50 Sondericker's Graphic Statics, with Applications to Trusses, Beams, and Arches. 8vo, 2 oo Taylor and Thompson's Treatise on Concrete, Plain and Reinforced 8vo, 5 oo * Trautwine's Civil Engineer's Pocket-book i6mo, morocco, 5 oo Venable's Garbage Crematories in America 8vo, 2 oo Wait's Engineering and Architectural Jurisprudence 8vo 6 oo Sheep, 6 50 Law of Operations Preliminary to Construction in Engineering and Archi- tecture , 8vo, 5 oo Sheep, 5 50 Law of Contracts 8vo, 3 oo Warren's Stereotomy Problems in Stone-cutting 8vo, 2 50 Webb's Problems in the Use and Adjustment of Engineering Instruments. i6mo, morocco, i 25 Wilson's Topographic Surveying 8vo, 3 50 BRIDGES AND ROOFS. Boiler's Practical Treatise on the Construction of Iron Highway Bridges. .8vo, 2 oo * Thames River Bridge 4to, paper, 5 oo Burr's Course on the Stresses in Bridges and Roof Trusses, Arched Ribs, and Suspension Bridges 8vo, 3 50 Burr and Falk's Influence Lines for Bridge and Roof Computations 8vo, 3 oo Design and Construction of Metallic Bridges 8vo 5 oo Du Bois's Mechanics of Engineering. Vol. II Small 4to, 10 co Foster's Treatise on Wooden Trestle Bridges 4to, 5 oo Fowler's Ordinary Foundations 8vo, 3 50 Greene's Roof Trusses 8vo, i 25 Bridge Trusses 8vo, 2 50 Arches in Wood, Iron, and Stone 8vo 2 50 Howe's Treatise on Arches 8vo, 4 oo Design of Simple Roof-trusses in Wood and Steel 8vo, 2 oo Symmetrical Masonry Arches 8vo, 2 50 Johnson, Bryan, and Turneaure's Theory and Practice in the Designing of Modern Framed Structures Small 4to, 10 oo Merrimon and Jacoby's Text-book on Roofs and Bridges : Ftri ! Stresses in Simple Trusses 8vo, 2 50 Part IL Graphic Statics 8vo, 2 50 Fart III. Bridge Design 8vo, 2 50 Part IV. Higher Structures 8vo, 2 50 Morison's Memphis Bridge 4to, 10 oo Waddell's De Pontibus, a Pocket-book for Bridge Engineers. . i6mo, morocco, 2 oo * Specifications for Steel Bridges * i2mo, 50 Wright's Designing of Draw-spans. Two parts in one volume 8vo, 3 50 HYDRAULICS. Barnes's Ice Formation 8vo, 3 oo Bazin's Experiments upon the Contraction of the Liquid Vein Issuing from an Orifice. (Trautwine.) 8vo, 2 oo Bovey's Treatise on Hydraulics 8vo, 5 oo Church's Mechanics of Engineering 8vo, 6 oo Diagrams of Mean Velocity of Water in Open Channels paper, i 50 Hydraulic Motors 8vo, 2 oo Coffin's Graphical Solution of Hydrr.ulic Problems i6mo, morocco, 2 50 Flather's Dynamometers, and the Measurement of Power I2mo, 3 oo 7 Folwell's Water-supply Engineering 8vo, 4 oo Frizell's Water-power. 8vo, 5 oo Fuertes's Water and Public Health i2mo, i 50 Water-filtration Works i2mo, 2 50 Ganguillet and Kutter's General Formula for the Uniform Flow of Water in Rivers and Other Channels. (Hering and Trautwine.) 8vo, 4 oo Hazen's Filtration of Public Water-supply 8vo, 3 oo Hazlehurst's Towers and Tanks for Water- works 8vo, 2 50 Herschel's 115 Experiments on the Carrying Capacity of Large, Riveted, Metal Conduits 8vo, 2 oo Mason's Water-supply. (Considered Principally from a Sanitary Standpoint.) 8vo, 4 oo Merriman's Treatise on Hydraulics 8vo, 5 oo * Michie's Elements of Analytical Mechanics 8vo, 4 oo Schuyler's Reservoirs for Irrigation, Water-power, and Domestic Water- supply Large 8vo, 5 oo * Thomas and Watt's Improvement of Rivers 4to, 6 oo Turneaure and Russell's Public Water-supplies 8vo, 5 oo Wegmann's Design and Construction of Dams 4to, 5 oo Water-supply of the City of New York from 1658 to 1895 4to, 10 oo Chippie's Value of Pure Water .Large i2mo, i oo Williams and Hazen's Hydraulic Tables 8vo, i 50 Wilson's Irrigation Engineering Small 8vo, 4 oo Wolff's Windmill as a Prime Mover 8vo, 3 oo Wood's Turbines 8vo, 2 50 Elements of Analytical Mechanics 8vo, 3 oo MATERIALS OF ENGINEERING. Baker's Treatise on Masonry Construction 8vo, 5 oo Roads and Pavements 8vo, 5 oo Black's United States Public Works Oblong 4to, 5 oo * Bovey's Strength of Materials and Theory of Structures 8vo, 7 50 Burr's Elasticity and Resistance of the Materials of Engineering 8vo, 7 50 Byrne's Highway Construction 8vo, 5 oo Inspection of the Materials and Workmanship Employed in Construction. i6mo, 3 oo Church's Mechanics of Engineering 8vo, 6 oo Du Bois's Mechanics-of Engineering. Vol. I. Small 4to, 7 50 *Eckel's Cements, Limes, and Plasters 8vo, 6 oo Johnson's Materials of Construction Large 8vo, 6 oo Fowler's Ordinary Foundations 8vo, 3 50 Graves's Forest Mensuration 8vo, 4 oo * Greene's Structural Mechanics 8vo, 2 50 Keep's Cast Iron 8vo, 2 50 Lanza's Applied Mechanics 8vo, 7 So Marten's Handbook on Testing Materials. (Henning.) 2 vols . .8vo, 7 So Maurer's Technical Mechanics ' , .8vo, 4 oo Merrill's Stones for Building and Decoration 8vo, 5 oo Merriman's Mechanics of Materials 8vo, 5 oo * Strength of Materials i2mo, i oo Metcalf's Steel. A Manual for Steel-users i2mo, 2 oo Patton's Practical Treatise on Foundations 8vo, 5 oo Richardson's Modern Asphalt Pavements 8vo, 3 oo Richey's Handbook for Superintendents of Construction i6mo, mor., 4 oo * Ries's Clays: Their Occurrence, Properties, and Uses 8vo, 5 oo Rockwell's Roads and Pavements in France i2mo, i 25 Sabin's Industrial and Artistic Technology of Paints and Varnish 8vo, 3 oo *Schwarz's Longleaf Pine in Virgin Forest,., izmo, i 25 Smith's Materials of Machines i2mo, i oo Snow's Principal Species of Wood 8vo, 3 5<> Spalding's Hydraulic Cement I2mo, 2 oo Text-book on Roads and Pavements I2mo, 2 oo Taylor and Thompson's Treatise on Concrete, Plain and Reinforced 8vo, 5 oo Thurston's Materials of Engineering. 3 Parts 8vo, 8 oo Part I. Non-metallic Materials of Engineering and Metallurgy 8vo, 2 oo Part II. Iron and Steel 8vo, 3 50 Part III. A Treatise, on Brasses, Bronzes, and Other Alloys and their Constituents 8vo, 2 50 Tillson's Street Pavements and Paving Materials 8vo, 4 oo Waddell's De Pontibus. (A Pocket-book for Bridge Engineers.). .i6mo, mor., 2 oo * Specifications for Steel Bridges i2mo, 50 Wood's (De V.) Treatise on the Resistance of Materials, and an Appendix on the Preservation of Timber 8vo, 2 oo Wood's (De V.) Elements of Analytical Mechanics 8vo, 3 oo Wood's (M. P.) Rustless Coatings: Corrosion and Electrolysis of Iron and Steel. . 8vo, 4 oo RAILWAY ENGINEERING. Andrew's Handbook for Street Railway Engineers 3x5 inches, morocco, I 25 Berg's Buildings and Structures of American Railroads 4to, 5 oo Brook's Handbook of Street Railroad Location i6mo, morocco, I 50 Butt's Civil Engineer's Field-book i6mo, morocco, 2 50 Crandall's Transition Curve i6mo, morocco, I 50 Railway and Other Earthwork Tables 8vo, I 50 Dawson's "Engineering" and Electric Traction Pocket-book. .i6mo, morocco, 5 oo Dredge's History of the Pennsylvania Railroad: (1879) Paper, 5 oo Fisher's Table of Cubic Yards Cardboard, 25 Godwin's Railroad Engineers' Field-book and Explorers' Guide. . . i6mo, mor., 2 50 Hudson's Tables for Calculating the Cubic Contents of Excavations and Em- bankments 8vo, i oo Molitor and Beard's Manual for Resident Engineers i6mo, i oo Nagle's Field Manual for Railroad Engineers i6mo, morocco, 3 oo Philbrick's Field Manual for Engineers i6mo, morocco, 3 oo Searles's Field Engineering i6mo, morocco, 3 oo Railroad Spiral. i6mo, morocco, i 50 Taylor's Prismoidal Formula; and Earthwork 8vo, i 50 * Trautwine's Method of Calculating the Cube Contents of Excavations and Embankments by the Aid of Diagrams 8vo, 2 oo The Field Practice of Laying Out Circular Curves for Railroads. i2mo, morocco, 2 50 Cross-section Sheet Paper, 25 Webb's Railroad Construction i6mo, morocco, 5 oo Economics of Railroad Construction Large i2mo, 2 50 Wellington's Economic Theory of the Location of Railways Small 8vo, 5 oo DRAWING. Barr's Kinematics of Machinery 8vo, 2 50 * Bartlett's Mechanical Drawing 8vo, 3 oo * " " Abridged Ed 8vo, 150 Coolidge's Manual of Drawing 8vo, paper, i oo 9 Coolidge and Freeman's Elements of General Drafting for Mechanical Engi- neers Obiong 4to, 2 50 Durley's Kinematics of Machines 8vo, 4 oo Emch's Introduction to Projective Geometry and its Applications 8vo, 2 50 Hill's Text-book on Shades and Shadows, and Perspective 8vo, 2 eo Jamison's Elements of Mechanical Drawing '. 8vo, 2 50 Advanced Mechanical Drawing 8vo, 2 oo Jones's Machine Design: Part I. Kinematics of Machinery 8vo, i 50 Part II. Form, Strength, and Proportions of Parts 8vo, 3 oo MacCord's Elements of Descriptive Geometry 8vo, 3 oo Kinematics; or, Practical Mechanism 8vo, 5 oo Mechanical Drawing 4to, 4 oo Velocity Diagrams 8vo, i 50 MacLeod's Descriptive Geometry Small 8vo, i 50 * Mahan's Descriptive Geometry and Stone-cutting 8vo, i 50 Industrial Drawing. (Thompson.) 8vo, 3 50 Moyer's Descriptive Geometry 8vo, 2 oo Reed's Topographical Drawing and Sketching 4to, 5 oo Reid's Course in Mechanical Drawing 8vo, 2 oo Text-book of Mechanical Drawing and Elementary Machine Design. 8vo, 3 oo Robinson's Principles of Mechanism 8vo, 3 oo S'chwamb and Merrill's Elements of Mechanism 8vo, 3 oo Smith's (R. S.) Manual of Topographical Drawing. (McMillan.) 8vo, 2 50 Smith (A. 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