T E LIBRARY OF THE UNIVERSITY OF CALIFORNIA. Accessions No Bfiek for Street Pavements. AN ACCOUNT OF TESTS MADE OF BRICKS AND PAVING BLOCKS, WITH A BRIEF DISCUSSION OF STREET PAVEMENTS AND THE METHOD OF CON- STRUCTING THEM. NEW EDITION, WITH A PAPER ON Prepared for the Engineers' Club of Cincinnati, April, 1894. 33Y . D. BURKE, C. E. CONTENTS. The Samples Submitted for Testing 5 How the Specimens were Prepared 7 Description of Specimens Submitted 9 How the Tests were Made 14 Abrasion and Impact 16, 42 Description of the Tables. 27 The Chemistry of Brick Manufacturing , 36 Discussion of the Tests. , 38 The Absorption Tests 40 Transverse Strength 41 Statistics of Traffic and Durability of Pavements 43 The Probable Durability of a Brick Pavement . . . 47 Municipal Methods 48 General Discussion of Pavements 53 What Shall be Specified 61 What Has Been Done 68 Tfte Matrix 76 Where Should Brick be Used for Street Pavements 78 Maintenance 81 What is in a Name. 83 Size of Paving Brick, 84 Country Roads 87 Brick for Street Pavements. AN ACCOUNT OF TESTS MADE OF BRICKS AND PAVING BLOCKS, WITH A BRIEF DISCUSSION OF STREET PAVEMENTS AND THE METHOD OF CON- STRUCTING THEM. NEW EDITION, WITH A PAPER ON COUNTRY ROADS, PREPARED FOR THE ENGINEERS' CLUB OF CINCINNATI, APRIL, 1894. BY M. D. BURKE, C.E. THE i" &SUO& CINCINNATI: ROBERT CLARKE & CO. 1894. / COPYRIGHTED, 1892. BY ROBERT CLARKE & CO. A large part of the contents of this pamphlet was con- tained in a report made to the village authorities of tests of material to be used in paving streets in Avondale, where the writer was employed as village engineer. The investiga- tion then made was as thorough as the time and means at hand would justify. Inquiries for the results of the work f\ - -^ have been so numerous, and requests for the same have b.een so frequently repeated, that it has been deemed advisable to publish the work in this form. If any information or suggestions herein contained shall aid in the construction of better pavements, or prevent the waste of money upon bad ones, or shall bring people to a consideration of placing municipal improvements under sys- tematic control and direction, or shall cause manufacturers to see that their true interest will best be subserved by plac- ing only good material upon the market, then this little pamphlet will have served a useful purpose. M. D. BURKE. CINCINNATI, March 16, 1892. BRICK FOR STREET PAVEMENTS. THE SAMPLES SUBMITTED FOR TESTING. It having been decided that the Main Avenue pavement "should be constructed of some form of clay product, a series of tests of the various materials in market was deemed ad- visable in order to aid in selecting the proper variety, and, if found practicable, fix a standard by which the different va- rieties might be adjudged and accepted or rejected, as their qualities and powers of resistance would determine. Ac- cordingly a circular letter was addressed to manufacturers and dealers, requesting them to ship to my office, at 41 Pike Building, Cincinnati, Ohio, samples consisting of twenty or more of each of the varieties of the bricks or blocks manu- factured or sold by them for street paving purposes, to be tested. In response to the circular letter, samples were kindly furnished by the following parties, and numbered as below : 1. Lithonia Georgia Granite, John Regan, contractor, city. 2. West Virginia Brick Co., Charleston, W. Va., H. C. Bruce, President. 3. The Diamond Brick and Terra Cotta Co., Kansas City, Mo. 4. The Pittsburg Sewer Pipe and Fire Clay Co., New Brighton, Pa. 5. Canton Brick Co. (red granite street pavers), Canton, Ohio. (5) BRICK FOR STREET PAVEMENTS. 6. The Royal Brick Co. (iron rock pavers), Canton, 0. 7. Purington Paving Brick Co., Galesburg, 111. 8. The United States Fire Clay Co., New Lisbon, Ohio ; M. R. Coney, agent. 9. The Middleport Granite Brick Co. (Hallwood Block), Middleport, Ohio. 10. L. B. Townsend & Co. (Townsend Paver), Zanesville, Ohio. 11. The Brazil Paving Block, Brazil, Ind., L. H. Mc- Cammon Bros., agents. 12. The Jones Paving Block, Zanesville, Ohio, L. II. McCammon Bros., agents. 13. The Ohio Paving Co. (Hallwood Block), Columbus, Ohio. 14. The John Porter Co., New Cumberland, W. Va. 15. The New York Paving Brick Co., Syracuse, N. Y. 16. Hallwood Block Granite Brick, manufactured by Tennessee Paving Brick Co., Robbins, Tenn. In this report the varieties are represented by the numbers above given, and the separate specimens by letters. Of each variety, except Nos. 1 and 16, ten bricks or blocks were used in making the various tests. A number always indicates the same variety, but only when the number and letter are the same, does it mean the same brick. Thus No. 1 always means a granite block, yet No. 1 A and No. 1 E are differ- ent blocks, but both Georgia granite. It was deemed advisable to ascertain, first, the essential chemical ingredients; second, the ratio of absorption ; third, crushing strength ; fourth, transverse strength ; fifth, the re- sistance to abrasion and impact. The Riehle testing ma- chine of Messrs. Otten & Westerihoff, appearing to be the most readily available, these gentlemen were employed, not only to make the crushing and transverse tests, but also to BRICK FOR STREET PAVEMENTS. make the chemical analysis and determine the specific grav- ity and ratio of absorption of the cubes which were pre- pared for the crushing test. How THE SPECIMENS WERE PREPARED. The testing of a single specimen of any kind being deemed insufficient, it was determined that three cubes of each variety be prepared for ascertaining the crushing strength. Accordingly three bricks or blocks of each va- riety were taken at random, and sent to the marble works of Joseph Foster & Sons, placed in the mill and sawed in two lengthwise, the cut being made so as to leave one piece about 2J inches in width. This piece was then cut by the saws trans- versely, so as to approximate as nearly as practicable to a 2-inch cube from the interior of the brick. The roughly sawn cubes were then placed upon a rubbing bed and worn down to the required size, with parallel and equal faces. Three such cubes were made of each variety. Of the gran- ite, A and B were made from one block ; C from another. Number 16, the three cubes were made from a single block, as of this number but three blocks were furnished. In making No. 15, which is of a very refractory material, the saw was unfortunately deflected in such a manner that cubes could not be obtained from two of the pieces, B and C, and they were rubbed down to two inches square by 1J inches high. Subsequent developments show that it would have been advisable to have made 1J inch cubes instead of 2 inch. The testing machine used has a capacity of 52,000 pounds. It was thought that very few, if any, of the specimens would show an ultimate crushing strength exceeding 13,000 pounds per square inch, but in this we were mistaken. By the same process above described, four " granite BRICK FOR STREET PAVEMENTS. bricks" were manufactured; that is, four pieces of granite 2Jx4x8 inches were made, to be subjected to the same tests as the bricks, in order to compare the resistance of the clay products with a standard paving material. It will be ob- served that great care Was taken in this work in order to preserve the material of each specimen intact and to pre- vent injury to it in any way. No cutting with chisels or spalling was permitted. Each specimen was numbered and lettered and its identity preserved throughout the entire series of tests. The cubes were used for three purposes : First, for obtaining the ratio of absorption ; second, specific gravity, and third, the crushing strength of the material. Another absorption test Was made with whole bricks, and in some instances the percentages obtained differed materi- ally. There are two reasons for these differences : A single cube only was used and it was immersed but twelve hours. For some of this material probably this length of time was too short for it to absorb all the water that it would ulti- mately take up, but generally the percentages obtained by immersing the cubes was materially higher than that ob- tained from the whole bricks, which is a result to be ex- pected when it is remembered that the outer portions of the bricks were in several cases salt-glazed and were gener- ally more dense and burned harder than the interior portion from which the cubes were obtained. The specimens sub- jected 'to crushing were lettered A, B, C, those lettered A being used for the absorption as well as the crushing test. No essential preparation of the specimens for the re- maining tests was necessary, They were all kept in a steam- heated room from the time of their arrival until used, which was about one week for the latest arrivals, and about four weeks for the earliest. All would be classed as perfectly dry. All adhering sand or 'dust was carefully brushed from BRICK FOR STREET PAVEMENTS. those tested for absorption or abrasion before weighing them. In selecting those used for ascertaining the transverse strength, perfect specimens, showing no fire cracks or other defects, were taken. In fact the manufacturers or agents had generally done the selecting and packing with such care that no outside defects were visible, except as noted for No. 10. DESCRIPTION OF SPECIMENS SUBMITTED. No. 1. Application was made to the Southern Granite Company for specimens of their material, but none was re- ceived, accordingly the samples used were obtained from Mr. John Regan, contractor, who was using Lithonia granite in paving a street, and the cubes and specimen bricks were sawed from the interior of the blocks, rubbed down, with- out the use of hammer or chisel, to the dimensions given as above noted, in the preparation of the specimens. No. 2 is a hard burned brick manufactured from plastic clay and burned in the ordinary clamp kiln. It is about 2J"x3f"x8", and if closely laid, about sixty-five of them would pave a square yard. Its record can be traced through the various tests in the following tables by its number. Its history as a street paver is said to be quite satisfactory in some localities, but it should not be used where the traffic is very considerable. No. 3 is manufactured from a shale or plastic clay which readily vitrifies. In size it averages 2J''x3f"x8", and about sixty- eight will be required for each square yard of pave- ment. The chemical analysis, as given in table No. 1, does not show that it contains an objectionable amount of lime, but other tests unmistakably manifest its presence in form and quantity to a highly detrimental degree. The brick is very hard and dense, ranking third in specific gravity, but it is rather small and quite brittle, the fracture being con- 10 BRICK FOR STREET PAVEMENTS. -choidal, and it will' yield to the trituration of animals' shoes rather than the grinding of the wheels of vehicles. I have no knowledge of its record in actual service as a street paver. No. 4 is what is known as a lire-clay brick. In color it is an orange buff. The average size is 2J"x4J"x8J". About fifty-nine \vould lay a square yard of pavement. It absorbs water rather freely, but not to a greater extent than many acceptable building stones, and in all the other tests its stand- ing is good. Nos. 5 and 6 are practically the same brick, manufac- tured from a shale or indurated clay. In color they are a dark red. They average 2J"x4i"x8f", and about fifty-nine of them will pave a square yard. The samples tested are all burned quite hard, but not in all cases to vitrification ; hence while they show great transverse strength, and resist abra- sion well, they are comparatively low in crushing strength and there is great variation in the percentage of absorption. Their record in actual use is quite satisfactory, but I have no statistics of the severity of the traffic to which they have been subjected. No. 7 is of a dark red color, 2J"x3f "x7f" in size. About sixty-nine will be required for each square yard of pave- ment. In all the tests this ranks among the best of the red bricks, and its record under moderate traffic is good. An increase in size so as to afford a greater weight of pavement would appear to be prudent if it is to be used under heavy traffic. No.. 8 is a fire-clay brick of a light buff color, 2 T 9 g"x 3|"x8 T y, of which about fifty -five will pave a square yard. The material of which it is composed has not been very finely ground nor very thoroughly compressed. As a con- sequence it has a low specific gravity, a moderately high rate BRICK FOR STREET PAVEMENTS. 11 of absorption, and is outranked by several other varieties in the other tests, but in the uniform quality of each individual brick as compared with the others of its kind, it stands at the head of the list. No. 9. In chemical constituents this coincides more nearly with No. 2 than any of the other samples submitted, yet the treatment of the material has been so different that the results are in no respect similar. It is a glazed Ha 11- woo'd block, 2 1 y'x3f"x8J", and about fifty-five of them will lay a square yard of pavement. The glaze is said to be a natural, and not a salt glaze. The corners are rounded to about one-half inch radius, and two J" groves extend length- wise around the block near its middle. The clay has been finely ground and completely vitrified, but inasmuch as it contracts greatly in burning, the blocks are liable to show cracks on the outside or cavities on the inside. When broken the blocks show an even dense texture of a dark brown color, and, were the defect above noted remedied (which it would appear to the writer, could be readily done), they would be greatly improved for street paving purposes. No. 10 had been assorted to some extent when they came into my hands, as more than one-fourth of the bricks had been broken in the box. The average size ?.s 2^' f x"x8^j", and fifty-eight of them will lay a square yard of pavement. They are dark brown in color, with corners rounded to about one-fourth of an inch radius; burned exceedingly hard, although they do not present the melted appearance of most of the vitrified bricks. While this brick has great hardness, with sufficient density for all practical purposes, :and even a high degree of tenacity under a steadily applied stress, yet it possesses great brittleness, and when subjected to shocks, shows a tendency to spall badly. Could the qual- ity of toughness be given it without materially diminishing 12 BRICK FOR STREET PAVEMENTS. its hardness, no essential of a desirable brick paver would be lacking. No. 11 is manufactured from a clay found in the coal measures but not termed a fire-clay. It is a salt-glazed block 2|"x4"x9J" in size, and each square yard of pavement will require about forty-eight blocks. The corners are slightly rounded. Little fault can be found with the chem- ical ingredients, although an additional amount of iron would be in better proportion to the quantity of alkalies present. The form and size of block has been well chosen if such a thickness can be properly burned, but the mechan- ical work of preparing the material and forming the block has been indifferently done and the burning decidedly un- derdone. No. 12, is of well chosen dimensions, being 2f // x4J"x9", and fifty-one blocks will lay a square yard of pavement. The material of which it is composed is about the same as that of which No. 10 is made, namely, a mixture of shale and clays found in the coal measures. The corners are rounded to about one-fourth of an inch radius. The blocks are re- pressed, with five grooves passing transversely nearly across one side, and eight diagonally nearly across the other. The sand, or possibly the oil, used in repressing, serves to give it a reddish brown color. Giving the block a form such that it should always be placed with the same side up ap- pears to be a refinement hardly required in practice. The material might have been made into a good paving block, ,but it was not. The clays were not ground sufficiently fine, neither was the burning carried to such an extent as to pro- duce a block that would withstand the abrasion of street traffic. The samples tested were obtained from an agent, and not directly from the manufacturers. No. 13, is salt-glazed, corners rounded to about one-half BRICK FOR STREET PAVEMENTS. 13 inch radius, with two grooves about one and one-half inches apart, passing lengthwise around it near the middle. About forty-six blocks will pave one square yard. It shows a higher percentage of iron than any other specimen analyzed, but appears to be mainly composed of a plastic clay, possi- bly indurated, which has been finely ground and skillfully combined. In the process of burning or vitrification, the iron and alkalies have combined so as to render the material practically impervious to moisture, but it has not quite as high a specific gravity nor the strength that should be obtained with this material. Its record -in practical use is very good, and under any thing like fair treatment will give satisfactory results. No. 14, is a repressed fire-clay brick, with corners rounded to about three-sixteenths of an inch radius. The average size is 2J // x4J // x8J", and sixty of them will pave a square yard. The material is very similar to No. 4, but the repressing has given it advantages in some particulars. It is of a buff color. It has been used as extensively for street paving as any other variety tested, and under mod- erate traffic its record has been satisfactory. A result ap- pears to be attainable with this material which is not al- ways secured, but when it is, leaves but slight room for ap- parent improvement in the manufacture of paving blocks. It is obtained by the fusion of the iron with the silica when acted upon by the alkalies or other fluxes, in the pro- cess of burning or vitrification, producing a block, which, when broken, presents a gray metallic or granitic texture, showing no traces of cleavage or granular structure, and perfectly uniform throughout. Of the sample bricks of this variety tested, about seventy-five per cent were completely vitrified as here described, while the others presented a granular appearance, either throughout or in the central por- OF THS 'n ". 14 BRICK FOR STREET PAVEMENTS. tion, but they were all very hard burned. The cube used for obtaining specific gravity and percentage of absorption was but partially fused, hence it shows great affinity for moisture. This fusion does not appear to add materially to the strength, but it does lessen the amount of absorption without materially increasing the brittleness. No. 15, is drab or brown in color, 2J /r x3 T y / x7| /r in size, requiring about seventy-five of them to lay a square yard of pavement. The clay from which this brick is made is evidently largely formed from the disintegration of lime- stone rocks. All the samples were thoroughly vitrified, and the product is an exceedingly refractory substance. Could the lime be eliminated from it before burning, the bricks would be as nearly indestructible as could be desired, but every brick tested manifested the presence of lime in quan- tity sufficient to impair its durability. No. 16, is made from a shale or clay found in the coal measures, although not described as a fire clay. But three of these blocks were obtained for making the tests, and each was quite a perfect specimen of its kind. This is a Hallwood block, corresponding in dimensions with No. 13, and if the samples fairly represent the product of the kilns, pavements properly laid with this material will be both dura- ble and satisfactory. How THE TESTS WERE MADE. Absorption. Of the cubes prepared as before described, the one lettered "A" of each variety was placed in a drying oven and maintained at a temperature of 212 Fahrenheit for twelve hours, in order to drive off any contained mois- ture. Each was then accurately weighed. The figures ob- tained are found in the second column from the left of Table No. 2. It was then immersed in water, where it re- BRICK FOR STREET PAVKMEMS. 15- mained for the succeeding twelve hours, when it was taken out, the adhering moisture wiped off, and again weighed, the results heing noted in the third column from the left in the same table. At this time it was also weighed in water, these last weights being found in the sixth column of Table No. 2. For a further test of absorption two whole bricks of each variety (except as noted in the table) were selected at ran- dom, lettered G and H respectively, placed on an ordinary counter scale weighing to quarter ounces, the results noted, and are found in the ninth column from the left in table No. 2. They were then placed in water and kept entirely submerged for seventy hours, when they were taken out, dried with a towel, again weighed, with results found in the tenth column of the same table. These results are only as accurate as the scales were, but the test can be readily re- peated at any time, and will give a fair practical measure of the absorption to be expected from whole bricks in a sim- ilar length of time. The samples had been kept in a steam- heated room during the preceding ten days, and the dust and sand were carefully brushed from them before the first weighing. Crushing Strength. For determining the crushing strength the cubes were carefully measured, 'their upper and lower surfaces protected by a thickness of blotting paper y and they were subjected to pressure in a Riehle Testing Ma- chine of 52,000 pounds capacity. The results obtained will be found in table No. 3. No visible effect was produced upon the granite except that " B" was very slightly spalled, as noted. No. 15 " C," which was about one and one-half by two inches, was set on edge after being tried the other way, and a pressure exerted exceeding 17,000 pounds per 16 BRICK FOR STREET PAVEMENTS. square inch, but it could not be crushed, although it spalled at one corner at a little over 7,000 pounds per square inch. Transverse Strength. The transverse strength was as- certained in the same machine in the following manner : Three bricks of each variety (except as noted) were chosen and lettered D, E and F. The lower knife edges were ad- justed at precisely six inches apart, the upper knife edge being placed centrally between them. Each specimen was carefully measured and its surface protected from direct abrasion at the points of bearing by two or three thick- nesses of blotting-paper, and the weight required to break it carefully noted. These results are found in table No. 4. ABRASION AND IMPACT. The method adopted for determining the relative re- sistance to abrasion and impact was that which is com- monly known as the rattling test. A cylinder about six feet in' length by twenty-eight inches in diameter, contain- ing pieces of cast iron, varying in weight from one to six or eight pounds, and in the condition in which it is ordina- rily used for cleaning castings, was selected for this purpose. Four bricks of each variety (with the exceptions noted in the table) were selected and lettered G, II, I and J, two of the specimens, G and H, having been soaked for the preceding seventy hours. The specimens were carefully weighed and .all placed in the rattler at one time. Billets of wood were put in with them, as is ordinarily done in cleaning cast- ings, to prevent breaking. The cylinder was revolved at a speed of about twenty-four revolutions per minute, and at the end of one thousand revolutions was stopped, the speci- mens taken out, weighed and the loss of each noted. The object of making this fl^rst test in this particular manner was to wear away the sharp angles or corners and bring BRICK FOR STREET PAVEMENTS. 17 each piece as nearly as practicable on a level footing with its fellow for that which was to follow. This first test, therefore, was intended more to equalize the several pieces than to measure their actual wear. On the following day the specimens were again placed in the cleaner, omitting the protecting billets of wood. The object now being to observe the survival of the fittest. The cylinder was given three thousand revolutions, occupy- ing something over two hours in time, and although all the pieces were in at the same time, excepting a fragment of ~No. 15 " I," which had broken off in the former test and was in- advertently omitted ; there was ample room for .motion and the loss in weight of every piece was a measurable quantity. The individuality of some specimens was lost, as the marks were in some cases almost entirely worn away, but there was no trouble in identifying the varieties ; hence, in tabulating the results of this work the percentage of loss in the sec- ond rattler test is given for each variety. This will be found in detail in table !N"o. 5. With the completion of the second rattler test closed the actual work upon the specimens, and the labor of col- lating the information obtained was commenced. Further investigation would appear to be desirable, especially some test that will more nearly resemble the attrition of the shoes of animals in passing over the pavement than do any of the tests that were made. But the information now gained would appear to justify seeking that knowledge by a prac- tical test of the brick in the street pavement itself. 2 18 BRICK FOR STREET PAVEMENTS. TABLE No. 1. CHEMICAL ANALYSES. No. OF SPEC- IMEN. SILICA. ALUMINA. PEROXIDE OF IRON. i i3 MAGNESIA. ALKALIES. UNDETER- MINED. TOTAL PER- CENTAGES. 2 73.32 14.82 8.34 0.70 0.99 2.26 100.43 3 64.37 19.73 9.07 0.82 2.32 1.89 1.80 100.00 4 67.36 22.05 5.61 0.86 0.36 2.70 1.06 100.00 5 67.65 18.36 8.34 0.80 1.02 2.58 1.25 100.00 6 68.12 18.63 8.53 0.68 0.71 2.58 0.75 100.00 7 68.69 17.95 7.25 0.76 1.47 2.83 1.05 100.00 8 64.08 25.32 5.44 0.30 0.29 0.63 3.94 100.00 9 71.57 17.06 8.34 0.50 0.58 0.56 1.39 100.00 10 61.80 20.76 8.70 1.38 1.09 1.44 4.83 100.00 11 77.67 14.77 3.63 0.38 0.27 2.43 0.85 100.00 12 65.08 22.39 7.97 0.62 0.74 2.33 0.87 100.00 13 66.30 18.62 9.78 0.40 0.84 1.89 2.17 100.00 14 15 69.02 67.67 22.07 11.67 4.53 6.53 1.70 12.74 0.38 0.95 1.34 0.80 0.96 100.00 100 . 36 16 70.57 15.19 7.97 0.78 0.32 1.15 4.02 100.00 Undertermined is water manganese oxide and possibly some titanic acid. OTTEN & WESTENHOFF, Chemists. BRICK FOR STREET PAVEMENTS. 19 I 1 o ll o .SP ||! S O o hi 0) 'i. fc+< >ad .S s ^ cc w> TJ*C1 i-H COOOOOi-HrH i-Hr-IOO i-KNr-l OOOrH r-IO C fil S 8 8 9 9 t if i 20 BRICK FOR STREET PAVEMENTS. TABLE No. 3. CRUSHING STRENGTH. SPECIMEN NO. || | LETTER. SIZE IN INC. AREA IN | SQUARE IN. SPALLED AT IN POUNDS. SPALLED AT II IN POUNDS PER SQ. INCH. || CRUSHED AT IN POUNDS. CRUSHED AT IN POUNDS PER SQ. INCH. REMARKS. 1 B 1 I g 1 B 2. 2. 2. 4. 40480 10120 Did not crush at 52000 lbs.=13000 Ibs. 2 A 1.97 1.97 1.94 3.82 29600 7749 35500 9293 per D". Soaked 12 hours. 2 B 1.94 1 94 1.94 3.76 28000 7447 35920 9553 2 C 1.94 1.97 1.94 3.82 Did not spall at 52000 Ibs. = 13613 Ibs. 3 A 1.97 1.97 1.97 3.88 32290 8322 37720 9722 per D". Soaked 12 hours. B 1.94 1.97 1.94 3.82 15200 3979 48000 12565 3 C 1.97 1.94 1.94 3.76 18100 4813 32720 8702 4 A 1.97 1.97 1.97 3.88 33110 8533 43120 11113 Soaked 12 hours. 4 B 1.97 1.97 1.97 3.88 36590 9427 Did not crush at 52000 Ibs. = 13402 Ibs. per Q". 4 C 1.97 1.97 1.97 3.88 Did not spall at 52000 Ibs. = 13402 Ibs. 5 A 1.94 1.97 1.94 3 82 50000 13089 per D". Soaked 12 hours. Did not crush at 52000 Ibs. = 13613 Ibs. per Q". 5 B 1.97 1.97 1.97 3.88 38850 10013 39150 10090 5 C 1.97 1.97 1 97 3.88 28000 7216 38850 10013 6 A 1.94 1.91 1.91 3.65 19650 5383 23100 6329 Soaked 12 hours. 6 B 1.94 1.94 1.91 3.70 37220 10059 51500 13919 6 C 1.97 2.00 1.97 3 94 Did not spall at 52000 Ibs. = 13198 Ibs. 7 A 2.00 1.97 1.97 3.88 25120 6471 51600 13300 per D Soaked 12 hours. 7 B 1.97 1.97 1.97 3.88 Did not spall at 52000 Ibs. = 13402 Ibs. per D''. 7 C 1.97 1.97 1.97 3.88 38550 9935 52000 13402 8 A 1.97 1.97 1.94 3.82 34000 8900 46460 12162 Soaked 12 hours. 8 B 1.97 1.97 1.94 3.82 25220 6602 44650 11688 8 C 1.97 1.97 1.97 3.88 25030 6451 39570 10198 9 A 1.97 1.97 1 94 3.82 24000 6283 39820 10424 Soaked 12 hours. 9 B 1.97 2.12 1 97 4.18 26000 6220 48270 11548 9 C 2.00 1 97 .94 3.82 17500 4581 39820 10424 10 A 1.97 1 97 .97 3.88 50750 13080 Soaked 12 hours. Did not crush at 52000 Ibs. =13402 Ibs. per Q". 10 B .97 1.97 97 3.88 35500 9149 51460 13263 10 C .97 1.97 .94 S 82 32000 8377 50050 13102 11 A .97 1.97 .97 3.88 27900 7191 50300 12964 Soaked 12 hours. 11 B .97 1.97 94 3.82 24000 6283 39400 10314 11 C .97 1.97 1.97 3.88 23880 6155 27250 7023 12 A .97 1.94 1.94 3.76 19700 5239 37330 9928 Soaked 12 hours. 12 B .97 1.97 1.97 3.88 14240 3670 17620 4541 12 C .00 1.97 1.94 3.82 10960 2869 28110 7359 13 A .91 1.97 1.97 3.88 28000 7216 48000 12371 Soaked 12 hours. 13 B .97 1.97 1.97 3.88 40000 10309 46600 12010 13 C .94 1.97 1.91 3.76 19500 5186 38380 10207 14 A .97 1.97 1.97 3.88 38800 10000 50770 13085 Soaked 12 hours. 14 B 1.97 1.97 1.97 3.88 Did not spall at 52000 Ibs. = 13402 Ibs. per D 14 c 1.97 1.97 L 94 3.82 Did not spall at 52000 Ibs. = 13613 Ibs. 15 A 1.97 1.97 1.97 3.88 27770 7157 per Q. Soaked 12 hours. Did not crush at 52000 Ibs. = 13402 Ibs per Q". 15 B 1.50 1.97 1.97 3.88 Did not spall at 52000 Ibs. = 13402 Ibs. 15 C 1.50 2.03 1.94 3 94 per D". Did not spall at 52000 Ibs. = 13198 Ibs. per D 15 c 1.94 2.03 1.50 3.04 35400 11644 Did not crush at 52000 Ibs. = 17105 Ibs. 16 A 2. 2. 2. 4.00 51660 12915 Soaked 12 hours. Did not crush at 52000 Ibs. = 13000 Ibs. per D". 16 B 2. 1.97 1.97 3.88 Did not spall at 52000 Ibs. = 13402 Ibs. per D". 16 C 2. 2. 2. 4.00 Did not spall at 52000 Ibs. = 13000 Ibs. per D . BRICK FOR STREET PAVEMENTS. 21 TABLE No. 4. TRANSVERSE STRENGTH. SIZE IN INCHES. SECTIONAL AREA IN SQ. INCHES. BREAKING WEIGHT IN POUNDS. MODULUS OF RUPTURE. AVERAGE OF THREE TESTS. REMARKS. | g " s M 1 M 1 R R .. 2.25 4.19 6.0 9.43 6590 1501 Only one specimen broken. Broke at D 2.31 3 82 6.0 8.82 4580 1222 one of the lower knife edges. E 2.31 3.75 6.0 8.66 6500 1801 -1444 F 2.31 3.875 6.0 8.95 5050 1310 D 2.125 3.625 6.0 7.70 5620 1811 E 2.19 3.625 6.0 7.94 7600 2377 -2040 F 2.125 3.44 6.0 7.31 5400 1932 D 2.50 4.125 60 10 31 11680 2472 E 2.50 125 6.0 10.31 8000 1693 2197 F 2.50 .06 6.0 10.15 11110 2427 D 2.50 .94 6.0 9 85 13320 3089 E 2.50 .00 6.0 10.00 11160 2511 -2963 F 2 44 .125 6.0 10 06 15170 3288 D 2.56 06 6.0 10.39 12460 2657 E 2.625 4.00 60 10 50 10870 2329 -2494 F 2.625 406 6.0 10 66 12000 2496 D 2 25 3.50 6.0 7.875 7020 2292 E 2.31 3.625 6.0 8.37 10250 3525 .2822 F 2.25 3.44 60 7.74 7840 2650 D 2 50 3.94 60 9.85 8320 1959 E 2.50 3.94 6.0 9.85 7850 1820 -1863 F 2.56 3.94 60 10.08 8000 1811 D 2.50 3.875 6.0 9.69 8730 2093 E 2.50 3.875 60 9.69 7410 1776 -1672 Round corners, grooved longitudinally. F 2.50 3.875 60 9.69 4790 1148 D 2375 3.94 6.0 9.36 9690 2365 E 2.31 4.00 6.0 9.24 8000 1948 -2299 Round corners. F 2.375 4.125 60 9.79 11610 2584 D 2.75 4.06 6.0 11.17 6780 1346 E 2.81 4.00 60 11.24 6000 1197 -1195 Round corners. F 2.75 4.00 6.0 11.00 5100 1043 D 262 4.06 6.0 10.64 8000 1668 E 2 55 F 2.55 4 19 4.25 6.0 6.0 10 68 10.83 9010 7770 1811 1518 -1666 Round corners, grooved transversely. D 3 00 3 875 6.0 11 .62 9760 1850 E 3.06 3.94 6.0 12.06 7830 1483 -1688 Round corners, grooved longitudinally. F 3.00 3.75 60 11.25 7640 1630 D 2.44 4.125 6.0 10.06 11660 2527 E 2.375 4.25 6.0 10.09 12710 2667 -2428 Round corners. F 2.375 4.18 6.0 9.98 9640 2091 D 2 .06 3.56 6.0 7.33 5750 1982 ^) E 2.06 3.50 6.0 7.21 8000 2853 ^2269 F 2.06 3.50 6.0 7.21 5530 1972 j .. 2.75 3.75 6.0 10.31 7150 1664 Only one specimen. Round corners, grooved longitudinally. For numbers 9, 10, 11, 12, 13, 14, and 16, the dimensions are those of the estimated equivalent rectangular sections. 22 BUICK FOR STREET PANEMENTS. i i O O 1 i II O- t-O "O *T3 a>o>a> 44^ ^44 08- OcS o-o 02CQ03 H S5 fc E" M >H CO 55 S5 I a I! Sg e 2 H H oocoeoc^^tOTjieoi^-^^u^aooor^cceor-iiN '^t-Hr-I^HrHr-cr-lr-lOr-( rHOOOOCOOOOOOO aaawaN] 'i/5iCOiOeO'Ol^l-~aooocooo BRICK FOR STREET PAVEMENTS. 23 s 'He d .C3>OC_ a) o o> o) 01-1 ,84 rH^ ^^ ^-" - 62 26 w ^oq OQ CQJ2; g g o 1- , 2 S MO ss g FINA WEIGH SB S ^ O O ^2 ^ 53 G5 C^l T-l O O r-l i-l T-l r-l O i-t O O O O O O l-t O 5C C O O 0550 2"g * o oo o o OO5 O> OOO O r-l ^J r-l r-l C C^ C^ C^ CO CO CO CO Tj< 1 ^t* rt* iC C iC lO CD BRICK FOR STREET PAVEMENTS. TABLE No. 6. COMPARATIVE RANK. RANK. ABSORPTION CUBES. ABSORPTION WHOLE BRICKS. CRUSHING STRENGTH. TRANSVERSE STRENGTH. ABRASION AND IMPACT. SPECIFIC GRAVITY. First 13 1 & 15 16 5 1 1 1 13 1 7 4 16 Third 15 10 15 6 16 3 Fourth 10 7 14 14 6 7 Fifth. 5 6 4 10 14 5-10 & 15 Sixth 7 12 7 15 5 12 Seventh 3 3 10 4 7 9 Eighth . . 9 14 5 3 15 11 Ninth 16 16 6 8 13 4 & 6 Tenth . . .-. 11 8 13 13 8 2 Eleventh 12 11 8 9 9 14 Twelfth 8 9 9 12 11 13 Thirteenth 4 5 2 16 10 8 Fourteenth 14 4 3 1 3 Fifteenth 6 2 11 2 12 Sixteenth 2 2 11 2 i BRICK FOR STREET PAVEMENTS. 25 TABLE No. 7 Loss OF BRICK IN TERMS OF GRANITE. SPECIMEN NUM- BER. FIRST RATTLER TEST. SECOND RATTLER TEST. ENTIRE RATTLER TEST. 1 1.0 1.0 1.0 2 8.1 5.0 5.1 3 3.8 5.1 4.9 4 1.9 2.0 2.0 5 3.0 2.1 2.2 6 2.6 2.1 2.1 7 3.0 2.7 2.7 8 2.6 3.4 3.3 9 2.0 3.8 3.7 10 1.7 4.8 4.5 11 2.1 4.6 4.3 12 2.5 5.3 5.0 13 1.4 3.1 2.9 14 1.4 2.2 2.1 15 20.0 1.4 2.9 16 1.4 2.0 2.0 26 BRICK FOR STREET PAVEMENTS. s a ~ o 'T* ^ 3 g I s * O o O O of each variety were broken, excepting numbers one and sixteen, of which but one each could conveniently be had. The bricks were supported on knife edges six inches apart, and the load was applied by another knife edge brought to bear midway between, and parallel to, the other two ; each point of bearing being protected from direct abrasion by two or three thicknesses of blotting paper. The modulus of rupture was computed by the ordinary formula: 3 wz in which W represents the breaking weight in pounds, 6, 30 BRICK FOR STREET PAVEMENTS. and Z, the "breadth, depth, and length, respectively, all in inches, and R the modulus of rupture in pounds. If the span I be measured in feet, while 6 and d are measured in inches, the formula becomes Hence, the modulus of rupture is stated by Prof. Rankine to be " Eighteen times the load required to break a bar of one inch square, separated at two points, one foot apart, and loaded in the middle between the points of support." While this is the ordinary formula used in the text-books, and identical with that adopted by Prof. Baker in his recent publication upon " The Durability of Brick Pavements," it should not be confounded with that commonly employed for determining the transverse strength of material, which is I W 4ad In which R represents the coefficient of transverse rupture ; W the breaking weight; a the sectional area; d the depth; I the length, all in inches. Results obtained by the latter formula will be found to be about J of those derived from the one first stated. In the table, the first column on the left gives the speci- men numbers ; the second, the letters by which they were designated; the third column is the breadth or thickness; the fourth, the vertical depth; the fifth, the length between supports, all of these dimensions being in inches. The sixth column is the product of the third by the fourth, being the area in square inches. The seventh is the weight in pounds at which the specimen was broken ; the pressure being ex- erted by the continuous working of the pump without shock BRICK FOR STREET PAVEMENTS. 31 until rupture was produced. The eighth column is the mod- ulus of rupture calculated by the formula first ahove given. This formula is stated in Professor Baker's pamphlet, page 5, in the following form : The letters having the same significance as above given, but a moment's inspection shows this expression to be identical with that used in calculating the table. The ninth column shows the averages of the three results given in column eight for specimens of the same kind or number. Table No. 5 is a detailed statement of " The Rattler Test," or the effort to measure the effect of abrasion and im- pact upon the specimens submitted. The method of con- ducting the test has already been briefly outlined. Tabulat- ing the result has been a tedious process, but it has been done with much care, and is believed to clearly show the re- sults obtained in such a manner that the value of the test can be judged from a correct basis. All the weights were carefully repeated, and, if errors have been made in the cal- culations, all the work is given in detail, so that corrections can be made by inquiring minds if incorrect results are found in any of the columns. Counting from the left,- the first column gives the speci- men number ; the second, its letter (those marked G- and II having just come from their bath in the absorption test Table No. 2) ; the third, its weight in ounces when placed in the rattler; the fourth, its weight after the first thousand revolutions, or at the end of the first test. There was an in- terval of nearly forty-eight hours between the first and sec- ond rattler tests, and the weighing was repeated before placing the specimens the second time in the cleaner, but the OZ BRICK FOR STREET PAVEMENTS. loss in weight by evaporation from the saturated bricks did not appear to be a measurable quantity by the instrument used, which was a new Fairbank counter scale, weighing to quarter ounces. The fifth column is the excess in the weights given in the third over those in the fourth, or the loss in ounces of each specimen in the first test. The sixth column gives the weight of each specimen at the end of the second or final test. In a few cases, there was uncertainty about the identity of some specimens, as the marks had been so defaced, but in all instances the varieties could readily be distinguished. Where figures are inclosed in parentheses, they include the weights of the pieces which had been broken off and were of sufficient size to be saved and weighed. The seventh column is the excess of the weights given in the fourth over those in the sixth, being the loss in the second test. The eighth is the sum of the seventh and fifth, or the difference of the third and sixth, being the total loss in both tests. The ninth is the quotient, multiplied by 100, of the fifth divided by the third, or the percentage, to the nearest tenth. The tenth column is the percentage of loss in the second test, and is obtained by dividing one hundred times the sum of the losses for specimens of the same number, taken from column seven, by the sum of the weights of specimens of that number, taken from column four. The eleventh column is calculated in the same manner, using the sum of the weights for each variety or number as given in column eight, and the sum of the weights of the same variety in column three. Table No. 6 is compiled from the results set out in the preceding five tables ; the several numbers being rated with each other in the order in which they have withstood the various tests to which they have been subjected. It shows some rather unexpected results and is worthy of very care- BRICK FOR STREET PAVEMENTS. 33 ful study. The rank is by averaging all the tests of each kind for each number or variety in each test. Thus, in the absorption tests, those numbers showing a less average per- centage of absorption are ranked higher than those showing a greater percentage. In crushing strength, those showing a higher power of resistance rank above those showing a less endurance. In this test, unfortunately, our machine had not the power to enable us to properly classify the better grades of material tested, but the rank so given is strictly in accordance with the results of the work. It is not thought that Xo. 16 is absolutely a stronger material than granite, but one of the granite cubes was slightly spalled at a lower pressure than was exerted when the No. 16 cube was spalled, but none of the cubes of either number were crushed, hence the actual endurance of the material remained undetermined. In transverse strength, the numbers having a greater average modulus of rupture are ranked above those having a less, which correctly classifies the material as to its tenacity under stress as it was applied in making tests, but furnishes but a poor criterion by which to judge of the quality of brittleness under percussion or shocks. Under abrasion and impact, the numbers are ranked according to the percentages of loss in the second rattler test; those suffering a less loss being ranked higher than those suffering a greater one. Table No. 7 is deduced from the percentages given in table RTo. 5, the loss of the granite being taken as one. The left hand column gives the specimen number; the second column its ratio of loss in the first test; the third column its ratio of loss in the second test, and the fourth column its total ratio of loss in both tests. For purposes of comparison it is recommended that the figures in the third column be used. It will be seen that the best bricks under the most 3 34 BRICK FOR STREET PAVEMENTS. favorable conditions suffer about double the loss which the granite does. Table ~No. 8. This table has been compiled for the pur- pose of comparing the work of other investigations with that herein described. The first analysis given is a Stour- bridge fire-clay used exclusively for the manufacture of glass house pots and furnace linings. It is a coal measure clay and probably contained traces of lime and magnesia, but no mention of such ingredients is found in Mr. Wills' s analysis. The second analysis by the same chemist is of a clay from a like source, but in this case he has determined the percent- age of lime contained, which is very small indeed. These clays are mined and used because of their heat resisting qualities, and are principally valuable because at white heat they do -not readily vitrify, but retain their form and tex- ture. The third analysis is of a Newcastle fire-clay, by Mr. Taylor, the product being less remarkable for resisting heat than wear. It is to be -observed that this clay contains in- gredients which at a white heat will unite or vitrify, but would hardly be likely to become fluid or even sufficiently plastic to greatly change in form. It is quite similar to our Nos. 4, 8, and 14, except that it contains much less iron. The fourth analysis, from Percy's Metallurgy, is of the Glasgow fire-clay, adapted to a variety of metallurgical uses, is an average of many determinations in which, unfortunately for our purposes, the percentage of alkalies is not given. With this exception it gives the characteristic ingredients of the coal measure fire-clays. The fifth analysis is of the white clay of the tertiary formation in Dorset, by Professor Way. It is used for the manufacture of fire-brick and could prop- erly be termed a modified fire-clay. The analysis gives the alkalies as " alkalies and alkaline earth," and the lime as a sulphate. This clay contracts very greatly in the process of BRICK FOR STREET PAVEMENTS. 35 drying and burning, to counteract which tendency it is cus- tomary to incorporate with it fine sand and ground burnt clay. Number six is the Beacon Hill clay from the Lower Bagshot Beds, which withstands the high temperatures of furnace linings without much tendency toward vitrification, but decrepitates or is worn away by passing currents. The seventh analysis is taken from a recent publication by C. P. Chase, on " Brick Pavements," and gives the composition of the clay used in the manufacture of the Hale paving brick. Mr. Chase gives the moisture at 212 degrees as 2.08, and combined water as 5.16, but does not determine the alkalies present, if any were contained in his sample. If the writer understands what is meant by the Hale paving brick, this should correspond with our No. 2, Mr. Chase's analysis hav- ing been made from the clay and ours from the brick, but the resemblance is not very close. The eighth analysis is copied from the same source as the preceding one. The ma- terial in its natural position more nearly resembles a fine- grained sandstone than a bed of fire-clay, but it pulverizes readily on exposure to the atmosphere, and its composition and position have given it its name. From it is manufac- tured the Hay den block, which is, in reality, a tile used for paving streets. No sample of this material was furnished for testing, but it has been used extensively as a paver, and in some localities is deservedly popular. When properly burned and annealed it presents a homogeneous, compact texture, and has great hardness without brittleness. Many persons would say that the material was " perfectly vitrified," but that expression needs specific explanation to be at all in- telligible. The ninth, tenth, and twelfth analyses are copied from the same author, who also gives the specific gravity, crushing strength, and percentage of absorption of the bricks manufactured from these clays. While he classes them 30 BRICK FOR STREET PAVEMENTS. among " our best paving brick," he gives no statistics show- ing their enduring qualities in actual use. They would more nearly coincide with our No. 3 than any other sample tested, although they might not resemble it in color. The writer would not regard No. 10 as a very promising composition, but all of these clays can be melted or vitrified very readily so as to present a compact texture that will not absorb moist- ure in any considerable .amount. The eleventh analysis is from the same author of a clay used by the American Brick and Tile Company, of Phillipsburg, New Jersey. This com- position is also said to contain sulphur 0.89, and phosphoric acid 0.13. No further information is given regarding the product except that the crushing strength averages from 7,000 to 7,500 pounds per square inch. The thirteenth and fourteenth analyses were made by Otto Wuth, of Pittsburg, the first being of the Porter fire-brick and the second of the ground clay from which such bricks are manufactured. These compositions, it will be noticed, are quite similar, ex- cept that the brick has had the moisture driven off in burn- ing. They closely resemble our No. 14, except that we find a much higher percentage of the alkalies, and herein lies the marked distinction between the fire-clay brick, which is suitable for furnace lining, and the one adapted to use in street paving. THE CHEMISTRY OF BRICK MANUFACTURING. The alkalies or potash in the clays is a residuum of de- cayed organic matter. It is an active fluxing agent, and in the process of burning, or so-called vitrification, causes an amalgamation of the iron and silica components which imparts a metallic tone or ring to the brick when struck. When aided by finely pulverized lime or magnesia in the presence of a large percentage of iron, a pale double silicate of lime BRICK FOR STREET PAVEMENTS. 37 and iron is formed, imparting a buff tint to clays that would otherwise burn red. In the fire-clays less than half of one per cent of potash or alkali produces no noticeable result, and the product has good heat resisting qualities, but when from one to three per cent of this ingredient is found in the clay and it contains from four to eight per cent of iron, which it generally does, with perceptible quantities of lime and mag- nesia at a high temperature (usually a white heat), these flux- ing components form vitreous combinations with the silica, producing a brick quite useless for resisting heat, but when the texture is uniform throughout, and it is allowed to cool gradually, without coming in contact with cold air until be- low the temperature of boiling water; or, in other words, is properly annealed, you have the so-called vitrified brick, which absorbs about two per cent or less of moisture, and has great strength to resist crushing or abrasion. This product may be used quite fearlessly for street paving. With the plastic clays or shales the melting or vitrifica- tion occurs at a lower temperature, and, owing to the fact that the ingredients are seldom uniformly mingled, there is greater danger of melting the bricks together in the kiln, or of leaving many of them without vitrification. To render them apparently impervious to moisture, many manufactur- ers have adopted the plan of glazing them with salt, which may be beneficial in some respects, but is objectionable in others. These clays usually contract to a greater extent in the process of drying and burning than the fire-clays do, tuid hence are more liable' to be warped from their proper form, or show injurious fire cracks. But no clay can be made into a good street paving brick, unless the process of firing or burning be continuously progressive and compara- tively slow to the maximum temperature, and the cooling down be gradual and continuous. This can not be done in BRICK FOR STREET PAVEMENTS. the ordinary clamp-kiln. A broken brick showing varieties of texture or color is a certain indication of defective com- bination or burning, and the fault is fully as liable to be in the burning as elsewhere. Uniformity in the product of the kiln is a necessary condition to the successful manufacture of clay of any kind into proper form to be used for street paving ; and only with such clays, and such appliances as will enable the manufacturer to attain this result, can he reasonably hope to achieve success. DISCUSSION OF THE TESTS. With the information now before us, what brick shall be selected? If the tests were of uniform value the numbers should range in horizontal lines across Table No. 6, the best material at the top and the poorest at the bottom ; but we do not obtain such results. There are other considerations that can not appear in the tables. Nearly 50,000 square yards of surface are to be paved, and the availability must be consid- ered. That which can be promptly furnished in large quantities should be chosen, even though an article may be manufactured which is better in some respects, but unattain- able without great delay. But people w r hose opinions are entitled to great respect will honestly differ as to the relative value of the several tests. For example, Prof. Baker, in his pamphlet on " Brick Pavements," expresses the opinion de- cidedly that, "As a test of the quality of brick or stone, the crushing strength is practically worthless." (Baker on Brick Pavements, p. 8.) He demonstrates in a concise manner that the weight on the wheel of a loaded vehicle is not likely to crush a brick, even though it be soft. Yet the profession gen- erally have considered, and probably will continue to regard it as essential, that the constructing engineer should be informed as to the crushing strength of the materials which he uses, BRICK FOR STREET PAVEMENTS. 39 and that, in connection with other information, it is an efficient aid in determining the relative value of different building materials. However, it is only one of the elements to be considered. For example, the crushing strength of cast iron, is about twice that of wrought iron, and of steel more than twice that of cast iron, but this does not make cast iron worth twice, nor steel four times as much as wrought iron for use under compressive stress. In fact, the best practice adopts wrought iron in preference to either of the others for many po- sitions, but a knowledge of the sustaining power of the mate- rial is, and must be, essential to the designer. A study of the preceding tables shows that those specimens having a high crushing strength also rank well in the test for abrasion and impact, and it is reasonable to assume that the power to sustain great weight without crushing would be necessary to the durability of a block placed in a roadway, and subjected to the attrition and grinding due to that position. It is true that many experiments or tests are conducted in such a manner, and the results given so incoherently, that they are of little value, but where the work is carefully done, and the record clearly set out, so that knowledge of the com- parative strength of different substances can be gained from it, information regarding the crushing strength of any pav- ing material to be used in the form of blocks, will be sought and esteemed as of great merit in determining the value of such material. A recent circular from the State of New York has been placed in the hands of the writer, in which it is stated over a name preceding the title of civil engineer, that the " average resistance to crushing per square inch is 44,- 000 pounds " for a certain description of brick which had been tested by him. Now, if that civil engineer had informed the public at large by what steps he had arrived at that remarkable conclusion, he would have conferred a benefit upon his fellow 40 BRICK FOR STREET PAVEMENTS. men. The same circular contains further information as fol- lows : " Under an abrasive test equal to a traffic tonnage of 100,000 tons per inch of width, the loss was nine-sixteenths of an inch, or six and one-fourth per cent of the depth ; thus under a daily traffic of 100 tons per foot ot width of street, this brick would have a traffic life of twenty-eight years." That conclusion appears to be quite definite and satisfactory, but there are ignorant people at large who know neither just what that abrasive test might be, nor by what process of reasoning such a result is reached. Some people might think that a daily traffic of 100 tons per foot of width for a period of twenty-eight years would not be equal to a traffic tonnage of 100,000 tons per inch of width, and thus conclude that, if the first premise is correct, such a pavement would be good for at least two or three centuries; even upon the assumption that when it was half worn out the abutting owners might want it renewed for a change. The work done at this time for determining crushing strength is very incomplete, owing to the limited capacity of the machine, but it is believed to be accurate as far as it extends, and enables us to properly classify the specimens not having a resisting capacity exceeding 13,000 pounds per square inch. THE ABSORPTION TESTS. For this class of paving material, a low ratio of absorp- tion is held by many to be a most essential condition, and therefore that this test is of the greatest importance. In our work this the.ory has not been accepted. Of all the speci- mens tested there is but one (No. 2) which should be rejected because of its excessive absorption alone, were all other characteristics satisfactory. Manufacturers have been told so frequently that a non-absorbent product is a necessary condition for marketable goods, it is so easy for them to BRICK FOR STREET PAVEMENTS. 41 bring the rate down to two or three per cent, and the test can be so readily made, that but few street paving bricks are in the market which absorb moisture as freely as any of the stone blocks except granite. It is probably unfortunate that no variety of stone, other than Georgia granite, was included in the tests made, but sufficient experiments have been made with the various building stones to show that when the per- centage of absorption is three or less, and the material is not laminated, they are neither perceptibly softened, nor made susceptible of destruction by climatic influences. Me- dina sandstone absorbs from two to four per cent of moist- ure. Oolitic limestone absorbs from three to five per cent, yet no one asserts that either of these stones is softened or affected detrimentally on this account, and the first is a stand- ard paving stone. Again, of the specimens crushed or subjected to abrasion, there is no indication, unless it be BTo. 2, in the Rattler test, that any one was weakened by its pre- vious soaking. Therefore, while it is undoubtedly true that a strictly non-absorbent material is the best, yet, among the paving bricks having percentages of absorption lower than three, while the advantage of an exceedingly low rate should not be ignored, other features may be considered. For in- stance, !N"o. 13 is shown to absorb less moisture than granite, and where it is not to be subjected to an excessive traffic, should on this account be favorably considered, but its en- durance under severe tests appears to be exceeded by some of the other varieties. TRANSVERSE STRENGTH. The manner in which the transverse strength of the specimens submitted was determined has been described and tabulated, but in doing the work much information was gained that could not be written out. An unexpected de- 4- BRICK FOR STREET PAVEMENTS. gree of strength was exhibited by a majority of the speci- mens. While this test shows the tenacity of the material under a stress continually increasing to the point of rupture,. it gives but little information about the ability of the same substance to withstand the effect of blows or shocks. The behavior of the bricks at the instant of rupture is instruct- ive. Some of those which carried the greatest weights were much shattered. One of the number fives broke into three triangular pieces of nearly equal size. Nearly every speci- men which exhibited the characteristic vitrified appearance,, threw off flint-like spalls, and presented an irregular fract- ure. Those specimens which in other tests manifested the greatest endurance were usually parted by a clean fracture almost at right angles with the brick, directly beneath the central bearing, like the granite ; while those having interior defects of any kind would separate at any point between the outer bearings. This test, therefore, is of much value to the experimenter, but the tabulated result is not a sure indica- tion of the value of the material for street paving purposes. ABRASION AND IMPACT. The manner of conducting this work has been so fully described, and the results set out in such detail in Tables 5 and 7, that further comment is hardly necessary, yet it is plain that it presents no condition at all similar to that which obtains in actual service. The bricks are loose and battered upon all surfaces, whereas in the pavement they are held firmly in place and subjected to abrasion upon one side only. But in this case they were all subjected to the same treatment, and their losses should give a fair measure of their relative powers of resistance. " The Rattler Test " has been frequently repeated by various parties, and a prac- tice is coming in vogue of assuming that a half hour or an BRICK FOR STREET PAVEMENTS. 43 hour in the rattler is equivalent to a year's wear in the pave- ment under a given amount of traffic, and from this assump- tion the probable life of the brick in actual use in the street is calculated. By a somewhat similar course of reasoning, although the premises are more fully and fairly detailed, Professor Baker has calculated Table No. 7, given on pages 32 and 33 of his pamphlet on Brick Pavements, in which the life of a pavement made of each of the varieties of brick which he tested, is given in certain streets of ten of the principal cities of this country. The daily traffic tonnage is taken from Captain Greene's statistics, and the results as tabulated are remarkable. His poorest brick would last four years on Broadway, New ^ork, and one hundred and sixty- five years on Olive street, St. Louis ;. while his best brick would last thirty-eight years on Broadway, and fifteen hun- dred and twenty years on Olive street. The writer does not dispute such conclusions, but has no facts from lar inferences can be drawn. STATISTICS OF TRAFFIC AND DURABILILTY OF Data regarding the traffic tonnage, and the effect of wear on street pavements and highways, has not been col- lected and preserved in this country in such form as to be available for ready reference. A few years since, Captain F. Y. Greene prepared a paper, "An Account of Some Observa- tions of Street Traffic," which was published in Volume 15 of the transactions of The American Society of Civil Engi- neers. The observations were made by employes of The Barber Asphalt Paving Company, under Captain Greene's directions, during the months of October and November, 1885, in the ten large cities in which that company had offices and works. " The agent in each city was instructed to select the three streets in that city paved with stone, 44 BRICK FOR STREET PAVEMENTS. asphalt, and wood (if any existed), which, by common re- port, had the heaviest traffic in the class of pavement used on that street. The record was in every case made on six consecutive days (Sundays omitted), at the same place, and it was continuous from 7 A. M. to 7 P. M., except when dark- ness prevented. No addition was made for this omission ; no record was kept during the night, and no addition was made as an estimate of night traffic." " The traffic is di- vided into three classes, light weight (less than one ton), medium weight (between one and three tons), and heavy weight (more than three tons). The Captain says : " I have discarded the weight of the horses altogether, not because they do not constitute a factor in the wear of the pavement, but because they were dis- carded in the English reports, and I desired, as far as possi- ble, to make comparisons with them." . . . "To obtain the tonnage, I estimated the light weight vehicles to average one-half ton each (including their loads), the medium weight two tons, and the heavy weight four tons." r l-horse carriages, empty or loaded. LIGHT WEIGHT INCLUDED -j l-horse wagons, empty or light-loaded. (. l-horse carts, empty. fl-1 ,.1-1 I 2-1 l-horse wagons, heavy-loaded. l-horse carts, loaded. -horse wagons, empty or light-loaded. ormore " The average tonnage per vehicle ranges from 0.68 on Fifth avenue (New York) to 2.08 on a portion of Wabash avenue (Chicago). On Fifth avenue, 91 per cent of all the vehicles weigh less than one ton, while on Wabash avenue, only 25 per cent of them have so little weight. The general average for all the cities is as follows : Less than one ton, 67 per cent; between one and three tons, 26 per cent ; more BRICK FOR STREET PAVEMENTS. 4 than three tons, 7 per cent. The average tonnage per foot in each city, so far as here observed, varies from 151 in New York to 30 in Buffalo, and the general average is 77. For all the cities in the table, the average daily tonnage per foot of width is 77, and varies from 273 tons on Broadway to 7 tons on a granite street in St. Louis. The average weight per vehicle is, for all the cities, 1.15 tons. The average width of street between curbs is 44 feet." This is believed to be the first carefully prepared census of travel made public in this country, and it was published by an officer of an asphalt paving company. It is fair to presume that one object in view was to show the durability of that kind of pavement under heavy traffic. Since its publication, a few annual reports have contained statistics upon the subject, and the investigation has been greatly ex- tended by the different asphalt paving companies. Obvi- ously, information of this kind should be officially compiled by municipal officers upon a uniform system throughout the country and its scope materially extended. The effect or wear upon the roadway of an observed traffic tonnage should be given, which has not been done except in a few of the English reports, and there mainly in cost of maintenance or repairs. Reports from Washington have given some data as to the cost of maintenance of certain pavements, and the English reports are usually quite explicit upon this point; but it would greatly benefit all municipal corporations in this country, were each to keep a record of the kind of street im- provements made, their manner and cost of construction; their durability and expense of maintenance, under a traffic, the volume of which could be noted with reasonable accu- racy, at but trifling expense. The omission of the horses from the traffic census is clearly a fault, as we know that they assist largely in wearing the roadway. For example, 46 BRICK FOR STREET PAVEMENTS. between the rails of street car tracks upon lines operated by horses or mules, the wear of the pavement is due almost ex- clusively to this cause, and it is known to be very great. The tonnage of vehicles, as estimated by Captain Greene, is heavier than many observers would assume it to be, and the percentage to be added for the weight of animals will vary with the nature of the traffic, being greater with the light and less with the heavy traffic. His estimate being, that on Fifth avenue, which carries 91 per cent light traffic, the ad- dition should be about 85 per cent for the horses, while on Wabash avenue, where but 25 per cent is light traffic, the addition should be only about 40 per cent. The effect of the horse's shoe upon the street surface is modified by the nature of the pavement. Probably sheet asphalt suffers as little from it as any known form of wearing surface, unless the blows fall successively upon the same place and thus effect a displacement of the material. The bowlder is seldom scarred by it, hence the material of the cobble stone pavement is practically indestructible from this cause. Granite blocks are spalled and rounded until they assume the form of bowl- ders, and, if very hard, become exceedingly slippery and af- ford insecure footing. Brick pavements would be rapidly destroyed were the bricks as widely separated as granite blocks usually are, but being placed in close contact, there is little room for the rounding away of corners. The brick surface is, however, affected as it would be by receiving a like blow from a cutting tool or chisel of similar form. From this cause, will result by far the greater portion of the wear, since the pavement, when unbroken, will be sufficiently smooth to present but slight obstacles to the rolling upon it of the wheels of vehicles, and it will suffer comparatively little from that cause. The blow delivered by the animal's shoe will be greatly increased at high speeds. It would, BRICK FOR STREET PAVEMENTS. 47 therefore, appear to be proper, that upon avenues carrying suburban travel, a census of traffic should take cognizance of the element of speed. THE PROBABLE DURABILITY OF A BRICK PAVEMENT. This chipping or abrasion of the surface by the shoes of animals traveling upon it will be its severest trial, and since no definite statistics are available by which to compute the traffic tonnage to which it will be subjected, and no test has been made which serves as an actual measure of the wear of a pavement under a given tonnage, the probable durabil- ity of this street can not be stated, but can only be predi- cated upon the endurance of the brick as compared with the granite. Judging this street by others upon which the cen- sus of travel has been taken, it seems fair to assume that the traffic will not greatly exceed 60 tons per foot of width per day, including the weight of horses, which will probably embrace one-half of it. The surface of a granite block pavement, as ordinarily constructed, is about 75 per cent granite, while a brick pavement is about 90 per cent brick. There is, therefore, about 20 per cent more brick than gran- ite to resist wear. The brick surface is comparatively smooth, while the granite is uneven. Wheels will roll smoothly over the brick, while they will jolt over the granite with a continual succession of blows. Let it be assumed that the wear due to horses on the brick will be 120 per cent of that due to the same cause on the granite, and the wear due to vehicles on the granite is 200 per cent of that due to the same cause on the brick : it follows that the total ef- fect on the brick is but 80 per cent of that on the granite. Now we find in table No. 7 the loss of the brick in our abrasion test to be 2.2 times that of the granite ; a traffic, there- fore, which wears off one inch from the granite pavement 48 BRICK FOR STREET PAVEMENTS. will wear one and two-thirds inches from the brick ; or, the time required to wear an inch from the brick will be about 60 per cent of that required to wear an inch from the granite. No record is known to exist showing that amount of wear from a granite block pavement under a similar traffic, but about five times the tonnage has worn some portions of our city pavements to about that depth in four years. The estimated traffic is about 60 percent of that on Fourth street between Walnut and Race streets, exclud- ing street cars, and quite similar in character, taking the en- tire width of pavement (omitting car tracks), and five years' wear has been estimated to have reduced the blocks one- fourth of an inch. This would seem to justify the belief that this pavement should be in fair condition after ten years* traffic shall have passed over it. MUNICIPAL METHODS. A cause for the lack of definite statistics upon these matters is apparent when municipal methods are considered. American civil engineers have achieved a world- wide repu- tation for the boldness and originality of their designs, the skill exhibited in their execution, and the economy shown in attaining results. Great industrial establishments have been built, lines of transportation, with all the works appertain- ing thereto, have been by them located and constructed, and they are accredited with being well toward the van, and of contributing their full share toward the progress and devel- opment of the country. In all such works facts have been collected and compiled, so that reliable data is available. Manufacturers are willing to guarantee a given mileage for their steel rails or car wheels, or a given strength for their iron and steel, from data made available by engineers, but in municipal matters the conditions or the results are in noway BRICK FOR STREET PAVEMENTS. 49 similar. The total amount of money annually expended by the municipalities of the country in opening, improving, cleaning, and repairing streets and highways, is an enormous sum, exceeding that applied upon all other public works in an equal length of time. The greater part of this fund is nominally disbursed under the supervision of engineers, but the results are not such as to add materially to the renown of the profession, or to supply exact data for their guidance in present or future works of this character. One reason for this appears to be found in the fact that these funds furnish the greatest of the existing causes of activity in local pol- itics. Municipal statesmanship is developed in levying, watching, and disbursing this money. Laws providing for its collection, control, and disbursement have been enacted, termed the municipal code, which is more complex and pe- culiar than any other system known to man. Boards and Bu- reaus, Councils and Commissioners, Supervisors and Direct- ors, Counselors and Barristers, have been created or called to govern the work, guard the public interest, acquire fame, and enjoy the advantages accruing to exalted official position. The pervading spirit of freedom abroad in the land being averse to the creation of such a class as controls similar matters on the continent of Europe, the rights of the people are sought to be preserved by the checking and balancing of sovereign and independent departments. When new things are to be done, additional statutes are enacted and more boards pro- vided. One authority will make an improvement and an- other will dig it up, while no one will repair it because the courts have not decided the question as to which fund shall be drawn upon for meeting the expense in cases of that na- ture. Volumes of annual reports from the heads of the sov- ereign departments and chiefs of the multitudinous bureaus into which they have been sub-divided, assure a confiding 50 BRICK FOR STREET PAVEMENTS. public, that, since the advent to power of the present incum- bent, the affairs under his control have been conducted upon strictly business principles, thus enabling him to grant more permits and file a larger number of papers than had ever be- fore been handled by similar officers in a corresponding length of time. When the balance of power between po- litical parties is indefinite, and changes in official stations become so frequent as to make employment uncertain, it is sometimes found expedient to further revise the stat- utes and make non-partisan boards, who then carefully di- vide the appointments and perquisites between contending parties, accurate data for the making of such partitions be- ing always available. The smaller municipal organizations copy the " systems" of the larger ones. Under such regulations no very considerable amount of " engineering " is required. A " chief engineer " of suitable political complexion is chosen to sign the necessary papers, to whom matters not well understood by other parties can be referred and reported upon, and who can be blamed when it becomes absolutely necessary to locate responsibility some place, and who is willing to allow officials and other influ- ential parties to appoint his assistants, clerks, rodmen, and superintendents. Men who have acquired skill and experi- ence in the construction of works under different regulations seldom take kindly to this order of things, and the field is left free to such as enjoy the surroundings. Many careful and painstaking men are engaged in city work who would make excellent records were they not handicapped by the regula- tions governing them, and almost the entire number are like the parents of heroes, " poor but respectable." Having little at stake except their integrity, that is manfully cher- ished. Occasionally an erring brother may fall, but he merely drops from the ranks which close in his place. The BRICK FOR STREET PAVEMENTS. 51 ammunition of the enemy, which is most dangerous, espe- cially to those of limited experience, is flattery. Not one person in ten thousand of those having experience upon public works would ever approach an engineer with money or a valuable consideration for corrupt purposes, but if the insidious agent can induce him to believe that his genius is apparent to all, and that the world, especially the official part of it, will soon be shouting his praises, such influences may cause the young man to make himself ridiculous. But there is a great following who have a sufficient knowledge of surveying to enable them to handle field instruments, set out work, and compute quantities, who have but little taste for such study or investigation as is necessary to acquaint them with materials, or render them skillful in designing or constructing engineering works; and there appears to be a greater demand for these persons on municipal, than upon any other class of public works. This is probably because they have more leisure for compiling political statistics than others, are less liable to have bothersome opinions about how things should be done, and can more readily discern the grade and character of improvements desired by those in power or opposed by those not in power, which is usually the same thing ; it being always understood among municipal statesmen that an election or appointment to office confers upon the recipient of such honor all the necessary knowl- edge and experience required, not only to choose an engineer, but to tell him what to do, and just how to do it. Many re- cruits are obtained from those estimable young men annu- ally graduated from our technical schools and colleges. The learned professors solemnly announce to such of their stu- dents as have pursued certain lines of study, that they are now civil engineers. The young men very properly have great confidence in their teachers, and believe what is told 52 BRICK FOR STREET PAVEMENTS. them to be literally true, but when they go abroad in the world and learn that what the professors really meant was, that they were qualified to obtain employment upon public works, where, by continual study and actual practice, they could become engineers; the shock is very great, many never recover, and some are engaged by municipal corporations. Such as do recover are achieving great success in professional work. The number and sovereignty of the departments, the uncertainty of the laws (for no one dare hazard any thing more than an opinion regarding the rule of action prescribed by a statute until the court of last resort has guessed at its meaning), and the strifes of contending factions have pro- duced conditions so different from those which would ap- pear to be proper that heroic measures may be required to effect desirable changes. Unless the people at large can be induced to look upon the matter of municipal government as a grotesque absurdity which is really being enacted at their expense, as it is, the code will continue to be enlarged and the Boards multiplied. When they induce the law-makers to re- peal the thousand and one statutes which now exist, and enact a plain, concise code of rules, and wot amend it, which will place the direction of public works under a single de- partment, with uniform regulations in like municipalities throughout the state; placing the designing and manage- ment in the hands of a corps of engineers who should ac- quire position and promotion by the record of their achieve- ments, and not by reason of race, creed, or previous con- dition of partisan servitude or influence, and who, being un- trammeled as in the world at large, would succeed or fail by merit alone, the principal of natural selection, or the survival of the fittest, would soon place the direction of such works in systematic order under competent control. Then would BRICK FOR STREET PAVEMENTS. 53 streets be built to remain undisturbed, as the bottom layers or drains and pipes would first be put down and carried to property lines, tben would the character of the pavement be adapted to the uses to which it would be subjected. Paving companies \vould construct streets and guarantee them to remain in proper form and repair until a specified traffic ton- nage should have passed over them. Manufacturers would furnish materials under like conditions. Order and uniform system would exist where chaos now reigns, and legislative interference would cease to trouble executive business. Probably the view is Utopian, and will never be realized until we pace those golden streets, but the patching remedies and special laws continually being enacted for the betterment of evils known to exist are only adding complications to complex affairs, and if thinking people are induced to direct their attention to a subject of such universal and vital inter- est, and make an effort in unison to better municipal govern- ment as applied to public works it will certainly result in some good. Politicians and bosses will undoubtedly offer great obstacles, but the mere absurdity of present methods will insure a change, and if engineers were accorded similar freedom and control, with such responsibilities and oppor- tunities as are given them upon other works, they would not ignore so inviting a field as that presented by the needed im- provements in these matters. GENERAL DISCUSSION OF PAVEMENTS. The office of a street pavement is to provide a wearing surface which shall fulfill the following conditions : First. It must present a secure and pleasant footing for animals. Second. It must have sufficient smoothness to render traveling in carriages agreeable, and traction easy and as nearly 54 BRICK FOR STREET PAVEMENTS. noiseless as is practicable, for all descriptions of wheeled ve- hicles (excepting those provided with flanged wheels). Third. It must be of such form and material that liquids falling upon it will quickly flow from it into proper conduits, and must furnish no permanent lodgment for street filth of any kind. Fourth. It must be capable of sustaining without change of form, any and all loads usually transported on public highways. Fifth. It must be reasonably durable, both as against the attrition of street traffic, and the destroying or dissolving action of the elements. Sixth. It must be economical. That is to say, sufficient comfortable use must be obtained from it to make it worth both the cost of construction and maintenance. Seventh. It must be capable of removal and replace- ment, or repair from failure at reasonable cost, and with materials and appliances within the control of the street re- pairing department. A study of these conditions at once reveals the reason why the " paving problem " is of such an intricate nature that it has so long remained unsolved, as well as a cause for so many unhappy failures in its attempted solution. For the first and second conditions, the dirt road in good repair stands without a rival, but it meets no other require- ment, hence its use is restricted to race tracks and country roads, which like canals are only navigable when the weather conditions are favorable. For the second, third, and fourth conditions, the asphalt pavement on proper foundation appears to be better fitted than any other that has come into such general use; but many persons say that it does not properly meet the first re- BRICK FOR STREET PAVEMENTS. 55 quirement, criticise it severely as to the fifth and sixth, and affirm that it utterly fails to meet the seventh. Stone block pavements meet the first requirement, but indifferently ; utterly fail in the second and third, when properly constructed ; are better adapted to comply with the conditions of the fourth, fifth, and seventh, than almost any other description of city street, but when a high charge for transportation is to be added to the cost of preparing the material, they fail to meet the sixth condition. Wooden block pavements meet the first, second, fourth, and seventh conditions fairly well, when made of suitable materials well combined ; but, as they have been built in this country, have signally failed to meet the third condition, and have fulfilled the fifth and sixth but very indifferently. The bowlder or cobble-stone pavement has been with us so long, and has been treated so badly, that familiarity with it has bred a species of contempt that is hard to overcome. It has become popular to consider it an all around failure, yet it meets the first and seventh conditions fairly well, and so far as the material is concerned, it stands unrivaled in the fifth. In many of our cities where horse cars have been operated for the past twenty or thirty years, and the street railway companies are required to maintain the pavements within their tracks, the bowlder pavements are still retained between the rails, while the residue of the streets have been paved with other materials, because in that position they are said to meet all of the conditions named, excepting possibly the second and third, better than any other substance yet offered for the wearing surface of roadways. This saying, however, does not appear to be any thing more than an expression of opinion, which can not be sustained by any process of rea- soning. The cobble-stone can be given no definite bearing on any foundation ; it can not be held in position by any bond 56 BRICK FOR STREET PAVEMENTS. that can be given it in construction. It does not present a suitable surface for vehicular travel, or that can by any pro- cess be kept free from filth ; yet it does not wear out, is easily restored if loosened from its place, and it does answer very well for street car horses to travel upon. Broken stone or macadam as commonly used, of mingled limestone and shale, meets none of the requirements. If, however, it is clean refractory material, properly prepared and combined by rolling, it fulfills all the conditions except the third (and even that reasonably well), providing the traffic is moderate, and the repairing is promptly and efficiently done. It may be set down as an established fact, however, that when a macadamized street is dug into for any purpose that it is never properly replaced. No one of these conditions can be entirely ignored, yet it is obvious that no pavement yet devised, fully meets all of them. Could the first be ignored, it would be an easy mat- ter to cover street surfaces with iron or steel plates that would fully meet all the others, but plainly this can not be done. The surroundings of the pavement and the extent and nature of the traffic to which it is to be subjected, must be considered in order to decide which of the conditions shall be allowed to determine its character. The first, that of furnishing a secure and reasonably comfortable footing for animals, can in no case be ignored, and in many instances must control all other considerations. Wherever the pave- ment is to be used as a thoroughfare for vehicular traffic at fair rates of speed, or when time, pleasure driving, or quiet- ness become elements of importance, then the first and sec- ond conditions must be met, and other features may or may not be caused to yield to their requirements. But the pres- ervation of life and health is the essential cause of business BRICK FOR STREET PAVEMENTS. 57 activity, hence the third condition, that of maintaining cor- rect sanitary conditions, should never be neglected. To those at all familiar with street construction, it is obvious that the wearing surface, or pavement proper, can not, and does not in itself, support the loads brought upon it, but that it more or less successfully resists the impact and abrasion incident to the traffic, and transmits the weight di- rectly to the bed or foundation upon which this surface ma- terial has been placed. It follows, therefore, that the fourth -condition can be met by any description of paving material which has sufficient hardness to retain its form under the pressure of street traffic, by merely placing it on a properly prepared foundation ; and further, that unless the pavement shall be placed upon a bed capable of sustaining under all conditions the loads brought upon it, the surface will yield regardless of the material of which it is composed, and that this condition not being complied with, no essential feature of a good street surface will remain. Failure to meet this condition is the error most commonly committed in the build- ing of pavements. In this latitude the winter frosts pene- trate to a depth of from one to three feet, or, when not acted upon by frost, the subsoil drainage is seldom so thoroughly efficient as to prevent the changing of the ground from a firm unyielding soil to one of almost complete saturation, thus materially affecting its sustaining power. It therefore follows that no pavement wlr.ch is to be subjected to a heavy traffic at all seasons of the year can be relied upon to retain the form originally given it, unless the foundation or bed upon which it is placed shall either be carried below the ac- tion of the frost, say three feet or more, or be so constructed as to distribute the weights of passing loads over sufficient areas to enable a comparatively weak subsoil to sustain them. The deep foundation is the ancient, and undoubtedly 58 BRICK FOR STREET PAVEMENTS. the most durable method, having apparently been the ordi- nary practice with the Romans, but the distributing coating is far more economical, and hence has become the established modern practice. Two methods are in vogue. First, to drain the sub- roadway as efficiently as is practicable, grade it to the proper form, compact its surface by rolling, and cover it with a layer of mingled broken stone and gravel, which is made smooth and firm by flooding and rolling with a steam roller ; the layer of metal being from six to twelve inches in thick- ness, according to the requirements of the locality or the specifications. On this layer or " foundation " is spread the bed of sand, in or upon which the pavement is set. Some- times broken stone alone, and again gravel only, is used for the bottom course. This style of " foundation " is used very extensively for all descriptions of pavements excepting as- phalt. With brick pavements the practice of placing a layer of bricks flatwise on the bed of sand, covering them with a thin coating of sand, and paving on it the wearing surface on edge, is quite common, and produces what is called the "two course" pavement. Still another method consists in covering the layer of sand with tarred boards, upon which the sand cushion and brick on edge are paved herring-bone style, producing the "Hale Pavement." In this, however,, the broken stone is generally omitted, the boards being sepa- rated from the subsoil by from four to six inches of sand only. These expedients tend to better the distribution of the weights brought upon the pavement, and have the merit of economy in first cost, but they are obviously inade- quate except where the subsoil is exceptionally good and the traffic very moderate. The method of combination is quite defective. When gravel is used that is free from loam, it will not compact under the roller, and if it does contain BRICK FOR STREET PAVEMENTS. 59 loam the water which comes from the subsoil, and percolates through it, is liable to carry the soluble substances with it down the gradients, and leave the pavement unevenly sup- ported. When broken stone and gravel, or broken stone alone, forms the foundation course, it is expected to be por- ous, and act, to some extent, as a subsoil drain. The voids, however, are liable to become the receptacles of the clay from beneath, which is brought up, or rather the stones brought down, by the pressure upon the pavement, or they will be filled by the sifting down of the bedding course of sand, caused by the jar of the travel, and this escape of the sand will leave the blocks unevenly supported. All of the varieties described in this first method are extensively used, and are made more or less expensive and durable, or cheap and temporary, as they are carried to greater or less depths, and as the work is thoroughly or carelessly done. But they are so constructed that natural causes would alone destroy them in a comparatively brief space of time, and when the forces of nature are aided by the disturbances to which the sub-grade of the street is ordinarily subjected, and the traffic upon the pavement, it follows that the life of such a founda- tion seldom exceeds the duration of the wearing surface, and the failure of the former very frequently accelerates the de- struction of the latter. The second method consists in preparing the subsoil by grading and rolling as before described, and placing upon it a layer of hydraulic cement concrete to serve as a founda- tion for the pavement. For equal volumes, the cost of the concrete is about three times that of the broken stone or gravel; but from one-half to two-thirds of the amount is required, hence the expense of the concrete foundation is one and a half to twice that of the broken stone or gravel. When properly made and undisturbed, it will not yield to 60 BRICK FOR STREET PAVEMENTS. the action of the weather, and the renewal of the pavement need extend to the wearing surface only. The expense of cutting through and replacing the concrete when the street must be opened for any purpose, is much greater (perhaps two to three times) than in the other forms of foundation, but such work can be done without serious injury to the re- mainder of the street ; and when repairs are properly made the opening of the pavement and its foundation is less in- jurious to the street having a concrete foundation than the one that has it not, because the concrete base will support the pavement over small cavities, while the broken stone or gravel will sink into them. The thickness of the concrete varies with the require- ments of the traffic, and other conditions, from four to eight or more inches. The ordinary practice is to use nat- ural cement in its composition, and make the coating six inches in thickness for roadways of medium traffic without car tracks. The condition of the subsoil should, however, be considered in determining the depth of concrete, for where it is soft or spongy, or trenches are to be spanned, a greater amount will be required. A concrete foundation is an absolutely necessary beginning for any really good and durable street pavement, and even for work of medium character and price it is economical. Pavements of sheet asphalt are always placed on concrete foundations, the wear- ing surface being separated from the cement by a cushion coat, ordinarily about half an inch in thickness. Stone, asphalt, wooden block, or brick pavements, are usually placed on a layer of sand from one to two inches in thickness over the concrete, but the practice regarding the cushion coat is by no means uniform, varying from an actual bedding of the blocks in the cement mortar to two or even three inches of sand, but the general custom in this country BRICK FOR STREET PAVEMENTS. 61 appears to be in favor of the sand cushion. Convenience in construction and repairs and the theoretical elasticity of sur- face being in favor of that combination. The choice of the sand to be used is of more than ordinary importance, since if it contains a considerable percentage of soluble substances, or is alternately coarse and fine in different places, displace- ment is likely to occur, and the pavement will become uneven. All block pavements, whether of stone, wood, asphalt,, or brick, should be as closely placed as is practicable, and the interstices filled with a non-absorbent material. Possibly a narrow spacing may be required on gradients paved with sawed wooden blocks to furnish footing for animals, but the wide spacing ostensibly for this purpose so frequently seen in all these varieties of pavements is undoubtedly bad practice,, since it so materially reduces the resistance of the material composing the wearing surface, facilitates the chipping from the angles, and produces an uneven, noisy street, with cavities to receive and retain filth. WHAT SHALL BE SPECIFIED. The writer has seen no specifications for brick pavements which either clearly or fairly describe the material to be used, so that manufacturers or bidders can know just what will be required upon a given work. The majority of the specifica- tions recite that "the brick to be used must be hard, free from defects of any kind, manufactured and burned espe- cially for street paving purposes, be equal in all respects to the sample filed with the proposal, and subject to inspection and acceptance or rejection by the engineer or inspector." With our present knowledge of this material, this phraseology may be accepted, but in reality it specifies very little. Its acceptance or rejection by an engineer is ordinarily regarded BRICK FOR STREET PAVEMENTS. by the corporation as a safeguard, but no parties entering into a contract can place a power that is wholly arbitrary and undefined in the hands of an engineer, who is in reality the executive agent of one of the parties. Because bricks have been manufactured and burned especially for street paving purposes, does not necessarily fit them for such use ; the term hard is an indefinite one, and without stating what constitutes defects, there may be differences of opinion as to whether or not they exist in a given article as well as to the equality of goods furnished with sample exhibited. Even sample paving bricks have been known to be worthless for street paving. The characteristic qualities and strength of the material are not clearly set forth as they should be. The power to accept or reject is left undefined, which should never be the case, neither manufacturer, bidder, nor tax-payer should be bound by the action of an engineer, unless that ac- tion shall be in accordance with known provisions and fixed rules. With the hope, therefore, of adding something to the information needed for bettering specifications in this re- spect, let us examine our work as tabulated. From Tables Nos. 1 and 8, we might select a chemical composition quite suitable for the purpose, but there are such wide variations in clays that it will probably be advisable not to be too definite in specifying ingredients. Silica may con- stitute from sixty to seventy -five per cent; alumina, from fif- teen to twenty-five ; iron, from five to ten; while lime and magnesia should neither exceed two per cent; and the al- kalies should be from one to two per cent. The form and proportions in which these ingredients are present, and the difference in results obtainable by variations in methods of manufacture are so great, that it will evidently be better to define the qualities which are required, and leave the manu- facturer free to produce them in his own way. Lime can BRICK FOR STREET PAVEMENTS. 63 be readily detected, and an excess of that ingredient might properly be prohibited by the specification. With suitable ingredients, properly combined and burned, the percentage of absorption will be small. An inspection of Table No. 2 shows that it varies greatly, indicating a lack of uniformity in results, which is to be avoided, or failure will result. The absorption should, therefore, be placed at the lowest limit which can be designated without excluding such bricks as are known to have withstood other tests credit- ably. I would recommend naming two per cent as a maximum. Specific gravity depends to some extent on the density of the material, and should, therefore, be as high as is ob- tainable with this material. Two and one-tenth might be named as a minimum, with credit for excess, as about two and three-tenths is attainable. The crushing strength determined from two inch cubes, prepared and treated as set out in describing the tests shown in Table No. 3, should not be less than 12,000 pounds per square inch. This might be named as the average crushing strength, the limit of variation of any sample not to exceed twenty-five per cent below. The modulus of rupture, as determined by the formula used in calculating Table No. 4, from tests of transverse strength, could properly be fixed at 1600. Tables No. 5 and 7 would indicate that unless a rather liberal allowance be made in the matter of abrasion as com- pared with granite, manufacturers may complain that many are called but few are chosen. One-third of the competitors in this test would be among the saved by placing the limit .at two and two-tenths times. It will be safe, therefore, to say that in any tests for determining the comparative loss of the brick under abrasion and impact, as compared with Lithonia 64 BRICK FOR STREET PAVEMENTS. granite, the loss in weight of the brick shall not be more than two and one-fourth times that of the granite. Uniformity in size and texture appears to be attainable, and lack of it produces many undesirable difficulties. Wide variations iu size result from faulty drying and burning. We must either specify how the drying of the brick and the tiring of the kiln shall be done, or describe what we want as the product of the kiln, and insist upon getting it. In the pres- ent state of our knowledge the safer plan will be to name the requirements and leave the manufacturer to wrestle with details. The amount or percentage of contraction in drying and burning varies with the different clays from one to twelve per cent. With the coal measure lire-clays it is usually about two or three per cent, while with the plastic clays and river silt it is very much greater. Excessive contraction is obviated to some extent by adding to the mixture ground burnt clay and a fusible sand. Unless other ingredients are present to obviate such a result, these components are liable to produce brittleness. In modern down-draft kilns with clays which do, and should contract as much as three per cent, rapid firing sometimes produces bricks from the upper courses, on which the flame acts directly, that are actually larger than the molds in which they have been formed. It follows that such bricks are much checked and cracked, ren- dering them unfit for use, but the cause is apparent. The contained moisture in the partially dried brick is expanded by being first turned into steam, and, while in this condition, the outside of the brick is fused, thus permanently fixing its exterior form and dimensions, except as modified by checks and fire cracks. Other bricks in the kiln, made in the same molds, will be shrunken to the full extent of their contrac- tility, thus producing not only a troublesome variation in BRICK FOR STREET PAVEMENTS. 65 size, but likewise wide differences in quality. These defects can be remedied by a gradual and continuous firing that will produce and permit the natural amount of contraction throughout the kiln. Absolute uniformity in size is not practically attainable, but a much nearer approach to it than is now common can be reached by specifying a minimum al- lowable deviation and rejecting material that does not com- ply with the requirement. I would suggest two per cent as the maximum allowable variation from the standard di- mensions adopted. Assuming that the clay has been properly ground and mixed, uniformity in texture is obtainable only by conducting the burning in a suitable manner, continuing it to a sufficient degree, and no longer, and then allowing the kiln to cool down without permitting drafts of cold air to come in con- tact with the bricks until their temperature has fallen below the boiling point of water. The degree to which the firing should be extended is ordinarily termed " complete vitrifica- tion," but would appear to the writer to have, been very un- happily chosen. To " vitrify " is ordinarily held to signify " turning into glass by the action of heat," which is not the desired result in this case. The term having been adopted by common consent, the meaning which defines the process must be given it, and would appear to be, that the alkalies and alkaline earths shall form vitreous compounds with the iron and more readily fusible silica, so as to give the brick a dense, uniform texture, obliterating the granular appearance completely, but not fusing or melting the brick so as to in- jure its form or exterior. This result is obtainable only by progressive firing to the right extent, but with the manufac- turer it is like Major Jones's exercises, the fine point consists in knowing just where to stop. In this particular feature the fire-clays are claimed to be superior to the shales and 5 66 BRICK FOR STREET PAVEMENTS. silts. The latter are more readily fused than the former, and when the melting point is reached the bricks sometimes lose their form and melt together. To avoid danger from this source sudden cooling is resorted to and the product is ren- dered practically worthless by the brittleness which results from such a course. It is claimed that the fire-clays can be held at a sufficiently high temperature to produce the re- quired " vitrification " without danger of melting together, and hence furnish the most reliable product for street paving purposes. Our investigations appear to point to the conclu- sion, that from neither clay has that uniformity of product been attained which is desirable, and that can and must be made before reasonable certainty in strength and durability can be assured ; for among the fire-clay bricks many are found that show scarcely any indications of fusion or " vitri- fication " at all. Many more that are but partially fused or " vitrified," the exterior portion being dense and non-ab- sorbent, while the interior, marked by concentric colored rings, surrounds a central portion of open granular texture, and still others present a closed metallic or granitic texture throughout. By firing and annealing in a proper manner, uniformity in texture without brittleness can be produced from any clay that is suitable for the manufacture of bricks for street paving. These qualities should be specified, and such manufacturers as can not and do not produce them, should not find sale for their goods, because the hopeful young industry will soon perish or be relegated to the smaller interior cities and towns, unless these essential qualities are produced. It may be asserted that such requirements will increase the cost of production. If need be let it be so, but such as furnish the required product will find a continued and increasing demand for their goods, giving a permanent value to the plant, and the only additional expense necessa- BRICK FOR STREET PAVEMENTS. 67 rily involved would appear to be more time and care de- voted to the burning and cooling. The following is suggested as an addition to the specifi- cations, arid as more knowledge is acquired, further revision may be necessary. " The bricks or blocks to be used for paving shall be straight, smooth, and free from checks or fire cracks. The corners shall be rounded to a radius of one-fourth of an inch. In size they shall not vary more than two per cent in any dimension from the standard adopted for the kind of bricks or blocks to be used. When broken, the fracture shall be smooth and straight, not conchoidal ; and the text- ure of the block shall be uniform throughout, and not gran- ular. The amount of moisture absorbed when tests are made either with the whole block or pieces, shall not exceed two per cent of the weight of any sample when continuously immersed for three consecutive days. ~No bricks will be ac- cepted which contain lime or other soluble substances in sufficient quantities to cause spalling or pitting of the sur- face when soaked in water for three consecutive days and then exposed to the air for a corresponding length of time. " When the bricks shall have been delivered upon the roadway, samples may be selected at random therefrom for testing, which must meet the following requirements : The average crushing strength of two-inch cubes taken from any part of the brick shall not be less than 12,000 pounds per square inch. " The modulus of rupture for transverse strength shall not be less than 1,600 pounds when calculated by the for- mula, 3 Wl 68 BRICK FOR STREET PAVEMENTS. R being modulus of rupture, W=load in pounds, 6=breadth, d=depth, and J=length, all in inches. " The specific gravity shall not be less than two and one-tenth when determined by the formula, W Specific gravity=- x W Where W=weight of specimen freed from moisture before immersion, W=weight of same after seventy-two hours' soaking, and W"=weight of same in water. " In any test for determining the resistance to abrasion and impact, the loss of the brick shall not exceed two and one-fourth times that of Lithonia Georgia granite when subjected to like test. " The material shall be subjected to inspection by the engineer placed in charge of the improvement, who will se- lect samples, not exceeding live in number, for each of the tests required for determining absorption, crushing strength, transverse strength, and abrasion and impact, and cause the necessary specimens to be prepared, the tests to be made, and will accept or reject the material in accordance with the results of such trials. An allowance of twenty per cent may be made for variation of single specimens, but the average results shall be in accordance with the provisions herein set forth, or the material must be rejected, and removed at the contractor's expense. The tests may be repeated upon the arrival of different shipments, as frequently as may be nec- essary to insure the acceptance of only such material as shall comply with the provisions of this specification." WHAT HAS BEEN DONE. Bidders were informed that proposals would be consid- ered for any of the varieties of brick which had been tested, BRICK FOR STREET PAVEMENTS. b ( J but that such as showed a crushing strength of less than 10,000 pounds per square inch, or a loss in the rattler test of more than three times that of the granite, would probably not be adopted. When the bids were opened it was found that proposals included Nos. 5, 6, 13, and 14 only, and the contracts were awarded for using No. 14. Subsequently it was decided to pave about 300 or 400 feet in length of the south end on the south contract w r ith Nos. 5 and 6, and a corresponding length on the south end of the north contract with No. 13, which has been done. The form given to the roadway is shown in the accom- panying sections. Figure 1 showing the street where occu- pied by street railway tracks, and figure 2 the section where no tracks were placed. Figure 3 is a full-sized section of the rail adopted. This was placed directly on the tie, or rather on a bearing plate but three-eighths of an inch in thickness, spiked directly to the tie ; each alternate plate having an outside brace to aid in holding the rails to guage, thus obviating the necessity of using any other appliance to effect that purpose. In surfacing tracks, the rail of each track nearest the center line of the street was placed one inch higher than the opposite rail of the same track. Tem- plates were used for forming the sand bed on which the pavement was placed. Figure 4 shows that used for the the central space between tracks ; figure 5 the one for the tracks, and figure 6 that for the spaces between car tracks and curb-stone. It will be noticed that the template used at the sides differs slightly from the form specified in the cross-section of street, but this variation is believed to be a betterment, being in the nature of a camber against the greater weight of traffic, and tending to confine the water near the curb. Stakes were given for the alignment and grade of tracks, 70 BRICK FOR STREET PAVEMENTS. amq o fe p * S % 2 is -S * -si f I I TH 0^ 3 o i CQ el . Si f*> S "S 5 i* - Vj ? 8 - ^ * w ^ - i^l 3*51 1 **| 5> S ^ 8 il ~05 IV |l *1 1 "*. "* t ^ A -> BRICK FOR STREET PAVEMENTS, 71 Fig. 3, 72 BRICK FOR STREET PAVEMENTS. [;as companies will carve it to erect their lamps. Each will re- place the disturbed material in his own way, and the street- cleaning department will haul away such as remains loose upon the surface. In the meantime no one looks for. or remedies defects in their incipiency, the street having just been paved is supposed to require no attention, and so long as it remains passable without danger to life and limb, is ;,iot repaired. If a drain becomes clogged no one knows any- thing about it until the owners of the inundated properties file claims for damages, which are promptly referred to the engineer and solicitor. If vehicles are wrecked or animals crippled the claims filed by owners go to the legal depart- ment, and not until the street has been absolutely destroyed will it receive any attention from the repairing department. If it should happen to have been constructed under the supervision of officials of an opposite political complexion from those now repairing it, money will be lavished upon it to show how utterly rotten and useless were the works con- C 82 BRICK FOR STREET PAVEMENTS. structed at enormous expense by the other party. Should it be some of their own work, it will be easy to show that it was honestly constructed, but was ruined by the actions of other sovereign and independent departments. Imagine the effect of placing railways under the control of half a dozen independent boards with no executive head, their revenues separated into distinct funds with sovereign boards to disburse them, each caring mainly that its minutes shall record resolutions, ordinances, or references in proper sequence and due form ; so worded as to guard the rights and actions of the board as a body, and show that various matters were considered, and would be acted upon when some other department had done something else. Think of any corporation conducting any business enterprise upon such methods, and cease to wonder why pavements are not kept in repair. During the first years of the life of a pavement it should be carefully watched, and the beginnings of evil to it should be checked, just as a new line of railway will require a heavier force of section men than one that, having been properly maintained, has been longer in use. Expensive re- newals may be needed as portions of the structure become worn by use, but care and watchfulness are of greatest use upon new work. And this is just as true of streets as it is of any like constructions. Contracts for street construction frequently contain provisions requiring the constructor to maintain his work for periods of time varying from one to five or more years, but the meaning usually given this clause by the contractor is, that, at the expiration of the time named he shall make such repairs of the portions of his work which have not been dug up in the interval by some other party as may be designated, and received the retained percentage. There is uncertainty about this provision re- maining in force for any considerable length of time. En- BRICK FOR STREET PAVEMENTS. 83 terprising attorneys may argue that assessments should be made for the cost of construction, and that the expense of maintenance should not be assessed, but borne by the corpora- tion, and no one can tell what the court will say until it speaks in deciding the case as then presented. An efficient force, under experienced, skillful direction, employed in the inspection and maintenance of streets would appear to be an absolute necessity in every municipality. If such an organi- zation exists in any American municipality, it has published no report of its services to date. If existing regulations can not be bettered, then our form of government as applied to municipalities is a failure. WHAT is IN A The title brick, as applied to clay products used for street paving, would appear to the writer as a misnomer. The name ordinarily conveys to the engineer or builder the idea of a brittle porous substance, so hungry for moisture that it must be saturated before being laid in mortar, solely for the preservation of the mortar, so brittle that unless combined in masses it has little strength, and in no way suited to with- stand the attrition or abrasion of street traffic. When peo- ple propose to use such a substance for paving streets, the idea is ridiculed, and they must explain that they are not using building brick, but an entirely different substance, manufactured by brick makers, and in explaining the matter use is made of the other unhappy term, " vitrified brick." The only clay product suitable for use in paving streets re- sembles a tile in more respects than it does a brick, and had the name tile been chosen in the place of brick a more cor- rect idea would have been conveyed. The first having gone forth, however, it may be expedient to concur in the usual practice, but it will always be necessary to bear in mind that brick as used in street paving is a substance radically differ- ent from brick as used in any other connection. 84 BRICK FOR STREET PAVEMENTS. SIZE OF PAVING BRICK. A glance at the tables giving dimensions of specimens reveals the curious fact that hardly any two manufacturers make bricks of the same size. One of the first steps to be taken by manufacturers should be the adoption of a stand- ard size for street paving bricks. Obviously their preference would be to make blocks of about the same dimensions as- building bricks for both uses. When they make paving blocks only, and sell by the square yard, their interest will lie in the direction of increased thickness and diminished width. A large majority of manufacturers supply material for brick masonry as well as for paving, and can assort their output without material loss, thus enabling them to supply better goods for paving when they are required so to do, without suffering the entire loss of the value of such as may be re- jected. This, from the manufacturers' standpoint, is the greatest argument in favor of making the dimensions of paving the same as building brick. The users side of the question should be considered. The width of the brick or block forms the thickness or depth of the pavement. This should not be less than four inches. If made much in excess of that depth its cost will be increased about in the ratio of the increased depth. In- asmuch as four inches will afford ample strength and weight to resist the wear of the traffic to which this description of pavement is suited, there appears to be no reason for mate- rially increasing the width beyond that named unless it be to meet exceptional cases. In the future, should it appear that brick are so perfected as to be able to carry the ex- tremely heavy traffic concentrated upon business thorough- fares, where granite block pavements are now thought to be most suitable, a greater width may be found desirable. The length of the brick or block should be about twice its width; BRICK FOR STREET PAVEMENTS. 85 its thickness should not exceed its width and may be made equal to it, providing such a block can be properly burned. The writer does not say that manufacturers can not properly dry and burn a brick three or four inches in thickness, but he does say that they do not do it. The conditions and the experience all indicate failure when massive pieces of clay are sought to be burned into bricks or blocks suitable for street paving. The nearest approach to success, has been at- tained by making the block hollow on the lower side in or- der to facilitate burning. For the solid block a thickness of two inches, or at most, two and one-half inches, is as great as should be attempted. Even where the clays can be melted or " vitrified " readily, there is great risk incurred in at- tempting to increase the thickness, for such clays usually contract greatly, and the outer surface is almost certain to be fixed or seared by the intense heat before the inner por- tions shall have been so acted upon as to produce the re- quired vitrification. As a consequence they come from the kiln either insufficiently burned, checked with " fire cracks," either internal or external ; or, like an ill-shaped casting, so affected by internal strains as to have no certain amount of strength. Better results are, therefore, likely to be secured by adopting about the building brick dimensions than by at- tempting to manufacture blocks of a larger size. Unfor- tunately those dimensions have never been determined with much accuracy in this country, but they should be, and then let manufacturers vary the dimensions of their molds as the contractility of the clays vary, so that bricks of equal hard- ness shall be of like dimensions. It may be argued that the increased number ot joints in a given area, caused by the thinner block, constitute an ele- ment of weakness and should, therefore, be avoided. The defect is more imaginary than real, since the proposition can 8G BRICK FOR STREET PAVEMENTS. not be true if made general. The perfect pavement would become one without joints, which is impracticable unless made of a substance sufficiently yielding or elastic to afford secure footing for animals, which practically makes it a surface of innumerable joints. An advantage claimed for brick pavements is said to be the fact that they can be so closely laid, and the joints so completely filled, that, while they furnish secure footing for animals, they are so smooth as to be quiet, and so impervious as to be cleanly. If this be true, the additional number of joints is not objection- able. They are not an element of weakness, since the load must in any case be carried by the foundation, and the up- per and lower surfaces being equal, the weight transmitted by the brick will be as its area. Should the surface of the foundation be uneven, the smaller block is less liable to be tilted by an unequal pressure than the larger one. Within reasonable limits, therefore, the safe course to pursue would undoubtedly lie in the direction of the thinner blocks ; or, in other words," to adopt a standard size for paving blocks corresponding with building brick dimensions. COUNTRY KOADS. INTRODUCTORY. In a paper which the writer read before the club some months since, the words " Country Roads " appeared in the title, but the feature of the subject then treated contained little of practical application, under existing conditions, to the improvement of highways. That paper was a plea for the betterment of surrounding conditions. This is written (by request) in the hope that it may contain information applica- ble, under existing regulations, to the improvement of our common roads. No attempt will be made to treat the subject either systematically or exhaustively, as the field is too broad to be so traversed in the limits of one paper; but certain features will be presented which we, as practicing civil engin- eers, should endeavor to keep before the minds of those who expend moneys for road improvements. Our efforts in this direction are from patriotic motives only, for, as engineers, we neither ask for, nor expect any part in the direction of such work until after the conditions which now environ it shall have been radically changed. There is continued and growing public interest in the subject. Quite recently we have been favored with the "Re- port of the Ohio Road Commission," which was appointed by our governor to investigate and report upon the matter. Some people have regarded the labors of that commission as disappointing, but their conclusion is, at least, a relief to us (87) 88 COUNTRY ROADS. for the present. When persons who are unaccustomed to wandering in the realms of applied science, get lost upon such expeditions the result should not be surprising. There is a constant tendency to exaggerate the subject, and make it appear necessary to expend millions of dollars for the building of costly highways in all localities, regard- less of the necessity or use for such things. It will be the aim in this paper to attract attention to methods by which existing evils in our common roads may be greatly alle- viated without adding to the burden of the tax-payer, and to a betterment of the results that are attainable where larger expenditures are being made for so-called road im- provements. LOCATION. By far the larger portion of existing country roads have been located along section lines or farm boundaries, without reference to the topography of the country through which they pass. In many instances these locations are as they should be, while in others their improvement and mainte- nance upon present lines are wasteful processes. When they are revie*wed or relocated, or when a new line is to be opened, the position of the road is dictated by three citizens acting in the capacity of viewers. The surveyor or engineer, which- ever he may be called, runs the line where he is told by them to place it. To many people it would seem that this regulation should be changed, but a hasty conclusion in the matter might make it worse, because, as between the intelligent farmer and the country surveyor who ordinarily officiates on such occa-' sions, the former is generally far the better road builder of the two. If the power to determine the location be placed in the hands of the surveyor, the regulation will be bettered only when he is better qualified to exercise that power than are the viewers. Such knowledge is not conveyed by statutory COUNTRY ROADS. 89 enactments, and these can be of little avail, except in the way of preventing incompetent persons from doing such. work. As a preliminary step, it would appear to be proper to so amend the law as to require the assent of the surveyor, or allow him to submit a minority report, and thus put at least as much responsibility upon him as a viewer has. In many oases this would be beneficial, and where the work should be done by an engineer having a knowledge of topography, it would enable him to prevent waste. In the opening of new lines likely to become thoroughfares, the application of fessional knowledge would be a desirable innovatio DIRT ROADS. Assuming the location as made, the next step i pare the soil to sustain the travel to be brought upon it. far the greater part of the mileage of our country high- ways is composed of dirt roads. This condition must so re- main for many years to come. If they are properly treated, they will be changed to other forms, only when they are re- quired to carry heavy and continuous traffic. The larger part of these highways can be made and maintained as good drives without great expense, and without covering them to any considerable depth with gravel, broken stone, or other paving. Natural forces are always at work disintegrating all substances on the surface of the earth, and turning them into soil. On those portions to be used as roads, our efforts should be to neutralize, as far as is practicable, the effect of these natural forces, and make those portions sterile and un- changeable. If then the surface be deprived of the lighter vegetable mold, be made compact and smooth, so that it will carry the traffic without being displaced by it, and so that water falling upon it shall neither remain thereon nor 90 COUNTRY ROADS. penetrate into it, we shall have a good dirt road, which, so long as these conditions obtain, is literally and truly the best road on earth. But how shall we bring about and maintain these conditions ? The attacking forces are wind, water, and frost. Excepting in arid regions, the arch enemy is water, frost not being detrimental, except when aided by moisture. Thorough drainage therefore is the first requisite. Inasmuch as the dirt road is neither suitable for, nor capa- ble of, carrying heavy and continuous traffic, its width should not be great. From 10 to 18 feet will be sufficient width for the roadway proper. The correct treatment for each caser can only be determined by the skillful practitioner. In some localities subsoil drainage is wholly useless, while, generally, no durable roadway can be made without it. Assuming that we have plows, harrows, scrapers, teams,, and hand tools common in the country, and in addition thereto an ordinary road grader and a five ton horse-roller, let us see what it will cost to make a mile of fairly good dirt road in what would be termed a level swampy country. The subsoil is a tenacious clay. The top 4 to 6 inches being a. light vegetable mold, the ideal position for an impassable road in wet weather. We have a profile of our line and find two places in the mile where we can discharge water, and at those points we lay 24 inch drain-pipes across the road- way. We do not find it advisable to make any material changes in the grade of the roadway, but decide to make a, space 16 J feet wide near the center, so that it can be traveled upon. We have no rock, but at an average haul of two miles, we can get a coarse sand or fine gravel from the bars in a small stream at a cost of 10 cents per wagon load plus, the hauling. Our profile shows that we can place tile drains 3 feet deep at the summits, give them a fall of 2 feet per 1,000 feet toward the outlets and that their average depth COUNTRY ROADS. 91 will be 4 feet. Of course the tile drains are larger near the outlets and smaller near the summits, but we find the aver- age size 5 inches and the average cost 5 cents per foot. We allow $3.00 per day for teams, $1.25 per day for labor. We adopt the following cross-section for our work and proceed with its construction in this manner : SECTION OF DIRT ROAD. (Scale One inch equals eight feet.) First with light plows to loosen it, scrapers to handle it,, arid our grader to give us a smooth surface, we remove the vegetable mold for a width of 24 feet. Then we pass over the surface with our roller to see that its sustaining power is uniform. Where it is not, we make it so, cutting from the high and filling in the low places, and rerolling until we ob- tain an equable foundation. Next, we lay out and dig our trenches and place the tile drains. We finish the trenches and lay the tile very carefully, for we must have close joints and uniform gradients. We use all the clay obtained from these trenches on our roadway, and find that by digging them 18 inches wide at the top and 12 inches at the bottom we can cover it 8 inches deep in the center and 4 inches- deep at the sides. We spread it evenly to this form, harrow it to break any lumps and make it smooth, and while it ia still moist from the trench and loose from the harrowing^ we spread very coarse sand or fine gravel over it to the depth of one inch, and roll it until the surface is perfectly 92 COUNTRY ROADS. smooth and hard. We fill over our tile drains in the bot- toms of our trenches to the depth of one foot with coarse sand, and the residue of the back filling is done from the waste banks of loam, except that at intervals of about 50 feet, we fill one foot in length of the trench with sand to the top. We compact this back filling by driving our wagon wheels on it, smooth out the gutters to a depth of about one foot, spread some loam on them, and sow them with grass seed. We must do all of this work like we do our farm work when the soil is in suitable condition. Now let us see what a mile of it will cost : Removing the loam, 6c. per lineal foot $316 80 Two tile drains, 5c. each^lOc. per lineal foot 528 00 Trenching, laying, and back filling, 7c. each=14c... 739 20 660 cubic yards sand or gravel, at 50c. per yard 330 00 Grading up and rolling.. 85 00 80 feet of 24" drain pipe in place, at $1.50 120 00 Seeding gutters , 10 00 Total $2,129 00 Or, in round numbers, $2,100.00 per mile will transform the very worst of our country roads into highways much better suited to the limited traffic which they have to carry than they would be were they changed to undrained gravel or broken stone roads. The treatment described is not suitable for universal ap- plication, but for the location outlined. Only those who from actual experience know the results that will follow, will have any faith in such work; but we do know, and we should induce others to try it and be convinced. In undulating countries, enough grading should be done to avoid the necessity of traveling up and down a succession COUNTRY ROADS. 93 of steep hills, and to form the roadway properly, but the construction of long embankments or deep cuts in order to comply with some theoretical gradient is very generally a mere waste of money. The direction of currents of water upon, within, and from the soil must be studied, and drains placed to intercept them and prevent the saturation of the soil which carries the traffic, and when it has been compacted in the proper form it will permanently remain a good road, unless the traffic is beyond its endurance, and that would not be the case upon ten per cent of the country roads. When that should occur, nothing that had previously been done would have been lost, for all of that work is necessary to prepare a foundation, and it would only be required to place upon it a wearing surface having a higher power of resistance. In level districts, the roadway should generally be a foot or more above the adjacent lands, which will naturally result from constructing the side drains. In no case should there be a sharp crowning of the center, as that always results in concentrating the travel upon the highest part, inevitably producing ruts. Whatever width may be given the road- way, every portion should be equally good, that the wear upon it shall be distributed. Loamy soils and clays can be made quite firm by com- pacting in thin layers, and so draining them as to hold the water line from two to four feet below the surface, but they absorb water with great avidity, and will become so satur- ated as to lose their sustaining powers for at least a foot above the level of standing or running water. The drains should, therefore, be from three to five feet below the surface of the roadway, wherever practicable. If subsoil drains are required between the side ditches, they should be made of 94 COUNTRY ROADS. coarse gravel or rock, wherever such material is obtainable, rather than of tile. Open side ditches of the requsite depth are generally objectionable, but where the subsoil is porous, like deposits of sand or gravel covered by loamy soil a few feet in thick- ness, a side ditch of moderate depth can be made to answer every purpose by sinking shafts in it, at frequent intervals, to the underlying gravel and filling them with gravel or coarse sand. These act as inlets to the pervious stratum, and conduct the surface water quickly to it. Wherever drains are laid, an accurate map should be made of their lo- cations, depths, and connections, and the record be accessi- ble to the parties having in charge the maintenance of the works. Where the soil is shallow, and rock in continuous ledges lies near the surface, deep ditches or drains may be utterly impracticable, but shallow trenches skillfully located may prevent the water from reaching the roadway, providing the ^exact dip and trend of the rock be known. Piling material on rock surfaces where the water is pocketed, will never re- sult in good, while the best of drives can be cheaply con- structed in such localities by properly draining them, and this can very generally be done at little expense. Occasionally roads must be constructed across marshy tracts where drainage, at the time, is impracticable. In tim- bered countries this affords " the corduroy road," which is merely a method of distributing the weight over a sufficient area to bear the load. A mattress of poles and brush cov- ered with earth is generally the cheapest and best construc- tion in such exceptional cases. Drainage can usually be had when the proper search is made and wider areas are em- braced in the examination. Combining materials found in close proximity to each COUNTRY ROADS. 95 other frequently adds greatly to the stability of the soil. A fine sand may be merely loosened by the travel and carried away by the winds and rains, while if covered, even lightly, by a coarse sand or fine gravel, it will remain in place and make an excellent road. A plastic clay may retain the moisture of each passing shower to such an extent as to be an unsuitable road, while if covered with a thin layer of sand or even sandy loam, its surface will become smooth and shed water like a tin roof. Where no sand can conveniently be had, a coating of burned clay a few inches in depth will make an excellent road for moderate traffic at small cost. In all clay and loamy soils, the drainage of the surface and subsoil is the first essential. Roads located along hillsides will require but a single ditch adjacent to the hill, which should be from one to two feet lower than the surface of the traveled way, and at fre- quent intervals outlets should be provided for the water to pass beneath the road to the adjacent lowland. In locali- ties where rock is not too expensive, the best conduit is the old-fashioned stone box drain with paved bottom and dry wall sides. The rock cover should have at least two feet of earth upon it. In the deep black muck of the prairies, especially where the descent to the water-courses is very slight, the ditches or side drains will need especial care, but even these soils will sustain a considerable traffic if the water level can be kept three or four feet lower than the traveled surface of the roadway. The principle involved in combining soils for a wearing surface, is the same that applies to the successful formation of a puddle wall or the making of concrete. Clay being com- posed of more minute particles than any other substance composing the soil, becomes the filler or mastic, which, com- 96 COUNTRY ROADS. bined with the coarser fragments of sand or rock, is by them held in position and prevented from forming a solution with water. Vegetable mold being lighter than any other com- ponent of the soil, having greater affinity for moisture, and expanding so greatly when frozen, has not been successfully treated as an element in road construction. On the contrary, its presence in any considerable quantity is sure to render the soil so weak as to require protection. If well drained, the light, loamy soils can be made to sustain a moderate traffic by a light covering of cinder, gravel, shells, or burned clay. The repairing of dirt roads involves only the work inci- dent to keeping the drains and ditches open, and the road surface smooth, so as to prevent the formation of ruts or de- pressions that will retain water. The broad tire, especially where the front axle of the four-wheeled vehicle is shorter than the rear one, is the best instrument yet devised for the preservation of road surfaces. Where there is a considerable descent in the side ditches, or the accumulation of water in them is great, means should be taken to prevent excessive washing. Placing obstructions across the ditch, so as to divide the descent into a series of low cascades, is frequently the most simple and effective means of preventing the formation of deep gullies. The se- cret of success in disposing of surface water lies in conduct- ing it to natural channels in small quantities, and thus avoid- ing the handling of great accumulations. The traffic which can be economically carried by the dirt road will vary greatly with different soils, but the treatment above outlined is all that is required upon more than two- thirds of the present mileage of public roads. As they ap- proach commercial centers, or connect towns, thus assuming the nature of thoroughfares, it will be necessary to supply a. COUNTRY ROADS. 97 wearing surface of greater resisting power, and next in rank will come THE GRAVEL ROAD, In almost all parts of the country there are deposits of gravel available for road construction, and it is the most economical material for road making, when it is found necessary to assist the bearing power of the soil, and the amount of traffic is not too great. Generally its applica- tion is merely that of a " dryer," but frequently the pebbles, sand and clay become united, forming a concrete that makes a serviceable road. The calcareous, or limestone gravels, are very popular in road making, because of their tendency to become consolidated, or "pack" under traffic. They are, however, more dusty in dry weather, more muddy in wet weather, and as a consequence, less durable and pleas- ant than the silicious gravels. Where no lime or clay is present, it is necessary to have the proper combination of sizes, or there will be a lack of " bond." Frequently clay or loam is added to induce consolidation, but this practice is generally wrong. Sands of various degrees of fineness are gener ally available, which, in combination with water and pressure, will form a bond that will not be disturbed, either by excessive moisture, or frost, as will the bond formed by the use of clay or loam. The proper formation of the grade preparatory to placing the gravel upon it, has been sufficiently described in that which has been said about the dirt road. It is just as essen- tial that the soil should be drained, given the proper form and compacted to receive th,e gravel, as that it should be, to carry the traffic itself. The rolling of a coating of gravel, about an inch in depth, into the subgrade, is good practice, but the use of the roller on heavy layers of gravel is of little practical utility. A little labor and water expended in keep- 98 COUNTRY ROADS. ing the surface smooth while the road- way is being com- pacted by the traffiic, is of greater benefit. As ordinarily applied, gravel is rather wastefully used, mainly from lack of care in forming the subgrade, and fre- quently from excessive use in repairs. A thickness of six or seven inches at the sides, and from eight to ten inches in the center of the roadway will be found sufficient where the ground has been properly prepared, to make very good roads where the traffic is not too heavy. On account of its insta- bility, the gravel road should be given a little higher crown in the center, than either the earth or macadam road, but the practice is greatly in excess of the requirement in this particular. On grades of three per cent or less, a rise toward the center of an inch in four feet will be found sufficient. On steeper gradients, the crown should be slightly increased. The gravel roadway is not suitable for long slopes or steep gradients. The practice of constructing a berm or earth shoulder at the side to hold the gravel in place is correct, providing the gravel be extended through this berm to the side ditches at frequent intervals in order to afford proper drainage. Such openings may be covered with earth, where grass is to be grown or to prevent wash, but they should in no case be omit- ted. As they are not expensive, it is better to provide too many than too few. Where sand is plentiful, a continuous layer two inches in depth beneath the earth shoulder, is good practice. "Where it is more economical, a space one foot wide by six inches deep, sunk three inches into the subgrade, at inter- vals of 50 feet on each side, will usually drain the roadway. The gravel road, while new, will require almost constant at- tention, or it will not remain in proper form under any con- siderable traffic. Its cost will be that of the gravel coating added to that of preparing the dirt road as heretofore de- COUNTRY ROADS. 99 scribed. This coating will cost from $800 to $1,500 per mile, varying with the width of roadway adopted, the value of the gravel and the distance it must be hauled. It is true, that two or three times the depth of gravel above mentioned piled along the center of a mud road without any particular attentiou to drainage will generally make a single track along it passable at most seasons of the year, but gravel roads of that description are not desirable improvements, and even if they are better than no change at all, they should be discouraged because they are wasteful. MACADAM OR BROKEN STONE ROADWAYS. The preparation of the roadway for the reception of the broken stone, is the essential feature necessary to secure a good road. An inferior, shaly limestone, but a few inches in depth, on a well drained, properly prepared grade, will make a better road than the best whinstone or crushed gran- ite of three times the depth, put on an uneven, undrained roadway. It is obvious that the soil must carry the weight, and that the covering of metal placed upon it can only serve two purposes, which are, first, to distribute the pres- sure ; and second, to resist the abrading effect of the traffic ; therefore, the preparation of a proper foundation is just as essential in road building as it is in any other engineering construction. This feature is, however, very commonly neglected, and probably no better way of illustrating the matter can be chosen than to first describe how such work is done, and follow by telling how it might be done. Let it be assumed that the people of a certain locality desire the opening of a new road a few miles in length, the route being partly in a rolling country of limestone hills, partly decending across drift deposits of clay and gravel, and partly in alluvial bottom lands. The usual forms of law in such 100 COUNTRY ROADS. cases have been complied with, the county engineer, in obe- dience to the order of the commissioners, has prepared a profile and an estimate that fits the appropriation with specifications that fit any thing of the kind, the work is advertised, bids are received, and a contract awarded for building the road and the work begins. The profile shows a succession of cuts and fills to a grade which the commission- ers wisely reserve the right to change as they may deem proper, or the state of the available fund may require. Sundry culverts or drain pipes are provided for, where the line is crossed by water-courses or ravines, but no other drainage is contemplated except that from the special fund. An embank- ment is placed upon the side of a limestone hill, but it refuses to remain in position as per plan, and sullenly moves down the slope carrying the proposed roadway with it and involving a few buildings and other improvements in disaster. A cut is made through a drift deposit, and a few acres of the adjacent ground on the upper side of the road slowly begin to gravitate into the cavity thus formed, carrying their burdens with them. These movements are sought to be checked by pile-driving, and the building of retaining walls. Injured property owners file claims for damages, the fund is exhausted, the contractor blamed, but no road is completed. An additional appropria- tion is had to save the money already expended. No part of the road has been completed, but all parts have been com- menced. The former and the latter rains, aided by the teaming incident to the grading, has rendered it necessary to cover the graded road-bed with some thing, and as fast as it can be brought to about the elevations which the " engineer " designates, the contractor hauls upon it the shaly rock from the limestone bluffs, dumping it in the mud to about the thickness specified for the bottom course of metal, and breaking the upper portion so as at least to make it passable COUNTRY ROADS. 101 for his own teams. On the "foundation " thus prepared he hauls broken stone of similar quality to the specified width and depth, covers the whole with gravel, cleans the mud from the side ditches, which he carefully banks against the stone to form the required berm. On the embankments he forms the berm by robbing the slopes, and when all is done securely, fences up his work until the commissioners inspect and accept it. This being done the road is opened to a de- lighted public. It is true that sundry damage claims are still in court, that the contractor has filed large claims for delays and extra work, that the slips are still moving, the road very muddy and almost impassable in places, but there is no money for repairs, the thoroughfare is opened and the county must now keep it open cost what it may. The same line of roadway might be opened in a differ- ent manner. Instead of running lines in impracticable places, the location might be made by a real engineer, one who observes the effect of natural causes and provides for the resultants of natural forces. He knows that there are currents of moisture passing beneath and through the soil as well as those visible upon its surface, and that in road build- ing it is as essential to provide for one as for the other. In the limestone hills, he knows that every layer of stone car- ries its film of moisture with the dip to its margin, whether that be an exposed edge or one covered with soil, and hence, that any change in the condition or duty of the soil must be coupled with a provision for the disposal of the soil water, or that disaster will as certainly follow as it would were he to erect x a structure of iron or steel exposed to changes of tem- perature and make no provision for the changes in length due to heat or cold. His survey will, therefore, locate the position, dip, and strike of the principal rock ledges, the di- rection and approximate flow of the underground currents 102 COUNTRY ROADS. that will be likely to affect his work, as well as those which visibly pass upon the surface of the earth. His examination of the drift deposits will be made with great care respecting their drainage and stability. His plans will show and speci- fications describe the work that is to be done. Landslides will not follow in the wake of his grading, because they do not come by chance, and his plans provide for natural re- sults. Should it become necessary to construct an embank- ment on a hillside, the foundation for such a till will be pre- pared and drained with as much care as it would be for erecting any other structure of equal weight. If an excava- tion is necessary through a supporting mass of earth, the cutting will be done and equilibrium restored in such a man- ner that motion will not be imparted to material which is desired to remain in place. Both soil and surface waters will be intercepted and led away from the roadway, so that its condition in regard to moisture shall be as nearly as practicable constant, or at least so that it shall in no case become saturated. In the limestone hills, the ditches may be shallow, but they will be so placed as to lead away the surface water and intercept the ground water, and it will always be borne in mind that the latter function is the more important of the two. In the clay soil and drift, the side drains will be placed from two to four feet below the soil of the roadway, and the trenches filled with sand or other porous material, always connecting them through the berm with the sand covering of the sub- grade. . In forming the subgrade, he will see that it is smooth and firm, and by rolling and dressing is given a uniform sus- taining power. On grades of three per cent or less, it will rise from the berm of the side ditch toward the center or crown of the street with a slope of one inch in five feet ; on COUNTRY ROADS. 103 steeper gradients it may rise one inch in four feet, but it will be smooth, firm, and all alike. He will cover it evenly with a layer of coarse sand or fine gravel for its entire width to a depth of not less than two nor more three inches. This sand will join that leading to and enveloping the subsoil drains. This layer of sand does several things. It inter- cepts and leads to the drains the moisture that exudes from the soil, especially on grades or slopes, preventing it from percolating into the broken stone. It prevents the frost from forcing the loamy clay upward into the stone in winter. It forms a cushion between the soil and the stone, accommo- dating itself to the shape of the rock and preventing the clay from rising into and through the stone when subjected to the pressure of traific. On this layer of sand he will cause to be spread broken stone unmingled with shale or clay to an even thickness of five inches. The office of this layer of stone is to distribute the weight of traffic upon the foundation. It is not essential that it should be of very refractory or expensive material, but it must not be such as will be disintegrated by frost or rain, and its crushing strength should not be less than 5,000 pounds per square inch. The fragments should be cubical or angular, not thin and flat, and should not exceed three inches in any dimension ; if the rock has a low crushing strength, four inch pieces would be admissible. It should be well compacted by rolling. The rolling should be commenced at the margins, and by laps of one-third or less of the length of the roller progress toward and finish at the center. It should be continued until the gravel begins to appear near the surface of the stone. The earth shoulders should be built up just in advance of the spreading of this bottom layer of stone. They should be placed on sand or be pro- vided with sand drains, as described in Gravel Roads. 104 COUNTRY ROADS. The road is now ready for the wearing surface. If it is a broad avenue thirty feet or more in width, which is to carry a burden of hundreds of vehicles daily, a depth of six inches of stone in the center and four inches at the sides may be used; but for the ordinary country road, like our "free pikes," four inches in the center and three at the sides will be found quite sufficient. The most refractory or hardest rock that can be obtained at reasonable cost must be used. It should be crushed, screened, -and used in three sizes, if they can readily be had. Trap, any of the granitic rocks or whin- stones, and most of the metamorphic rocks, make excellent road surfaces. Limestones are more common, and when only sound crystalline stone is used they are quite durable. The first layer spread on the street as above described should be in fragments not exceeding two and a half inches in any di- mension, and it should be raked to an even surface about three inches thick, being a little thicker at the center than at the sides. It should be covered with spalls, that is, fragments of rock varying in size from one-quarter to three-quarters of an inch, in quantity just sufficient to fill the voids in the stone, which will be from thirty to fifty per cent of the quantity of the larger size of crushed stone. Fifty per cent will seldom be too much, because the spalls will work downward in the bottom course until they meet the sand. They should be worked into the stone with steel brooms over every portion of the surface dry, as long as any will go down, then drench the layer with a sprinkling cart, and pass the roller over it once or twice, but do not roll it hard. Now, if you have rock broken to one and one-half inch size, put on a layer of it about two inches in depth, spread and broom into it all the spalls it will take, drench it, roll it, and keep on sweep- ing in spalls and rolling until the surface of your road is as hard as, and resembles a mosaic pavement. You may leave COUNTRY ROADS. 105 a light surplus of spalls on top, but very light ; there must be nothing loose for muddy wheels to pick up, and no frag- ments of stone to be in the way. With banks all smooth, drains and ditches all open, your road is ready for use. The contractor can now receive his final estimate, but an agreed amount or percentage should be retained; for his liability should not cease for at least one year after the roadway shall have been opened to public use. The contract providing that during that period of maintenance some one in his em- ploy shall pass over the road at least once each week and re- pair any washes or slips that may occur in the slopes, see that all ditches and drains are in working order, remove any fragments of stone that may have been loosened by the traf- fic, and resurface and reroll any portion of the roadway that may show signs of looseness or movement. The statement will be made that the kind of work here described would be so expensive as to preclude its general adoption, but this assertion can be truthfully met by saying that the cost per mile of this work will be little if any greater, and in most instances actually less than that now used in so-called road improvements that do not greatly improve. If crushed and screened stone can not be had to supply the sizes above indicated, use sound stone of the kind which the locality affords and break it by hand. In this case a clean gravel should be used instead of spalls for filling the voids in the broken stone. The gravel should be screened, so as to contain no pebbles exceeding an inch in diameter; there should be no loam, and little if any fine sand in it, but plenty of coarse sand, grit, and small pebbles. It should not be put on the top of the stone and left to chance, but it should be incorporated with it and compacted by water and pressure. If no roller can be had it must be cared for and kept smooth until compacted by the traffic. The word spalls as used in 106 COUNTRY ROADS. this paper means small angular fragments of crystalline rock, not the shale, dirt, and rubbish that may be separated from the crushed stone, and commonly called screenings. It follows from what has been said that three essentials are necessary for the construction of a good macadam or broken stone road : First. That the ground or soil upon which the metal is to be placed shall be properly graded, drained, and compacted, so that its condition and bearing power shall remain constant, or as nearly so as is practicable. Second. That the soil thus prepared shall be covered with a coating that shall be permeable to the escaping ground water and lead it to the drains, but shall not be dissolved or removed by it, and shall distribute the weight of the traffic without any internal movement, over sufficient areas to enable the soil to carry it. Third. That a wearing surface shall be placed upon the roadway so firmly compacted and smooth that it will be impervious to the rainfall, that shall not be displaced by the hoofs or wheels of traffic, and that shall resist the wear for a reasonable length of time. All of these conditions can be met at reasonable cost, providing nothing goes into the metal that will readily make a solution with water, and intelligent, careful supervision be given to the entire work. There is nothing new in this, for these are the principles enunciated and practiced by MacAdam and Telford nearly one hundred years ago ; but the belief has become general that the building of a road consists in stirring up the surface along its length by a process called grading, and then cover- ing a streak of it with broken stone and gravel, and that no especial knowledge or skill are required to do this. It would be as reasonable to expect to get a good time-piece by buying a watch-case and putting some wheels in it as to obtain any reasonable return for money thus expended in road building. COUNTRY KOADS. 107 We are not suffering so much from stealing or corruption in office in these matters, as from incompetence and crass ig- norance. If the moneys now wasted could be expended un- der honest, competent supervision, a very few years in time would show such betterments in the condition of our country highways that any additional funds that might be shown to be necessary for further improvement would be forthcoming without a murmur. Those who officiate as engineers are not entirely at fault, because ordinances or even statutes generally prescribe not only that which is to be done, but the method of doing it, and specifications must be drawn to meet these requirements of the ordinance or statute. The first essential toward bet- terment must be to convince people that knowledge and skill are necessary in road making. Neither lawyers, mer- chants, farmers, nor engineers can successfully direct such work until after they shall have acquired a knowledge of the principles which should govern it, and by experience learned how to apply them. The statutes pertaining to road making assume that no training or skill is required to qualify any person to direct the work. That fallacy must be corrected before any essen- tial saving can be effected from the funds now being wasted. The building and maintenance of roads in the more densely populated districts must be placed under the direction of engineers skilled in the work, owing no allegiance to, nor subject to any disturbance from politicians, before any perma- manent betterment can be expected in this matter. In the smaller villages and rural districts the dissemination of knowledge upon the subject will be useful but slow in pro- ducing results. If a person skilled in the construction and maintenance of roads and streets, and in the organization and direction 108 COUNTRY ROADS. of forces in executing public works, were to equip and effici- ently employ in each county such a force as, with the neces- sary materials to be used, would equal in cost each year the amounts levied and collected in labor and money in that county for the improvement and maintenance of roads, ten years would not elapse until every highway in each county would have received all the improvement necessary to make it at all times passable and suited to the traffic which it would be required to carry. There might be exceptions, but as a rule this statement would be true. We are confronted with the fact, however, that such a proceeding would not be in accordance with law, and when our solons are asked for a betterment of the laws, great obstacles are found in the way. The only remedies furnished by them is in adding additional burdens to tax-payers, more offices to be filled by incompe- tent persons, and more money to be wasted in ignorance or knavery. The very muddiness of the subject is a disgrace to the country, the loss and waste is sufficient to pension all the politicians in the land, but betterment may come when the folly of submitting to existing conditions is apprehended by a majority of the people. RETURN MAIN CIRCULATION FORM NO. DD6 BERKELEY, CA 94720 '