ity UNIVERSITY OF CALIFORNIA AT LOS ANGELES GIFT OF Ov;en T Neill REPORTS, SPECIFICATIONS, AND ESTIMATES PUBLIC WORKS UNITED STATES OF AMERICA COMPRISING THE PHILADELPHIA GAS WORKS. RESERVOIR DAM ACROSS THE SWA- TARA. TWIN LOCKS ON THE SCHUYLKILL CANAL. DELAWARE BREAKWATER. PHILADELPHIA WATER WORKS. DAM AND LOCK ON THE SANDY AND BEAVER CANAL. DAM ON THE JAMES RIVER AND KANAWHA CANAL, VIRGINIA. LOCKS OF EIGHT FEET LIFT, ON THE SAME. AQUEDUCTS ACROSS RIVANNA RIVER AND BYRD CREEK, ON THE SAME. SUPERSTRUCTURE, ETC., OF FARM BRIDGES, ON THE SAME. LOCK GATES AND MITRE SILLS. EDITED BY WILLIAM ^TRICKLAND, ARCHITECT AND CIVIL ENGINEER. EDWARD H. GILL, CIVIL ENGINEER. HENRY R. CAMPBELL, CIVIL ENGINEER. EXPLANATORY OF THE ATLAS FOLIO OF DETAILED ENGRAVINGS ELUCIDATING THE ENGINEERING WORKS HEREIN DESCRIBED. LONDON: JOHN WEALE. M.DCCC.XLI. PRINTED BY W. HUGHES, KING'S HEAD COURT, GOUGH SQUARE. CONTENTS. ty The Philadelphia Gas Works ...... 1 Y Reservoir Dam across the Swatara, Pennsylvania . . 86 s 5 s * s ! | i Q | ^ K FQ 00 CC I ij 5 5 S * ? s for amount invested .... : l 6 Q CO ill| THE PHILADELPHIA GAS WORKS. 29 (B) Greatest number of Size of Tubing. Greatest length allowed. Burners. % inch. 6 feet. 1 burner. I it 20 3 )} | tl 30 6 M tl 40 12 M A tt 50 20 M 1 ti 70 35 M 11 >t 100 60 H ,, 150 100 2 " 200 200 " Size of Meters. Greatest number of Burners. 3 light. 5 burners. 5 10 t> 10 20 20 40 tt 30 60 Jt 45 100 tt 100 250 REPORTS COMMITTEES OF COUNCILS, &C. PREVIOUS TO THE ESTABLISHMENT OF THE GAS WORKS. The Committee to whom was referred a resolution of Coun- cils directing an inquiry into the expediency of lighting the city with Gas, Report That, impressed with the importance of the inquiry re- ferred to them, not only as regards the amount of investment required to carry the project into successful operation, but the moral effect that must be produced by increasing the comfort, convenience, and safety of the inhabitants, the Committee have bestowed great attention, and made minute inquiries, in order to be fully satisfied in their own minds of the propriety of the measure, before recommending any course to Councils in relation thereto. In the course of their investigation they examined with care the establishments for the manufacture of gas now ex- isting in Baltimore, New York, and Boston. In these cities carburetted hydrogen gas is made from different materials and dissimilar apparatus ; and they consequently have been enabled, by comparing the expense of each gas, taking into view their respective illuminating powers and cost of appa- ratus, to determine the nature of the works which will be found most advantageous in the event of any system of gas lighting being adopted. These investigations have resulted in a strong conviction THE PHILADELPHIA GAS WORKS. 31 on the minds of your Committee, of the great advantages that would result to the community by the adoption of a system of public lighting, which they believe is far superior and more economical than that now pursued; and in this opinion they are supported, not only by their own obser- vation, but by the experience of every individual at all con- versant with the subject. In arriving at this conclusion, the Committee directed their attention First, to a comparison between the economy of oil and gas as a means of illumination; Second, to the material from which gas may be produced with greatest advantage; Third, to the objections against gas works as dangerous and offensive ; and, finally, to the proper location and probable expense of construction. To these points, severally, the attention of Councils is requested. Comparison between Gas and Oil. In treating of this subject it is not the intention of the Committee to enter into any estimate of the cost of manufacturing gas, for two reasons; first, because in the end any such estimate must prove fallacious, as the expense attending any species of manufacture depends upon many contingencies which cannot be taken into account ; and, secondly, it is deemed improper, after the candid manner in which these inquiries have been met by the gentlemen interested in gas works, to expose to public view any calculations tending to affect their interests. It is believed the end may be fully accomplished by com- paring the selling prices of the several gases respectively with oil, and showing the state of the concerns of those engaged in its manufacture, so far as it may be proper to make them public. The Baltimore Company manufacture gas entirely from bituminous coal ; the New York Company from resin ; and Mr. Robinson, of Boston, a gas from the two materials com- bined. The several estimates of value, as compared with oil, are, in the judgment of those concerned, as follows, viz. Coal Gas specific gravity = 400, at <^3 33 per thousand 32 THE PHILADELPHIA GAS WORKS. cubic feet, is equivalent to oil at 66 2-3 cents per gallon. Resin Gas specific gravity = 750, ^7 00 per thousand cubic feet, is equivalent to oil at 80 cents per gallon. Combined Gas specific gravity = 600, is equivalent to oil at 70 cents per gallon or, in other words, 200 cubic feet of coal gas, costing, at ^3 33 per thousand, 66 2-3 cents or 114 feet of resin gas, at ^7 00 per thousand, 80 cents or 140 feet combined, costing, at ^5 00 per thousand, 70 cents, will, respectively, give the same light in the same time as one gallon of oil. It should be borne in mind, in all inquiries respecting the illuminating powers of different bodies, that the quantity of light in the same time must be carefully considered. This remark is made for the reason that the Committee have found this circumstance generally overlooked. Frequently it has been observed to them by consumers, that gas light was quite, if not more expensive than oil ; but when pressed upon the subject, they acknowledged that their stores were better lighted, which readily accounted for the increased expense. In taking the estimate of the comparative value of coal gas as here given, on the correctness of which all sources of information agree, it is very clear that the public lamps could be supplied with gas at a less expense by 33 per cent, than with oil, the same quantity of light being obtained, pro- vided the gas could be purchased at 000 Suppose 12,000 burners (private), each burning from five till ten five hours, consuming 3| cubic feet per hour, or 12,000 X 5 X 3 for consumption = . 210,000 Total number of cubic feet 315,000 To furnish to consumers 315,000 feet of gas in one night, and compensate for waste in its transmission and condensa- tion in pipes, 66 coal gas retorts, with proportionate appa- ratus for condensing, purifying, and storing, will be required. In determining the cost of these extensive Works, your Com- mittee are guided by a comparison with similar establish- ments, and by such information as could be gained, with- out making complete drawings and accurate estimates from them. Being inclined to give the fullest latitude to every contin- gency, they are of the opinion that 200,000 dollars will cover the whole expense, including the transit main from Ashton- street to the Dock-street station, together with three gaso- meter stations, and four gasometers on the eastern plane of the city, but exclusive of conduit pipes. The expense of laying the pipes for the transmission of gas throughout the city can be determined with considerable accuracy from the experience already had. From the plan laid down, the measurement of the several sizes has been made with due allowance for branches and hubbs, as follows : The prices are per foot, and including every expense : 1 1,1 46 feet of 10-inch main at %\ 95 . . .#21,734 70 83,703 "6 " 1 07 ... 89,562 21 349,620 "4 " 71 ... 248,230 20 108,396 " 3 60 65,037 60 ^424,564 71 THE PHILADELPHIA GAS WORKS. 43 Brought forward . . . ^424,564 71 Add cost of Works as above 200,000 00 2,500 lamp-posts, including lamps and fixtures, at ^25 62,500 00 Total expense ,#687,064 71 In preparing this estimate the Committee have been careful to avoid deceiving themselves or the Councils as to the eventual cost of the Works, being unwilling to be reflected upon hereafter for having induced the Councils, by imaginary calculations, to engage in any work more costly than they were led to believe ; they have therefore placed the estimate on so liberal a footing, that they feel confident the whole work may be executed considerably within that amount. Several years must elapse before the whole plan can pos- sibly be carried into execution, and it will rest with future Councils to determine whether it shall stop, or to what extent it shall be carried. In the mean time, with the expenditure of less than half of the capital stated, the Works may be completed so far as may be required to convey the gas through the business parts of the city. That portion of the city will yield all the profit that can ever be expected to arise from the sale of the gas, and will of itself be suffi- cient gradually to extend the pipes to such parts of the city as will remain, and in which the gas will only be required for public purposes. An expenditure, it is believed, of 250,000, or to the extent, 300,000 dollars, will carry this plan into complete effect, provided the Works are not charged with the interest thereon. If the idea suggested by a com- mittee appointed by the last Councils be carried into effect, namely, the construction of these Works out of the income of the Girard estate, the Councils may rest assured that the annual appropriation for light will be for ever extinguished, and one object of the benevolent testator carried into full effect that of decreasing the burden of taxation. The Committee are unanimously of the opinion, that the Councils have full authority, in Mr. Girard's will, to appropriate the 44 THE PHILADELPHIA GAS WORKS. surplus income of the estate for this purpose, and in this opinion they are supported by the City Solicitor. In accordance with these views the Committee have pre- pared an ordinance, the adoption of which they recommend. As the summer is the period of active operation, so the winter is the time for preparation; and as it would be ad- visable to have the Works in readiness, and sufficient pipe laid to render them available for purposes of revenue before the ensuing winter, the necessity of an early decision is suggested. In preparing the ordinance provision is made for a standing committee on lighting and watching. The object of uniting these two branches of public service under the superintendence of one committee is the intimate con- nexion which exists between the manufacture and consump- tion of the gas. Inconvenience has been found to exist in other cities from the public lamps not being under the control of the Gas Company's agent, an evil which it may be as well to avoid. All which is respectfully submitted. (Signed by the Committee.) Philadelphia, 1st January, 1833. The Committee to whom the remonstrance of sundry citizens against the introduction of gas was referred, having duly considered the several objections urged, concluded their Report in February, 1833, in which they introduced the fol- lowing abstract from the Report of a Committee of the British Parliament on a similar subject in the year 1823 : " Your Committee are of opinion that the danger likely to arise from gasometers and gas works is not so great as has been supposed, and that therefore the necessity of inter- ference by legislative enactments, pointed out in the Reports referred to them, does not press at the present period of the session. " It appears that great improvements have taken place THE PHILADELPHIA GAS WORKS. 45 in the apparatus, machinery, and management of gas works since 18 14, the date of the Report from the Committee of the Royal Society, which have very much lessened the danger from such works ; and that improvements are daily making in every part of them, that must still further lessen the danger necessarily attendant on such establishments. " The evidence sufficiently supports the opinion, that the risk of accident or danger is but small if the ordinary care and attention necessary in every large establishment is paid by the officers and workmen employed on the premises. " It is in evidence that carburetted hydrogen gas, usually supplied to the public, is not of itself explosive, but that, in order to render it so, a mixture of from five to twelve parts of atmospheric air, and the application of flame, is necessary ; whilst the manner in which the gasometer houses are gene- rally built renders it extremely difficult to form the mixture requisite for explosion, and, consequently, renders the chance of accident remote. " The danger attendant on the use of gas in the streets and passages appears also to be small, and that it will, probably, by the better management and care of the persons employed in these establishments, be henceforth lessened. " Your Committee cannot close their Report without ex- pressing their satisfaction that the public have obtained so great and so rapidly increasing a means of adding to the convenience and comfort of society as the use of gas, under due management, must afford ; and they are of opinion that, as a means of police, much benefit would be derived from its general introduction to light the streets of this metro- polis." As the remonstrance of the citizens referred especially to numerous accidents which were stated to have occurred in the United States, the Committee considered it their duty to lay before Councils the best information they could obtain on the subject : they therefore addressed a letter to the Mayors of Boston, New York, and Baltimore, of which the following is a copy : 46 THE PHILADELPHIA GAS WORKS. SIR, The Councils of the city of Philadelphia have appointed a Committee to inquire whether it is expedient to adopt a system of gas lighting in preference to oil, on which subject they have reported. Doubts have been expressed by a number of respectable citizens of the propriety of the measure on several grounds. Among the most prominent are, the danger from fire to which houses are liable that are lighted in this way, and the great loss of life and destruction of property from explosions where this mode of lighting has been adopted. With a view to elicit, from the highest source of informa- tion, facts from which the Councils may arrive at correct conclusions, the Committee have directed me to address you this letter, and respectfully request that you will at your earliest convenience reply to the following inquiries : Has there been any increase in the number of fires in your city since the introduction of gas, and if so, do you attribute that increase to the gas ? Has there been any instance in which houses are known to have caught fire from gas, and if there has, on what evidence does the statement of the fact rest ? Do you consider the introduction of gas into buildings as more darfgerous than the use of lamps or candles ? Has there been any instance within your knowledge of great loss of property, loss of life, or serious personal injury, by the explosion of gas in the works or pipes ? With much respect,. S. V. MERRICK, on behalf of the Committee. Philadelphia, 18th January, 1833. The replies of the gentlemen to whom this letter was ad- dressed were highly satisfactory to the Committee ; and another letter having been written by Mr. Merrick to the President of the New York Gas Company, in which infor- mation was requested from a Fire Insurance Company, " as to any difference in risk, or preference between buildings lighted with gas or oil," the opinions of the Presidents of seven different Fire Insurance Companies in that city were obtained, and thus expressed by Mr. Worthington, then President of the Franklin Fire Insurance Company : " I THE PHILADELPHIA GAS WORKS. 47 have the pleasure to state, that upon the first use of gas in this city, the fire companies generally came to the con- clusion, that their risks were not enhanced thereby, and premiums were of course not varied. Indeed, it is obvious that the fixed position of the gas lights renders them less liable to communicate to any combustible material than portable lights of either candles or oil lamps." On the 2nd of January, 1834, a resolution was passed by the Select and Common Councils, "authorizing the Gas Committee to engage a competent person to proceed to Europe for the purpose of examining gas works, with a view of obtaining the best information as to the construction of works, the manner of manufacturing gas, &c." S. V. Mer- rick, Esq., was selected for this mission, and in December of the same year made the following Report : To the Select and Common Councils of the City of Philadelphia. GENTLEMEN, IN pursuance of a resolution of your body, passed on the 2nd of January, 1 834, and of instructions from the Committee charged with an inquiry into the expediency of lighting the city with gas, received on the 18th of March last, the undersigned immediately embarked on his destined mission ; and during the course of the past summer has made a careful examination into the various plans and processes employed in manufacturing carburetted hydrogen gas, for private and public illumination, now in use in the principal establishments of Great Britain, as well as a cursory view of the works in Paris, Brussels, and Ghent. In conducting these investigations, I have to acknowledge the friendly reception I met with from gentlemen connected with gas manufactories, either as engineers or managers, in most places which came under examination, to whose liberality I am indebted in general for opportunities granted for a free inspection of their works, and in many cases for the entire confidence with which their modes of operation and results were communicated. The gas works which I visited on the Continent being all of English origin, and under English control, I was unable to obtain 48 THE PHILADELPHIA GAS WORKS. from them any information of material value not already derived from original sources which had been brought under previous notice. In the course of this communication, therefore, my observations will be confined to comparisons between systems used in England or Scotland, believing that the purposes of the mission will be fully attained by such comparisons as may there be made. In preparing this Report I have deemed it my duty, upon re- viewing the instructions, rather to take a general view of the ar- rangements and machinery best adapted to the wants of the city, and to point out the system which appears most conducive to its interests, than at this late day to enter into any laboured argument to prove the general expediency of a measure which has received the sanction of so many years' experience. Arriving in a country, the capital of which consumed during the past year a quantity of gas equivalent in illuminating power to nearly forty million pounds of candles, which possesses within its limits and populous suburbs forty-seven stations for making and storing gas, erected by twelve different companies, who have in their construction profitably invested an aggregate capital of near eleven millions of dollars, and whose arrangements are not now sufficient to supply the growing demand, it appeared too late to inquire whether gas as a means of illumination was preferable to any other substance. If I add to this the universal testimony of the citizens of that metropolis, and of high public functionaries, as to the moral effect experienced by the facility of producing, at a moderate expense, a brilliant light in the streets and narrow passages with which that city abounds, adding to the safety, comfort, and convenience of society, it will not be expected that much time will be occupied in demonstrating what is thus forced upon our attention. If other evidence is wanting to prove the consideration in which this system is held in Great Britain, I may instance the fact, that during five months' travelling in that country I scarcely ever passed a town or village, to which the material was accessible, that was not provided with this indispensable means of obtaining light, or was in preparation for it ; and so great has been the extension during the past year, that all the foundries which came under my notice were full of contracts for the delivery of pipes and retorts. As far as I have been enabled to collect the history of these small works, they have generally been erected by the owners of real estate as an improvement to their property, and, when completed, leased to THE PHILADELPHIA GAS WORKS. 49 any individual who would keep them in repair, and pay the best interest on the cost. Believing, as I do, that the formidable objections raised when this subject came under discussion during the past year were entirely refuted by the Report of the Committee, who examined into their truth, and being confirmed in the opinion as to the correctness of the statements made by that Committee, it is sufficient to refer to that document in case such evidence should now be deemed requisite. In considering the kind of gas works best suited to the wants of Philadelphia, it will be necessary to take a general view of the systems now practised in Great Britain, the materials employed, and the mode of constructing the apparatus for distillation, giving a comparison of the advantages of each plan. As regards the materials which may be used in the manufacture of gas to the best advantage, enough has been said in the Report of the Committee made to Councils in March, 1832, who carefully investigated this part of the subject, to show how much will be gained by the use of bituminous coal instead of the more costly material heretofore partially adopted in this country and in Europe ; and I deem it an argument of no small moment in favour of this mode of lighting, that every material used in the fabrication of gas will be the product of Pennsylvania labour. The bituminous coal from which it is to be made may be drawn from the rich mines now open in the interior of this state ; the fuel from the exhaustless beds of anthracite, and the lime for purification, from our own vicinity ; and not a lamp will shed its rays over our streets which has not paid a tribute to the internal improvements of the state. If any evidence be required in confirmation of their opinion, it is to be found in the fact that the use of oil as a material for the production of gas has long since been abandoned in both countries, and the works used for making resin gas ; even this material has failed to make a successful competition against the cheaper substance, having finally given way after a long struggle. The resin gas works of Great Britain have been, or are about to be, converted at a heavy expense into coal gas works, and in New York the Company who are now erecting their works for supplying the upper part of the city have been compelled in part to change their plan and adapt them to the use of both materials. Believing therefore that coal in great abundance and of good 50 THE PHILADELPHIA GAS WORKS. quality may be had for the supply of the works, my attention will be confined to it as a gas-making material, and to the plans now in use for its manufacture. The coals used in Great Britain for this purpose are various in their properties and values, but for our present purpose may be divided into two general classes, viz., the Cannel or the Parrot Coal of Scotland, and the soft or bituminous coal, more abundant in England. The former of these ranks highest for the purpose, containing a larger proportion of carbon and volatile matters, with less bitumen than the soft coal; producing a gas highly charged with olefiant gas, and possessing an illuminating power superior to any other known in the kingdom. This material is in use in Manchester, Stockport, and some other towns in England, and almost universally in Scotland, yielding gas having a specific gravity nearly equal to resin gas. The coke from this coal is of but little value in comparison with that produced from the soft coal, being of less bulk than the material from which it is made, and furnishing but a small quantity for sale, after deducting that required for fuel to heat the retorts. From this material, therefore, but little profit is derived from any product except the gas; but the superior quality of that gas, in connexion with the low price of the material, warrants its use in those works which have adopted it, and the proprietors have been compelled to pay undivided attention to increase the quantity of gas without reference to profit from the residuums. As in America there is no coal yet discovered bearing any re- semblance to this material, it would be useless to dwell here upon the systems used in its carbonization, except as showing the ex- perience of several works, having used precisely the same material on different systems, and in apparatus varying in construction from each other, but bearing a comparison with those used for the car- bonization of fat or soft coals. I shall advert, therefore, to the Cannel coal works, after treating of the plans adopted in England for the carbonization of the soft coal; among which the Newcastle, yielding about thirty-five per cent, of volatile matters, seems to stand pre-eminent in reputation, producing in the usual mode of operating from 10,000 to 12,000 feet of gas per chaldron. Specific gravity from 4- 10 to 4' 30. It may" be proper here to remark, 'that although the specific gravity of gas will not give precisely its value or power of illumi- THE PHILADELPHIA GAS WORKS. 51 nation, still, as a general rule, the approximation is so near that I adopt it as an indicator of the value of the gas, for want of a more accurate standard, which may be referred to in general terms. The various proportions in which the component parts are found incorporated in the bituminous coals of Great Britain, yielding gas of different qualities, and more or less in quantity, add much to the difficulty of comparing the several systems of working with each other. The results of all comparisons must therefore be mere ap- proximations, except where coal from the same mines affords the To seek, therefore, a series of works in which the same coals were used appeared to me essential for definite purposes, while I continued ' to confirm my results by observation elsewhere. The coal I found in most general use was that already alluded to, from Newcastle on Tyne, being preferred in London, and on the eastern and south coast of England, to any other within reach ; and as some of these works varied in their modes of distillation, it became for all practical purposes a standard material by which to compare the respective operations of each, diminishing the difficulty of se- lecting a plan best adapted to our purpose. The system upon which gas is to be made at the least cost first claims our attention, and resolves itself into three points : 1. The expense of fuel and material for carbonization. 2. The expense in wear and tear of apparatus. 3. The labour attendant upon its manufacture. This is a subject on which much diversity of opinion exists among gas engineers : the plan of retort, the duration of the charge, and the temperature at which the process of carbonization is to be con- ducted with best advantage, are points of controversy among them at this day. To describe all the plans would be quite useless. I shall therefore confine all observations to those which appear most deserving of merit, and necessary to our present purpose. The first plan claiming attention is the oven of Mr. King, with which we are familiar at the coal gas works of America ; the di- mensions being 5^- feet wide by 6 feet long, 1 8 inches high at the crown of the arch, and 1 2 inches at the spring, carbonizing about 10 bushels of coal at a heat, or 1 ton in 24 hours. These ovens are made of thick boiler iron firmly riveted together, with the bottom of the same material set in an arch of brick-work, heated by one fire, the bottom being shielded with fire-tiles to 52 THE PHILADELPHIA GAS WORKS. protect it from the direct action of the flame, with longitudinal flues under it ; the draught, passing over the top of the oven, makes its exit in the crown near the front. Some ovens of this description are in use at Liverpool, with cast-iron bottoms, but their value has not been determined on by practice. This plan of carbonization I found nowhere in extensive use, except at the Liverpool Works, constructed by the inventor. Of the cast-iron retort there are many modifications, varying in dimension and shape with the caprice of the conductor, and in many cases without any definite idea of the principle to be aimed at. They may be divided into three general classes : 1st. The circular retort, from 12 to 20 inches in diameter, and from 6 to 9 feet in length. This retort is used in Manchester and some other places, in general for the distillation of Cannel or Scotch Parrot coal. It answers for the distillation of a coal which retains its form in lumps, and is advantageous only from the facility with which its position is changed, when partially destroyed by the action of fire on the under side. 2nd. The small or London D retort, so called in consequence of its having first been used by the Chartered Company in London, being still in use at their works, and recommended by their engineer. This retort is 12 inches broad on the base, 11 inches high, and 7 feet long, carbonizing 1^- to 2 bushels at a charge. 3rd. The York D retort, (so called in consequence of its having been introduced by Mr. Outhit, of York,) and the modifications of it, among which I should include the elliptic retort, as having the same general purpose in view. The difference between the London and York D retorts consists only in an extension of surface upon which the coal is spread, the latter varying from 18 to 30 inches in width, and about the same dimensions in length and height. These cast-iron retorts are set in benches of from two to nine in a set, usually enclosed in an arch of brick-work, heated with one or two fires, arranged with shielding tiles, so as to prevent a direct action of the flame upon the metal ; some with ascending, some with descending flues. To describe the particular mode of setting on each plan would require drawings in detail ; a labour entirely uncalled for, as the proper plans will be prepared of the arrangement deemed most effectual. In addition to these I have found retorts or ovens composed of fire-brick, built in form, or of clay moulded to the shape in the arch THE PHILADELPHIA GAS WORKS. 53 constructed to receive it, varying in dimension and shape from 2 to 4 or 5 feet in width, which will be treated of in the sequel. The plan of retort, and the system of working to produce the greatest quantity of gas of the best quality, is at present a subject of controversy among engineers, and to form a just opinion requires a careful comparison of the operations of each. As the whole economy of gas-making depends upon the expense of carbonization, it was an object of much solicitude to obtain from the books at the respective works such statements of their daily operations as would enable me to form a correct estimate of their advantages, rejecting mere theoretic opinions and verbal statements, if unaccompanied by satisfactory testimony. In giving the general result of these examinations it will not be requisite to record the names of the works, as such a publication would be a betrayal of confidence highly unjustifiable. These statements have been generally obtained for a short period of time, to avoid multiplicity of figures, but have been compared with the workings for much longer periods, often six and twelve months : the results may, I think, be received with confidence. The following have been taken as the elements of comparison : 1st. The quantity of coal used for carbonization and fuel. 2nd. The product of coke in weight. 3rd. The product of gas and quality. By deducting the second from the first we shall have the net amount of material consumed to produce the third element or pro- duct of gas in cubic feet, its quality being considered generally. This mode of comparison has been preferred to the more usual estimate of ascertaining the proportion of fuel used to the coal car- bonized ; because the latter method is liable to error, as the quantity and quality of the gas is improved by adding to the temperature at which the distillation is carried on, and consequently increasing the amount of fuel burnt. In this comparative view all residuums, save the coke, are re- jected ; not because they are worthless, but on account of the great difficulty in obtaining a correct statement of the quantity made, and variation in value of the other residual matters. The vast quantity of tar and ammoniacal liquor made in Great Britain has rendered them so far unsaleable that the latter is often evaporated under the retorts or flues, and the former accounted of more value as a fuel for heating retorts than as a marketable pro- duct. Such residual matters, therefore, in a comparative statement, 54 THE PHILADELPHIA GAS WORKS. do not constitute an item of sufficient importance to affect the result in an appreciable degree, though some difference must exist in the quantity of tar made when very high degrees of heat are used in the carbonizing process. The system of carbonization which has longest obtained, and which at the present day is in most general use, is to fill the retorts with coal, leaving space for the increased bulk of the coke, and for the insertion of tools for its removal, carbonizing with a moderate heat, and allowing the charge to remain exposed to the action of the fire for six or eight hours. The opposite to this is to charge the retorts with less coal, or a thinner strata, and to increase the temperature so as to work off all the gas contained in the charge in three, or at most four hours. By the first mode of operating less fuel is required to carbonize the same weight of coal, and the retorts being subjected to more mode- rate heat will remain fit for service a longer period of time. It is, therefore, contended by its advocates that the saving of fuel and saving in retorts more than compensates for any advantages to be obtained by the short charge system. The opposite doctrine is not new, having been held and practised in the early stages of the art, under many practical disadvantages ; but the more easy operations on the long charge system have been practised in a majority of the works using the bituminous or soft coal. The attention of several skilful engineers has of late been directed to an improvement in the quality, and increase in quantity, of gas produced, which they have effected, in a material degree, by ope- rating with high temperatures and a thin strata of coal. Their practice has been founded upon the following theory : That the first products from the distillation of coal, after the water has been evaporated, contains the greatest quantity of olefiant gas, and consequently has the highest illuminating power. That if this gas be evolved at a high temperature, it carries with it in combination a portion of carbon, which, at a low temperature, would not be disengaged as gas., but would pass over as tar. That, as the process advances, the proportion of carbon evolved diminishes, while the proportion of sulphur increases. That, after the first two hours, the quantity of gas and its specific gravity diminish in a rapid grade. To test the accuracy of this theory certain experiments were insti- tuted, intended to ascertain the quantity and quality of the gas THE PHILADELPHIA GAS WORKS. 55 evolved during different periods of its distillation, varying the quan- tity charged at each time, the temperature at which it was carbo- nized, and the duration of the process, so as to embrace a fair com- parison of the two modes of working. The first experiment was made with two York D retorts, 22 inches broad by 7 feet long, charged with 200ibs. each of Lambtou's Prim- rose (Newcastle) coal, heat kept up to a fair red, and continued for nine hours. The result was that the production of gas, from 400fts. of coal (5 bushels), amounted to 1,620 feet, or less than 11,000 feet per chaldron ; that four-fifths of this quantity were evolved during the first six hours, and more than half evolved during the first four hours. Specific gravity 4' 5. The next experiment, made with the same retorts, heated to a higher temperature, charged with 140fts. each, and worked off in six hours. The gas produced from this charge of 280 fts. was 1,750 feet, or in the ratio of 18,000 feet of gas per chaldron; six- sevenths of the whole product being evolved in four hours. Specific gravity 5' 18. The charge being then reduced to 120fts. to each retort, or 240fts. total, was worked off in five and a half hours, producing the same ratio of gas to the chaldron. Eleven-twelfths of the whole product being evolved in four hours ; the product in gas evolved after the four hours not being worth the fuel taken to produce it. By carefully repeating these experiments, and taking the specific gravity at various stages of the process, it was found to decrease in each successive half hour as the work progressed after the second or third trial ; while the result, as respected quantity, proved equally in favour of the short charge system. The result of these experiments clearly establishes the fact, that the greatest quantity of gas and the best in quality may be pro- duced by working a diminished quantity of coal in the recipient at a high heat. So far, therefore, as quality and quantity of gas produced are con- cerned, the principles to be followed are, 1st. An extended surface, and thin strata of coal in the retort. 2nd. Rapid carbonization at a high temperature. From insulated experiments, such as have been detailed, no judg- ment can be formed on the other points of comparison : although care was taken to note the quantity of fuel used in each experiment, the correctness of the statement cannot be assumed as a guide to continuous work. 56 THE PHILADELPHIA GAS WORKS. To determine the expense of fuel required under different circum- stances, recourse must be had to the continuous operations of works using the same material for carbonization, and dividing the amount of fuel into the product of gas made, instead of the quantity of coal carbonized : for this mode of estimation the reasons have been given. The statements now presented are from works carbonizing New- castle coal at four and six hour charges. As I could obtain no returns from works using the same coal at eight hour charges, the comparisons will be confined to the first two, which are sufficient for our purpose. Station No. 1. London D retorts, area of surface 7 feet, set two to one fire ; the lower retort cased in tiles, and the return flue passing under the top retort unprotected ; the whole covered with a fire-brick arch, charged every four hours with 1 bushel, or SOfts. coal. Whole amount of coal used for fuel and carboni- zation in pounds 154,800 Deduct coke made 59,166 Total material consumed . . . 95,636fts. to produce 551,387 feet of gas, or to each pound 5 '75 feet. Specific gravity 4'8. Station No. 2. Retorts and setting the same as No. 1, area 7 feet, charged every six hours with ]| bushels, or lOOfts. coal. Whole amount of coal used for fuel and carboni- zation in pounds 69,520 Less coke made 22,433 Total material used 47,087fts. to produce 222,600 feet of gas, or to each pound 4'6 feet. Specific gravity 4*4. Station No. 3. York D retorts, setting the same as before, are of a surface 12 feet, charged once in four and a half hours, 1| bushel of coal. Whole amount of coal used for fuel and carboni- zation in pounds 25,360 Deduct coke made 8 700 Total material used 16,660fts. to produce 91,550 feet of gas, or to each pound 5'40 feet. Specific gravity 4 '70. THE PHILADELPHIA GAS WORKS. 57 Station No. 4. Elliptic retorts, area of transverse section 8^- feet, set seven in a bench, shielded from the action of the flame by fire-lumps, covered with a brick arch, charged with 2 bushels, or IGOfts. every six hours. Whole amount used for fuel and carbonization in pounds 105,720 Deduct weight of coke 43,680 Total material used 62,040fts. to produce 308,000 feet of gas, or to each pound 4*8 feet. Specific gravity 4'33. Station No. 5. York D retort, set same as No. 1, area of surface 13 feet, charged every four hours with 1|- bushel of coal. Total coal consumed for fuel and for carbonization in pounds 23,600 Deduct coke made 9,240 Total material consumed . . . 14,360fts. to produce 92,500 feet of gas, or to each pound 6'44 feet. Specific gravity 5' 10. It will be here seen that the result of the comparison between the two systems, as illustrated in these five statements, is as fol- lows : No. 1. London D, 4 hour charges, 5*75 feet to pound. 2. Do. 6 do. 4-60 do. 3. York D, 4 do. 5'40 do. 4. Elliptic, 6 do. 4'80 do. 5. YorkD, 4 do. 6'44 do. The quantity of gas produced from a pound of material used, and the quality, as indicated by the specific gravity, invariably give the advantage to the short charge system. It should be observed, that the coke produced upon this system is lighter than by the old plan, and the bulk increased. These points being established, we are next to compare the economy of the plans respectively, taking into view the wear and tear, and the labour required to keep up the supply. It does not necessarily follow that an increased temperature will create a corresponding increase of wear in the retort, as variable heats have a much greater effect upon them than high heats if they are kept uniform. The results are not so disastrous upon the retorts used in the short charge system as might be supposed, provided care 58 THE PHILADELPHIA GAS WORKS. is taken to keep the temperature the same ; but the difficulty of keep- ing high heats equable exposes the retorts worked on this system to greater risks than by the opposite plan. To determine, therefore, what will be the duration of them is difficult, as experience on a large scale has not yet been had to settle this point ; although, in small works, whose operations have been brought immediately under the eye of the engineer, but little difference in duration has been found between the two plans. Still it would not be wise to draw from their experience conclusions, and refer them to works on a larger scale, which must be intrusted to a greater number of stokers, and which cannot be kept so completely under control. In Great Britain the proportion of gas required during the summer months is so small in comparison to the other parts of the year, that during this period a great majority of the retorts are thrown out of service ; consequently in a set of retorts, the usual duration of which is eight months, a sufficient number will be saved to do the work of the other four, or summer months ; for, except in large cities, the public lighting is entirely suspended during that term, and the private lighting diminished in a great degree. In a work, therefore, in which the retorts can stand eight months' active service, they will require renewal annually to keep the stock whole. In works operating with six hour charges I have found a better average duration than here stated, and that two complete renewals in three years, being equal to working twelve continuous months, may in general be calculated on. This duration is more than many works attain, and may be considered the highest average that can probably be allotted to them. Retorts working eight hour charges often remain in continuous service eighteen or twenty-four months ; indeed I have known them thirty. No economy is derived from such long use, because, although the retort will not leak, the product is constantly diminish- ing, while the proportion of fuel increases from the contracted space in the retort occasioned by the solid particles of carbon which collect on its internal surface. Indeed this obstruction takes place shortly after the working commences, and the incrustation increases so fast that it is doubtful whether there is much saving effected by retaining a retort in service past one season. But it is needless to go into minute calculation upon this point. If we lay aside the retorts working eight hours, and form the com- parison between those working four and six hour charges, we shall THE PHILADELPHIA GAS WORKS. 59 find that the additional duration of the last is compensated for by the diminished number required to do the same work on the first plan, on account of the rapidity of the working, and the additional gas produced from the same material, leaving the wear and tear about equal. Thus, to make 100,000 feet of gas in twenty-four hours by the six hour system, producing 11,000 feet to a chaldron of Newcastle coal, would require 9 chaldron 4 bushels. Say 41 retorts each, 2 bushels to a charge, 4 charges in 24 hours. 41 x 2 x 4 = 328 bushels, at 11,000 feet per chaldron, 100,000 feet. To make the same gas by the short charge system, at 15,000 feet to the chaldron, would require 6 chaldron 24 bushels coals; say 27 retorts, 1^ bushel to a charge, 6 charges in 24 hours. 27 x 1| x 6 = 243 bushels, at 15,000 feet per chaldron, 101,245 feet. Thus the number of retorts required to produce the same quantity of gas bear the relation of 41 to 27. Now if the retorts on the six hour plan require renewing twice in three years, there will be required for that period 41 X 2 = 82 retorts. While on the other system, lasting but one year, there will be required 27 x 3, or 81 retorts. Thus, notwithstanding the duration of the retorts upon the four hour plan is less than upon the other, when the expense of renewal is divided upon the quantity of gas made during an extended period of time, the difference is ^inappreciable ; while the former possesses the advantage of requiring less space, and less capital in the original construction of the works. From this statement it is evident that, as the labour must bear a proportion to the number of retorts at work, and the quantity of ma- terial to be handled, the advantage is decidedly in favour of the last named plan. In these remarks reference has been had to cast-iron retorts only ; but so far as the amount of production is considered, they refer equally to the oven of Mr. King. These ovens, it has been observed, are made of malleable iron, and in point of economy in wear and tear have a decided advantage over the cast-iron retort, for the work they are capable of, requiring less fuel than many of the other works. I should be much inclined to adopt them in preference to the cast- iron, were it possible to work them on the short system. 60 ' THE PHILADELPHIA GAS WORKS. The shape of these ovens is such as to carry out the principle laid down to the fullest extent, but the extended surface of the bottom renders it impossible to heat them to the requisite temperature with- out early destruction to their shape, and soon rendering them unfit for useful service ; but I am not at all certain that the adoption of wrought-iron retorts of smaller dimensions would not be conducive of advantage. The high price of iron in this country led me to examine with care into the plans in use, and experiments now making in England and Scotland to carbonize in retorts or ovens made of fire-clay or brick. The original inventor of these ovens was, I believe, Mr. Grafton, of Cambridge ; and one work in Brighton now operates with them successfully. The manager of the station spoke of them favourably ; but I could not obtain an exact statement of his operation, nor could I hear the same good opinion expressed elsewhere, though many had tried them. At one station I found two of his ovens in operation, which required as much coal for fuel as for carbonization ; but this was accounted for in the thickness of the walls, which had been built of nine-inch brick. Independently of the high per-centage of fuel required by the ovens of this material, other difficulties occurred in the use of it which almost proved fatal. In the first place it was found that the clay, unless made very thick, was a material of too little tenacity to resist any undue pres- sure, especially where the separate pieces were joined together by cement ; and that any accident occasioning a stoppage of gas in the pipes re-acted so violently as to burst or injure the retort. This difficulty was remedied by building stays or ties into the retort, connected with the outer arch. But the evil most difficult to be cured was the tendency to leak at the junction of the cast-iron mouth-piece, and at the joints, owing to the contraction and expan- sion of the material under different temperatures. When the retorts are first brought to their heat, time will elapse before the cement in the joints attains the consistency of the other material, and becomes entirely gas-tight ; but, while the temperature is kept uniform, little difficulty is experienced when once they have been made tight. The constant variation in demand for gas makes it incumbent on the manufacturer to vary the number of retorts in action as it in- creases or decreases. Hence the necessity of letting down the re- THE PHILADELPHIA GAS WORKS. 61 torts, an operation during which the joints, being the weakest part, give way as the brick contracts ; and it is more difficult to refill these cracks than to make the original joints with fresh brick and cement. This difficulty has been partially overcome by filling the joints before re-heating with clay cement, and washing them with a mixture of salt and potash, or some other glaze. To produce a perfect retort of clay, the only desideratum wanting is such a combination of material as will not be subject to change of dimension from any change in the temperature, so that the fires may be let down and rekindled without causing a waste of gas. To this end Mr. Spinney, of Cheltenham, an engineer of practical knowledge and skill in his profession, has instituted a vast number of experiments, and succeeded by a mixture of fire-clay, pipe-clay, and silex, in producing the desired results. The Cheltenham Works, under the charge of that gentleman, are provided with retorts or ovens of this description entirely ; and the operations of that Company are conducted in a manner highly bene- ficial to those interested and to the public. Heretofore single ovens, of a dimension smaller than Grafton's, have been used by him, each heated by one fire ; and while the quantity of gas from the coal carbonized is quite as much as would be produced by the same system of working in iron retorts, the fuel account is materially increased the great saving being in the wear and tear, an item reduced to a very limited amount. In some new benches erected Mr. Spinney has reduced the size of the retort still more, and set two to one fire, carrying on the carboni- zation at a lower rate than with the single oven ; but this bench has not been in operation long enough to decide whether the saving in wear is not more than compensated by increase of fuel, though, as far as a judgment could be formed, the result was satisfactory. It should be observed that these works were operating with eight hour charges, and therefore not obtaining all the advantage which might accrue from using an indestructible material. I am inclined to think, however, that the clay retorts will be found a valuable acquisition to the gas-maker in this country, and am con- firmed in this opinion after examining the works of Scotland, in two of which the clay retorts are in constant use with highly beneficial results. Here, as well as in England, immense difficulties have been encountered in bringing them to perfection, but their efforts have been crowned with success. At the work in Glasgow a fair example is offered of the value of 62 THE PHILADELPHIA GAS WORKS. this material in comparison with iron retorts, in both of which the same species of coal is carbonized. The principles laid down of working at high temperatures are here carried to a greater extent than any work in England, seven or eight charges being worked off in twenty-four hours, each retort being made to produce near 5,000 feet of gas in that period. To enable cast-iron retorts to stand such excessive heats at all, it is necessary to shield them at all points with fire-lumps, rendering them as inaccessible to the action of the fire as if they were composed entirely of clay. The result is in this case, that the fuel account is quite as high as with the clay, while the wear and tear is ten to one in favour of the latter material ; for, with their utmost care, it is difficult to preserve the iron retorts more than four months, while the clay last from twenty-four to thirty months, and cost far less in construction. The difficulty which exists in the iron retorts of contracting inter- nally in consequence of the deposit of carbon, has here been reme- died in the clay retorts by occasionally leaving the interior in con- tact with the action of the atmosphere a few hours while at a red heat, the oxygen of which combining with the carbon separates it from the clay surface. In the work alluded to, the most decided preference is given to the clay retorts, where, as well as at the Paisley Work, which operates with brick retorts on the same principles, the quantity of gas pro- cured from a pound of coal is ten or twelve per cent, greater than in those works using the same material where milder heats, incident to the use of cast-iron, are in practice. Although, from a careful examination of this subject, I feel per- suaded that the use of fire-clay retorts will be found more conducive to economy than those made from any other material in this country (where the price of iron is more than double its price in Great Britain), and that in the event it will be resorted to, yet I am by no means prepared to recommend its immediate adoption. We have no reason to suppose that our skill will enable us to bring to perfection at once a material which has cost so much labour and loss to experienced engineers, who have for years been endeavouring to bring it into successful operation, and who have not yet brought it to that state of perfection of which it is evidently susceptible. The immediate success of an infant gas manufactory depends so much upon the first impressions with which it is received by the public, that it would be unwise to abide any risk of failure by stepping THE PHILADELPHIA GAS WORKS. 63 out of the beaten track at the commencement, and I should by no. means recommend any change from plans already known and well tried. It will be ample time to make experiments for the improvement of the process and apparatus when experience has made us masters of the business. I have therefore selected, as the most suitable for the purpose, the retort described as the York D, of cast-iron, set in such a manner with three to a fire, as will allow of the substitution of the clay retort whenever such a change in the system of operating is deemed ad- visable. This retort has been selected, because, under all circumstances, it appears to be the one with which the principles laid down may be carried out with the best advantage, being large enough to give them free scope, and least likely to become distorted by the high heats to which it may be subjected in the process of carbonization. Having in the preceding remarks attempted to show the system to be pursued for the carbonization of coal on the most economical plan, our attention is next called to the capacity of works required to meet the wants of the city, the mode of construction, and their location, before proceeding to describe the machinery in detail. To determine the ultimate demand for gas to supply with light an improving city like Philadelphia, is a task for which we can com- mand no certain data, and which, if attempted, must be purely hypo- thetical. Before planning new works the usual and most natural course is to make an approximate estimate of the wants of the place, and pro- bable demand ; but in most old works that have come under no- tice, laid out upon such estimates, the demand has increased of late years so unexpectedly that the sites and arrangements are found far too limited for present purposes, and the respective parts of these establishments are in many cases disproportionate to the work re- quired of them. To plan works on any hypothetical calculation as to eventual demand would without doubt be a fruitful source of error, requiring some parts more extensive than would at present be required, with the risk of their being too small for future exigencies. Such estimates, therefore, are only requisite for the purpose of determining the size of the leading mains, or great arteries, for the transmission of the gas from the works to the city, which without C4 THE PHILADELPHIA GAS WORKS. doubt ought to be laid of sufficient capacity to meet any contingency ; but for the works themselves the estimate of capacity should be con- fined to the probable present demand, and -the establishment con- structed complete as a whole to meet that demand, leaving the future wants to be supplied by a similar range of works constructed by the side of the original establishment. The advantages which may be expected from such an arrangement I apprehend will be, 1st, That the works may be built upon a uniform and symmetrical plan, with the capacity of each part calculated to meet the wants of every other part. 2nd, That no unnecessary capital may be expended in preparing, on a scale commensurate with future wants, parts of the work now required of a small dimension, such as purifiers, condensers, &c. 3rd, That in any future increase the fullest advantage may be derived from our own experience, and the advancement of the art elsewhere, in adopting improvements that may occur. A fourth reason for recommending the plan of a series of minor works has forced itself on my attention while passing through some of the great works of England, viz. : the difficulty of pre- serving a uniform system of working, and of placing individual responsibility on the workmen engaged in managing long ranges of retorts. I have scarcely ever seen in a large work a uniformity of heating, or found the superintendent who could form an accurate judgment of the results of any particular mode of operation. In such establishments a general knowledge of average operations can be readily attained, but nothing definite. It is all-important in a work where so much depends upon the care of stokers, that means should be in the hands of the manager to judge accurately of the operations of each, which can only be effectually done by subdividing the work, having a station meter attached to each division to record the product of every bench of retorts. I have generally found small works doing much better than those upon a large scale. It is probable that the cost of labour will be a little enhanced during the summer, when full work is not required; but this dis- advantage will be more than counterbalanced by the important be- nefit that will result by being able to keep the operation of the works under the most perfect control. In selecting a site upon which to construct the works, the choice must be governed by very simple principles. THE PHILADELPHIA GAS WORKS. 65 The specific gravity of the gas being less than that of atmospheric air, the natural tendency of that fluid is to ascend ; the level, there- fore, of the distributing station should be at the lowest point of the plane to be lighted. Such a location is always desirable, and if it can be obtained should be preferred ; but as it is not always practi- cable, experience has shown that considerable depression may be overcome without affecting in an undue degree the equality of the issue at the burners. When great descents are to be overcome, distinct stations are deemed necessary effectually to attain this object. I apprehend that, without resorting to this expensive mode of regulation, depressions of 40 feet may be overcome in a district so small as this city. The evil resulting from inequality of pressure is most felt when the gas is sold by the time of burning, and not by the quantity con- sumed. In the former case the consumers are very careless about re- gulating the issue of their gas, as the expense to them is unchanged, and the cost of the additional quantity consumed by those burners placed on an elevated position is borne by the gas-maker. If, how- ever, the meter system is adopted and carried into universal effect, the consumers take care to regulate their flame to their own wants, and no loss accrues to any one. Other important considerations in fixing the location are its conve- nience to navigation, to a coal-market, and to a market for vending coke. All the materials used in the manufacture of gas are bulky, and consequently of expensive transportation. To avoid this addi- tional cost is a matter of paramount importance. It is fortunate that the natural position of the city is such that an easy distribution of gas is compatible with all these objects. Under the view here stated it is only requisite to enter into an estimate of the capacity of works suitable to the immediate wants of the community, giving a general idea of the probable cost of their construction. This estimate will be based on the supposition, that the most popu- lous part of the city will first claim the attention of Councils, and that provision for 4,000 public and private lights will probably be sufficient to meet the demand for two or three years, divided in the ratio of 300 public, and 3,700 private burners. In estimating the capacity of the works for the supply of this demand, the greatest quantity of gas required in any one night must be the basis of calculation. P 66 THE PHILADELPHIA GAS WORKS. Say 300 public lights burning 13 hours, at 4 feet of gas per hour, 300 X 4 x 13 15,600 3,700 private burners, average time of burning 4 hours, at 4 feet per hour, 3,700 x 4 x 4 59,200 Total gas required in one night, cubic feet . . 74,800 It has already been shown that the retorts recommended will carbonize one and a half bushel of coal at a charge, which at six charges in twenty-four hours makes a total of 9 bushels of coal to each retort. How far we may be successful in obtaining a coal which will yield a quantity of gas equal to the Newcastle coal, is yet to be deter- mined ; but I feel warranted in saying that there will be no difficulty in obtaining a material to produce 12,000 feet of gas to the chaldron, and shall therefore estimate the produce of each retort at 3,000 cubic feet. To insure against accident and loss in distribution, there will be required a bench of thirty retorts to produce this quantity ; and I recommend that the works be constructed on that scale. In stating this proportion of public and private lights, it should be observed that the ratio is likely to diminish after the pipes pass into streets less occupied for business, until the gas is generally intro- duced into private houses. In estimating the cost of the station here described, it must be observed that the data are of the most general character, because, until the location is fixed, the works laid down in detail upon plans, and a knowledge had of what walls, levelling, wharfs, &c. are re- quired, no accurate estimate can be given. It is sufficient for our present purpose to say, upon a comparison with similar stations in England, and making due allowance for dif- ference of cost in the two countries, that the station here noticed will not exceed 35,000 dollars, and probably come much under that sum. This is exclusive of mains to convey the gas into the city, or effect its distribution when there, but includes the retort-house, gasometers, and all other apparatus necessary. After taking a view of the carbonizing process, a brief sketch of the machinery required to prepare the gas for use and distribute it over the city, will close this part of the subject. After leaving the retorts, the gas passes through a large pipe termed the hydraulic main, in which it deposits a part of the tar and THE PHILADELPHIA GAS WORKS. 67 ammonia which flow into their proper receivers, and itself goes to a vessel called the condenser. The process of condensation first claims our attention, and on the judicious selection of apparatus for this purpose will depend not only the ready purification of the gas, but the prevention of an accu- mulation of offensive matter in the street mains. The general impression appears to have been, that the only requi- site to insure a perfect condensation of gas is a reduction of tem- perature ; but it would appear from some circumstances that more is required, and that the process is effectually completed only by bringing the gas into contact with cold solid substances. In some of the works in Scotland this principle is carried out to an extreme length, and their condensing apparatus is arranged so as to filter all the gas through vessels filled with " fern," " oak twigs," " stones," or any other substance, the effect of which is to separate the par- ticles of gas from each other during their passage, and bring them in contact with the substances through which they pass. So far as observation leads to a correct opinion, it would appear that works in which a reduction of temperature alone is regarded, the condensation is but imperfectly completed ; but when means are taken to bring the gas in contact with solid substances by filtration, or a constant change in the direction of the conduit, the effect is made evident by a more perfect condensation. In works which have come under notice, the condensers are made in every variety of shape which suited the views of the constructor, without, however, in many cases keeping in mind these principles. While it would be a useless task to describe each variety, they may be divided generally into two classes, the air and the water con- densers, or those in which the temperature is reduced by the action of the air, or by immersjpn in water. The water condensers are usually either pipes immersed in water, or oblong boxes of cast iron, communicating at their ends, and ex- tending from 200 to 700 feet in length ; or in some cases, upright pipes, connected at the top and bottom, surrounded with a cast-iron tank filled with water. The air condensers are usually a series of upright pipes, connected at the top and bottom, having vents at the lower bends for the dis- charge of the condensed matters, tar, &c. The general principles upon which this part of the apparatus is to operate being known, its form may be varied to suit the circum- stances of the place in which it is to be erected ; and that form (58 THE PHILADELPHIA GAS WORKS. which is the simplest, taking up the least space, and which costs the least money, is undoubtedly to be preferred, provided it will perform its functions with equal certainty. As the air condenser comes under all these conditions, I give it the decided preference, taking care to vary its form from the mere series of pipes, so as to increase the surface with which the gas may be brought in contact. The first impression natural to a view of this condenser is, that during the heat of summer the temperature of the atmosphere may be so high as to disable it from producing the desired effect ; but this is not the case, for by the aid of a small stream of water sufficient to keep the outside of the pipe moist, an evaporation takes place which reduces the temperature as low as is desired, while at all other seasons the object is gained by an exposure to the air alone. The usual mode of construction is to erect the pipes on the north exposure, protected from the direct rays of the sun, and this appears in many respects preferable to the water condenser. The tar and other condensible substances having been deposited from the condenser into their proper receivers, the volatile products, or gases, flow to second vessels, called purifiers. The volatile products from the distillation of coal are various in their nature and properties, being valuable for the purposes of illumination, in proportion as the pure olefiant gas and carburetted hydrogen can be separated, and preserved distinct from the other products. To separate these valuable gases from the others, numerous plans have been put in practice successfully, but all with the same agents. The heavy or condensible matters have all been partially disposed of ; but there still remain in solution some portion of ammonia, and all the gaseous products which cannot be condensed. To effect an entire deposition of ammonia requires the presence of water, for which it has a strong affinity, while lime has been found the best material for depriving the gas of sulphur, the impurity held in the largest quantity, and of the most deleterious quality. The effect produced by its presence during the combustion of gas is to send forth a suffocating odour, and to tarnish metallic polishes whenever it comes in contact with them. Water and lime therefore being the substances best adapted to separate the impure matters from carburetted hydrogen gas, it naturally followed that a solution of lime in water was first used THE PHILADELPHIA GAS WORKS. 69 for the purpose of purification, and vessels of various constructions were rendered subservient to this purpose, by passing the gas through the liquid, keeping the lime in solution by constant agitation, and changing the water whenever the application of gas to paper satu- rated with acetate of lead or nitrate of silver was found to produce a change of colour : experience soon taught the operators that it was requisite to wash the gas in three distinct changes of water to free it entirely from its impurities. So far as regards the economy of material only this plan has undoubtedly the advantage, because the particles of lime, being held separately in solution, may each individually be brought into contact with the gas, and be saturated with impurities ; an effect which cannot be produced so perfectly when the lime is not held in solution, owing to the amalgamation of many particles together, which protect each other from the action of the gas. This process, however, must in some degree prove a nuisance, from the difficulty of getting rid of so large a quantity of liquid material impregnated with nauseous vapours. To avoid the disagreeable effects upon persons residing in the vicinity, by whom complaints were often made, recourse was had, in many cases, to a discharge of this refuse underground into neigh- bouring rivers or streams ; but when this was deemed objectionable, extensive cesspools were resorted to, from which the liquid was gradually conveyed under the retorts and evaporated. By any mode the discharge of this fluid is troublesome, and requires great care to prevent its becoming offensive to those residing near the works. The disagreeable nature of this residuum led Mr. Phillips, of Exeter, to propose the purification of gas by means of dry lime, and to construct the proper apparatus for its use. The plan proposed by this gentleman, with some modifications, has obtained precedence very generally in Great Britain, and is now adopted, except in some of the larger works, which still adhere to the original plan of wet lime. The original expense of material by the dry lime process may generally be considered as double that which is incurred by the wet lime process ; but this cannot for a moment be considered, when placed in connexion with the entire freedom from nuisance of which the dry lime process is susceptible. It has been said that the presence of water is necessary to absorb the ammonia. The process of Mr. Phillips was called dry lime, in 70 THE PHILADELPHIA GAS WORKS. contradistinction to the lime cream or wet lime plan, while, in fact, the lime is saturated with water to a consistence that would adhere if pressed between the fingers. In some cases this admixture of water, together with the conden- sation, was deemed sufficient to free the gas from ammonia ; but the process being imperfect, recourse was had to washing the gas in clear water, previous to condensation, with success. It has been found advisable to pass the nascent gas from the hydraulic main through a reservoir of pure water, which takes up much of the ammonia that would otherwise be lost, producing a highly saturated liquor of value, and materially assisting the process of condensation. The dry lime purifiers consist of a series of large square boxes of sheet iron, having projections placed on the sides, to receive sieves or wire gratings, upon which lime, slaked and moistened, is laid in strata of 1 to 3 inches thick, as lightly as possible, so as to allow the gas freely to percolate. At the Paris works a stratum of fern or moss is spread on the sieves under the lime, to assist its free circulation. Considering therefore that the works may, if properly arranged, be freed entirely from all offensive or disagreeable odour by the adoption of the dry lime system, it appears to me far better to over- look the difference between the economy of the two plans, and to adopt that system in any works to be erected in this city. In the construction of gasometers many improvements have been made of late years, tending to reduce the expense and simplify their action. The constructors have at last discovered, that as gas may be safely retained in a vessel no stronger than a silk balloon, there is no occasion for building gasometers strong enough to retain steam, and the heavy iron and wooden framings with which they were formerly encumbered are dispensed with. No ribs or braces are now inserted, except such as are required to keep the vessel in shape until filled with gas. The capacity of gasometers must, of course, vary with that of the works. It is not generally the custom, but I think it judicious, to have nearly as much gasometer room as the retorts can fill in a day. In many instances I found the disadvantage from being cramped in gas store-room very manifest. In the depth of winter, when the demand for gas is at its maximum, the want of an adequate supply in store is often severely felt ; and in some cases recourse has been had to working extra benches of retorts for the night only. THE PHILADELPHIA GAS WORKS. fl The consumption of fuel during the day to keep up the heats for night work must necessarily be very disproportionate to the object gained. The necessity of letting down retorts during the suspension of public lighting upon moonlight nights, is an evil which can only be remedied by an excess of store-room. Indeed, in many places, where the capacity of the gas-holder is too limited, it is found expedient to keep the public lamps lighted during moonlight nights, rather than incur the expense of letting out and re-heating retorts. It is believed, therefore, that true economy points out the policy of a full share of store-room notwithstanding the expense is con- siderable, especially in a new and growing work, where extensions may be looked for very soon. The store-rooms being determined, the capacity of the gasometers must approach the quantity already named of 74,000 feet. To avoid accident, it will be judicious to have this capacity divided into two vessels, which will fix the size at 50 feet diameter, by 18 feet deep, vessels well proportioned and of convenient dimension. Gasometers of this size do not require counterbalancing, as the pressure upon the gas to sustain the whole weight will be less than the resistance due to a column of water 3 inches high, a pressure quite convenient when the weight of the gasometer is not used to regulate the flow to the burners. The usual method now adopted to equipoise large gasometers is to insert cast-iron frames on the top of the tank, with guide rods and friction rollers to preserve a steady motion up and down, allowing the vessel to play upon the gas within. This plan is far preferable to the old plan of suspension from the centre of the gas-holder crown, which was liable to the objection of creating a flickering in the lights whenever the vessel was agitated by external causes. Another method of suspension has lately been put in practice, which answers even better than the guide rods for keeping the vessel steady. This is, to suspend at three points, with chains tending to and terminating at one point, by a triangular frame of wood- work ; to these chains connected a counterbalance was hung. The plan of triangular suspension has one decided advantage in a climate liable to falling or drifting snow. The weight of snow falling on one side of the vessel will not affect its perpendicular position, while, with the guide rods, it might affect the free play of the gas-holder. 72 THE PHILADELPHIA GAS WORKS. On the whole the triangular suspension appears preferable, and the expense is not much more than the guide rods, the weight required being merely sufficient to keep the gas-holder steady. The practice of enclosing gasometers within buildings, which from their size must entail a heavy expense on the establishment, has long since been abandoned, and they are now universally placed in the open air, even in the northern part of the island, where the climate is quite as severe as that in which we are placed. There may perhaps be seasons in which the extreme severity of the weather will affect the water in the tank, but in general the constant supply of fresh gas, at a temperature much above freezing point, will prevent any accident from impeding the free motion of the gasometer, while temporary precautions may be taken, if ordinary means should fail. The liability to frost is the only objection which can be raised against the exposure of gas-holders in the open air, and the ease with which that evil is guarded against precludes the necessity of incurring the heavy expense incident to the construction of buildings. There is another advantage, however, which ought not to be overlooked. I allude to the impossibility of any serious accident occurring from the explosion of gas in vessels placed in the open air. It has been shown on a former occasion, that the only time a gasometer can be put in a condition liable to explosion is during the act of expelling the air and introducing the gas in the first instance, but that afterwards, if a rent or hole be made in it, the only evil that can result is a loss of gas ; for the weight of the gasometer will cause the gas to flow out of such hole, and entirely prevent the admission of atmospheric air, to create an explosive mixture within. It is clear, therefore, that if the gas escape by accident or design, the loss in the open air is the sole evil to be apprehended, as an explosive mixture cannot be formed outside of the gasometer, there being no building to confine it. The danger from explosion is an evil the fear of which has long since passed away in all places where gas is in general use. It is there looked upon as an idle chimera. The nature and properties of gas are now so well understood, and the precautions to prevent accident so well known, that notwith- standing the immense number of works existing at this time, a disaster is of rare occurrence ; and when one does happen, the injuries are not extended, as formerly, beyond the damage done to the vessel itself where the explosion takes place. THE PHILADELPHIA GAS WORKS. ^ The tanks to contain water, into which the gas-holders are in- verted at some works, are cast-iron plates bolted together, with a bottom of same material, but more generally of brick or stone, having the bottom well puddled before the pavement is laid, and the outside round the wall secured in the same way. The latter method is preferable, whenever the nature of the ground will admit of such a structure, on account of the greater economy in the construction ; and as the brick is a worse conductor of heat than iron, the water is less liable to be affected by frost. In such cases it is usual to sink the tank entirely beneath the surface, thus keeping the gasometer as low as possible. 4 Having disposed of the gas when made in its store-houses, we have to consider the mode of distribution to the consumers, and the regulation of the pressure so as to insure an equal flow at the burners, points which materially affect the value of the works as a source of public convenience. The gas is conveyed through the streets in mains or pipes of cast iron, to determine the proper size of which has heretofore been a difficult task, and one which has proved a fruitful source of error and vexation . To avoid the heavy expense incident to laying down great mains, engineers have often erred on the other extreme, and contented themselves with pipes far too small for the wants of the public ; an error which has in some cases led to a useless expense in laying mains unnecessarily large. Unfortunately, there are even at this day no fixed principles known respecting the flow of aeriform fluids 5 which will guide us surely in determining this point ; but we must be guided by the ex- perience of others, applying as nearly as possible their practice to our circumstances. Before entering upon this subject, it is proper to determine the quantity of gas which will be required to pass the leading mains in a given time, and the location of the works from which the mains are to be laid. The first reply as to the quantity of gas required must be a mere assumption, for no one can prophesy the extent of the demand. In Great Britain, it has in growing towns almost invariably ex- 4 The accident which recently occurred at the Ratcliffe Works, London, where the gasometer tank (being an old hrewhouse vat) burst with the weight of water, shows us the importance of sinking the tank underground, to prevent the possi- bility of such a disaster. 5 This desideratum is supplied by the Formulae in ' Tredgold on the Steam Engine.' Weale, London. 1838. ED. 74 THE PHILADELPHIA GAS WORKS. ceeded the most sanguine calculations, and we are not likely to be behind-hand in appreciating an improvement, when the value is once understood. I cannot assume, however, a demand of less than 20,000 lights, including public and private ; suppose for the eastern front of the city 14,000, and for the western front 6,000, consuming an average of four feet per hour. To supply the eastern front, (dispensing with gasometer stations,) will require to be passed in one hour 14,000 X 4, equal to 56,000 ft. Western front, 6,000 X 4, equal to . . . . 24,000 Total consumption in one hour in cubic feet . . 80,000 In estimating the size of the mains, it is requisite to know the location of the works, because, if they are to be placed on the eastern front either above or below the city, it is clear that the mains must be of a capacity sufficient to pass the whole quantity within the city limits ; but if the location formerly selected be still adhered to, on the western front, then the part of the city between the works and Broad-street may be supplied direct from the works, while the main need only be of a capacity to pass that portion required for the eastern front. By this means Broad-street will be the point from which the draught on the main will commence, and to which the pipe must be of sufficient capacity to convey the whole quantity required as fast as it is consumed on the eastern front of the city. By ascertaining the delivery of gas through mains in such cases as I have been able to make observation, I have found one instance of a six-inch main, extending the same distance, in which a pressure of six-tenths of an inch was ample to deliver the gas at a velocity of 10 feet per second. Taking into consideration the difference of friction in a pipe of such dimension, and in one the capacity of which will be sufficient for our purpose, we may feel quite safe in laying a main which will pass the required quantity at the same velocity, or even something less. The discharge through the main alluded to being 7,000 feet per hour at that pressure, or one-eighth the quantity stated before, the main, according to this rule, must be eight times the capacity, or 17 inches diameter; but as the rubbing surface or area, in proportion to the quantity passed, is so much less in the latter than in the former, I should not hesitate to reduce the size to 15 inches diameter, believing that the proportional diminution will be compensated for by the difference in the friction. THE PHILADELPHIA GAS WORKS. 75 In this I am confirmed by reference to another instance, where 23,000 feet per hour are passed five-sixths of the distance through a main 10 inches in diameter, which would give the size required to pass 56,000 feet per hour, by the same rule, 15f inches diameter : this example shows a decrease of friction in greater ratio than in the length of the pipe. Whether this main of so large dimension should be laid at once or divided into two, of half the capacity each, may be hereafter de- termined when the plan of distribution comes under final consider- ation ; it is sufficient for our present purpose to know the whole size which will be required. The capacity of this main has been considered without reference to any assistant station for storing gas or regulating pressure. It will be recollected that, on a former occasion, the Committee of Councils deemed it necessary to appropriate a station on the eastern front for this purpose, and designated the public lot in Dock-street as a suitable position. In doing this, they certainly acted with sound judgment, believing that the regulating station there would have great effect in preserving an equal flow of gas from the burners in all parts of the city ; and it is quite possible that a resort to a regulating station on the eastern front may, in the event, be found not only useful but necessary. As, however, there seemed to be a strong objection among many citizens to such a disposition of that lot, I took some pains, by comparing the situation of this city with others, to ascertain whether the descent from Broad-street was likely to affect the flow to such a degree as to render an easy regulation impracticable, and now feel satisfied, that if the mains are of ample size, no difficulty will arise in distributing from works on the Schuylkill without any auxiliary stations whatever. If experience shall testify to the correctness of this opinion, a very heavy expense in stations will be saved. It is possible that a diffi- culty may occur on the eastern wharfs, which being the lowest point may be affected by unusual draughts from above. The only evil to be apprehended is, that as there will be an excess of pressure on the upper burners of four-tenths of an inch over those on the lower level, the size of the apertures in the burners will require to be varied to meet the difference in the rapidity of flow ; an in- convenience of no great moment, as it will affect principally the burners below Front- street, where more than half the depression takes place. It is not, therefore, deemed expedient to take any measures to 76 THE PHILADELPHIA GAS WORKS. provide for the regulation of pressure beyond what may be accom- plished at the manufactory, until experience proves the necessity. The mode adopted in some \vorks for regulating the flow to the burners, is by taking off or adding to the weight which counter- balances the gasometer. But this is a clumsy and laborious plan, and one likely to prove defective, unless the gas-holder is nicely poised with compensating weights. Instead of this arrangement, the co- nical valve has been substituted, which, by being closed or opened, regulates the quantity of gas flowing from the gas-holder through the exit pipe by changing the size of the opening. This valve is sometimes opened by hand, but its regulation by the judgment of the workmen does not in all cases answer the desired end, for if a number of lights are suddenly extinguished, the ad- ditional pressure on the pipes causes an excess of flow through all the remaining burners ; thus, although long experience enables the workmen to regulate with tolerable certainty, yet errors and loss of gas will constantly happen. To remedy this evil a self-acting governor has been put into use, which consists of a small gasometer, to which is attached the stem of the conical valve. This gasometer is counterbalanced to the weight required to force the gas to all the burners. Any change in the con- sumption of the gas operates at once to raise or depress this gaso- meter, and of course regulates the flow by closing or opening the conical valve. Thus, with a self-acting governor, the flow and pres- sure upon the mains is regulated with great nicety to the exigences of the moment, requiring only that there shall be more weight upon the main gas-holder than upon the smaller one. The plan for laying pipes, as usually practised, is perfectly well understood here, differing from water-pipes only in one particular ; that is, a regular grade of elevation and depression must be pre- served, in order to give a descent for the flow of condensed water (which sometimes accumulates in the pipes) to certain points where it may be received into suitable receptacles, and removed, otherwise an obstruction in the flow of gas might occur. These recipients are called syphons, or, more properly, con- densed water-boxes, and are to be provided at every point of depression. The mains require to be laid out of reach of the frost ; in this climate from 18 to 24 inches below the surface. They are usually laid on each side of wide streets, or, if narrow, one row in the middle is ample, the openings or trenches being made and closed on THE PHILADELPHIA GAS WORKS. 77 the same day, so that the passage of the street is never materially impeded to the inconvenience of travellers ; so slight a trench being made that the earth is easily rammed in, and the pavement relaid without waiting for the natural settlement of the earth. A method has been partially adopted lately which I think far superior to the old mode, in all cases where the pipes are laid over solid ground. By this plan the hubb of the pipe is bored, and the small end turned, each with a very slight taper. The two ends of the pipe, being covered with a mixture of white and red lead, are entered, the small end into the hubb, and driven home with a mallet. The joint thus made is perfectly tight, and the taper so slight that no contraction by change of temperature will render it subject to leak. It is plain that this mode of making joints can only be carried into effect in straight lines, or with slight cur- vatures ; in all other cases the old plan of lead joints must be resorted to. Where the lines are straight, as in this city, great facility is presented for using the bored and turned joints, which are undoubt- edly preferable to lead joints wherever they can be introduced. The service pipes from the street main to private meters are some- times made of small cast-iron tube of three-fourths or one-inch diameter, but more generally of malleable iron or lead. The use of malleable iron for this purpose has been almost universal, but it has been found that whenever it comes into contact with ashes, gravel, or sand, it is acted upon and destroyed in ten or twelve years, while in clay no such difficulty is experienced. The extreme ductility of lead, which is often used, renders it objectionable ; being liable to short bends, in which water may lodge and obstruct the flow of gas. To obviate this, lead pipe is sometimes laid in grooved brick, which effectually overcomes the evil, while the expense is enhanced beyond that of iron pipe. For internal tubing lead or tin is often substituted in place of copper, of which metal the small tubes were formerly almost univer- sally made. It has been found that the hard solder joints of the copper tubes were apt to crack in the bending, the cracks being almost impercep- tible, but still sufficient to cause an escape of gas and an unpleasant smell. The tin or lead being too ductile to crack, answers the purpose exceedingly well in all places where the pipes can be sup- ported in a straight line. The apparatus for internal fittings, burners, &c., are as various as the taste of the maker or consumer 78 THE PHILADELPHIA GAS WORKS. may desire. Samples and drawings of most of those made at Birmingham are in my possession, together with the prices of every article appertaining thereto. After thus taking a view of the most approved processes of manu- facturing and distributing gas, there remain several points to which, by the instructions, my attention has been directed ; among the most prominent are the nature and disposition of tire residuums left from the carbonization of coal. The only residuums which will be available are the coke, the ammoniacal liquor, and the tar. For the coke, there is no doubt an ample market will be found. The high price of charcoal, for which it is a substitute of value, both for the use of founders and for culinary purposes, insures for it a ready sale, the price bearing a proportion to the cost of the coal from which it is produced. The ammoniacal liquor is useful for the manufacture of sal- ammoniac, and sells for a small price in Baltimore, where there is a manufactory of that article. The produce of a chaldron of coals is from 20 to 30 gallons, but the liquor need not be considered of much value here for some years, or until a sufficient quantity is produced to make it worth manufacturing ; for the cost of transportation to Baltimore would make that market of little avail to the works in this city. The last residuum is the tar, which, in many ways, is of value. It will sell in its raw state for a fair price ; but when the quantity is considerable, a good profit may be derived from it by extracting the naphtha, now an article used to some extent in the manufacture of gum elastic, which leaves, after distillation, about half its bulk of concentrated tar, more valuable than in its original state. Of the process of manufacturing the naphtha I have obtained a description. Under all circumstances it is extremely valuable as a fuel for heating the retorts, three gallons being estimated, for that purpose, equal to a bushel of coke. The consumption of tar as fuel, in connexion with an equal quan- tity of water, is practised in some works ; and the advantages derived from this combination being doubted, have elicited much spirited controversy during the past summer : to this plan my at- tention was called during a visit to Mr. Rutter, the inventor, at Lymington. It is the usual custom in most gas works not conve- niently situated to a market for tar, to consume their product by con- veying it through a tube upon the red-hot bed of fuel on the grate THE PHILADELPHIA GAS WORKS. 9 bars. This process, from the quantity of smoke discharged, and the deposit of solid matter on the other fuel, gave clear evidence of the imperfection of its combustion, and that but a small quantity was made available for the purpose of heating the retorts. To give the burning tar, in which the carbon is in excess, its due proportion of hydrogen for the production of flame, and oxygen for its support, Mr. Rutter introduced a portion of water, by the decomposition of which a complete combustion of the tar was effected, and the whole of its heating properties made available. Without taking any part in this controversy, I may be permitted to say, that in no works in the kingdom which came under notice was there any thing like so perfect a combustion of the tar as in those where this process was used, and I had a fair opportunity of comparing the economy of the heating process with and without its use in the same works, which gave decided evidence of the saving effected by the plan of Mr. Rutter. The prices at which the residuums are sold being dependent entirely on local circumstances, vary so much that no useful purpose would be accomplished by detailing them. In some works the price of coke is fixed from time to time to cover the price of the coal used to make it, and the other residuums are considered of no value for sale. In others, on the contrary, the coke is quite unsaleable, and consumed as the only means of getting rid of it. At some works, too, the refuse lime is sold for prime cost as manure, being con- sidered, from its strong impregnation with ammonia, as being im- proved in quality for that purpose ; in other places, where lime is not valued as manure, this product is but refuse. For the value of these residuums we must refer to our own cir- cumstances, and I am justified in saying that the ammoniacal liquor will be of little moment for some time to come, but that the lime, tar, and coke will produce valuable results ; indeed, for the latter, an offer has already been made for more than the works will supply. In disposing of the gas, when made, two modes are adopted : the one by meter or measure ; the other by jet, or burner. The latter method is open to extensive frauds, and the effects have been severely felt by those companies who have been unable to change the system. The quantity of gas which will flow through the aperture of a given burner to produce flame of a given height being ascertained by experiment, and also the aggregate number of hours during a year for which light is required, a contract between the parties is made, and the jet furnished. 80 THE PHILADELPHIA GAS WORKS. If the consumers would all adhere to their contract, and if the pressure in all parts of the town were uniform, no difficulty would arise ; hut whenever a customer raises the flame higher than his contract admits, or hums more hours than allowed by his agreement, he not only defrauds the manufacturer, hut injures all customers who do not take such advantages ; because the manufacturer, to obtain the cost of his gas and his profit, must enhance the nominal price per thousand, requiring the honest customer to pay the same as he who consumes twice as much as he is entitled to : the correct customer is therefore paying for light surreptitiously obtained by his neigh- bour. The evils of this system are so severely felt, that some companies do not receive more than one half the value of their gas taken at its sale price, which they are obliged to keep up, to the cost and dis- advantage of the honest consumers. To avoid this evil, an ingenious mode of measuring gas was con- trived in the early stages of the art ; which, though liable to some objections, has been gradually improved, until at this time all diffi- culties are in the main obviated. This instrument is called the gas-meter; and consists of a hollow metal drum, revolving in an air-tight case, filled to a certain point with water : this drum is divided into four compartments, each having two openings, one for the exit, the other for the entrance of the gas. As the drum re- volves, one division fills with gas as the opening ascends out of the water ; while, at the same moment, the opposite division descends, and gas is forced by the water out of the opening to the burner. The cubic contents of each division being accurately measured, it is clear that the quantity of gas contained in the drum, and which passes out during one revolution, must be known. This revolving drum acts upon wheel- work attached to indicators, which point, on a watch-dial, the number of revolutions, and of course the number of cubic feet that have passed through the meter d.uring the time it has been operating. The meters are usually examined every three months, and the gas used during that time ascertained. The more completely to exem- plify the action of this instrument, I have obtained, through the politeness of Mr. Crosley, the maker, a model in glass, which is now on its way from London : by an examination of this model, its construction will be more perfectly understood. It will be seen that the accuracy of this measurement depends upon the position of the water-line, which must be kept at a uniform THE PHILADELPHIA GAS WORKS. 81 height. From want of attention to this circumstance, errors will occur ; but the internal arrangements are such, that an error cannot extend far without discovery, in no case exceeding five per cent., and that in favour of the consumer. The greatest obstacle to the success of the meters has been the decomposition of the material composing the internal drum, by the action of the gas, or some of its impurities, while stationary. I have seen meter drums, made of sheet tin, corroded into holes in five years, which, until discovered, recorded false measurements. After countless experiments, Messrs. Crosley, of London, have discovered an alloy, which is not acted upon by any product evolved from coal, and the use of this composition appears to render the meter an instrument of such accuracy, that it may be depended upon, and should be universally adopted. Another instrument has been invented in this country, called a dry meter, because it is used without water, which would be an ad- vantage, all other things being equal. This instrument I have not seen, and of course can give no opinion as to its merits. The price at which gas is sold in Great Britain varies rather with the amount of competition and cost of production, than with any reference to the expense of lighting by other means. The gas companies appear to be in far greater dread of rival establishments than from oil or candles. Indeed the latter do not, at this late period, give them a moment's thought ; for so many ad- vantages are found to accrue from the use of gas in all situations where fixed lights are admissible, that little impression would be made on the sale of it, even if the price of other light were reduced below that of gas. In Scotland, where greater attention has been paid to the quality of the gas, it is now the usual light in private houses, as well as in more public situations. The best houses in Edinburgh are thus served, and the consumption of gas is fast increasing. The extension of gas-lights in private houses is not so much the result of its cheapness as a material for lighting, as on account of its cleanliness, its safety, and saving of labour ; and contrivances are constantly being made to obviate the inconvenience of having sta- tionary lights, the only obstacle to its universal introduction. In England it has heretofore been confined, in the main, to public streets and buildings, shops, churches, &c., but its use in private houses has begun to spread rapidly, as more care is taken in the purification. In London especially, its introduction into private G 82 THE PHILADELPHIA GAS WORKS. houses has been very limited, 6 for the companies have rather re- tarded than urged its adoption, finding more profitable consumers elsewhere, who kept pace with their means of supply. Within a short period the price of gas has been very materially reduced, varying now from 8s. to 12s. per 1000 feet, with a scale of discounts for large consumers by meter, proportioned to the quan- tity used in the year. To compare the cost of lighting by gas with that of lighting by oil might be difficult upon satisfactory data, because the comparisons at the works there have been made universally with candles. The fine sperm oil of our market is comparatively little used in England, and is retailed at from 6s. to 6s. 6d. the gallon. For public lighting (where gas cannot be had), Greenland or other common oils are used, which sell by wholesale at Is. 9d. to 2s. 3rf. per gallon, or an average of 50 cents. This is the imperial gallon, which contains one-fifth more than the wine gallon used here for the same measures. This oil is retailed at 2s. 6d. to 2s. 9d. per gallon, and is used for common purposes of lighting. The greater consumption (exempting gas) is in candles of various kinds. In my endeavours to procure a comparison between the cost of lighting by the two systems, I was fortunate in procuring such a statement as may be considered satisfactory, inasmuch as it is the result of a series of experiments made to show the difference between the illuminating power of gas, made in different parts of England, referring each to a candle as the standard of comparison ; the result being given during the last summer, in evidence before a Committee of Parliament, on the application of an oil-gas company to change their works for the manufacture of coal gas. This statement may therefore be taken as authentic, and re- ferred to our own case. The results being an average of the quantity of gas made in ten manufactories, which by comparison of shadows was found to be equivalent to 100 pounds of mould tallow candles (burned clear), of six to the pound, 9 inches long, was 2477 feet. Say 2477 at #3 per thousand (here) . . . 7 43 100 pounds of candles, at ^10-50, cost . . .1050 Difference in favour of gas . . &3 07 or near 30 per cent. This is the saving, under the supposition that 6 It is now extensively used both publicly and privately, and of a superior kind ED. THE PHILADELPHIA GAS WORKS. 83 the candle is all consumed or made available, and always gives the same clear light. The prices here stated are the retail prices ; but it must be re- membered that the gas is measured out to the consumer, and burned as fast as it is measured ; consequently, he receives the benefit of all that he pays for, leaving the loss of all leakage between the works arid place of consumption to fall upon the manufacturer ; while, on the contrary, the loss and waste incident to the consumption of candles fall upon the consumer, and cannot be estimated at less than 15 percent. Again, during all the period of burning gas, a clear undiminished light is produced, while any light having a solid material for a wick must diminish in brilliancy the longer it continues to burn. Taking into view all circumstances, it must be admitted that the use of gas possesses advantages which can belong to no other means of illumination. It may here be proper to give some general idea of the amount of capital required to carry into execution the works as here described, which, for reasons already given, must be mere approximations : The works, as before stated, will not exceed . . . ,#'35,000 Considering for the moment, that the works will be located on the Schuylkill, north of the Permanent Bridge, and that the leading main will be divided into two, having the aggregate capacity of a main of 15 inches diameter, one now laid will cost 20,000 Pipes for distribution, in all 5 miles, say 3 miles, of 6-inch, at ^3'25 per yard 11,444 Three miles of 3-inch, at <^1- 80 per yard -. . . 9,504 ^75,948 If to this sum be added the expense incident to walling, levelling, and wharfing the lot, construction of public lamp-posts and lamps, with a floating capital necessary to keep up the supply of gas, we may consider that a capital of 100,000 dollars is quite ample for the works, as here described. As this sum will include the expenses incurred by enclosing the property, laying one-half the great main, and a considerable proportion of the larger pipes of distribution, we may safely conclude that the second division of the works will not cost more than two-thirds this amount. 84 THE PHILADELPHIA GAS WORKS. In conclusion, I beg leave to suggest, as the result of my exami- nations on this subject : 1st. That all information which has come into my possession, either in Europe or in this country, has tended to confirm the opinion that the proposed system of lighting by " gas" will be found preferable to any other, as regards economy, safety, and con- venience. 2nd. That a " gas " manufactory judiciously constructed, and managed with skill and economy, cannot fail to return a handsome profit to its constructors. 3rd. That the art of gas-making has so far advanced at this day, as to place within our reach such information as will enable this city to entertain the measure with a feeling of perfect security as to the result. 4th. That the objections to the measure, and the fears expressed by many valued citizens on a former occasion, are either totally ground- less, or very easily obviated, and that the effects which will be pro- duced by a judicious execution of the measure will be beneficial, both in a moral and pecuniary point of view. 5th. That the improvements made within a few years render it an easy task so to construct the works as to avoid all danger from explosions, or inconvenience from the offensive nature of the process, or residual matter connected with the manufacture of gas. 6th. That the works be constructed upon a moderate scale, com- mensurate with the immediate wants of the city, and made complete ; but that land sufficient for the increase of the works should be ap- propriated for their extension, to satisfy the demand in all parts of the city, and that the mains or pipes be laid of such capacity as to insure their aptitude for any future demand. All which is respectfully submitted. S. V. MERRICK. December 11, 1834. Note. At a meeting of the stockholders in the Philadelphia Gas Works, held on the 22nd of January, 1838, the following resolution was unanimously adopted : " That the Trustees be hereby authorized to appropriate the sum of six hundred dollars to be expended on the purchase of one or more pieces of plate ; to bear such inscription expressive of the approbation of the stockholders as they may think proper ; to be presented to Samuel V. Merrick, Esq." THE PHILADELPHIA GAS WORKS. 85 The Committee, to whom was referred the item of un- finished business in relation to lighting the city with gas, presented the following final Report on the 26th December, 1834: " The Committee have not been able, after all their in- quiries and reflections on this subject, to arrive at any other conclusion than that contained in the Reports of all former Committees that have been charged by Councils with the consideration of this subject: viz. That it is expedient for Councils to introduce this mode of lighting the city. (( If any thing could be necessary, in addition to the facts formerly reported to Councils on this subject, to satisfy the minds of the timid and sceptical, abundance is found in the able Report of the agent lately returned from Europe. So universal is the practice of lighting by gas becoming on the continent of Europe, but more particularly in England and Scotland, that not only are the large cities, but many of the villages, and even some of the turnpike roads, illuminated by this means; and in our own country nearly all the prin- cipal cities are pursuing the same course. " Philadelphia, confessedly the best adapted, having every possible advantage that nature and art could confer for the purpose, and owning too all the materials for its manufacture, she, who possessed every inducement to take the lead in this great modern improvement, doubts and fears even to follow her sister cities. " Believing, as the Committee do, that Councils cannot longer hesitate on this subject, they now present an Ordinance for the erection of gas works to light the city, to be con- structed on a limited and economical plan, embracing the most modern improvements in the art." (Signed by the Committee.) [The Ordinance for the construction and management of the Works was enacted by the Select and Common Councils of Philadelphia on the 21st of March, 1835; and, as appears by the second Annual Report of the Trustees, a portion of the city was lighted with gas on the 10th of February, 1836.] RESERVOIR DAM ACROSS THE SWATARA, PENNSYLVANIA, CONSTRUCTED BY THE UNION CANAL COMPANY. (Plate No. XIV.) THE following description of this important Work is taken from the Report of WILLIAM READ, Esq., President of the Union Canal Company. The Managers adopted a plan furnished by Canvass White, their chief Engineer, and commenced operations in October, 1828. The work is located in a narrow part of the gorge through which the Swatara passes ; the width of the pass at this place is 430 feet. The dam is divided into two parts, each constructed on different principles : the part on the western side is of crib- work, filled in with stone, to which is added a backing of earth ; the other, which connects it with the eastern side, is of stone and earth. The crib-work measures 200 feet across the stream, and 40 feet in perpendicular height : the timbers are 10 by 12 inches square; those at the base are of white oak, and the superstructure of white pine laid at right angles, forming squares of from 6 to 8 feet from centre to centre, firmly trenailed, filled with stone, and strongly fitted against the mountain on the west side, which furnishes an excellent abutment of solid rock. The east side of the cribs is sup- ported and confined by a stone abutment laid in hydraulic cement, which rises to the height of 48 feet, or 8 feet higher than the cribs. The apron in front of the cribs is formed of white oak plank. The cribs extend up-stream 110 feet, with a backing of earth extending in the same direction 110 feet more, RESERVOIR DAM ACROSS THE SWATARA. 87 making the base 220 feet up the stream by 200 feet across the same. The second part, viz., the embankment of earth and stone, reaches from the stone abutment to the east side of the gap, a distance of 230 feet, and extends at the base 260 feet up- stream, and 60 feet wide at the water surface ; the east side of the embankment rests against a natural abutment of rock in the mountain ; the embankment rises 2 feet higher than the stone abutment, and is 50 feet high. The whole has been executed in a substantial manner. The sluice-gates, twelve in number, are of cast iron, each comprising a surface of 2 square feet, are connected with pieces of yellow pine timber, extending several feet above the level of the water, and can be raised or lowered by means of screws. The sluice-gates and machinery are sur- rounded by a strong frame-work to guard the whole from the injurious effects of ice-freshets and floating timber. The sluice-house is connected with the western shore by means of a light bridge, raised beyond the utmost height of the water in the reservoir, so that the gates may be regulated at every stage of the water. The water from the reservoir passes through a stone lock of 10 feet lift ; the reservoir when filled forms a lake covering a surface of nearly 800 acres, and contains about 600,000,000 cubic feet of water, affording a navigation of 6 miles extend- ing towards the coal mines. The dam cost 22,000 dollars. TWIN LOCKS ON THE SCHUYLKILL CANAL AT PLYMOUTH, MONTGOMERY COUNTY, PENNSYLVAN-IA. PLATES Nos. XV. XVI. exhibit this Work. These locks were completed in April, 1834, and are the first of the kind erected in the United States. They were designed by and constructed under the superin- tendence of EDWARD H. GILL, Civil Engineer. The foundation is rock, and to prevent leakage through the seams, which were numerous, the bottoms of the cham- bers were covered with a layer of hydraulic mortar 6 inches in depth, and a space extending 12 feet above each mitre sill was covered by a double floor of inch boards firmly secured to the rock, and rendered perfectly water-tight. In preparing the pits and foundations, about 3000 cubic yards of rock were removed, most of which lay below the surface of the water in the river. The side walls are 8 feet on the bottom and 5 on the top, receding by three offsets or steps of 1 foot each ; the centre wall is 12 feet in thickness, and the height from the founda- tion to the top of the coping is I7i feet. The walls are faced with hewn sandstone procured in the vicinity of Lawrenceville, about 26 miles distant, and con- veyed to the work in boats. The top, bed, and joints of each face stone are cut the same distance back that it measures in height on the front. Headers or bond stones 4 feet in length are placed 10 feet apart throughout each course, and the courses vary in height or thickness from 12 to 20 inches. The backing is composed of large hammer- dressed limestone laid close, and grouted with a composition of hydraulic lime and sand. The face stones were laid in TWIN LOCKS ON THE SCHUYLKILL CANAL. 89 hydraulic cement of superior quality, manufactured in the vicinity of Reading. The lock-gates are constructed of white oak timber ; the heel and toe posts are 10 by 14 inches square, the bars or girths 8 by 10, except the upper and lower ones, which are 10 inches square. The gates are planked with 2-inch yellow pine planks. The wickets or valves are 2 feet 8 inches long by 18 inches deep, and are formed of cast iron, and move vertically, being opened and closed by a rack and pinion secured to the lever beams. The mitre sills are formed of white oak timber 15 inches wide by 12 in depth, and are secured to the rock by iron bolts 30 inches in length, with fox wedges. (See Plate XVI.) I BAY OF DELAWARE AND THE DELAWARE BREAKWATER. (Plates Nos. XVII. and XVIII.) THE following description of the Delaware Break- water is compiled from the Report of a Board of Commissioners to the Secretary of the Navy, which was approved by the President of the United States in February, 1829. The commission was composed of Commodore Rodgers, U. S. Navy, Brigadier-General Bernard, U. S. Engineers, and William Strickland, Architect and Engineer. After an examination of the lower part of the Bay of Delaware, but two points in that broad expanse of waters were found suitable for an artificial harbour, the roadstead under Cape May, and that under Cape Henlopen. The shallowness of the former, the danger and difficulty of access, arising from its proximity to the extensive breakers called the Over-falls, as well as its remoteness from the main ship- channel, were deemed conclusive objections against its adop- tion. Cape Henlopen roadstead presenting none of these disadvantages, and facilitating by its location the chief ob- jects in view, was selected as the most suitable site for the work. The same location was recommended in a former Report, dated July, 1823, by Commodore Bainbridge, U. S. Navy, and Brigadier-General Bernard and Lieut.-Colonel Totten, U. S. Engineers. The anchorage ground of Cape Henlopen roadstead lies between the southern shore of Delaware Bay and the sea- ward end of an extensive shoal called the Shears : this shoal makes out from the Delaware shore, at and near the mouth of Broadkill inlet, about five miles west-north-west of Cape Henlopen. The opposite curvatures of the main land, and of the Shears, comprehend the roadstead. DELAWARE BREAKWATER. 91 It appears from surveys and soundings made under di- rection of the Board, 1st. That the distance between the seaward end of the Shears and the Bay shore exceeds 2 miles. 2nd. That a line drawn from the Cape to the western end of the Shears leaves to the west between it and the curve of 24 feet depth, a space of more than 3 square miles. 3rd. That this curve runs close to the Cape shore, but leaves it gradually as it advances to the west: at a point 1200 yards west of the Cape, it approaches the shore within 150 yards, and at a point 2000 yards from the same Cape, it is at a distance of 400 yards from the Bay shore. 4th. That in assuming a curve of 18 feet depth for the termination of the Shears, the eastern end of this shoal presents over it a depth of water varying from 8 to 18 feet. 5th. That the average rise and fall of tide is 4 feet 8 inches, the highest spring-tide 6 feet 8 inches, the average summit elevation 5 feet 8 inches, and the highest tide known 9 feet. This roadstead is exposed to all winds from east to north- west, round by the north. It is besides represented as being often obstructed by floating ice, at the breaking up of the river and bay. On this latter point it must be remarked, that the currents of both ebb and flood-tide set constantly in a direction parallel to this portion of the Delaware shore; and that while the former brings the ice from above, the latter causes its accumulation in the roadstead, by retarding its course down to the sea. With regard to the winds blowing in the roadstead, the north-east and the north-west are the most violent, and both are on our coast the most prevalent, during the season at which a safe anchorage is most needed. The north-east cornes from the sea, and the north-west blows freely through the chops of Delaware Bay. The Shears are not sufficiently shallow to moderate the action of the sea raised by these winds ; and the Cape May shore is too far off to afford any protection against the effect of the northerly winds. The objects to be gained by an artificial harbour in this roadstead are, to shelter vessels from the action of waves, 92 DELAWARE BREAKWATER. caused by the winds blowing from east to north-west, round by the north ; and also to protect them from injuries arising from floating ice, descending from the north-west. It appears that even the curvature of the shore west of Cape Henlopen does not afford a spacious anchorage shel- tered by the land, from the winds blowing from east to west, round by the south. Indeed, a line drawn from the Cape in a westerly direction would leave between it and the curve of 24 feet depth, a superficies of only about one-tenth of a square mile. But by inclining this line to the north a greater space would be obtained, which would be protected from all winds south of this line produced. An obstruction erected along such a line would shelter a space inside of it from the waves raised by the winds blowing from the points above mentioned. But veering still more towards the north, the space open to the effect of winds west of north would be proportionally increased : for instance, should it incline so much as to assume a position directed to the north-west, the space inside of it would become entirely open to the action of the waves from the north-west. Thus, while the line in its former position would not cover a surface of sufficient extent, it would, in the latter, leave too much of the space open to the north-west. Hence, a line has been assumed intermediate between the two preceding, as reconciling the advantage of space with that of shelter. It runs from east- south-east to west-north-west, and affords between it and the curve of 24 feet water, a space with a mean breadth of 600 yards, sheltered from all winds. An obstruction raised in a straight line would check the action of the waves, but would not protect the anchorage from floating ice. It must, there- fore, be rounded off at its western end, in order to deflect the descending mass. An ice-breaker will at the same time increase in the harbour the space sheltered from the north- west. Its direction has been assumed west and by south, forming an angle of 146 15' with the direction of the Break- water. The entrance of this artificial harbour will but seldom be used by vessels descending the river and bound to sea : its DELAWARE BREAKWATER. 93 main purpose is to provide a safe refuge for vessels from sea, designing to ascend the river, or seeking shelter during stormy weather. The entrance will be located, therefore, to the east of the harbour, where it will be accessible during all winds from the sea. Its width must be sufficient to afford a free passage to descending ice floating along the shore; besides, it is desirable that the volume of water running through the entrance should provide the ebb-tide with a momentum sufficient to counteract the effect produced on the Cape shore by the flood-tide. Indeed the latter, by setting from the south, washes the sea-shore south of the Cape, and causes an accumulation of sand to the seaward of it, which forms the shoals and breakers called the Hen and Chickens. The projecting part of the Cape is represented from the same cause as making gradual approaches toward the north. The current of ebb-tide, stronger generally than that of flood, has probably hitherto counteracted the effects of the latter, and arrested the advance of the sand deposit towards the north. It is therefore of importance that the ebb- current should j^be preserved in its present course, and whilst the assumed line of direction of the Breakwater does not disagree much with the direction of the current, the opening or entrance between this line and the Cape shore must be calculated for the passage of a large body of run- ning water, the velocity of which would be rather increased than diminished, on account of the acute angle formed by the work and the shore. These considerations led the Board to recommend for this entrance a width of 500 yards, measured between the eastern 'end of the Breakwater and the curve of 24 feet depth. A greater width would have increased the space within, so as to expose it to the north-east wind. Besides this main entrance, it was thought advantageous to keep another open at the western end of the work ; and with this view it was recom- mended to detach the ice-breaker so as to leave a passage 350 yards in width between it and the main work. By such an arrangement a commodious entrance will be 94 DELAWARE BREAKWATER. obtained, and the space within the harbour will be increased. Care should be taken that the eastern end of the ice-breaker should shelter the inside of the main work from the north- west. These two entrances open to the east and to the north winds, which blow very seldom on our Atlantic coast, not more, it is believed, than twelve or fifteen days throughout the year. Such is the location, and such the general outline, which the Board recommended for the work under consideration. As to its extent, 1 200 yards are allowed for that portion of it destined to perform the office of a breakwater ; and 500 yards for the part designed more particularly to act as an ice- breaker, making the whole length of the two 1700 yards. The preceding results were used as guides in laying out the work, which was done in the following manner : A line is drawn tangent to the extremity of the Cape, at high water, and in the direction of west-north-west. A point taken on this line at a distance of 1000 yards from the point of tangency will determine the eastern extremity of the interior line of the top of the work. The western extremity is situated on the same line, 1200 yards distant from the eastern. Having thus laid out the interior line of the top of the Breakwater by producing it 555 yards further, a point is obtained on the interior line of the top of the ice-breaker. A line drawn through this point at an angle of 146 15' will coincide with the interior line of the top of the ice- breaker. The eastern and western extremities of this line are obtained by laying off distances of 272 and 228 yards respectively. This delineation will shelter a space of one-sixth of a mile from the waves raised by winds from north-west to east round by the north, and a space of -^ of a square mile from the waves caused by winds from north-west to north-east round by the north. These spaces are measured between the work and the curve of 24 feet depth ; that comprehended between the work and the curve of 18 feet depth, and sheltered from the waves raised by the north-east wind, will be -^ of a square mile. DELAWARE BREAKWATER. 95 It remains now to determine the transversal section of the Breakwater, and the arrangement and size of the materials to be used in its formation. With respect to these objects, upon which the solidity and durability of the work so essentially depend, it must be acknowledged that theory and mere speculation are utterly incompetent to fix, within precise limits, the degree of resistance to be given to a work exposed to so many and such incalculably violent efforts of the sea. But valuable inferences may be deduced from experimental results afforded by the construction of similar works in Europe, and described in an able paper presented to the French Institute by M. Cachin, General Inspector of French Civil Engineers. Thus the stupendous works erected at Cherbourg in France, and at Plymouth in England, have been resorted to as guides in the investigation of the leading principles upon which the Breakwater under consideration should be constructed. A cursory view of these two works becomes necessary to eluci- date the subject. The road of Cherbourg is the only one possessed by France on the channel; its projecting situation and its prox- imity within 70 miles of the southern shore of England render this road vitally important to the French navy. But its entrance between Pelee Island and Querqueville Point is no less than 4^ miles wide, leaving the bay entirely open to the stormy winds from east to west round by the north. It was this opening which was to be covered by a breakwater, leaving two entrances, one to the eastward between Pelee Island and the main, the other between the western end and Querqueville Point. The work planned to fulfil the object in view was formed of two lines, presenting to the sea a very obtuse angle, and having together a length' of 2^ miles. The depth of water at the lowest spring-tide here is 46 feet, and at the highest 69 feet. This work was commenced in 1784, was interrupted during the French Revolution, but was afterwards continued with energy from 1802 to 1813. If the road of Cherbourg is of the highest importance to 96 DELAWARE BREAKWATER. France, that of Plymouth is probably of equal importance to Great Britain; as, among other advantages, it enables her to assemble at one point the fleets destined to watch the movements of her neighbours in the roads of Brest and Cherbourg ; added to which, the connexion of the road of Plymouth with an extensive naval arsenal makes it a matter of much consequence that it should be rendered perfectly secure. The works at Cherbourg fully answering the purposes for which they were erected, and demonstrating their import- ance, the Government of Great Britain caused the erection of a breakwater to be undertaken in the road of Plymouth, which was accordingly commenced in 1812. The road of Plymouth is sheltered from east to west round by the north by the mountains of Devonshire and Cornwall : its entrance is three miles and a half wide, lying open to southerly winds. The configuration of the shore has per- mitted the location of this work far inside of the entrance, and has thus procured the great advantage of having the Breakwater exposed only to the action of waves raised by winds from south-east to south-west, round by the south. The work consists of a straight line, bent at the two ends towards the interior of the road. The whole length is nearly 1,500 yards; the depth of water at the lowest spring-tide is 36 feet, and at the highest spring-tide 54 feet. This work is considered as completed. It leaves between its extremities and the shore two entrances ; the eastern 900 yards, and the western 1,550 yards wide. This breakwater, like that of Cherbourg, has for its trans- versal section a trapezium, the basis of which rests on the bottom, whilst the summit line forms the top of the work : the two other lines are the sides of the work, that seaward having a greater slope than the other. At Plymouth the interior slope has an inclination of 57 feet altitude to 90 feet base, making an angle of 32 with the horizon. At Cherbourg this slope is of 45 inclination ; and, since it has stood firmly under an altitude of more than 70 feet, it may be inferred that at Plymouth the interior slope DELAWARE BREAKWATER. 97 might also have been kept at 45, which would have saved the filling up of the space comprehended between the actual slope and that of 45. The Board was therefore of opinion, that as the Delaware Breakwater must be 18 feet lower than that of Plymouth, and 30 feet lower than that of Cherbourg, there should be no hesitation in adopting the slope of 45. Respecting the width at the top, the work at Cherbourg is 55 feet, and that of Plymouth 30 feet; both being measured at 3 feet above the highest spring-tide. But when it is con- sidered that these two works, and more especially that at Cherbourg, are higher and more violently battered than the Delaware Breakwater can be, since it will be partially shel- tered by the over-falls and the shears, that the latter work will be struck principally by a rising mass of water only 5 or 6 feet high, which is the difference between the two tides, whilst at Cherbourg this altitude is 23 feet, and at Ply- mouth 18 feet; and, finally, that as the work at Plymouth has been most severely tested in its solidity, 30 feet may be considered the maximum width for the top of the Delaware Breakwater. Twenty-two feet ought, however, to be tried during the construction of the first portion of the work, in order to test the power of the waves, and lessen the expense as much as prudence will permit. It remains now to determine the inclination of the exte- rior slope of the work, and the elevation of the top above the highest spring-tide ; both very important points, and re- quiring the most careful investigation. Indeed, the former will have to receive all the efforts of the sea, and should be calculated not only to resist but to evade their violence ; while the latter must be sufficiently high above the surface of the water to insure to vessels at anchor a safe shelter during the prevalence of extraordinary tides and tempestuous weather, and to secure the interior of the harbour from fire- ships. With regard to the exterior slope, it seems to have been contemplated at Cherbourg, when undertaking the work in 1784, that the base of this slope should be three times its altitude. The projectors of the work were led to H 98 DELAWARE BREAKWATER. this conclusion by observations made on inclinations affected by waves on sea or river shores, acting on materials of stone ; but, during the prosecution of the work, experience demon- strated that it belonged exclusively to the variable and incal- culable effects of the sea itself to fix irrevocably not only the inclination of the slope, but also its very shape. At Cherbourg, as at Plymouth, experience has taught, that if human power was able so to heap up materials as to fill up such a space in the deep, it required the agency of tempestuous waves so to dispose of them as to secure their permanent stability. On this score it would seem that the results obtained at Cherbourg from vicissitudes in 1812 were but partially known to the able projectors of the Ply- mouth Breakwater. Indeed, the base of 180 feet of that work, and its altitude of 57 feet, have received precisely the same ratio as that which the action of the sea had fixed between the base of 228-^ feet, and the altitude of 72-^ feet of the work at Cherbourg. The surface of the former work having been assumed to be a plane, while at Cherbourg the efforts of battering waves have produced a curvated sur- face, it is hence to be apprehended that at Plymouth it may become necessary, in progress of time, to add new materials to the lower part of the slope. The Board, anticipating the progressive effect of the sea, recommended, if not exactly the curvilinear line of the Cher- bourg profile, at least to adopt it for the profile of the De- laware Breakwater, so that during the construction of this work a similar result might be kept in view. The slope herein submitted has been framed out of the following facts and principles afforded by the Cherbourg Breakwater. 1st. The part above the highest spring-tide having been for a short time battered by the waves, which had lost by their ascension a portion of their momentum, received from the action of the sea an inclination of nearly 2 feet base to 1 of altitude. 2nd. The part comprehended between the highest and lowest spring-tide is exposed, during the time of its rise DELAWARE BREAKWATER. 99 and fall, to the greatest violence of the waves. Thus perma- nently swept by the sea, this portion of the slope has re- ceived an inclination of 1 1 feet base to 2 of altitude. 3rd. The part comprised between the lowest spring-tide and a horizontal plane 15 feet below it, is exposed to the shock of the waves only during the interval between the ter- mination of the fall and the commencement of the rise of tide : it has, therefore, to withstand the efforts of the sea under a less inclination, viz., 3 feet base to 1 foot of alti- tude. 4th. The lowest part of the slope comprehended between the latter plane and the bottom of the sea, remaining per- manently submerged, and to a depth at which the agitation of the waves has attained its minimum, has assumed an inclination still less than the preceding, viz., 5 feet base to 4 feet of altitude. These experimental results show that the effect of water against loose materials is to give to the mass in progress of time a slope, the inclination of which will increase in propor- tion to the force exerted against it. It is on these data that the profile of the Delaware Break- water has been delineated. The Board was, however, aware that local circumstances and the bulk of materials might render a modification of this profile necessary ; but it may be considered as the nearest possible approximation, sufficient to found upon it an estimate of the expense, and to direct in the construction of the work. The preservation of the works above the highest spring- tide was a point upon which the Board had again to consult experience. At Cherbourg it was at first contemplated to keep the top of the breakwater a foot only above the highest spring-tide; but it was subsequently observed that extraor- dinary rises of sea caused by violent storms not only jeo- pardized the vessels moored in the roads, but threatened destruction to the upper portion of the work. It was, there- fore, resolved to raise the top 9| feet above the highest spring-tide. At Plymouth the top had been kept but 3 feet above the highest tide, but in January, 1817, a violent storm 100 DELAWARE BREAKWATER. having raised the water 6 feet above the usual elevation, that part of the work which had been completed was swept at its top 200 yards in length and 90 feet in breadth ; and all the blocks, weighing from 2 to 5 tons, were thrown on the in- ward slope. Such an extraordinary effect could not readily be ascribed to the pressure and velocity of a body of water however great, were it not for the fact that blocks of stone lose by immersion one-third of their weight. This fact, with others not dissimilar which have happened at Cherbourg, shows that the top of a breakwater must be elevated beyond the reach of submersion, and loaded with the largest and heaviest materials that can be procured, which should be laid in such a way that each shall present to the action of the sea the smallest possible superficies, and to the lateral materials the largest surface of friction. When it is considered that the Delaware Breakwater will not, like the works at Cherbourg and Plymouth, be exposed to any perpendicular shock; that towards the open sea it will be exposed only to waves raised by the east-north-east wind ; that the greatest rise of water caused in Cape Henlopen roads by heavy storms, never, it is believed, exceeds 2 feet, the Board was convinced that by keeping the top of the Delaware Breakwater 5^ feet above the highest tide, there would be no danger of submersion. If, however, during the construction of the work, experience should afford more accurate data, the top might then be raised higher, if found necessary. These considerations induced the Board to recommend for the Delaware Breakwater a profile, or transversal section, of the following dimensions : the inward slope at 45, the top 30 feet in breadth, and at 5 feet above the highest spring- tide; the outward slope of 39 feet altitude, and of 105 f feet base; both dimensions measured in relation to a horizontal plane passing by a point taken at 27 feet below the lowest spring-tide. The base bears to the altitude nearly the same ratio as similar lines in the profiles of Plymouth and Cher- bourg Breakwaters. It remains now to make an estimate of the work, and DELAWARE BREAKWATER. 101 to submit some views in relation to the mode and pro- gress of construction ; but it is necessary previously to de- termine the various sizes of the materials best calculated to secure the permanent stability of the whole mass. The experience acquired at Cherbourg has taught 1st. That stones of small size are not sufficient to with- stand even a moderate action of the waves ; for, being con- stantly tossed about, they acquire by attrition a round and smooth surface, which prevents their assuming any settled place in the mass. 2nd. That stones measuring 18 to 24 cubic feet, and weigh- ing 1^ to 2 tons, present a suitable resistance to the efforts of a moderate sea. 3rd. That larger blocks are required to withstand a violent sea; and that in the more exposed parts of the work their size should be still larger. 4th. That if small materials were to be used, it would be indispensable to protect them externally by others of larger size. 5th. That the smaller the external surface of a large block, the greater will be its stability. 6th. That the largest blocks should be placed towards the top, in order to compensate, by their greater steadiness, the loss of weight and of stability caused by immersion to the materials located immediately under the water line. At Cherbourg and at Plymouth the blocks used at the top measured each from 72 to 90 cubic feet, and weighed 5 to 6 tons. The Board, in consideration of these facts, recommended the following arrangements and size of materials in the formation of the Delaware Breakwater, viz. : for the part comprehended between the sea bottom and a horizontal plane 6 feet below the lowest spring-tide, the mass to be formed of stones weighing from to 2 tons, those of 2 tons comprising three-fourths of the mass. The slopes of this part to be covered with blocks weighing from 2 to 3 tons. For the part comprised between the latter horizontal plane 102 DELAWARE BREAKWATER. and the lowest spring-tide, the mass to be composed of stones weighing from | to 2| tons; those of 1| to 2 tons forming three-fourths of the mass. The slope of this part to be pro- tected by blocks weighing 3 tons. For the part comprehended between the lowest and highest spring-tide, the mass to be formed of blocks weigh- ing from 4 to 5 tons, and laid as regularly as practicable. The slopes of this part to be formed of the largest blocks, and to be laid headwise. Respecting the precautions to be taken during the erec- tion of the work, it must be borne in mind that the waves will act against the loose materials in two distinct ways. 1st. When striking the rock in a perpendicular direction, their effect will be to lift the materials, and force them up along the slope, where they will accumulate and assume a steeper inclination to the horizon. 2nd. When the waves are forced obliquely against the work, they sweep off the materials longitudinally along the slope, and cause an accumulation of materials inside of each end of the work, where they consolidate. With the view of guarding against such effects, the Board recommended that the work should be commenced simul- taneously, beginning at the western end of that portion de- signed particularly for a breakwater, and at the eastern end of that portion intended for an ice-breaker. Thus the latter end would shelter the former from the effect of winds from the north-west, and leave less danger to be apprehended from an accumulation of materials inside of the eastern extremity of the work. Besides, by such an arrangement a partial result would be annually obtained, and the work could progress according to the appropriations which Congress might think proper to make for the gradual execution of the whole plan. It was also recommended, that in commencing the work the materials should be thrown inside of a line drawn parallel to the interior line of the top of the work, through a point at 22 yards distance. For it has been stated before, that the breadth of 30 feet may be safely deemed a maxi- DELAWARE BREAKWATER. 103 mum, and that a smaller breadth may be tested during the execution of the work ; that of 22 feet will probably be found sufficient, especially for the ice-breaker. It was deemed advisable, that as soon as the work should make its appearance above low-water mark, materials of weight should be heaped up at the head of the outward slope, with a view to prevent the stones lifted up along this slope from passing inside of the work. The estimate submitted by the Board was as follows: The profile of the work (exhibited in Plate XVII.) rests on a bottom of 29-iV feet, on an average, below the lowest spring-tide, and has a superficies of 535,472 square yards; which, being multiplied by 1700 yards (the whole length of the work), gives for the capacity of the mass 910,302-^ cubic yards. The contract approved by the naval department to supply the Breakwater with stones weighing from of a ton to 3 tons and upwards, allowed ^2*20 per perch, or 25 cubic feet. The cubic yard will therefore cost &2'3'J6, which, mul- tiplied by 910,302-^, will produce the sum of ^2,162,878-50, and by adding, for contingencies, 2 per cent., ^54,071*96, will make the whole cost of the work ^2,216,950-46. The price of stone included, agreeably to contract, its transportation to the Breakwater and its deposition in the water at the place designated. With regard to the quantity of materials, no allowance was made in the estimate for the settling of the work, be- cause the stones, which by contract were to be perched at the quarry, would, when thrown promiscuously into the water, occupy such additional space as to supply any de- ficiency from settling. As to the defence of the harbour, a small casemated tower (estimated to cost about <#! 5,000), mounting six guns, and protecting a temporary battery, was considered suffi- cient. The foregoing description of the Delaware Break- water includes, with occasional alterations, the Report 104 DELAWARE BREAKWATER. of the Board of Commissioners. The Work has been executed so far in accordance with the views and plans therein detailed. The dimensions recommended in the Report have been adopted in its erection, with the exception of that portion designed for a Breakwater, which is 1000 yards in length ; the length recom- mended was 1200. The Work may be considered now so far finished as to have accomplished materially the purposes for which it was projected. Indeed, the plan of com- mencing the Work at the adjacent extremities of its two portions has tended to yield a shelter to vessels during the whole progress of its construction. (See Plates XVII. and XVIII.) WILLIAM STRICKLAND, Architect and Engineer. Philadelphia, Feb. 12, 1840. PHILADELPHIA WATER WORKS. THE following description and details of this va- luable Work have been compiled from the Reports of the Watering Committee, made to Councils at various times. Plates XIX. to XXIV. exhibit the most im- portant portions of it, and were copied from the original designs prepared by FREDERICK GRAFF, Esq., the En- gineer and Superintendent of the Water Works, who promptly furnished every information required by the Editors respecting them. DESCRIPTION. This important Work, the property of the city of Phi- ladelphia, was commenced by Ariel Cooley, with whom a contract was made for the erection of the dam, the locks and canal, the head arches to the race, and the excavation of the race from a solid rock, for the sum of 150,000 dollars. This work is a monument to his memory ; and he had nearly completed it, when he was taken off by a disease, supposed to have been contracted by his exposure to the sun and night air, at the closing part of his work. His talents, his integrity, and his general worth, will long be held in grateful remem- brance by the citizens of Philadelphia. It will be proper, in this stage of the Report, to state the nature of the work that was to be accomplished, and to expose certain of its difficulties. The river is 900 feet in width, one-fourth of which, at the bottom, on the eastern side, is supposed to be rock, covered with about 11 feet of mud; the remainder is of rock. The greatest depth is 30 feet at high water; and it gradually shoals to the western shore, where the rock is left bare at low tide. The river, 106 PHILADELPHIA WATER WORKS. whose average rise and fall is 6 feet, is subject to sudden and violent freshets. Mr. Cooley determined, where rock was to be found, to sink cribs, formed of logs, 50 feet up and down stream, by 17 or 18 feet wide, which were sunk and filled with stone, and securely fastened to each other above low water, having the up-stream side planked from the bottom to the top ; and the space immediately above filled to some extent with earth and small stones to prevent leakage. In that part where mud was found a mound is made with quarry spalls and earth, and raised about 15 feet higher than the dam ; the base of this mound is 150 feet, and its width on the top 12 feet; and the whole of the top and of the up-stream side from the water edge is paved to the depth of 3 feet with building stone. Between the mound and the dam there is sunk on the rock, in 28 feet water, a stone pier, 28 feet by 23 feet, which supports the end of the mound, and protects it from injury by ice or water. The contraction of the river by the mound suggested to Mr. Cooley the idea of forming the dam in a diagonal line running up-stream, and when nearly over to run the rest of the distance at right angles towards the shore, so as to join the head pier of the guard-lock on the western side, by which means a large over-fall was created, and the rise above the dam, in case of freshet, considerably abated. The whole length of the over-fall is 1,204 feet; the mound 270 feet; the head arches 104 feet ; making the whole extent of the dam, including the western pier, 1,600 feet, and backing the water up the river about six miles. The water power thus created is calculated to be equal to raise into the re- servoir, by eight wheels and pumps, upwards of 10,000,000 gallons. The lowest estimate of the quantity of water afforded by the river in the dry season is 440,000,000 per 24 hours; and as it is calculated, allowing for leakage, waste, &c., that 40 gallons upon the wheel will raise one into the reservoir, the quantity raised would be 11,000,000 gallons per day. On the west side of the river there is erected a pier PHILADELPHIA WATER WORKS. 107 and guard-lock, whence there is a canal extending 569 feet to two locks 7 of 6 feet lift each; below these locks there is a canal into the river 420 feet long. The locks are built of cut stone; the upper canal is walled on the east side, and on the west it is rock. The outer front of the locks and canal is protected by a wall. On the east side of the river the whole of the bank was a solid rock, which it was necessary to excavate to the width of 140 feet, to form a race and site for the mill-houses running parallel with the river. The length of the mill-race is 419 feet, the greatest depth of the excavation is 60 feet, and the least 16 feet : the gunpowder used alone cost the contractor upwards of 12,000 dollars. At the upper part of this excavation were erected the head arches, three in number, which extend from the east end of the mound to the rock of the bank, thus forming a continuation of the dam. On the west of the excavation are erected the mill-houses, forming the west side of the race, which is supported on the other side by the rock rising above it 70 or 80 feet perpendi- cularly. The south end, or wall of the race, is also of solid rock ; and the mill-houses are founded on rock. The race is about 90 feet in width, and is furnished with water through the head arches, which allow a passage of water of 68 feet in breadth and 6 feet in depth, to which the race is excavated below the over-fall of the dam, and of course room is allowed for a continual passage of 408 square feet of water. These arches are on the north of the race, and the mill-buildings being on the west, the water passes from the race to the wheels, which discharge the water into the river below the dam. The gate of the centre arch is upon the principle of a lock-gate, and admits the passage of boats, &c., into the race ; at the south end of the mill-buildings there is a waste-gate, 8 feet wide, by which (the upper gates being shut) the water can be drawn off to the bottom of the race. The mill-buildings are of stone, 238 feet long and 56 feet wide. The lower section is divided into twelve apartments, four of which are intended for eight double forcing-pumps. ' These locks have since been doubled. 108 PHILADELPHIA WATER WORKS. The other apartments are for the forebays leading to the water-wheels. The pump and forebay chambers are arched with brick, and are perfectly secure from the inclemency of the winter. Those now in use are kept warm by means of large iron stoves, heated to great advantage and economy with coal. A gallery is erected, extending the whole length of the building, from which all the wheels may be seen at one view. The centre part of the buildings is 190 feet by 25 feet, with circular doors to the pump chambers, and a range of circular windows over the archways of the wheel-rooms ; on a line with the cornice of the central part is the base course of two pavilions, with Doric porticoes, which terminate the west front. One of these is used for the office of the Water- ing Committee, and the other is the residence of the person who has the general charge of the property at Fair Mount. On the east front, immediately over the pumps and forebay rooms, is a terrace, 253 feet long and 26 feet wide, paved with brick, and railed, forming a handsome walk along the race, and leading, by steps at the end, to the top of the head arches, mound-dam, and pier. In the erection of the mill-buildings, Mr. John Moore was employed as the mason ; and to his care and skill we are much indebted, not only for the excellence of the work in appearance, but for its sub- stantial properties, it being ascertained that in the whole ex- tent of the foundation along the race, under a six feet head of water, there is no leak. Mr. Frederick Erdman, the car- penter, also deserves particular notice for his part of the work, which has been most faithfully done. It has been from the commencement determined, for the present, to erect only three wheels and pumps, which are now completed, 8 and with them the most important part of the duty of the Committee. The first of the wheels is 15 feet in diameter and 15 feet long, working under 1 foot head and 7 feet fall. This was put in operation on the 1st of July, 1822, and it raises lj million gallons of water to the reservoir in twenty-four hours, with a stroke of the pump of 4^ feet, a diameter of 16 inches, and the wheel making ll K There are now six. PHILADELPHIA WATER WORKS. 109 revolutions in a minute. The second wheel was put in operation on the 14th of September, 1822, and is the same length as the first, and 16 feet diameter ; it works under 1 foot head and 7i feet fall, making 13 revolutions in a minute, with a 4| feet stroke of the pump, and raising 1 million gallons in twenty-four hours. The third wheel, which went into operation on the 24th of December, 1822, is of the same size as the second, and works under the same head and fall, making 13 revolutions in a minute, with a 5 feet stroke of the pump, and raising 1| million gallons in twenty-four hours. It is not doubted that the second wheel can be made to raise an equal quantity ; thus making the whole supply upwards of 4,000,000 gallons in twenty-four hours. The wheels are formed of wood, and put together with great strength. The shafts are of iron, weighing about 5 tons each. The great size and weight of the wheel give it a momentum which adds greatly to the regularity of its motion, so necessary to preserve the pumps from injury under so heavy a head as they are required to work, which is a weight of 7900 Ibs. ; the height 92 feet. The wheels being sunk below the usual line of high water, it might be supposed that they would be obliged to stop at that time ; but this seldom happens, except in the spring- tides, at the full and change of the moon, which, upon the average, stops them about sixty-four hours in a month. It is found that they are very little affected until the back-water is about 16 inches on the wheel. The excellence of the work in the wheels and gates, with the whole arrangement of the mill-works, does the highest credit to Mr. Drury Bromley, whose attention has been most assiduous, and whose skill is of the first class. The pumps were made by Messrs. Rush and Muhlenberg, according to the designs of Mr. F. Graff, Engineer, and are worked by a crank on the water-wheel, attached to a pitman, connected with the piston at the end of the slides. They are fed under a natural head of water, from the forebays of the water-wheel, and are calculated for a 6 feet stroke ; but 110 PHILADELPHIA WATER WORKS. hitherto it has been found more profitable to work with not more than 5 feet. They are double forcing-pumps, and are connected each of them to an iron main 16 inches in dia- meter, which is carried along the bottom of the race to the rock at the foot of Fair Mount, and thence up the bank into the reservoir. At the end of the pipe there is a stop- cock, which is closed when needful for any purpose. The shortest of these mains is 284 feet long; the other two are somewhat longer. The water being raised into the reser- voirs, 102 feet above low tide, and 56 feet above the highest ground in the city, is thence conveyed to the city in iron pipes. The satisfactory test to which the dam was exposed on the 21st of February, 1822, by an ice-freshet, which rose 9 feet above the over-fall of the dam, and which is supposed to be the greatest that has ever been known in the Schuylkill, has quieted all fears as to its safety, and done away all the objections that ever could be raised to resort to water power, where nature had kindly done so much. The cost of the whole work done since the ordinance passed, April 18th, 1819, viz. Purchase of White and Gillingham . . . ^150,000 Erection of the dam, locks, head arches, race, and piers, including estimate of damages for over- flowing by the dam 181,000 Three pumps ...'.... 11,000 Mill-houses, mills, and other work connected with them 71,250 Iron raising mains ...... 4,480 New reservoir ...... 8,600 Amounting together to . .