Vary. 
 
 PUB- y 
 
 REPORT 
 
 APPOINTED TO RKCOMMEXD A PLAN FOR THE 
 
 NEW YORK AND LONG ISLAND BRIDGE 
 
 ACROSS THE EAST RIVER, 
 
 Blackwell's Island. 
 
 New York ; 
 
 X UK GRAPHIC COMPAN Y, 
 
 39 & 41 Park Place. 
 
Avery Architectural and Fine Arts Library 
 Gift of Seymour B. Durst Old York Library 
 
REPORT 
 
 OF 
 
 APPOINTED TO RECOMMEND A PLAN FOR THE»° 
 
 NEW YORK AND LONG ISLAND BRIDGE 
 
 ACROSS THE EAST RIVER, 
 
 Blackwell's Island. 
 
 New York: 
 
 THK GRAPHIC COMPANY, 
 
 39 & 41 Park Place. 
 
Entered according to act of Congress, in the year 1877, by the 
 NEW YORK AND LONG ISLAND BRIDGE CO., 
 In the office of the Librarian of Congress, at Washington, D. C. 
 
REPORT 
 
 New York, February 21, 1877. 
 
 To the President and Directors of the New York and Long 
 /stand Bridge Company : 
 
 Gentlemen : — Upon being appointed a board of consulting- 
 engineers, on the 10th of December, 1875, for the purpose of 
 recommending a design for your proposed bridge across the East 
 River at BlackwelPs Island, the undersigned at once entered 
 upon an examination of the plans then in the possession of the 
 Company. 
 
 These plans formed eleven sets or designs, and had been 
 submitted by the following gentlemen : 
 
 Mr. C. Bender, 
 Messrs. Flad & Pfeifer, 
 Mr. J. B. Eads, 
 Mr. W. P. Trowbridge, 
 Mr. E. W. Serrell, 
 Mr. G. E. Harding, 
 
 Mr. I. D. Coleman, 
 
 The Baltimore Bridge Co., 
 
 The Watson Manuf. Co., 
 
 Mr. A. F. Wendt, 
 
 Mr. L. W. Wright. 
 
 Most of these, however, were more in the nature of prelimin- 
 ary studies than of matured designs, and few of them were 
 accompanied with the necessary strain sheets, computations of 
 quantities, or estimates of cost. None were backed up by pro- 
 posals for construction at a specified price. 
 
4 
 
 A short examination showed not only that these plans were 
 fragmentary, but that they were based upon different assump- 
 tions ; either as to the traffic to be accommodated, the loads to 
 be provided for, or the safe limit of strength of the materials to 
 be employed. 
 
 That, in fact, each plan was predicated on a different specifi- 
 cation ; some of them not being in accordance with the well- 
 settled principles which govern the distribution of forces in 
 bridge structures, and thus conducing to unsafe constructions. 
 
 It became evident, therefore, that the Board of Consulting 
 Engineers must first state some general basis as to the arrange- 
 ment of the bridge and its approaches, and lay down some 
 general rules and principles to govern the designers, before the 
 merits of their plans could be compared with each other. 
 
 Some additional surveys, which were found necessary, were 
 accordingly made, and a set of specifications carefully prepared, 
 a copy of which is hereto attached, marked Appendix No. i. 
 
 A profile of the ground and grades was also published, which 
 is herewith given as Appendix No. 2. 
 
 These provided not only for a railroad connection across the 
 bridge, but for main and return approaches for carriage ways, 
 and also for passenger elevators at the abutments, so as to give 
 access to the bridge from all the points that seemed to promise 
 traffic. 
 
 A circular was issued on the 1st of May inviting designs to 
 be handed in by the 1st of July, 1876, a copy of which forms 
 Appendix No. 3. This was sent to nineteen bridge builders 
 and designers and to some forty other persons, most of whom 
 are civil engineers or bridge experts. 
 
 Answers were received from some twenty persons expressing 
 the intention to furnish plans ; but the completeness of the in- 
 formation called for by the specifications, the shortness of the 
 time allowed, and the uncertainty then thought to exist about 
 the future construction of the bridge, deterred the designers from 
 perfecting their plans by the specified time. 
 
 Upon our report to your board, a resolution was passed by 
 you, on the 9th of August, extending the time for receiving de- 
 signs to the 1st of December, 1876, and offering three premiums 
 of $1,000, $500 and $250, respectively, for the first, second and 
 third best plans to be presented. The circular issued by us in 
 
5 
 
 accordance with this resolution is given in Appendix No. 4. 
 A copy was sent to each of the gentlemen who had previously 
 been invited to furnish designs, and to a number of other par- 
 ties who applied for it. 
 
 By the 10th of December nine sets of plans and designs had 
 been received, with more or less explanatory information. 
 Much of this information, however, was found incomplete and 
 insufficient. In some instances strain sheets were not furnished, 
 or else they did not provide for all the various strains due to 
 different conditions of loads and wind. Some computations of 
 quantities were not given, and the estimates did not show the 
 quantities and prices of material, so that they might be checked 
 over and a judgment passed upon their sufficiency. 
 
 It became necessary, therefore, to call for the lacking inform- 
 ation. This was done at once ; and the Board, having been 
 enabled to secure the services of Mr. C. C. Schneider, an 
 engineer of experience in bridge construction, to verify the 
 strain sheets and check over the various computations, entered 
 upon the examination of the plans and the information received. 
 
 Much of the additional information asked for came in very 
 slowly ; some of it, in fact, is not yet received ; but enough has 
 been secured in every case to obtain a proper understanding of 
 the designs presented, and to form a judgment as to their adapt- 
 ation to the local circumstances and surroundings of the loca- 
 tion, and to their relative economy. 
 
 The plans received may be classified and described as fol- 
 lows : 
 
6 
 
7 
 
 % 8 
 
 O 
 U I 
 — H 
 
 •U1B( [ 
 
 X 
 
 3 rt 
 
 j a h 
 
 J 2 
 
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 Q 
 
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 Pi 
 
 rtCU 
 
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 fit* 
 Q 
 
8 
 
 The chief feature of interest and novelty about your proposed 
 bridge is the fact that spans of 734 and 618 feet, respectively, 
 are required across the two arms of the East River, at an eleva- 
 tion of at least 130 feet above one of the most busily navigated 
 streams in this country. These great spans, although forming 
 but one-eighth of the total length of the structure, will cost con- 
 siderably more than one-half of the whole, and, with one single 
 exception, are unprecedented for railroad purposes. The Niag- 
 ara Suspension Bridge, of 800 feet clear span, alone surpasses 
 the length of the proposed spans, while the following railroad 
 bridges approach this magnitude : 
 
 The Cincinnati Southern Bridge, truss, 517 feet span clear. 
 The St. Louis Bridge, braced arch, . 515 feet span clear. 
 The Kuilenburg Bridge, trussed girder, 493 feet span clear. 
 The Britannia Bridge, tubular girder, . 460 feet span clear. 
 Saltash Bridge, double bowstring girder, 455 feet span clear. 
 The Cincinnati Bridge, truss, . . . 420 feet span clear. 
 The Louisville Bridge, trussed girder, . 400 feet span clear. 
 The Diershau Bridge, lattice girder, . 398 feet T span clear. 
 The Conway Bridge, tubular girder, . 400 feet span clear. 
 
 Our examinations of the strains and computations, therefore, 
 have principally been directed to the plans for the two long 
 spans ; and although we have also given due attention to those 
 for the approaches and lesser spans, our discussion of the merits 
 and demerits of the various designs will here mainly be con- 
 fined to those proposed for the stretches across the East River, 
 as these form the most novel and costly features of your struc- 
 ture. 
 
 The remainder of the work is of no unusual character, and 
 the requirements are readily provided for by the types of metal- 
 lic structures in common use. 
 
 DISCUSSION OF PLANS. 
 
 I. The plan submitted by Mr. L. W. Wright for the long 
 spans consists of a species of lattice girder, with considerable 
 cambre, as shown on plate I. 
 
 There are no strain sheets or estimates. 
 
c 
 c 
 c 
 
9 
 
 We feel confident that were the designer [to make a careful 
 and correct estimate of the strains developed in the bridge by 
 its own weight, he would essentially modify the plan. 
 
 II. The design submitted by Mr. G. A. Karwiese for the 
 great spans consists of a hinged arch, of which the lower mem- 
 ber is a parabola and the upper member is slightly cambred. 
 The upper and lower members are composed of wrought-iron 
 pipes, and the general arrangement of parts is shown on plate II. 
 
 Were the location over a deep chasm with natural rocky 
 abutments high above the stream, Tthe main features of this 
 design would not be inapplicable, and ft might be perfected so 
 as to be economical. The hinging of the parabolic arch at the 
 crown and at the abutment would eliminate the strains from 
 changes of temperature, while the upper member would impart 
 rigidity. The necessity for building abutments up from the 
 bottom, at the proposed location, would, however, prove some- 
 what costly, while the limitation of the head room by the 
 haunches of the arch would materially obstruct the free naviga- 
 tion of the river, and probably contravene the terms of the 
 charter. 
 
 The side elevation of the longest span (which the designer 
 proposes to make 760 feet in the clear), while showing a height 
 of 135 feet at the apex, gives 130 feet of head-room for a length 
 of but 230 feet in the centre, and of only 97 feet at a distance of 
 80 feet from the abutments, at which points sailing vessels must 
 occasionally pass. 
 
 The method proposed for placing this span in position — by 
 raising it along the margin of the river, one end resting on a 
 pivot at the abutment, and the other on floats, and of afterwards 
 swinging it across, thus describing a quarter of a circle, with 
 the abutment as a pivot, strikes us as extra-hazardous. It 
 would not only involve temporary obstruction to the navigation, 
 but also great risk of disaster and wreck to the entire structure. 
 
 These objections appear to us so serious as to warrant putting 
 this design aside, as not fulfilling the conditions of the charter 
 and of the specifications. 
 
 III. The design presented by Mr. W. J. Morris, for the Cin- 
 cinnati Bridge Company, consists, for the great spans, of a 
 
10 
 
 braced suspension cable, which it is proposed to make of steel 
 wire, stiffened by two parabolic trusses built upon them and 
 meeting in the centre, as shown on plate III. 
 
 This is the only suspension system among the designs pre- 
 sented in which the stiffening members are so arranged as to 
 provide for a rigid railway bridge. Although the plans are 
 probably too defective to be admissible as they are, they yet 
 present the excellent features of providing for a structure, the 
 parts of which will work in harmony with each other, and in 
 which there will be no doubt as to the resulting strains coming 
 upon each member. To insure this, however, it seems to us 
 that the cables should be hinged at the centre of the spans. 
 The designer states that this is to be done, but the plans do not 
 show how it is to be accomplished, and it seems to us difficult 
 to apply this feature to a wire cable. 
 
 The details of the design, however, are so imperfect as to 
 preclude us from recommending it. The great length of the 
 back stays would produce a rise and fall of 4 3-10 feet at the 
 centre of the span under changes of temperature, and not only 
 has the dead weight of the structure been somewhat under- 
 estimated, but there are serious errors in the computations of 
 strains, under certain conditions of load, the rectification of 
 which would increase the quantities of materials required and 
 the estimate of cost. 
 
 These errors and deficiencies, affecting important parts of 
 the structure, vitiate the design to such an extent as to render 
 it inadmissible under the specifications and circulars inviting 
 plans. 
 
 IV. Mr. A. Lucius proposes a structure which conforms very 
 closely to the existing types and practice for ordinary spans. 
 
 The approaches are on iron trestle-work, and the great spans 
 are standard " Pratt " trusses, modified as suggested by their 
 own dead weight, which becomes so great as not to require 
 counter-bracing against the effects of the live load. 
 
 A sketch is shown on plate IV. 
 
 So far as we have checked them over, his calculations of 
 strains and computations of quantities are correct, and the 
 design fulfils all the conditions of the specifications as to sta- 
 bility, strains and provisions for thoroughfares. 
 
11 
 
 This plan well illustrates how certain types of bridges, 
 well adapted to certain lengths of span, become uneconomical 
 when applied to greater spans and other circumstances of 
 location, and how little any type may be said .to be absolutely 
 the best. 
 
 Thus, for an opening under 20 feet we employ a simple stick 
 of timber or an iron beam. For spans of about 40 feet, plate 
 girders form an approved construction ; while for stretches from 
 100 to 400 feet, various styles of trusses, varying somewhat in 
 design and arrangement with the span, have been found best 
 adapted to the requirements of each case. 
 
 As we reach spans of 600 and 700 feet, departures from 
 existing practice recommend themselves, and the types adapted 
 to spans even as great as 400 and 500 feet are no longer the 
 most economical. In partial recognition of this fact, various 
 proposals have from time to time been made by designers for 
 the introduction of new types of bridges. Many of them have 
 proved worthless, and inasmuch as the opportunities for build- 
 ing great spans are very rare, such of them as possess merit 
 have not developed the advantages and economy which they 
 would show for long spans, in the short spans to which they 
 have been applied. 
 
 It will be seen that Mr. Lucius, on the other hand, by adher- 
 ing too closely to existing types, has produced a design which, 
 whatever its other merits, cannot be said to be cheap. 
 
 The cost is estimated at $2,523,072 for a single track bridge, 
 without the tunnel, while there are at least four designs which 
 will cost less than $2,000,000 for the same elements. 
 
 There is, moreover, a difficulty and danger involved in the 
 method planned for placing these spans in position. He pro- 
 poses to erect them upon the land, one end, however, project- 
 ing over the water; to place that end on a float (the greater 
 span complete weighs 4,418,000 pounds) and to haul it across 
 the channel, rolling it out over the abutment, until it reaches 
 its final position. He estimates that this operation would 
 obstruct the navigation no more than one day for each span. 
 
 This seems to us a hazardous undertaking, and in view of pos- 
 sible interference from passing vessels, from wind and tide, and 
 unexpected delays and difficulties, one upon which the entire 
 destruction of so costly a structure should not be jeoparded. 
 
12 
 
 We would not advise taking so great a risk, even if the struc- 
 ture were more economical. 
 
 V. Mr. W. S. Pope proposes for the Detroit Bridge Works 
 a suspension bridge, with an auxiliary girder. The cables are 
 to be of steel wire, and the form of the long spans as shown on 
 plate V. 
 
 The information accompanying the plans is more full and 
 complete than any other which we have received. The strain 
 sheets, computations of quantities, and description of parts are 
 so intelligently arranged as to give a clear idea of every part 
 of the design. 
 
 We cannot agree, however, with some of the assumptions 
 made as to the distribution of the strains. The stiffening girder 
 which carries the roadway across the great spans is suspended 
 from the cable and also from a series of inclined stays, which 
 reach about one-half of the distance from the end towers to the 
 centre, as at the Niagara Suspension Bridge. So far as both 
 of these systems extend, it is assumed that one-half of the loads 
 will be carried by the cables and the other half by the inclined 
 stays. These form two distinct and independent systems of 
 suspension, and there is no evidence whatever that the load at 
 any one point will distribute itself in the particular proportion 
 assumed. However accurately the two systems may be ad- 
 justed when first erected, the changes of temperature are sure 
 to change their relative positions and lengths and to vary the 
 relative proportions of the loads which they bear. This is the 
 case with the Niagara Bridge, the contraction of the cable on a 
 cold day in winter raising up the platform and taking the weight 
 from the stays, so that they become loose and are visibly 
 crooked. The cables in that bridge are therefore made strong 
 enough to do all the work, with a factor of safety of about 4^, 
 and the stays are merely relied on to stiffen the truss. 
 
 We find, moreover, that this design does not provide for 
 strains arising from changes of temperature, which will be very 
 considerable in the long spans. 
 
 The aggregate cost condemns the plan. It is estimated at 
 $3,700,000, without the tunnel. It is fair to state, however, 
 that this includes an allowance of twenty per cent to cover 
 engineering and contingencies, and that, when these are de- 
 
> 
 
 - 
 
13 
 
 ducted, the estimated cost stands at $3,066,400 for a single 
 track bridge, leaving it, however, still the most expensive struc- 
 ture on the list. 
 
 VI. The plans submitted by E. W. Serrell & Son provide 
 for a suspension bridge, the cables of which are composed of 
 wrought-iron links, which, together with a system of diagonal 
 stays, sustain a stiffening girder, as shown on plate VI. 
 
 We are unable to agree that this design fulfils the require- 
 ments of the specifications, which require that the structure 
 should be so designed as to provide for the maximum strains 
 which can by any possibility come upon any part of the bridge. 
 
 The designers assume that all the dead weight of the struc- 
 ture in the long spans will be carried by the chain, which is so 
 far right ; but they also assume that, in that portion over which 
 both systems extend, all the live load will be carried by the 
 stays as far as they go, and that the chain will carry the 
 remainder — t. e., that portion of the live load which comes 
 between the ends of the stay-rod systems. There is no proof 
 satisfactory to the entire Board of the correctness of this 
 assumption. 
 
 Of course, in planning a compound structure in which sev- 
 eral systems are expected to carry the load, as in the case of a 
 chain and diagonal stays, or that of an arch and truss, it is 
 natural to assume that the load will be divided in some ratio 
 between them, but in such cases it is absolutely necessary for 
 safety that each should be made strong enough to bear all the 
 load which can by any possibility come upon them ; and, as in 
 the case under consideration, both the dead and the live loads 
 are mainly concentrated on the same floor, it is probable that 
 strains resulting from both will follow the same law of stability 
 and take the shortest available road to the top of the towers, as 
 governed by the location of the loads and the adjustment of the 
 bridge. 
 
 The calculations of strains from the effect of the live load 
 carried by the cable between the ends of the stay-rod systems 
 and those due to the wind strains for the towers of the river 
 spans leave much to be desired. 
 
 The stiffening trusses, as designed, are only 12% feet in 
 depth. This is thought by some of us to be too shallow, and 
 
14 
 
 that it would make the middle portion of the spans so flexible 
 that its parts would be unduly strained if trains run over 
 (as they should) at full speed. 
 
 The designers propose an ingenious arrangement for insuring 
 the working in unison of the main chains and of the stays under 
 changes of temperature. They propose to suspend a lever from 
 the saddles over the towers and to attach the stays to a series 
 of pivots placed on the line of this lever, so placed that its 
 movements shall compensate for the different contractions and 
 expansions of the chains and stays under the changes of tem- 
 perature. We are not prepared to say that this would or 
 would not prove efficient. If it were certain that all the vari- 
 ous members of the bridge would always be equally exposed to 
 the sun and equally heated and cooled, and that the vertical 
 motion due to the expansion and contraction of the cable and 
 stiffening girder would take place regularly, instead of con- 
 forming to a curve, the radius of which changes with the 
 temperature, the result expected by the designers would doubt- 
 less follow. Further study, however, would be necessary 
 before we could venture to recommend the adoption of a 
 method which, however ingenious, is yet an untried experiment. 
 
 It will be noticed that none of the designs which have been 
 submitted for suspension bridges meet the requirements of the 
 case or of the specifications. This arises partly from deficien- 
 cies in the designs and partly from the difficulty of adapting 
 this system to the necessities of the traffic to be accommodated, 
 which require a rigid structure. Suspension bridges wich stiff- 
 ening girders have been largely and successfully erected for 
 carriage roads, over which the rolling loads are light and pro- . 
 ceed at low speed, thus giving a flexible structure time to adjust 
 itself to the changing position of the weights to be carried. 
 When, however, the heavy, concentrated loads of railway 
 engines and trains are to pass at high speed (as they ought in 
 a bridge two miles in length, so costly as to require the profits 
 on a large business to pay interest on the capital invested) the 
 structure should be so rigid as not to be disturbed and racked 
 under the effects of the live load. This indispensable rigidity 
 may be conferred, it is believed, by an auxiliary truss, but the 
 very rigidity of the truss, if continuous, prevents its working in 
 harmony in varying states of temperature with the cable, if, as 
 
4 
 
15 
 
 in the road bridges we have alluded to, and as in the Niagara 
 Bridge (which only permits slow motions of trains), the truss 
 is continuous. Hence the compulsory resort to trusses hinged 
 at the centre. This arrangement, or others hitherto proposed 
 (which we have not room to discuss), involves very consider- 
 able departure from the ordinary methods of suspension, and 
 none of the designs submitted (except, perhaps, that of the Cin- 
 cinnati Bridge Company) seem to recognize this fact. 
 
 VII. The design of Messrs. Henry Flad & Co. consist, for 
 the large spans, of straight link suspension, or, more properly 
 speaking, derrick bridges, which are planned for a double 
 track throughout, including the approaches. 
 
 A sketch of the main span is shown on plate VII. 
 
 The difficulty in preventing the long suspension links from 
 sagging down from a straight line by their own weight and 
 thus destroying the theoretical adjustment of the bridge, is quite 
 ingeniously met by a system of braces and ties, which unite all 
 the links by circular arcs and prevent their becoming catenaries 
 instead of straight lines. This detail we believe to be quite 
 novel and to overcome, in a great degree, the objections which 
 have heretofore been raised concerning derrick bridges. 
 
 The calculations of strains and computations of quantities 
 are correct, but there are some deficiencies in the wind bracing 
 between the two principal trusses, which would somewhat in- 
 crease the quantities of material estimated. The most objec- 
 tionable feature about the design, however, is the fact that both 
 the roadway and the sidewalks are placed upon projecting 
 brackets outside of the line of the trusses, the brackets being 
 imperfectly connected to the boom, thus giving a narrow base 
 and objectionable arrangement. The plan, nevertheless, is a 
 good one, but not the most economical one. It is estimated to 
 cost $2,610,785 for a double track throughout, the designer not 
 having furnished a plan for a single track bridge susceptible of 
 future enlargement. 
 
 The greater cost of Messrs. Flad & Co.'s design is probably 
 due to the fact that, as each set of straight suspension links sup- 
 port a uniform length of 50 feet, they have to provide for the 
 maximum live load which occurs upon such a span, say 4,750 
 pounds per lineal foot, while the maximum weight which can 
 
16 
 
 come upon the whole of the 734 feet aggregating these spans 
 averages only 3,370 pounds per lineal foot. 
 
 It is but just to mention, in this connection, that two meritori- 
 ous designs for double track railway and roadway bridges, on 
 the derrick plan, were originally submitted to your Company 
 by Professor W. P. Trowbridge of New Haven. We regret 
 that his many engagements did not admit of his revising them 
 to conform to our specifications, especially as Professor Trow- 
 bridge was one of the earliest to interest himself in the project 
 for a bridge at Blackwell's Island and to propose a derrick plan 
 therefor. We have received from him a communication and 
 -estimate concerning the cost of a tunnel at the location pro- 
 posed for your bridge, which we submit to your Board here- 
 with. 
 
 But few of the seven plans which have thus far been dis- 
 cussed are accompanied with direct tenders from bridge firms 
 for their construction. Some of the estimates of cost, therefore, 
 may require revision as to prices, as well as to quantities of 
 materials needed to supply deficiencies. 
 
 The two plans which remain to be described, however, are 
 not only the best in themselves, as we are all agreed, but are 
 backed by responsible bridge contractors of high standing, who, 
 as we understand, are prepared to enter into contracts for their 
 construction at the specified sums. 
 
 Either of the designs is a proper one to be adopted and 
 erected ; and, with such modifications and improvements as 
 the builders would doubtless wish themselves to make in pre- 
 paring their final plans, is likely to give good satisfaction. 
 
 VIII, The firm of Clarke, Reeves & Co., of the Phoenixville 
 Bridge Works, submit a design in which they propose to erect 
 for the spans across the river the plan of hinged arch invented 
 and patented by Capt. James B. Eads, the distinguished engineer 
 of the St. Louis Bridge. 
 
 A side view is shown on plate VIII. 
 
 The arch proper consists of two Lenticular struts or girders 
 resting against each other in the centre, where they are hinged, 
 and also hinged at the top of the piers. To sustain these hinge 
 points, struts, made like the girders, continue the arch form to 
 abutments on the rock foundation below. 
 
< 
 - 
 
17 
 
 The main arches, or top members, are to be of " Phoenix ' ' 
 columns of wrought iron, 30 inches in external diameter, put 
 together in straight pieces, each one panel in length, except 
 where the openings for rail and roadways occur. At these they 
 will be at least two panels in length, and the adjoining joints in 
 the contiguous columns will be likewise additionally strength- 
 ened. 
 
 The lower members, or counter arches, are made of plates 
 and angles, riveted together so as to form channel beams. The 
 web members are 10 inch channel bars, attached to the upper 
 and lower arches by pin connections. These form between the 
 piers two semi-arches or " lunettes," the thrusts of which are 
 mainly carried to the foundation by the braced continuation or 
 arched strut already mentioned. 
 
 The piers, which are composed of Phoenix columns, and 
 braced both transversely and diagonally, are designed to take 
 only such strains as may come upon them from unequal load- 
 ing of the arches and a portion of the strain from wind pressure. 
 These strains are alternately compressive and tensile, and the 
 piers are therefore designed to resist compression as well as 
 tension, and to be anchored to their foundations. 
 
 The floor system consists of iron cross-floor beams two feet 
 deep, made of plates and angle irons, and of longitudinal string- 
 ers fifteen inches deep. The cross-floor beams are suspended 
 from the arch by flat bars of varying length latticed together, 
 the longest suspender being at the centre, and eighty feet lon^. 
 The floor is divided by four ribs or arches into three roadways 
 of equal width, the central one being occupied by the railroad 
 and the outer ones by the roadways and sidewalks. This is a 
 convenient arrangement for a single track road, but if a second 
 track is to be hereafter added, provision must be made for it 
 now by building the outer arch strong enough to carry the in- 
 creased load hereafter to be thrown upon it. The cost of this 
 is estimated by the designers at $151,000. The total width of 
 the structure is fifty-seven feet from out to out, thus affording 
 good opportunity for lateral bracing. 
 
 As was to be expected from the known experience and abil- 
 ity of this firm, the plans are very thoroughly and carefully 
 worked out in all their details ; the strain sheets, calculations 
 and computations, so far as submitted, are found to be correct, 
 
18 
 
 and the design not only possesses great merits intrinsically, but 
 has been so nearly perfected as to leave but little room for im- 
 provement. 
 
 It may be objected that it does not leave throughout its entire 
 length an unobstructed head room of the full height required by 
 the charter for the middle of the river (130 feet). In the plan 
 presented the lowest part of the bridge is 135 feet above mean 
 high tide at the middle ; at a distance of 200 feet from the cen- 
 tre it is 130 1-10 feet ; at the shores it is 108 feet. The arrange- 
 ment is stated by the firm not to be indispensable to the success 
 of the design, and that the arches can be raised if thought to 
 obstruct navigation. In accordance with this last suggestion a 
 modified design has been prepared and sent to us, on which 
 the clear height at the shores is 120 feet, or the same as for the 
 Brooklyn Bridge. This change is stated to require no modifi- 
 cation in the estimates. 
 
 This plan of a hinged arch would be an admirable one for 
 a deep sunken stream, with precipitous rocky sides, as at the 
 Niagara Suspension Bridge. The topography of such a loca- 
 tion, and the absence of all navigation, would also greatly facili- 
 tate and cheapen its erection ; for, in a span of 700 or 800 feet, 
 one of the chief problems to be solved is, how to get it into 
 place without inadmissible expense and without danger of 
 wreck during its construction. 
 
 Messrs. Clarke, Reeves & Co. propose to adopt a method 
 somewhat similar to that employed at the St. Louis Bridge, and 
 to project each semi-arch, panel by panel, from the shore, sus- 
 pending it, as it progresses, from a series of inclined stays 
 fastened to temporary towers at the piers, and anchored back to 
 the shores. Each semi-arch would thus project beyond the 
 stays until both meet in the centre of the river, where the cen- 
 tral hinge could be inserted, and the weight taken oft' from the 
 stays. This method proved successful at St. Louis for spans of 
 515 feet. Whether it could as successfully be applied to this 
 one of 749 feet admits, perhaps, of some question, as the 
 weights to be controlled are larger, and their leverage greater, 
 while the circumstances of the case are somewhat different. 
 
 Although the erection would, at first sight, appear to be diffi- 
 cult, expensive, and perhaps hazardous, we are informed by the 
 projectors that they have convinced themselves of its entire 
 
L9 
 
 practicability, and provided for it in the estimates by careful 
 calculations of the cost of erection. 
 
 In view of the high character and known skill of these gen- 
 tlemen, therefore, we do not feel authorized to dwell upon this 
 point further. 
 
 In consequence of an ambiguity in our specifications, as to 
 whether the formula given for calculating the strains upon com- 
 pression members applied to sections shorter than 24 radii of 
 gyration, the designers (construing the clause strictly against 
 themselves) have calculated the strains upon the main arches at 
 8,000 pounds to the square inch of section, and thus provided for 
 a structure materially stronger than would have resulted from 
 the alternative construction of the clause (as adopted by the other 
 designers), which gives as a result in some cases about 11,000 
 pounds to the square inch, and would have saved some 900,000 
 pounds of material in the largest span alone in this design. 
 
 We are informed by Messrs. Clarke, Reeves & Co. that 
 1,100,000 lbs. of iron, included in their estimate of weights, is 
 wholly required in the erection of the bridge. This amount of 
 iron should therefore be deducted from the actual weight of the 
 completed structure. The large amount estimated for raising 
 the arches may be taken as an evidence of the regard to safety 
 in designing the means of erection. 
 
 Objections might perhaps be taken to the necessity of sus- 
 pending the floor from the panel points of the arch, but the 
 designers have judiciously planned to lattice together the sus- 
 pension ties (the longest of which is eighty feet long) in order 
 to give the floor platform lateral stability and counteract the 
 tendency to swing sideways from the effect of the wind. 
 
 We may notice the following points which would require 
 attention, were the plan to be selected for erection : 
 
 1. The lateral bracing is necessarily omitted out of eight 
 panels in the counter arch and four panels in the main arch, in 
 order to allow for head room in the roadway where its line in- 
 tersects that of the arches. This would require the strengthen- 
 ing of the joints and columns past these points. 
 
 2. The piers being designed mainly to form, with the in- 
 clined struts, fixed points for the hinges of the lunettes, and 
 bearing none of the dead load, cannot form supports against 
 strains from the live load, arising from partial loading, without 
 
20 
 
 being anchored down to the foundation ; and this feature seems, 
 therefore, inherent in the design. 
 
 3. Changes of temperature will tend to move the tops of the 
 piers in the line of the axis of the bridge. This motion, how- 
 ever, will amount to but \ % inches for the whole range of 150 
 degrees provided for by the specification, and the piers may 
 bend so much without danger. 
 
 As a whole, the design provides for a structure of great merit. 
 The cost for a single track throughout, without the tunnel, is 
 estimated at $1,767,274. For double track approaches on the 
 New York and Long Island sides, and single track across both 
 arms of the river and across BlackwelPs Island, it is $1,932,878. 
 If, however, it is desired to provide for an eventual second 
 track, the cost of first erection will be increased by $151,000, 
 say to $2,083,878, while the addition of the second track (at 
 present prices) would cost $202,400 more ; thus making the 
 cost of a double track structure throughout $2,286,278. 
 
 IX. The plans presented by Mr. Charles Macdonald for the 
 Delaware Bridge Company propose, for the spans across the 
 East River, a novel modification of the Cantilever type of 
 bridges. 
 
 This type has hitherto been planned with only two chords or 
 booms, placed as far apart vertically as proved most economical 
 for the intermediate connecting web. This arrangement is the 
 existing and correct practice for girder or truss bridges, and 
 insures economy of material, by carrying the strains as far from 
 the neutral axis as possible. 
 
 In a Cantilever bridge, however, the two Cantilevers, bal- 
 anced over each pier, form brackets, the shore ends of which are 
 anchored down, and their outer ends sustain a central span, 
 merely resting upon them, and free to expand and contract with 
 changes of temperature. 
 
 These brackets, therefore, perform a double function. They 
 sustain their own weight and their proper rolling load to the 
 extremity of their arms, and they also sustain the weight of the 
 central span and its proper rolling load, extending between 
 the ends of the brackets. 
 
 The Delaware Bridge Company propose to avail of this 
 division of functions, by sub-dividing the Cantilever vertically 
 
21 
 
 into three brackets, superposed to each other by means of inter- 
 mediate chords as shown on plate IX. 
 
 The designer claims that, by this arrangement, the weight is 
 kept as low as possible, and that by avoiding the necessity for 
 carrying all the weight to the top of the central tower over the 
 pier, there results not only great economy in this tower, but 
 also in all the compression members of the web, which become 
 of the simplest form and most manageable lengths, while the 
 stability is greatly increased, and the erection becomes so sim- 
 ple and cheap that the structure furnishes its own false works 
 except for the central space. 
 
 Each Cantilever, or bracket, is divided by the two interme- 
 diate chords into three subsidiary brackets superposed to each 
 other, and 36 feet deep. These again are divided vertically into 
 panels 30 feet long by the posts, those posts alone carrying the 
 live and dead load, to which the diagonal ties are attached ; 
 the posts above these merely serving to carry the weight of the 
 Cantilever chords, and to prevent them from sagging below a 
 straight line. 
 
 The process of erection consists in extending the parts with a 
 balanced beam, panel by panel, each side of the pier, using each 
 subsidiary bracket as the foundation for that overlying it, and 
 then, after the brackets are completed, rolling a counterbalanced 
 wooden truss, 300 feet long, into the intervening space, on and 
 around which to erect the central span, which is 200 feet in 
 length. 
 
 The shore ends of the Cantilevers are sustained by three piers, 
 through which the anchorage is distributed. 
 
 There are three trusses, the bridge being divided by them in 
 cross section into two roadways, one for the railroad, and the 
 other for a double carriage roadway 20 feet wide ; the sidewalks 
 being placed on brackets overhead of the carriage roadway. 
 When a second track is to be added, it is to be provided for by 
 independent trusses on the other side of the carriage roadway, 
 which would then be in the middle. 
 
 The lower boom, or chord, is composed of 24-inch iron 
 plates and 8-inch channel bars, riveted together into the form 
 of a continuous box girder open at the top. The vertical posts 
 consist of two channel bars each, latticed, and the diagonals and 
 the suspension chains, or upper chords, are of flat bars, 6 inches 
 
22 
 
 wide. All the verticals, diagonals and suspension chains, or 
 chords, are connected with each other and with the lower chord 
 and towers by pin joints. The towers are composed of posts 
 made of plates and channel bars, latticed, and are braced both 
 transversely and diagonally. 
 
 The shore piers, on which the arms of the Cantilever rest, 
 are similar to the towers, and anchored to the foundation so as 
 to resist both compression and tension. 
 
 The floor consists of iron cross-floor beams, made of plates 
 and angle irons and of longitudinal iron stringers, braced by 
 diagonal lateral rods. The main cross-floor beams are sus- 
 pended from the pins at each panel point. 
 
 The sidewalks are carried on brackets fastened to the ver- 
 tical posts above the main floor. The central span is a Pratt 
 truss, with pin connections, and a double system of diagonals. 
 The posts and upper chords are made of plates and channel 
 bars, and the tie rods and lower chords of flat bar links as in 
 ordinary spans of that class. This span merely rests upon the 
 outer ends of the arms of the two Cantilevers, one end being 
 provided with rollers to allow of expansion and contraction. 
 
 Not only is the structure rigid, economical and capable of 
 erection with great ease and without danger of disaster or inter- 
 ference with the navigation, but it seems to us capable of still 
 further improvement by revising the general proportions, the 
 most economical arrangement of which, it may well be, the de- 
 signer has not attained in so novel a plan. 
 
 The sections of the compression members have been calcu- 
 lated by the formula given in the specifications for parts exceed- 
 ing twenty-four radii of gyration, which results in strains of 
 about 9,000 pounds per square inch, and some of these mem- 
 bers, therefore, have relatively less section than the correspond- 
 ing parts in the design of Clarke, Reeves & Co. 
 
 Some of the wind strains are also deficient in consequence of 
 an under estimate of the developed surface exposed by some of 
 the parts. 
 
 In addition to this we may call attention to the following 
 minor deficiencies : 
 
 1. There is no provision made for carrying the wind strains 
 past the openings in the central towers through which the road- 
 ways run. This can readily be overcome by suitable portals. 
 
23 
 
 2. The foundation of the main towers is not spread sufficiently 
 wide to overcome the overturning tendency from wind strains. 
 In order to avoid the consequent necessity for anchoring the 
 posts down to their foundation, which is an objectionable 
 arrangement, it would be advisable either to spread the base of 
 the towers, or to design the bridge with only two trusses instead 
 of three, so as to concentrate all the weight upon the outside 
 posts. 
 
 3. The effect of the live load, when only one arm of the 
 Cantilever is loaded, will be to produce a bending strain in 
 the towers and to throw the weight upon one set of tower 
 posts instead of distributing it over the whole. This requires 
 some changes in the connection of the chords or chains with 
 the tops of the towers, so that the weights may be transmitted 
 without producing a bending strain. 
 
 The cost for a single track throughout, without the tunnel, is 
 estimated at $1,778,315. For double-tracked approaches on 
 the New York and on the Long Island sides, and single track 
 across both arms of the river and Blackwell's Island, the cost 
 will be $2,031,425, while for a double track structure through- 
 out it will be $2,479,458 ; and the Delaware Bridge Company 
 makes a formal tender to take the contract at these prices, 
 
 NON-COMPETING PLANS. 
 
 During the last week in January the Passaic Rolling Mill 
 Company brought in a set of plans and a tender for the con- 
 struction of your bridge, which other engagements had pre- 
 vented that Company from completing sooner. 
 
 These we could not in fairness consider with the other de- 
 signs handed in at the specified time in competition for the pre- 
 miums offered, nor was it expected that we should ; the parties 
 who had been at the trouble and expense of finishing them sub- 
 mitting the plans mainly as the evidence of their being pre- 
 pared to undertake such works. 
 
 These plans, which were prepared by Mr. C. O. Brown for 
 the Passaic Rolling Mill Company, are sound and good. They 
 provide for a Cantilever bridge, the main feature of which is 
 the long central span of 330 feet. It is shown on plate X. 
 
24 
 
 So far as we have been enabled to check them over, the com- 
 putations of strains and quantities are correct. The estimate of 
 cost however, is somewhat higher than for the plans of Messrs. 
 Clarke, Reeves & Co. or the Delaware Bridge Company, being 
 $1,885 000 f° r a single track structure, without the tunnel, or 
 $1,985,000 including the tunnel; at which price the parties 
 made a formal tender for the whole work. 
 
 We regret that Mr. Charles Bender, who originally made a 
 valuable preliminary report to your Board of Directors and 
 presented plans for a Cantilever bridge possessing great merit, 
 did not find himself at leisure to revise those plans and estim- 
 ates of cost, in order to make them conform to our specifica- 
 tions, so that we might consider them in competition with the 
 others. Mr. Bender was among the first to take an interest in 
 your enterprise and to make valuable suggestions about its con- 
 struction, by which all designers have probably profited ; while 
 his original plan contained such excellent features that we should 
 probably have had the satisfaction of recommending it among 
 the best, had it been made to conform to the terms of the circu- 
 lar inviting designs. 
 
 We also regret that the Baltimore Bridge Company, which 
 had originally sent in a preliminary study for a counter-balanced 
 Cantilever span, was unable, from press of other engagements, 
 to complete the plans which we understand them to have begun. 
 We would have been quite certain to receive good plans from 
 this skillful and experienced firm. . 
 
 GENERAL FEATURES. 
 
 Whether the structure shall be for a single or double railway 
 track depends upon the estimates of its future business. We 
 would recommend that the tunnel and the approaches, on both 
 the New York and Long Island sides, be built for double track, 
 and that the main spans and trestle across Blackwell's Island 
 should be for single track, with provision for an eventual second 
 track, if required. For these elements the bridge proper will 
 cost, according to the estimates of Clarke, Reeves & Co., 
 $2,083,875 ; and according to those of the Delaware Bridge 
 Company, $2,031,425. The tunnel will probably cost about 
 
25 
 
 $200,000 more, and. if the office expenses and engineering be 
 estimated at from $116,122 to $168,575 more i the total cost of 
 your enterprise will be $2,400,000, exclusive of the right of way. 
 If built for a single track throughout, the cost will not exceed 
 $2,100,000, exclusive of the right of way. 
 
 ORDER OF MERIT. 
 
 Having now completed our general review of the competing 
 plans, it only remains for us to advise vou as to which we deem 
 the three " best " designs and to indicate the relative rank, in 
 our estimation, of these three. 
 
 In this connection we quote the resolution of the Board of 
 Directors of August 9, 1876 : 
 
 Resolved, That the time for receiving plans be extended to December 1, 1876, 
 and that the Engineers give notice, with a view of bringing out the best talent in 
 the country, that this Companv will pay to the party whose plan shall be adopted 
 as the best the sum of one thousand dollars ; for the second best, five hundred 
 dollars, and for the third, two hundred and fifty dollars. Plans so paid for to be 
 the property of the Company. The awards to be made by this Board under ad- 
 visement of the consulting engineers. 
 
 Our estimate of relative merits will be best rendered by the 
 following transcript of minutes of proceedings of the commis- 
 sion of consulting engineers on the evening of February 5, 1877 : 
 
 "The individual opinions of the members of your consulting engineers upon 
 the order, each being taken absolutely without modifications, and as entirely with 
 reference to its strain sheets and specifications, are as follows : 
 
 ( Best — Delaware Bridge Company* 
 O. CHANUTE, \ Second— Clarke, Reeves & Co. 
 
 ( Third — Flad & Co. 
 
 I Best — Clarke, Reeves & Co. 
 J. G. BARNARD, I Second — Delaware Bridge Comp'y. 
 ( Third — Flad & Co. 
 
 I Best — Clarke. Reeves & Co. 
 Q. A. GILLMORE, - Second — Delaware Bridge Comp'y. 
 
 I Third — Edward Serrell & Sox. 
 
 Taken, however, as a whole upon the general question, as to 
 which plan we would recommend to be adopted for practical 
 
26 
 
 construction by your Company, with such improvements and 
 modifications as suggest themselves, the order of our preference 
 would be as follows : 
 
 i Best — Delaware Bridge Company. 
 O. CHANUTE. < Second— Clarke, Reeves & Co. 
 
 ' Third— Flad & Co. 
 
 i Best — Clarke, Reeves & Co. 
 J. G. BARNARD, ■ Second — Delaware Bridge Comp'y. 
 ( T/u'rd—FL\D & Co. 
 
 i Best — Delaware Bridge Company. 
 Q. A. GILLMORE, < Second— Clarke, Reeves & Co, 
 ( Third — Edward Serrell & Son. 
 
 From the foregoing it will appear that, while there is entire 
 unanimity as to the two best plans which we advise for award, 
 the same is not found as to the order of merit of these two. 
 
 Two out of the three pronounce the plan of Clarke, Reeves 
 & Co. the best, if taken absolutely without modification, and 
 entirely with reference to its strain sheets and specifications. 
 
 While two out of three pronounce the Delaware Bridge 
 Company's plan " best " to recommend to be adopted for prac- 
 tical construction by your Company, with such improvements 
 and modifications as suggest themselves. 
 
 With regard to the " third k best '," two out of three agree in 
 giving the award, on both the grounds on which the votes were 
 taken, to Flad & Co. One, Gen. Gillmore, considered, under 
 both points of view, the plan of Edward Serrell & Son as en- 
 titled to that rank. 
 
 Submitting the foregoing as the result of their united action, 
 the individual members will, to the extent they see fit, set forth 
 their reasons for their individual preferences. 
 
 Respectfully submitted, 
 
 O. CHANUTE, 
 J. G. BARNARD, 
 Q. A. GILLMORE. 
 
27 
 
 SUPPLEMENTARY REPORT OF GEN. BARNARD. 
 
 New York, February 21, 1877. 
 
 To the President and Directors of the New York and Long 
 Island Bridge Company : 
 
 Gentlemen : — 
 
 The concluding paragraph of the joint report of the Board of 
 Consulting Engineers to your honorable body of this date, closes 
 with the statement : " The individual members will, to the ex- 
 tent they see fit, set forth their reasons for their individual pre- 
 ferences." As my own views on the subject of two of the com- 
 peting plans would be incompletely expressed without such an 
 exposition, I herewith present the statement therein contem- 
 plated. 
 
 I am very respectfully, 
 
 Your most obedient, 
 
 J. G. BARNARD, 
 A I ember of the Board of Consulting Engineers. 
 
 The undersigned, a consulting engineer, to select the best 
 plan for your proposed bridge, and to advise as to the awards 
 to be made by your Board for " best," " second best " and 
 " third best " plans, having recorded his opinion, that, whether 
 considered u absolutely s without modification," or as a "plan to be 
 adopted for practical construction by your company, with such 
 improvements and modifications as suggest themselves," the 
 
28 
 
 plan of "Clark, Reeves & Co." is entitled to the award of "best," 
 briefly submits the following reasons for his preference : 
 
 I. — Simplicity of design. 
 
 In this respect it is unrivalled. The arch is recognized as 
 theoretically the form for bearing compressively a permanent 
 load — the parabola, its proper trace, when the load is uniform. 
 The combination in this bridge, while giving the arch as the 
 permanent load-bearer, breaks it at the crown and skewbacks 
 (by hinges) to avoid temperature strains. In this point of view 
 the principle is again the most simple and elementary in bridge 
 building — the juxtaposition from the opposite banks (when the 
 span becomes too great for a single beam) of two struts meet- 
 ing at an angle in the middle. 
 
 In short spans, where this simple triangle of parts first finds 
 its application, the thrust is usually taken by a tie or chord. 
 For»large spans, if a tie be used, the deflection due to load is 
 thereby doubled, since the tie is stretched as much as the arch 
 member is compressed. 
 
 Hence the advantage claimed in this design of carrying the 
 thrust direct to the ground by a short compression member (a 
 continuation of the arch form) reaching from the abutment 
 hinges to the ground. The two struts into which the arch is 
 divided are stiffened each by a counter-arch, also parabolic, 
 giving a "lunette" or lenticular form to these members almost 
 exactly corresponding to that demanded by the maximum strains 
 — a correspondence of which the ordinary " girder" (with par- 
 allel chords) is necessarily destitute, and for which the gradua- 
 tion of weight of metal in its parts is the imperfect substitute. 
 
 The resulting external form, an arch springing from the very 
 shores, gives to the structure a singular beauty ; a point by no 
 means to be disregarded. It should be further stated in this 
 connection, that while the design is called an invention, the 
 word refers exclusively to the combination by which, for spans 
 of extraordinary length, the same simple elements are made 
 available as those which for ages have been in common use for 
 the shortest. In this point of view there is nothing whatever 
 " experimental," the action of every part is well known by ex- 
 perience. 
 
29 
 
 The u cantilever " principle is far more open to the charge of 
 being untried or " experimental." In endeavoring to cite a 
 precedent for such a bridge, Mr. Bender * is driven to the irrele- 
 vant structure, a " cantilever bridge with two arms," as he calls 
 it, the Brest drawbridge, consisting of two balanced swinging 
 arms, the longer members of which, together, span a clear 
 interval of 354 feet. This is no railroad bridge. A narrow 
 carriage-way with sidewalks alone occupies it, and no long 
 independent truss fills a vacuum in the middle and hangs with- 
 out connection, almost, with its total dead and live load, on the 
 extreme ends of the so-called " cantilevers." On the contrary, 
 these members of the Brest bridge k ' are wedged together in the 
 centre so as to act partly as an arch, when the load comes upon 
 it." The numerous wooden and cast-iron bridges in Holland, 
 England, Germany, etc., also cited, are too insignificant, or too 
 irrelevant to be referred to as furnishing any experimental basis 
 for great span cantilevers ; the great variety of designs for 
 which are sufficient proofs that there is no such basis. 
 
 II. — Perfect, or almost perfect, eli?nination of temperature 
 
 strains. 
 
 This — one of the difficulties of long span bridge construction 
 — is accomplished by the hinges at the crown and at the abut- 
 ment, by hingeing the suspended floor at its middle point, and 
 by allowing play for variations of length at its connection with 
 the counter-arches. 
 
 The slight temperature strain thrown upon the pier by the 
 abutment strut — easily calculated — may be disregarded. This, 
 too, might be completely eliminated if it were worth while. 
 
 III. — Perfect deter minateness of strains, ?zot only in the nor- 
 
 mal configuration, but when under the slight distortions 
 produced by partially distributed '* live " loads. 
 
 The first condition flows from the simplicity of design. So 
 also does the latter ; but it is by no means inseparable from the 
 first. A slight distortion of the piers in the cantilever may very 
 seriously alter the actual strains from those of calculated strain 
 
 * " Letter to your Company, September 20th, 1875.'' 
 
30 
 
 sheets, and the fact is strikingly illustrated in the competing 
 cantilever plan for which, to avoid such strains, remodelling 
 is required.* 
 
 IV. — Perfect fulfillment of the requirements, not merely of 
 
 our specifications" which leave some latitude for ar- 
 rangement, but of convenience, in the disposal of the 
 thoroughfares. 
 
 The ample width of 57 feet, from outside to outside of exter- 
 nal arches, allows to be centrally placed (as it should be) the 
 railway track, while the two outside compartments are given 
 up to exclusive use of the two roadways, each with its sidewalk. 
 The breadth of base which allows this ample room for the thor- 
 oughfares, is also an important element in the stability of the 
 bridge against wind strains. 
 
 V. — Superiority in the main elements which constitute the, 
 
 structure, and fewness of parts. 
 
 The great bearing elements, i. e. : the main " arch " of each 
 " lunette," or half strut, the abutment strut which continues 
 the arch form to the ground, and the columns of the piers, 
 etc., are made of the "Phoenix columns," admittedly the best 
 wrought iron " post," or compressive member, yet designed, 
 and, in my opinion, incomparably preferable to the latticed 
 channel-iron posts, or compressive members, we find in all the 
 other competing designs. The Phoenix columns have been 
 found experimentally to have (see Bender, "Iron Truss Bridges 
 in America," p. 35) an ultimate strength far higher than given 
 by Hodgkinson's and Gordon's formulas, by which it is usual 
 (as our specifications require) to determine the quantity of metal 
 in such members. These members, therefore, thus calculated, 
 possess an excess of " safety " beyond our safety " coefficients." 
 But not only do they possess this extra strength, but they have 
 been calculated (according to the specifications) so as in no 
 case to receive a compressive strain of more than 8,000 pounds 
 per square inch. Under the formula which follows this specifi- 
 cation, but which was qualified by it, for compressive members 
 
 See on this point Mr. Bender's pamphlet, 11 Iron Truss Bridges in America," p. 24, §2 . 
 
31 
 
 longer than twenty-four times the radius of gyration, com- 
 pressive strains much higher have been taken for the posts of 
 the Delaware Bridge Company's bridge. This accounts for 
 any difference there may appear to be in the weight per foot 
 in favor of the latter bridge. 
 
 To this superiority of form and fewness of parts of the main 
 elements is incidental a comparative smallness of exposed sur- 
 face, which is hence more easily and inexpensively protected 
 from corrosion. 
 
 Nl.— Rigidity. 
 
 In this important feature — one of no secondary importance 
 when the subjection of the bridge to railway trains moving at 
 full speed is considered — it surpasses, in virtue of the essential 
 character of the design (alluded to under I. head) all others. 
 A reference to the deflections under live load of the bridge in 
 question, and the Delaware Bridge Company illustrates the fact, 
 for the former, .30 of a foot (in the centre) ; for the latter .356 
 (end of cantilever), to which must be added the deflection of 
 the 200 foot span (.16 of a foot) connecting truss, making the 
 total .517 of a foot, or nearly double the former. The Passaic 
 Company's cantilever furnishes about the same result. 
 
 VII. — The completeness and thoroughness of the design as it 
 is actually presented for your consideration. 
 
 No " modifications " materially affecting the design as now 
 presented have been suggested and none are required. It is 
 not pretended by the designers that all the details have been 
 worked out ; that there might not be, with improvement, some 
 changes made. But what is maintained here is, that such 
 requirements refer rather to filling up of details than to actual 
 modifications. 
 
 VIII. — Economy. 
 
 As this is determinable from the estimate, the cost is about 
 the same as for the three or four least costly competing bridges, 
 the Delaware Bridge Company's bridge included. 
 
 In consideration of the completeness of the design of Clark, 
 Reeves & Co., the superiority of its component parts, and the 
 
32 
 
 manner in which its weight of metal has been calculated, I be- 
 lieve it to be much the least expensive bridge of any. 
 
 Having set forth what I consider the points — and they cover 
 the whole field of inquiry — in which I consider the Clark, 
 Reeves & Co.'s bridge as not only entitled to the award of 
 " best " absolutely, but as the one which should be " adopted 
 for practical construction," I shall briefly allude to the objections 
 offered ; and first, as to 
 
 I. — Anchorage. 
 
 It is a peculiarity of the design that the piers, as they are 
 called, are not under normal conditions, either weight or thrust- 
 bearing. They receive the strains (whether compression or 
 extension) by which a moving load would tend to displace the 
 hinge-point, and they receive, in a large degree, wind strains. 
 The mere fact, that anchorage is necessary to meet these strains, 
 is no more an objection than it is (where equally necessary) 
 in a cantilever or suspension bridge. 
 
 II. — The want of provision by lateral and diagonal bracing 
 for wind strains in the openings for the roadways. 
 
 It is not believed there is any defect here which can not be 
 provided for, and so it is stated in the main report. These mat- 
 ters are not exhibited in the drawing. The designers state that 
 they have been fully considered. Something equivalent is com- 
 mon to all through trusses, and a nearer resemblance is found 
 in the St. Louis bridge. The cross and lateral bracing is neces- 
 sarily interrupted, and substitutes for these members is found 
 in greatly strengthening the main members and in a proper 
 application of braces or brackets. 
 
 It is to be remembered that though the lunettes rise to a 
 height at point of meeting of 80 feet above the floor (90 feet in 
 the second design), the point of attachment of the floor suspend- 
 ers is generally comparatively low, rising to the extreme height 
 only through a short interval near the centre of the bridge ; 
 hence the floor weight (including the total live load) is not in 
 reality borne high. 
 
33 
 
 III. — An objection brought against the design (alluded to in the 
 joint report) is that a large portion in length of the floor is sus- 
 pended and subject by the wind to harmful vibrations. That 
 the measure of this destructive power had not been taken in earlier 
 days of suspension bridge construction is notorious, and the list 
 of English, French and American bridges which have been 
 injured or even destroyed would be great. Even the Menai 
 bridge was thus injured soon after it was built. It was subse- 
 quently re-inforced, and its ordinary roadway and foot passen- 
 ger floor, 5S0 feet long and only 28 feet wide, weighing but 950 
 pounds per foot, and suspended by 800 i-inch square iron rods, 
 varying from 10 to 53 feet in length, has since maintained itself 
 for half a century. The long half spans of the flooring of the 
 Covington and Brooklyn suspension bridges, 800 feet long in 
 the latter case, present greater difficulties. In the case in hand 
 the object is believed to be fully accomplished by the horizontal 
 " wind truss " underneath the floor, having 57 feet depth, by the 
 rigid (latticed) suspenders, and by their overhead cross-bracing. 
 The suspended length is, in one design, but 400, in the other 
 but 480 feet. 
 
 IV. — To the objection of difficulty of erection I was at first dis- 
 posed to give much weight. I am informed, however, by the 
 very responsible designers that the matter has been fully con- 
 sidered, the cost embraced in the estimates, and that they are 
 prepared to undertake to build the bridge for the estimates. 
 
 V. — Finally, I will allude to an objection much insisted upon, 
 that the hinged arch design does not lend itself to furnishing clear 
 head-room as do the others. The second, or alternative tracing, 
 gives the same head-room throughout as the East River Bridge 
 gives ; indeed, it gives more, for the floor holding-down stays 
 of that bridge start 22 feet below the floor at the piers and 
 reach out nearly 200 feet, reducing the 120 feet at the piers to 
 less than 100 feet. But the projectors, in submitting their de- 
 signs, expressed their readiness to put it at any i-equired 
 height. I do not think any raising above the height of the 
 second tracing at all necessary; and, at the same time, I affirm 
 that there is no bridge proposed to us so capable of giving 
 great height for a large central space — a space quite wide 
 
34: 
 
 enough for the free passage of all large vessels (which will 
 avoid close approach to the shores) — as this hinged arch design. 
 You have simply to raise the Jloor fifteen feet to get a clear 
 head room of very nearly 150 feet, of 300 feet width on the first 
 design and 370 ieet width on the second. 
 
 Respectfully submitted, 
 
 J. G. BARNARD, 
 Member of Board of Consulting Engineers. 
 
35 
 
 SUPPLEMENTARY REPORT OF GEN. GILLMORE. 
 
 New Y ORK, February 26, 1877. 
 
 To the Directors, Neiv York and Long Island Bridge Com- 
 pany, New York City : 
 
 Gentlemen : 
 
 In the report of your Board of Consulting Engineers recently 
 submitted, I am on record as having expressed my preference 
 for the three best plans of bridges before them, in the following 
 order, upon the assumption that the plans are to be considered 
 strictly with reference to the specifications and strain-sheets 
 which accompanied them, viz : 
 
 1. The design of Clarke, Reeves & Co. 
 
 2. " the Delaware Bridge Company. 
 
 3. " Edward W. Serrell & Son. 
 
 With certain modifications which suggest themselves, and of 
 which the designs are susceptible, without resorting to any 
 radical change in the character of the structures, my preference 
 was expressed in the following order, viz : 
 
 1. The design of the Delaware Bridge Company. 
 
 2. " Clarke, Reeves & Co. 
 
 3. " Edward W. Serrell & Son. 
 
 It seems proper that I should state, although I do not propose 
 to discuss at any length, the grounds upon which my judgment 
 in the matter was formed, with regard to the two first named 
 designs. 
 
 The design of Clarke, Reeves & Co. is the only one submitted 
 to us that I would be willing to recommend for adoption by 
 your company, as it stands, and without modification. 
 
36 
 
 It possesses, in my judgment, sufficient strength and rigidity, 
 while any tendency to overturn bodily, by the lateral pressure of 
 high winds, appears to be suitably guarded against by the width 
 of the bridge (about 55 feet), and by anchoring the towers to 
 their foundations. Inasmuch, however, as both the centre of 
 gravity and the centre of form are comparatively high, I think 
 the towers should be widened 10 to 12 feet, by spreading them 
 5 to 6 feet on either side. 
 
 I apprehend no undue or dangerous strains from the tension 
 in the towers, caused by a moving load upon the main span, as 
 the horizontal thrust would be amply resisted by the rigid trian- 
 gular system at each of the shore ends, composed of the towers 
 themselves and the lower lenticular trusses. There is, however, 
 an inherent local weakness against wind strains, resulting from 
 the openings left for the roadways, which seems more difficult 
 to guard against in this design than in that of the cantilever 
 presented by the Delaware Bridge Company. It is also more 
 difficult to erect ; but, inasmuch as a responsible and well- 
 known company is willing to undertake its construction and 
 erection for a specified sum, this point possesses no special 
 significance. 
 
 I do not think it safe to assume that a clear height of only 120 
 feet at the towers, will be all that the general government will 
 require at Blackwell's Island. That height was accepted, it is 
 true, for the Brooklyn Bridge, but the decision in that case was 
 not a general one. 
 
 Although it is understood that Clarke, Reeves & Co. are will- 
 ing to raise the bridge at the towers to a height of 130 feet 
 above high water without extra charge, if required to do so, 
 their design does not lend itself, as readily as the cantilever or 
 the suspension plans, to such an increase of height. 
 
 While it may be conceded that the principle of the hinged 
 arch is applicable to longer spans than 750 feet, one of the 
 advantages claimed for it — that of great economy of material — 
 would be more largely realized in shorter than in longer spans. 
 
 By widening the towers, as already suggested, the plan 
 would, in my judgment, be suitable for adoption. 
 
 The design of a cantilever bridge submitted by the Delaware 
 Bridge Company exhibits an excellent application of the prin- 
 ciple involved in that method of bridge construction. The 
 
37 
 
 centre of gravity is kept comparatively low (always a consider- 
 ation of great weight) by making all the mainstays parallel to 
 each other, and the same with the backstays. The vertical 
 pressures are therefore not accumulated at the top of the towers. 
 But the bridge is, in my judgment, too narrow for entire security 
 against wind pressure, the width of the towers at the base, 
 for a single track railroad being only 49 feet over all, or about 
 46 feet between the centres of the outer posts. The whole 
 system — bridges and high trestles — appears to be deficient in 
 lateral stability. By increasing the width of the towers suffi- 
 ciently to remove this serious objection, making them say 68 or 
 70 feet wide at the base for a single track railway, and keeping 
 the loot-paths on the same level with the roadways, with other 
 changes of detail naturally resulting from these, the design would, 
 in my judgment, be preferable to that of Clarke, Reeves & Co. 
 In the design for a single track road as submitted, Clarke, 
 Reeves & Co.'s two bridges cost $55,599 more, and their whole 
 project, inehiding approaches, $11,041 less, than in that of the 
 Delaware Bridge Company. The modifications recommended 
 in the two cases would make the difference in total cost still 
 greater against the Delaware Bridge Company ; and, as you 
 would have a good bridge in either case, you would be justified 
 in giving due weight to the question of cost. 
 
 A cross section of the modified towers for the cantilever design 
 might be somewhat like the sketch 
 on the margin, in which a is a 
 carriageway and foot-path, b the 
 same, and c a single track railway. 
 When a second track is added it 
 would be placed at d, and the two 
 inclined tension members moved to e. 
 By this method, or something equi- 
 valent to it, the weakness against 
 wind pressure caused by the roadway 
 openings would be entirely obviated. 
 
 I think highly of the plan for 
 a suspended girder prepared by 
 Edward VV. Serrell & Son, but as I 
 am the only member of the Board 
 whose opinion of its merits places it among the three best 
 
 mm. 
 
38 
 
 designs submitted for competition, it seems unnecessary for 
 me to discuss its features. It is the least costly project before 
 the Board, and would most likely remain so, even after certain 
 modifications of details, which appear to me to be necessary, 
 shall have been provided for. 
 
 Very respectfully, your obedient servant, 
 
 Q. A. GILLMORE. 
 
39 
 
 ADDITIONAL SURVEYS AND SPECIFICATIONS. 
 
 [Appendix No. i.] 
 SPECIFICATIONS FOR DESIGNS 
 
 For a Bridge from the City of New York to Long Island, Crossing over Blackwell's 
 
 Island. 
 
 The designs shall consist of : 
 
 i st. An approach on the New York side 4,580 feet long, of which 
 about 1,000 feet shall be in tunnel, extending from a connection with 
 the tracks of the Harlem Railroad on 4th Avenue, in the vicinity of 
 73d Street, to the crossing of Lexington Avenue ; whence shall begin 
 an iron structure, curving to the centre of the blocks between 76th and 
 77th Streets, and continuing eastward through the same to the west 
 bank of the western channel of the East River. 
 
 2d. Of a single span across the said west channel 734 feet long in 
 the clear. 
 
 3d. Of an iron structure across Blackwell's Island, about 700 feet 
 long. 
 
 4th. Of a single span across the eastern channel of the said East 
 River, 618 feet long in the clear. 
 
 5th. Of an approach on the Long Island side, 3,900 feet long, ex- 
 tending to the high ground. 
 
 The total length of said bridge is thus 10,532 feet approximately. 
 
 Spans of 100 feet in the clear shall be provided across the 8 Avenues 
 shown on the profile. The other spans in the approaches and over 
 Blackwell's Island may be such as the respective designers shall deem 
 most economical. 
 
 There shall be main approaches for carriages ; and in addition 
 thereto, there shall be two return auxiliary approaches for carriages, 
 ascending with gradients of 4 feet per 100. The return approach on 
 the New York side from the vicinity of Avenue A, and that on the 
 
40 
 
 Long Island side from the vicin : ty cf Vernon Avenue, to an intersection 
 of the main approaches, as shown on the profile. 
 
 There shall also be two double elevators for foot passengers, with 
 the necessiry steam power ; one on the New York and the other on 
 the Long Island shore, at or near the end of the bng spans, with a 
 capacity of 30 foot passengers per lilt platform. 
 
 General Disposition. 
 The bridge shall be designed to accommodate : 
 
 A. A single track railway extending over its entire length, and occu- 
 pying a width of 14 feet. To be so arranged that a second track can 
 be added hereafter without materially changing the general arrange- 
 ment of parts or the loads imposed upon them, or interfering with the 
 current use of the bridge. A preference will be given to those designs 
 which make the future addition of the second track an integral part of 
 the plan. 
 
 B. Two roadways for carriages, extending from 3d Avenue to the 
 high ground on the Long Island side, each 10 feet wide, which shall 
 preferably be placed side by side, and which may be placed on the 
 ground beneath the trestle carrying the railway from 3d Avenue to 
 2d Avenue, on the New York side, and from the foot of the grade (as 
 shown in the profile), to the high ground on the Long Island side. 
 The return approaches from Avenue A, and from Vernon Avenue, 
 may be placed either side by side, or separately on each side ; but 
 should on the Long Island side preferably, and peremptorily on the 
 New York side, be arranged within the line of the main trestle legs, 
 so that the same shall occupy as little width as possible on the ground. 
 The returns, where they join the main approaches, shall be sufficiently 
 wide to admit of an easy turn for carriages, and shall present a level 
 grade for 60 feet. 
 
 C. Two sidewalks, each 5 feet wide, extending either alongside or 
 overhead of the main carriageways or the railway, but not along the 
 auxiliary return approaches. 
 
 Gradients. 
 The gradients shall be as follows : 
 
 On the Railway. — The maximum grade shall be 2-^,,- feet per 100, 
 or 116 feet per mile, on the approaches on both the New York and 
 Long Island sides, and level across Blackwell's Island. The end sup- 
 ports of the long spans shall be on the san e level, but there may be 
 such camber in these spans, not exceeding a gradient of 2f$ feet per 
 100, as the designers shall prefer. 
 
41 
 
 In each of the long spans, the lowest part of the bridge shall be 135 
 feet in the clear above mean high tide, at the middle of the river. 
 
 On the Roadway. — Across the long spans, and across Blackwell's 
 Island, the roadways for carriages shall be on the same floor as the 
 railway, thus requiring a total available width of 34 feet. On both the 
 direct and return approaches the gradients shall be 4 feet per 100 feet, 
 with level resting places as shown upon the profile. 
 
 A clear headroom of 16 feet shall be allowed in all'instances for the 
 roadway, and there shall be a clear headway of 20 feet above the rail- 
 way. 
 
 On the Sidewalks. — The grades on the sidewalks may be ar- 
 ranged as most convenient to the designers. In case of a relative 
 change of level with reference to the roadway, it will be preferred that 
 they should be ramped to an inclination not exceeding 1 in 12, rather 
 than to resort to staircases. 
 
 Foundations and Masonry. 
 
 Wherever practical, the design shall provide for carrying the founda- 
 tions to the rock, the approximate line of which is shown upon the 
 profile. The masonry provided for shall, in all cases, be first-class, 
 and laid in hydraulic cement mortar. A gross sum of $100,000 shall 
 be allowed by each designer in his estimates, to cover the cost of the 
 coffer-dams required to lay the foundations for the abutments. These 
 latter shall consist of masonry from the bed rock to a height of at least 
 10 feet above mean high water ; above this they may be of masonry, 
 or they may be towers of cast-iron, wrought-iron, or mild steel, as 
 preferred by the designers. 
 
 All masonry shall be so designed that the distributed weight, in- 
 cluding that of the loaded superstructure, shall nowhere produce pres- 
 sures exceeding 180 pounds to the square inch, and the foundation 
 castings of iron columns shall be proportioned so as to limit the strain 
 upon their surface of contact with the pedestal stone to 300 pounds 
 per square inch. 
 
 Iron or steel used in the towers shall be proportioned in accordance 
 with the specifications hereinafter given for their employment in the 
 other parts of the bridge. 
 
 Moving Loads. 
 
 In addition to the weight of the structure itself, and of its floors and 
 appurtenances, the following moving loads shall be provided for : 
 
 1st. For the Railway. — Of two 45-ton Mogul locomotives coupled, 
 occupying each, with its tender, a length of 48 feet, and with 75,000 
 
42 
 
 pounds on a driving wheel base of 1 5 feet, followed by a train of loaded 
 freight cars weighing 1.500 pounds per lineal foot of track. The 
 weights imposed by this load upon different lengths of .track will be as 
 follows : 
 
 700 to 800 feet 1,620 pounds per lineal foot. 
 
 oco " 700 " 1 640 " " " " 
 
 500 " 600 " 1 670 ' 
 
 400 " 500 '• 1,710 
 
 300 " 400 " 1,780 
 
 200 ■' 300 " 1 920 " '■ " " 
 
 150 " 200 " 2,040 " " " •' 
 
 100 " 150 " 2.34° " " " " 
 
 80 " 100 " 2,500 " " " " 
 
 60 " 80 " 2,700 " " " " 
 
 40 " 60 " 3,000 " " " " 
 
 25 " 40 " 3 3°° 
 
 15 " 25 " 4,000 
 
 15 feet or less 5,000 
 
 In computing the loads for distances very near to the above dividing 
 points, varying weights per foot shall be used, so that the aggregate 
 moving load shall never be less than if computed for a shorter dis- 
 tance at the next higher rate per foot. 
 
 The strains are to be calculated for such position of the driving 
 wheels and loads as will produce the maximum effect upon the differ- 
 ent members. 
 
 2d. For the Roadways. — A moving load shall be allowed of 75 
 pounds per square foot, or of 750 per lineal foot upon each roadway, 
 10 feet wide, for all spans up to 100 feet; for the long spans across the 
 river, the moving load shall be assumed at 50 pounds per square foot, 
 or 500 per lineal foot of roadway, 10 feet wide, 
 
 The floor beams and joists shall, however, be calculated for a local 
 load of 100 pounds per square t foot. The floor of the roadway shall 
 consist of oak plank 3 inches thick, with suitable guards, and the main 
 floor beams shall be of wrought-iron. 
 
 3d. For the Sidewalks. — A moving load shall be assumed of 75 
 pounds to the square foot, or of 375 pounds per lineal foot upon each. 
 The floor shall be laid with 2-inch Southern pine, surfaced, and with 
 suitable railing and guards. 
 
 The points of application of these various moving loads on the tres- 
 tles are indicated by the gradients on the profile. The designs shall 
 show how it is proposed to provide for the second railway track. 
 
 Strains Allowed. 
 
 In every case the plans shall provide for the maximum strain which 
 can by any possibility come upon each part of the structure. 
 
 All its parts shall be so designed that the strains coming upon them 
 
43 
 
 can be accurately calculated by the usual formulae recognized as cor- 
 rect by bridge engineers. 
 
 The strains arising from the wind shall be calculated upon two sup- 
 positions : ist. That the various parts of the bridge are fully loaded 
 with the assumed rolling loads, and that the wind exerts a pressure of 
 24 pounds per square foot, at right angles to the bridge line, upon the 
 exposed surface of the structure, and of a train of cars 10 feet high 
 standing thereon. 2d. That the wind exerts a pressure of 40 pounds 
 per square foot at right angles, upon the exposed surface of the un- 
 loaded bridge. 
 
 For both of these supposed cases, the factor of safety shall be 3, and 
 the base of the trestles shall be spread so wide as to counteract all 
 tendency to overturning. 
 
 Changes of temperature to the amount of 150 degrees shall be pro- 
 vided for, and the parts so designed as to admit of expansion and 
 contraction, and to provide for the strains resulting therefrom. 
 
 The various spans shall be so designed that their deflection, under 
 the assumed maximum moving load and strains, shall not exceed 
 the Tiou part of their length. The side deflection or motion from the 
 assumed wind effects shall be limited to the tuu part of the spans, and 
 in both cases the parts shall be so proportioned as to return to their 
 original line after the load is withdrawn. 
 
 Tension Members. — f or the weight of the structure, for the effects 
 of the wind and of changes of temperature, a factor of safety of three 
 (3) shall be adopted, while for the rolling or live load the factor of 
 safety shall be eight (8). 
 
 The amount of material in the several parts of the structure shall be 
 proportioned for these combined factors of safety ; that is to say, that if 
 it is desired to use in a part strained in tension, double rolled refined 
 iron, with an ultimate breaking strength of 54,000 pounds per square 
 inch, in long specimens, this may be strained up to 18,000 pounds per 
 square inch if it carries only dead load, or up to 6,750 pounds per 
 square inch if only exposed to live load. 
 
 The size or sectional area of the various members in tension shall, 
 therefore, be ascertained by adding to the number of inches required to 
 carry the dead load at the rate of 18,000 pounds, the number of inches 
 required to carry the live load, at the rate of 6750 pounds per square 
 inch.* 
 
 In proportioning the parts for the combined dead and live loads, re- 
 gard shall be had to the frequency with which the estimated load is 
 
 *Note. — The average effect of these combined strains will be as follows : 
 
 ist. When dead load = 2 live loads — an average strain of 14,250 pounds per square inch. 
 
 *d. When dead load = live load — an average strain of 12,375 pounds per inch. 
 
 3d. When dead load - live load — an average strain of 10,500 pounds per square inch 
 
44 
 
 like.y to be imposed in working, and a greater proportional strength 
 shall be allowed for parts likely to be strained to the calculated intens- 
 ity by every passing train or carriage, than for those upon which the 
 assumed load can only come occasionally ; thus, iron floor-beams and 
 floor-hangers shall only be strained up to 6,750 pounds per square inch, 
 while chord-bars may be strained up to the full average obtained from 
 the combined dead and live loads. No part less than 5 feet long shall 
 be strained in tension more than 7,000 pounds to the inch. 
 
 All tensile members shall be preferably of refined wrought-iron, of 
 soft, fibrous texture, rolled twice from the puddle-bar, with an ultimate 
 breaking strength of at least 50,000 pounds per square inch in long 
 specimens, and an elastic limit of not less than 26,000 pounds per 
 square inch. It shall elongate at least fifteen per cent before break- 
 ing, and the elastic limit shall be understood to be the point at which 
 the elongation produced by the strain ceases to increase in the same 
 proportion as the strain, being the point at which the bar shows the 
 first signs of a considerable permanent set. 
 
 If designers propose to use steel in tension, they will be required to 
 furnish evidence of its adaptability for this purpose, both as regards its 
 resistance to tensile strains, to impacts and repeated vibrations, as well 
 as to the absolute certainty of uniformity in its production, as ascer- 
 tained by "experiment. 
 
 Compression Members may be of cast or wrought-iron, or of mild 
 steel. 
 
 For wrought-iron, when the length of square end pillars does not ex- 
 ceed twenty-four times the least radius of gyration, the part may be 
 subjected to a strain of 8,000 pounds to the square inch. 
 
 When the member has a greater proportional length, its size, if of 
 wrought-iron, shall be determined by Gordon's formula for square end 
 pillars, in the following modified form. 
 
 40,000 
 
 F— 
 
 l 2 
 
 T + ■ 
 
 40,000 r a 
 
 In which P denotes the ultimate strength per square inch of section, / 
 the length, and r the least " radius of gyration " of cross section, 
 
 For this ultimate strength a factor of safety shall be used, of 3 for 
 the dead load, and of 6 for the live load, or the equivalent dead load of 
 both combined shall be arrived at by the formula : 
 
 3 dead load + 6 live load 
 
 = equivalent dead load. 
 
 3 
 
 For which the factor of safety shall be 3. From the results thus ob- 
 tained, twenty (20) per cent shall be deducted for each pin-joint in a 
 strut or post. 
 
45 
 
 A preference will be had for those shapes, in compression members, 
 which are most accessible for inspection, cleaning and painting. 
 
 Designers who propose to employ steel in compression will be required 
 to furnish evidence based upon reliable experiments, that the strains 
 which they propose to impose upon it are relatively as safe as those 
 herein provided for wrought-iron, and of the absolute certainty of uni- 
 formity in its strength, as ascertained by experiment. 
 
 In the absence of such proof, strains allowed upon steel shall not be 
 more than 20 per cent in excess of those which would be allowed upon 
 wrought-iron. 
 
 Cast-iron shall not be used for the principal members of the trussed 
 spans. It shall be proportioned for compression by Rankine's modifi- 
 cation of Gordon's formula,* with a factor of safety of 4 for the dead 
 load, and of 8 for the live load. No cast-iron part shall be designed to 
 be less than }i of an inch thick, nor shall it be used where it is liable to 
 receive a transverse or a tensile strain, or where there is any probability 
 that the shape of the parts will cause imperfections in the castings, 
 such as floating of cores, blow- holes, &c. 
 
 Strain sheets are to be furnished for the examination of the engineers, 
 showing separately the strains due to the dead and to the live load, as 
 well as those due to the wind, and to changes of temperature. 
 
 Estimates of weights and cost shall be required in sufficient detail to 
 admit of their accuracy being tested, showing both the quantities of each 
 kind of materials, and the prices at which the designers propose to fur- 
 nish them erected in place. 
 
 Details of Construction. 
 
 The erection of the structure shall be so designed as not to interrupt 
 the navigation of the East River, or the use of any public road, street 
 or avenue. 
 
 A preference will be given to those designs which, at an equal cost, 
 occupy the least width on the ground on the New York side, so as to 
 reduce the cost of land damages. 
 
 The designs shall be based upon the use of the best quality of 
 materials. 
 
 Cast-iron may be used in towers, bed-plates, pedestals and washers. 
 It shall be of the best quality of soft gray iron. 
 
 A preference will be had for upset ends in all tension members. 
 Where welds are proposed to be used by the designeis, a statement will 
 
 80,000 
 
 *NOTE. — P= 
 
 I + 
 
 3200 r' 2 
 
46 
 
 be required of the mode in which it is proposed to make these welds, 
 and to prove their workmanship. 
 
 Rivet-holes in wrought-iron members may be punched, but an accu- 
 rate fit will be required. All other holes shall be drilled. The enlarged 
 ends of eye-bars shall be of such form that the cross section of metal 
 in the head, exclusive of the pin-hole, shall be fifty per cent in excess of 
 that in the body of the bar. The pin-holes shall be bored so that the 
 bars shall not vary in length more than 1-64 of an inch. 
 
 Pins shall be of wrought-iron, and shall be turned to fit the pin-hole 
 within 1-32 of an inch. They shall be of such section that the shearing 
 strain shall not exceed 7,000 pounds to the square inch, and their diame- 
 ter shall not be less than two-thirds of the largest dimension of any ten- 
 sion member attaching to them. It will be preferred that all the 
 various members attaching to pins shall be arranged as compactly 
 as possible. 
 
 All screw connections shall be enlarged to such diameter as to pro- 
 vide for an excess of material of ten per cent after deducting the depth 
 of the screw thread, with nuts of equivalent strength, and shall have at 
 least 3 threads projecting beyond the nuts. 
 
 All details of manufactured bars shall be of such sufficient strength, 
 that, upon being tested, fracture shall sooner occur in the body of the 
 bar than in any of its connection details. 
 
 No wrought-iron cr steel shall be used less than of an inch thick, 
 except in places where both sides are always accessible for cleaning 
 and painting, or where the entire surface is bedded in some non-corro- 
 sive material. 
 
 Designs may provide for a wooden trestle on the Long Island side, as 
 far as the same may be more economical than iron ; so arranged as to 
 admit of the timber being renewed piece-meal as it decays. 
 
 0. CHANUTE, ) 
 
 I G. BARNARD, > Consultitig Engineers. 
 Q. A. GILLMORE, ) 
 
47 
 
 [Appendix No. 3.] 
 
 New York, May 1, 1876. 
 
 M 
 
 The undersigned, aboard of consulting engineers, appointed by the 
 New York and Long Island Bridge Company to select a plan for its 
 proposed bridge crossing the East River at Blackwell's Island, will re- 
 ceive designs, estimates of cost, and proposals for construction, until 
 the 1 st day of July, 1876, for a bridge and its approaches from the City 
 of New York, in the vicinity of 76th street, to Long Island. 
 
 This will require two spans across the East River, 135 feet above 
 tide ; the one 734 feet long, and the other 618 feet long, in the clear ; 
 together with approaches and an intermediate structure across Black- 
 well's Island over 100 feet high. 
 
 We herewith inclose a profile and specifications, and will be pleased 
 to receive designs, estimates, and a proposal for building, from you. 
 
 Parties who have already furnished designs to the Company are re- 
 quested to revise them so as to conform to the present specifications, 
 and to furnish new estimates of cost and proposals for construction. 
 
 The adoption of a plan shall not, however, be understood as binding 
 the Company to enter into an immediate contract for the prosecution 
 of the work, and the right is reserved to reject any or all proposals or 
 plans. 
 
 It is expected that the designs received in answer to this circular 
 shall be exhibited at the Centennial Exhibition, unless otherwise re- 
 quested by the designers. 
 
 Plans and communications may be sent to the undersigned either at 
 their respective offices, or at the office of the Company in the German 
 Savings Bank Building, corner of 14th Street and 4th Avenue. 
 
 O. CHANUTE, Erie Railway, New York. 
 
 J. G. BARNARD, Army Building, New York. 
 
 Q. A. GILLMORE, Army Building, New York. 
 
 Consulting Engineers, 
 
48 
 
 [Appendix No. 4.] 
 
 New York, August 11. 1876. 
 
 M 
 
 At a regular meeting of the Board of Directors of the New York 
 and Long Island Bridge Company, held on the 9th of August, 1876, it 
 was resolved : 
 
 " That the time for receiving plans be extended to December i, 1876, and that 
 the engineers give notice, with a view of bringing out the best talent in the coun- 
 try, that this company will pay to the party whose plan shall be adopted as the 
 best, the sum of one thousand dollars ; for the second best, five hundred dollars ; 
 and for the third, two hundred and fifty dollars. Plans so paid for to be the prop- 
 erty of the company. The awards to be made by this Board, under advisement of 
 the consulting engineers." 
 
 Please advise us at your earliest convenience whether you shall com- 
 pete for the above premiums, under the general requirements of our 
 circular and specifications of May 1st. 
 
 O. CHANUTE, ) 
 
 J. G. BARNARD. \ Consulting Engineers. 
 O. A. GILLMORE, ) 
 
IRE FliOrOSED 
 
 BRIDGE AF 
 ISLAJS'D. 
 
 BLA CK WELL'S 
 
 DISSATISFACTION WITH TnK AWARD OF PRIZES FOR 
 THE PLANS OF THE STRUCTURE. 
 
 As the construction of this bridge will gofartovrard 
 soling the question of fiuding cheap suburban 
 homes wit hin easy reach of the business portion of 
 Now- York, everything concerning it must possess 
 great interest to citizens. The Tribune pub- 
 lished a few weeks ago a diagram of the plan to 
 which the directors of the company had awarded the 
 first premium of $1,000, and also a synopsis of the 
 report of the consulting engineers. It has since 
 been ascertained that much dissatisfaction exists at 
 this award, which was given to the plan of the 
 Delaware Bridge Co., designed by Mr. McDonald, 
 C. E. The following is the substance of the resolu- 
 tion of the board of directors inviting the submis- 
 sion of plans : 
 
 Resolved, * * * -with a view of bringing out the beet 
 talent in tiie country, that this company will pay to the 
 party whose plan shall be adopted as the beet the sura 
 of $1,000; for tae second best, $500. and for the third, 
 $250. * * * Awards to be made by tnis board, under 
 advisement of the consulting engineers. 
 
 The commission of consulting engineers to whom 
 the plans were referred consisted of Gens. J. G. Bar- 
 nard and Q. A. Gill more, United States Engineers, 
 and Mr. O. Chanute, C. E. These gentlemen made a 
 joint report, iu which, referring to their individual 
 views as to the merits of the various plans, they 
 make the following statement : 
 
 Two out of the three pronounce the nlan of Clarke, 
 Reeves <fe Co. the best, if taken absolutely" without modi- 
 fication, and entirely with reference to its strain sheets 
 and specifications ; while two out of three pronounce tne 
 Delaware Bridge Company's plan "best" to recommend 
 to be adopted for practical construction by your com- 
 pany, with such improvements and modifications as 
 suggest themselves. 
 
 The resolution of the Board of Directors clearly 
 indicated that the first prize would be awarded to 
 the best plan submitted, aud not to a second-rate 
 one which the consulting engineers, after careful 
 examination of all the others, might improve by their 
 own suggestions, and thus make it virtually a plan 
 of the judges "themselves. There would certainly 
 be only little inducement to present a care- 
 fully matured plan, which would probably 
 cost nearly or quite as much as the highest 
 premium offered, if the awards were not to be made 
 on the merits of it, as submitted. Messrs. Barnard 
 and Gillmoro made separate reports in addition to 
 the joint one made by the three consulting en- 
 gineers. Gen. Barnard strongly urged the plan of 
 Clarice, Reeves & Co. as greatly superior to all the 
 others, modified or unmodified ; while Gen. Gillmore 
 says of it, " The design of Clarke, Beeves & Co. is 
 the only one submitted to us that 1 would be willing 
 to recommend for adoption by your company as it 
 stands, and without modification." The award of 
 the first premium to the Delaware Bridge Company 
 by the Directors, in view of their resolution inviting 
 plans, and taken in connection with the views ex- 
 
 pressed by two of the three consulting engineers, 
 sreated much surprise at the time, and a subsequent 
 development of facts has caused this feeling to grow 
 into one of decided dissatisfaction among some of 
 those who desire the construction of a first-class 
 structure. 
 
 When the commission of engineers waited in per- 
 son upon the Board of Directors with their report 
 they were told that no action would be taken on it 
 until it was printed, and that when this was done 
 they would be asked to come before the board for 
 advisement, as provided, in the resolution above 
 quoted. When the report was printed, however, a 
 special meeting of the board was held, at which a 
 bare quorum was present. Gens. Barnard aud Gill- 
 more were not notified to be present, but Mr. 
 I Chanute was on hand, and without any refcrenco of 
 , this important subiect to a committee, without cou- 
 ' suiting any engineer except Mr. Chanute, who advo- 
 cated the Delaware Bridge Company's plan, and 
 without waiting for the regular monthly meeting, 
 the directors present awarded the first premium to 
 that company, the second one to Clarke, Reeves <feCo., 
 and the third one to Henry Flad & Co., and, 
 it is understood, by resolution adopted the plan 
 of the Delaware Bridge Company as the one on 
 ! which the bridge should be constructed. 
 
 There is little or no difference in the cost of the 
 plans proposed by the Delaware Bridge Company 
 and that of Clarke, Reeves & Co. The first is 
 known as a " cantilever," with an intermediate 
 truss 200 feet long in the middle of the span, which 
 truss is supported on the two ends of the canti-. 
 levers. Clarke, Reeves & Co. propose an arch 
 which springs from the natural rock foundation on 
 the main shore, with a single span of 1,030 feet, to 
 the natural rock on Blackweli's Island. The arch 
 is ptirabolic in form, and for boldness and beauty 
 of design surpasses anything of the kind in the 
 world. The center of the arch is about 200 feet 
 high above the river. Iron towers rising from the 
 water's edge on each shore, with a clear opening of 
 734 feet between them, are secured to the arch and 
 virtually reduce its span to this width, as the por- 
 tions of the arch from the tops of these towers to 
 the rock and the towers themselves constitute 
 in reality the abutments of the arch proper. 
 If the selection of a design for the bridge only con- 
 cerned the competitors for the premiums it would 
 be a matter of small moment, but as the public are 
 deeply interested in the early election of a thor- 
 oughly substantial structure, they have a right to 
 criticise the informal and hasty action of the direc- 
 tors in a decision which, by inviting capitalists to 
 invest their money upon a plan as yet not only un- 
 tried but condemned in strong language by Gen. 
 Barnard in his supplementary report, delays the 
 time when the shores of New-York and Long Island 
 will be connected by a steam railway bridge, and 
 rapid transit be obtained to the cheap and sparsely 
 
 \ settled section adjacent to the other end of the pro- 
 posed structur e.