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 REPORT OF THE BOARD OF ENGINEERS 
 
 ON THE 
 
 SUBJECT OF RAPID TRANSIT THROUGH NEW-YORK. 
 
 The undersigned have been requested to consider the question of a sub-way 
 under Broadway, in the city of New- York, with the view of relieving that street 
 from its present interruptions, and of affording a more convenient and speedy 
 transit, for passengers and for merchandise, without injury to the property upon 
 the line of the street, or diversion of the established classes of business thereon. 
 
 The New- York Arcade Railway Company have laid before us their plans for 
 accomplishing these purposes, and we have had under consideration other plans 
 which have, from time to time, been proposed for the same objects. 
 
 It is considered unnecessary, at this time, to compare the relative advantages of 
 these several plans, and we therefore, for the present, will confine ourselves to the 
 consideration of the necessities of the case, and how far the plans of the Arcade 
 Company meet them. 
 
 We observe, in the report of the Engineer of this company, the following re- 
 marks : 
 
 " The rapid growth of New- York City in wealth and population, with the corre- 
 sponding increase in trade and travel, have so crowded the thoroughfares and over- 
 burdened the means of transportation that there is an imperative and universal 
 demand for relief, while a settled conviction pervades the public mind that this 
 relief can only be afforded by the construction of a sub-surface railway. A thorough 
 investigation of this subject, made by a commission appointed by the Senate of 1866? 
 and composed in part of able and scientific engineers, resulted in the conclusion, 
 * That underground railways, passing under streets, present the only speedy remedy 
 for the present and prospective wants of the city of New- York, in the matter of a 
 safe, rapid, and cheap transportation of persons and property.' " . . 
 
 It is apparent, therefore, that what is demanded, is — 
 
 1. To convey passengers between that portion of the city which is devoted to 
 business and that occupied by residences with speed, comfort, and convenience. 
 
 2. To convey merchandise along the main channels of trade and distribution 
 with dispatch, cheapness, and convenience. 
 
 3. To accommodate the existing business along this avenue, and preserve the 
 street to its original purpose ; and 
 
4. To secure the above-mentioned objects with the least possible temporary 
 obstruction of the travel and trade pawing through the street, and of the business 
 now transacted thereon. 
 
 This street is now used tor the transportation of what may be termed local and 
 through passengers and merchandise. That which requires the slowest movement 
 controls the speed of tlisi t which demands the fastest transit. The transportation of 
 merchandise now so completely gorges not only the main artery, but also the cross- 
 ing streets, as frequently to render all progress, for a time, impracticable. Hence, a 
 plan which will systematize the travel will, of itself, afford a certain degree of relief; 
 and one which not only accomplishes this object, but also duplicates Broadway, 
 will much more than double its present capacity. 
 
 A sub-way which will permit of a rapid movement for the through travel, and a 
 slower but still rapid movement of the Local travel, will not only accommodate 
 these two classes of travel, but will remove from the upper surface of Broad wav so 
 large a number of vehicles as to leave it free for carriages moving rapidly, and carts 
 moving slowly, without impeding, as now, the progress of both. 
 
 The object aimed at should be, not to turn travel from IJroadway, but to 
 accommodate it in its most accustomed and natural channel. Any plan which 
 tends to such diversion is not only injurious to the property along Broadway, but 
 also to the public, exactly in proportion to it> success. 
 
 It is worth remembering that it now costs almost as much to convev freight 
 from Thirtieth street, where it is left by steam, to the business portions of the city, 
 as it does from Albany to New- York; and to convey it across the city, as it does 
 to Liverpool. 
 
 By this sub- way railway, the cost of movement along its route, connecting, as it 
 will, with the steam railways entering New-York, will be very nearly in proportion 
 to its distance, and not, as now, by a change of conveyance more than tenfold as 
 expensive. 
 
 The following, among other incidental advantages will be obtained by means of 
 this sub-way, namely, 
 
 A convenient vault for placing the water and gas-pipes, and the sewers, where 
 they may be examined, repaired, or relaid, without disturbing any portion of the 
 street, sub-way, or convenient use of any of the buildings. 
 
 The surface of the upper street, no longer liable to be disturbed by breaking up 
 the pavement to reach these pipes and sewers, will remain intact for years, and thus 
 savj large sums to the city, and render Broadway the most perfect carriage-road in 
 the world. 
 
 The most valuable storv in anv of the buildings is the one level with the 
 sidewalk. By this sub- way a story almost as valuable will be added to each 
 building. 
 
 This sub-way will be well lighted and well ventilated without any sacrifice to the 
 upper street. 
 
 The general plan of construction we understand to be : The excavation of a 
 sub-way street, with sidewalks for foot passengers, at a general level of twelve feet 
 below the grade of the present sidewalks, and between these sidewalks a central 
 roadway some three feet lower, in which are to be placed four railway tracks, the two 
 middle ones designed for fast-moving trains by steam power, stopping at intervals of 
 perhaps a mile, and two exterior tracks, designed for local or shorter travel and con- 
 
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 necting with tlie fast trains; the upper street to be supported on columns and 
 girders, with arches between, and completed with a road-bed and pavement of the 
 most approved construction. 
 
 An area or space of six feet width, adjacent to the buildings, to be left for 
 ventilation and light ; and a portion of the sidewalks, made of glass, increasing 
 the light to the sub-way, so that it will, in this respect, be far better lighted than the 
 basement stories now on the street. The existing vaults may be rebuilt under the 
 lower sidewalks. 
 
 The sewers to be carried through the space between the two middle tracks, and 
 the water and gas-pipes between the other tracks. The water and gas-pipes may 
 be suspended over the sidewalks, as is done in the sewers of Paris. 
 
 The motive power is assumed to be steam ; and to avoid the exhalation of the 
 gases of combustion, the locomotives may take their supplies of steam at certain 
 localities where it will be generated in stationary boilers. For the same reason, the 
 exhaust steam should not be discharged into the tunnel, but should be condensed in 
 cold-water tanks attached to the locomotives. 
 
 It is alleged that compressed air, of the same pressure as the steam, might with 
 advantage be substituted for the latter, the exhaust of which into the tunnel would 
 be unobjectionable. This kind of power has been successfully applied for many 
 years at Mont Cenis and Hoosic tunnels ; but further examination would be re- 
 quired before it should be determined upon as a substitute for steam power. 
 
 The plan of working, as arranged, contemplates no interruption to the travel 
 along the street, nor to the accustomed occupancy of the buildings thereon. 
 
 A series of parallel bridges are proposed to be used which will allow a vehicle 
 to stand opposite each building, and yet allow four other vehicles (two on each side 
 of the street) to pass "each other ; similar bridges along the sidewalks, allowing 
 the foot passengers to pass freely ; these bridges to be elevated four feet above the 
 level of the street, with sloping approaches at each end, to be removed at mid- 
 night, panel by panel, as the work progresses ; side steps to each building giving 
 access thereto. 
 
 The surplus materials taken out of the street and the new materials required, 
 are all proposed to be removed through the completed subway, without in any case 
 using the street therefor. 
 
 The engineers of the company estimate that the average rate of progress of the 
 work will be a lineal yard each day for each place of working. And to tinish the 
 whole road, or any section of the work in two years would require three places of 
 working on each mile, and in that proportion for any other desired rate of progress. 
 There are places where the presence of rock or water will not permit of a progress 
 of a lineal yard per day ; and in such cases more frequent working places must be 
 provided. It is proposed to excavate the rock by quarrying and not by blasting. 
 
 The foundations of ail the buildings erected during the last twenty years are 
 below the proposed level of the excavations. Where it becomes necessary to ex- 
 cavate below the foundations of any of the older buildings, it can be done without 
 danger or injury, by the exercise of the same care as is now practiced in extending 
 the foundation of one building deeper than that of the adjacent ones. 
 
 The method proposed for executing the work will prevent interruption to the 
 supply of water and gas, and to the discharge of the sewage. 
 
 The new pipes and sewers will be placed in their proper positions in the sub-way, 
 
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 and the connections to be made, provided with shut-off cocks, with all of the adja- 
 cent buildings. Meanwhile, the present system of pipes to be maintained, first 
 by supporting them from the temporary bridge, and subsequently from the sub-Way 
 girders. As frequently as may be desired, temporary connections may be made 
 with tha existing pipes, and the water and gas turned from the bid to the new 
 system in less than an hour. 
 
 We have to some extent examined the details of construetion, and are satisfied 
 that they have generally been well designed to meet the necessities of the ease. 
 There will, no doubt, be found many modifications improving the plan and perhaps 
 lessening the cost of the work. 
 
 The engineers of the company have laid before us their estimates for this, vary- 
 ing fro u $1,600,000 to $2,000,000 per mile. All of the important items of cost are 
 of easy determination, and the highest of these siuns would in general he sufficient 
 to cover the cost. 
 
 The most obvious difficulty in the construction of the road is in the crossing of 
 Canal street. The method which most readily sugire-t- itself is one whieii would 
 greatly enhance the value of all the property affected ; that is, to raise the grade of 
 Broadway, Canal, and the adjacent streets. This plan, however, is not likely to he 
 adopted, and the engineers of the company have proposed to' carry the sub way 
 across Canal street by a water-tight iron caisson. 
 
 A portion of the sewage which comes down from the east side of Broadway will 
 require to be transported across Broadway ; but much the largest portion may be 
 intercepted and conveyed under the sub-way, where its bottom grade is sufficiently 
 high to allow the under passage of the sewer. 
 
 The plans, as thus developed, seem to have been arranged to meet all the objec- 
 tions which would naturally occur in a careful examination of the project. 
 
 A resume of the foregoing statements, and discussion of the subject, shows that 
 a Sub- Arcade Railway will accomplish the objects desired, namely, 
 
 1. It provides a pleasant, rapid transit for through passengers between the lower 
 and upper ends of the island, and a slower but still speedy movement for the local 
 passengers. 
 
 2. It provides a cheap and convenient channel for the conveyance of freight be- 
 tween the termini of the steam railways, and a large portion of the business houses 
 in the city. 
 
 3. It classifies the travel and trade, and removes from the present street so many 
 of its vehicles as to render it more useful and pleasant for carriages. 
 
 4. It furnishes an arcade avenue and promenade, convenient for pedestrians at 
 all times, in warm, cold, or stormy weather. 
 
 5. The sub-way will be well ventilated and lighted, so that its use will be 
 pleasant and healthy. 
 
 6. It can be constructed without interruption either to the travel on the street 
 or the convenient use of the buildings adjacent, and without occupying the street 
 for the hauling of the materials required from or to the work ; and it can be built 
 without end mgering any of the structures along the street, and with arrangements 
 for a better location of the water and gas-pipes, and sewers, and without any in- 
 terruption of the present connections. 
 
 7. The route selected, namely, that along Broadway, is determined by the topo- 
 graphy of the island. 
 
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 8. It in no case occupies or injures any private property, but in nearly all 
 cases greatly enhances the value of the property along its route. 
 
 9. There are no difficulties attending the construction of the work which can nut 
 he overcome with engineering skill, and at a comparatively moderate cost. 
 
 Finally, it meets a necessity in the most complete and unobjectionable manner. 
 
 (Signed) George B. McClellax, 
 
 William J. McAlplne, 
 Egbert L. Yiele, 
 Julius W. Adams, 
 Sylvanus H. Sweet, 
 
 I. F. QuiNBY, 
 
 John B. Jarvis. 
 
 New-York, March, 1870. Silas Seymour. 
 
 New- York, March 5, 1870. 
 Having well considered the subject of a sub-road as a means of passenger and 
 merchandise transit in a city, and having advised myself as to the design and de- 
 tails of the sub-road in operation in the city of London, 1 concur in all of the es- 
 sential elements of the statements and opinions above expressed, and also entertain 
 the opinion that the ventilation of the roadway can be very materially increased in ad- 
 dition to that shown in the plan submitted. Further, the effects of the depression 
 of the surface of Broadway at Canal street, and the existence of ooze at Union 
 Scpiare, can be met without arresting the operation of the sewer at the first place, 
 or involving the stability of buildings at the latter. 
 
 Charles H. Haswell, 
 Civil Engineer and City Surveyor. 
 
 OPINION OF GENERALS WRIGHT AND NEWTON, U. 8. CORPS OF ENGINEERS. 
 
 Xew-York, March 23, 1870. 
 
 The undersigned, having had submitted to them, for an opinion upon its merits, 
 the project for the Arcade Underground Railway, in Broadway, and having given 
 the subject attentive consideration, coincide in the views presented in the report of 
 the Commission of Civil Engineers, composed of General George B. McClellan, W. J. 
 MeAlpine, Esq., and others, as regards the necessity for some such mode of communi- 
 cation for the purpose of affording relief to the over-crowded thoroughfares of Xew- 
 York, as to the practicability of the project proposed under an engineering point of 
 view, and its efficiency when completed, and generally of the mode in which the 
 project is to be carried out. 
 
 The undersigned have not, however, had the opportunity of investigating the 
 estimate of cost, and do not, therefore, express any opinion thereon. 
 
 H. G. Wright, 
 John Xewton.