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Lorsque le document est trop grand pour dtre reproduit en un seul cliche. 11 est fiimA d partir de I'angle supArieur gauche, de gauche it drolte, et de haut en bas, en prenant le nombre d'images n^cessalre. Les diagrammes suivants iliufttrent ia mAthode. 1 2 3 1 2 3 4 5 6 MB o, } I c '•7 f^;-'" Blade. ->;^i:^L-'- REPORT ^•-**-,.^ -/^i OK A RAILWAY SUSPENSION BRIDGE, PROPOSED FOR CROSSING THE ST. LAWRENCE RIVER AT QVEBEO MADE TO HIS WORSHIP THE MAYOR AND THE BT EOWABD WILLIAM 8S&BI1LL, ENGINEER. QUEBEC: PHINTSU BV AtJ»lJ8TI]V COTJt: & Co. Cljy PRINTERS. r 1853. I I ; I i- i I TO HIS WORSHIP THE MITOB AND THB CITY COUNCIL OF QUEBEC Agreeably to youiT resolution ofah October last, requesting me to repair to Quebec to examine the proposed sites, for a Bridge to cross the Saint-Lawrence River, at or near your City and also desiring me, if the undertaking should be deemed practicable, to submit plans, specifications and estimates for the same, I have the honor to state, as already communica- ted in my letter of'kth November last, which gave an account of the progress of the field operations to that date, that 1 first surveyed a site near the River Cfiaudidre, about four miles from the mouth of Cape Rouge Creek. After which a line from the terrace of the old Palace of Saint-Louis to Point-Levy, was explored, and another from a few hundred yards above Cape Diamond to the opposite shore was inspected. Careful reconnaissances of the whole river and harbour contiguous to the City and on the lines designa *ed, sections of the banks, and soundings in the river, with instrumental measurements of distances, were made. The result of these operations, is a conviction in my mind of the entire practicability of the undertaking. That is, I see no insurmountable engeneering difficulties in the case ; — IV — no reason/or thinking^ that a substantial Bridge, iuitabh for railway and other travel^ cannot he built here ; and thai too, within the means at your command, I accordingly herewith respectfully submit the accompany- ing Maps j Plans and Report. ' i / l\ 1 - V V i'V ': .t .'-I V-'!i ., ' >.viVa ■ ■ * ■ REPORT OF THE DIFFERENT SITES PROPOSED. The proposed crossing near the Chaudiere River, desi- gnated as N*' 1, on the general outline Map A., herewith submitted, will require a Bridge with an extreme length equal to three thousand four hundred feet. The banks here are high and rocky ; on the North side, the top is one hundred and sixty-iive feet, and on the South, it is one hundred and forty feet above extreme high water. The lines of the shores arc two thousand four hundred and forty feet apart. The beaches slope gradually; they are rocky, and at low water, the river is one thousand eight hundred and fifty feet wide. In twelve feet deep at low water, on each side, the dis- tance is reduced to one thousand six hundred and twenty- five feet. Beyond this the water becomes suddenly very deep, towards the middle, until it reaches upwards of one hundred and eighty feet. The currents set in both directions accordingly as the tide is rising or falling. There are two tides every twenty four hours and the average rise is about twenty feet. At the site marked No. 2, on the Map, the distance between the Terrace of the Old Palace Saint-Louis and the top of the bank at Point Levy is found to be four thousand six hundred feet, and twelve feet deep at low water on either side, would be two thousand nine hundred and eighty-seven feet apart. — — Here the slopes of the beach arc less gradual than dt site N®. 1, and very deep water is found all across the river. At five hundred feet from low water mark on the North Side, it is forty-five feet deep ; at a corresponding distance on the south side, it is one hundred and twenty six feet deep. In the middle of the river, which is nearly the deepest part, it is about one hundred and seventy feet deep. All these soundings are reduced to low water level. The precise lenijth of the line N^. 3, was not determined, but it is known to be several hundred feet more than No. 2. The soundings, etc., upon it were undertaken, at the ins« tance of one of the City Council, who believed very shoal water would be found for many hundreds of feet out on either side. ■'.-.. ■ Unfortunately, however, this was not the case and nothing was observed to warrant a comparison between its, and the other two proposed sites. GENERAL COMPARISON BETWEiiN PROPOSED SITES. The very considerable disparate, in the cost of construct- ing at the proposed sites, would leave but little room for ar- gument in favour of the one from the Palace Saint-Louis, to Point-Levy if the Bridge was the only question to be considered ; as however the province of the Bridge, when built, will be to connect the northerly with the southerly side of the River Saint-Lawrence, at Quebect it would not be abeying its legitimate ends, if built at the upper site, unless a suitable mean was at hand to connect it with the City. On Map A. a line for a proposed railway, is marked from the site N*. 1, to Saint-John's Gate, with a branch to the Lower Town. This Railway will be six and one quarter miles in length, to Saint-John*8 Gate. On this route the grades will not exceed fifty feet per mile, which is less than the maximum grade of the Quebec and Richmond Railway, while the curvatures arc greater in radius than the minimum of the best constructed Rail- ways. By it all the business going to the Southern Shore of the River, could be, for passengers brought within less than fifteen minutes distance, in time; and for freight and heavy articles less than three quarters of an hour. The connection with any great trunk line of Railway, to Halifax or any part of the Lower Provinces, must neces sarily come to the river in such a way as to admit of an easy junction. Major Robinsons route, coming from Halifax on the line of the second concession, can be as easily if not more easily connected with the crossing of the river at this site than at any other. Greater facilities exist at this site for connecting with the Richmond Railway, than at any other point of crossing that could be occupied by a Bridge. At the site N**. 2, it would be necessary for the Bridge to be at least thirty five feet higher ^ than at N*'. 1, as the lar- gest class " men of war" are frequently in the Harbour, while, if I am correctly informed, they have never been up the river beyond Woolf s Cove, since the country has been in the British dominions. In case of war, operations, in all probability, upon the wa- ters above Quebec, would be carried on by steamers, as ves- sels of more than 600 tons burthen could not pass through Lake St. Peter (M. Culloughs, Geography). Another advantage in favor of the upper site is the facility with which it can be connected with the shipping — 8 — and the commercial part of the City, in (ho Lower-Town, by means of the hranch from the proposed Railway. This connection if made from Palace Saint-Louis terrace, would require four miles of yradienU^ to descend to the same level, at the proposed maximum grades of the Halifax and the Richmond Railways. In view, then, of the many and very decided advantages in favor of the site N*'. 1, or that near the Cliaudicrc River, and the fact that there is nothing of a general puhlic nature for the Bridge to perform, which it cannot do, ns well at the upper as the lower site, I deem it to the interest of the City to recommend to you in the most unequivocal manner^ that the bridge should be constructed at the site designated as No. L I have therefore prepared drawings in detail of the propo- sed work ; and at the same time submit an outline of what would be necessary at the Lower Site N*. 2, with a rough e!«tiraate of the cost of the same, in order that you may com- plete the comparisons yourselves. OF THE PLAN rROrOSED. In presenting the accompanying plans for your adoption I am aware that, in all probability, opposition arising from long standing prejudices, will have to be met with and com- batted, as at this moment, the opinion of the scientific world is divided on the matter at issue. I trust however that the facts here adduced will be sufficient to entitle the project to consideration, if not to settle the question. The plan proposed is usually known as the teire Suspen- sion Bridge' It consists of two massive towers of masonry, built in the river in twelve Ipet deep of water at average low tide. These towers will be in total height from their base, abou ihree hundred and thirty feet ; they will be fifty two -by one tn of I tmv^ — 9 — hundred jiuil thirty •seven feet square at the base and will battnr rcfj^ulnrly upwards. Tliey will bo sixteen hundred and ten feet apart at their centres. It will be observed that the bridge will not cross quite at right angles to the river: this is done on account of the posi- tion of the shoalost water near the shores. The towers are however in the line of the currents. The towers being so small at their base compared with the width of the river, will produce little or no effect on it. On the banks, suitable abutments of masonry of proper proportions, will be erected as ^presented, forming revet- ments for tlic embankments. The roadway at the abutments is to be one hundred and sixty-two feet above extreme high water, and will rise to the centre of the bridge eight feet. The height at the central will therefore be one hundred and seventy feet above high water. The roadway will consist of two carriage ways, each ten and one half feet wide in the clear, and a railway track of such width or gauge as to match the railways which may connect with it. The space for it is eleven feet in the clear. The entire width of the roadway is .0 be thirty-two feet in the clear inside the parapets. All the parts forming the roadway and parapets are to be of oak. The roadway for common travel is to be on either side of the railway separated from it by a suitable railing as re- presented. The whole is to be supported by beams four feet apart at their centres. These beams are to be twelve by fifteen inches section ; they are to be braced underneath so B — 10 — as to stiffen the bridge transversely by a king post and iron tension bars. The . 2, and so proportioned that the weight which comes upon them from the cables shall be transmitted over the surface of the bare. So far QS the examinations on the ground developped the formation of the bed of the river, it appeared to be com- pact rock covered with a light coating of gravel and largish boulders. F >m the nature of the rock, which is slate inters- perced with lime stone, fissures of any very considera. bio magnitude are not likely to be met with ; on the contrary the bed of the river is most likely to be very solid and gene- rally an even plane at the sites for the towers, sloping tow- ards the middle of the river. The rise of the tide is on an average twenty feet, and the foundations being set in twelve feel of water at low tide, it becomes an undertaking of no ordinary magnitude to place foundations securely which are intended to sustain the enor- mous weights which these are to carry. ■ Various methods have been employed with more or less success in similar undertakings in England, France and the United States, and perhaps that which is most highly approved of is the construction of coffer-dams. In England this method was for many years the only plan used, recently however others have been employed. When rock is met with near the surface of the bed in deep water, a difficulty almost insurmountable presents itself to the construction of ordinary coflfer-dams, as there is little or no hold for the piling. Owing to the very great pressure the case of the tow- ers have to sustain, the Caisson plan so successfully used by the French and in the United States, is here objec* tionable. — 20 — It is a matter of every great consequence to have the masonry rest on the solid rock if possible. With a view therefore to bring about these results, that is to construct by means of a coflfer-dam, which shall not be subjected to the perils of a slight hold in the uncertain lands on the top of the rocks, and at the same time to avail as much as possible of the comparative cheapness of the caisson plan, I have endeavored to suggest such a structure as shall combine both, which has already been descri- bed. • It has been suggested to me to employ blocks made of tim- ber in cribs with loose stones in them, sunk in the same manner as the piers near the City, and upon these to build the towers. Independently of the objections which will arise to this method from want of permanency in the material used and the method of putting together, there would be great danger of the mass changing its position on the shelving surface of the bed of the river, and should such be the case the entire structure above must be irreparably ruined. There being no doubt that the solid rock bed of the river will sustain a load equal to many times the weight of the bridge, it is proposed to demonstrate the strength of the towers. It is shewn in Appendix C, that the weight which comes on the towers will under all circumstances be direct verti- tical pressure, and for this reason, the forces coming in this direction only have to be provided for, except for such parts of the system as sustain a lateral pressure within themselves. . . i That part of the tower which has the least sectional area is immediately under the saddle plates. At the four points of bearing there are 1440 square feet of surface to sus- tain the pressure. To these points there will be transmitted ^ 21 — from the cables 67,960 tons net weight. See Appendix D . The towers above the base will contain 108,687 tons net weight of material,and consequently there will be transmitted to the lower section above the base the weight of the towers and pressure from the cables. The bases will contain 5120 square feet of section, there will therefore be about 1/5 of a ton net pressure on every square inch of that part of the tower where all the di- rect pressure will come. It is proposed to build the towers of the most sui- table stone selected from the quaries near Victoria Cove or farther up the river. The stone is compact lime, hard and durable, it may be seen in many of the most elegant buildings of Quebec and vicinity. Heavy iron bars and castings are to be worked into the towers for additional se- curity, and the entire work is to be laid in hydraulic ciment of the most approved mark. The courses are lo be well bounded and the joints to be worked true. The architectural effect is partially shewn in the accom- panying drawings. According to the most reliable published accounts stones of the formation proposed to be used, well selected, will sus- tain by experiments made by Kennie, Daniell, Wheatstone aijd others, a force equal to about three tons net per square inch section before crushing. It will therefore be seen there is sectional surface equal to fifteen times that which would be crushed by the greatest weight which could ever come upon them. Appendix. The towers as designed are proportioned, as to strength and the weight they have to carry, about the same as an average obtained from the dome of Saint- Peter's, at Rome, Saint- Paul's, London, and the Church Toussaint, Angei-s, (a) in (a) Mahan's Civil Engineering. 2-2 — all of tho al)ovo some variety of liino stone \h employed. I*roviou8 to building however, very iiccuratc experiments hliould be made on the particular kind of stone to be used, on which alone the ultimate proportions should be based. If the lines of the apix of the curve of the centre span and the attachments at the retaining walls remained always on tho same level, there would be no occasion to provide for any motion of the cables on the towers. But as the atmospheric changes, by contracting and expanding them, will cause tho entire roadway from the revetments to the centre to rise and fall, it becomes necessary to adopt such saddle and bearing plates under the cables, between them and the masonry of the towers, as shall allow a slight movement to keep an equilibrium established between the centre and land spans. The saddles consist of iron plates so constructed as to re- ceive the cables where they pass through the tops of the tow- ers. They will bo made segmental in form, on the upper side, with grooves for the cables to lie in. A system of eylendrical rollers is to be so placed between the saddle and a lower plate of cast iron, which rests on the masonry, that as the cables expand and contract an oscilla- tory motion will take place upon the rollers, and so continue the direction of tho forces in parallel lines to the axes of the towers. . Similar rollers set in vertical planes on tho inside of the 'Saddles will transmit the horizontal strain of the cables on to the masonry arch, between one saddle plate and the other. I ,. . I ' It will thus bo seen that although the pressure ol the ca- bles will not always be quite in the axes of the towers, it will never be oblique to them, but always either directly through or parcUel to them slightly on one side or the other. — 80 — EFFRCTS OF IC:' Inquiries will naturally arise respecting tlic effects of the enormous niuises of ice wliich accumulate in the river and which will come with great force against the works of the hridgc. In reply it is stated that great as are the fields which are seen in motion on the river, their size and thickness )>eing known with their velocity, their effect can ho calculated with precision. It then only remains to so proportion the parts as to bo cupahle of sustaining any shock which will be re- ceived. This it is believed has been done in the plans here submitted. Ice breakers both up and down stream arc provided for, as already described. Besides the ice breakers which arc separate constructions from the towers and therefore do not transmit the shocks received to them, a very considerable part of the force of floating ice will be taken off the work by the ice it- sel " grounding " on the bottom of the river in front of the ice breakers, and thus receiving the pressure of the floa- ting masses. 1 am credibly informed that at the upper end of the lake Saint-Peter there are boulders of not more than twenty- flve feet diameter, in the river about half out of water, which annually receive the entire force of the masses of ice which come out of this part of the river, without the slightest dis- turbance. Immediately at your City also will be seen the out- side blocks for loading and unloading vessels. These are usually about twenty-five by fifty feet at base, and are sunk in various depths of water from four to thirty feet at low tide. These blocks or peers, are built of crib work of — 24 — timber, loaded with stone and although they frequently change their positions and lean sideways by the under- run of the river, they are not moved or injured by the fields of ice, which at this part of the river strike them more forcibly than they would above. ' Some of those belonging to Mr. Gilraour, Mr. Lampson, and others, have stood upwards of twenty five years. If then these comparatively temporary works will sustain without injury the same or more force from the floating ice, than is likely to be met with at the site for the propo- sed bridge, surely the heavy masonry cithe towers guarded with the ice breakers and protected by the coflFerdam below low water, need cause no alarm for their safety. ^ Besides the reasons given above may be mentioned the fact that the ice will attach itself to the ice breakers, the shores &c., or will " take " as locally known, and thup leave the channel comparatively clear, that which has " taken " guiding the running ice into the middle of the river, where there are no works proposed, except such as are so far above as to be entirely out of reach. Sbodld it be thought necessary diagonal piers of rough material may be built as represented in dotted lines on sheet N*. 1, this would throw the whole of the ice through the centre opening. > It is however believed there will be no occasion for these addi^' onal guards and consequently they are not recommen- ded and are not estimated for. . f .^ ;, ; , : , OF THE STRENGTH OF THE ANCHORS. It is intended that the anchors shall be made of the very best refined iron, which is capable of sustaining eighty thousand pounds per sectional inch. The gre&,test weight which can come upon them cannot exceed the ultimate tensile force of the main cables, c , iu i i >? ' — 26 — I have estimated them to h% of such section that at the ultimate strength of the cables they will be strained with only two thirds their breaking load. This considerable excess of strength, proportionally to the other parts of the work, is necessary from the form of the material. Large bars and forgings ai-e never proportionally so strong as small Giles of the same kind of iron. • .. The direction of the stratification and the position of masonry arches which are put in, to obtain a hold upon a greater quantity of rock, w '11 be such that within the lifting lines of the tangents of the arches there will be 30,000 tons net of rock, or more than seven times as much as the strain which will come on it. Besides the weight of the rock itself which has alone been considered the tensile force of its particles is very considerable, probably equal to twice its weight. The position of the masonry in the segment, is such that the forces which come upon them will be directly trans- mitted to the rock and foundations of the retaining walls in right lines across the natural beds of the stones employed. OF THE LOADS WHICH WILL COME ON THE BRIDGE AND THEIR EFFECTS. i It is estimated fiiat a train of the first class locomo lives and tenders, fxUing the track on the bridge from end t9 end will be the greatest load which can be brought on the railway in motion. An extraordinary train of freight in this country or Europe will not exceed one hundred and sixty tons engine and all. The gradients upon the lines of railway in progress or projected, that will connect with this bridge, will not allow of trains heavier tlian this upon them, economically. Thus the load estimated for is equal to one thousand six — 2(5 — hundred tons, betweou the towers, or on the centre span, and eight hundred tons on each of the land spans. Besides this very great load, I have estimated that by some unforeseen circumstance the entire roadway may be filled with people. This is the greatest load unless put on purposely, that is at all likely to come upon the bridge, that is, a Ime of loco- motives and tenders reaching from one end of the bridge to the other, and the roadways filled with as many people as can stand upon them (a). At the usual standard this is equal to thirty pounds per square foot. The weight will then be : . , Net, tons. Locomotives and tenders. -------•■ ,-200 People. - - - . 966 4,166 One half of this will be on the centre span. - - 2,088 In appendix B, it is shewn that the strain on the cables of the land spans, is equal to that of the cables of the centre span, consequently as the cables are the same strength in each, the calculations fur the centre span will den&onstrate also the strain on the land spans. It has been shewn at page 18, that the strain on the cables in place arising from their catenarian position would leave one half of their ultimate tensile strength to support the weight of the bridge and the loads upon it. Estimating the roadway as oak at sixty pounds per cubic foot, and taxiing the weight of the ca- bles, the suspending bars, brans, and every kind of suspendended weight, there is in the centre span, tons net. 7,019 ■ I - warn ■ (a) The number of people here estimated it equal to upward* of one third of all the inhabitants of Quebec and the neighbouring district!. 27 — Add to this the moveablo weight of trains, peo- ple, &c., as aboye. -_-.. 2,083 9,102 As it is necessary, in order to be safe, that the strain should never exceed one third oi the strength of the material strained, we multiply the weight of the bridge, and its greatest load by three, and we have 27,306 tons ; therefore as the 80,000, strands are capable of supporting in their catenarian position 30,000 tons, net, we have 2,694 tons of surplus strength. It must be borne in mind that the load upon the bridge is estimated at such a quantity as can never be exceeded, while the usual load which the bridge will carry, will not exceed one hundred and eighty tons, including a train of cars and such transient loads as may be expected, cattle, &c. Now the eflfect of this great or maximum load if uni- formly distributed over the bridge, will be no more than though the bridge itself weighed such an additional quan- tity, provided the load is at rest. See Appendix E, I shall therefore estimate the eflFect of a load more than ordinary, say, the passage of a train of four hundred tons distributed over four hundred I'^et only. This is, however, much more than can possibly occur in so short a spacp during the ordinary working of a railway. Any load whatever either the weight of the bridge itself or any passing load at rest, upon it, must be transmitted through the intervening mechanisms, directly to the points of support, that is, to the cables at the tops of the towers, where (appendix A.) all the accumulated loads will exert themselves. ,, Now if the bridge was perfectly rigid, and remained a true horizontal line without flexure, and the rails were a perfect plane, the w^heels ol the cars and locomotives, being — 28 — circles, without irregularities, no more effect would be due to the passage of a train than to the same wHght at rest on the bridge. But as all mechanical work is more or less irregular, there would be disturbing causes to operate, the tendency of which (such as the eccentricity or irregularity of the wheels of the machinery, or one part of the track being slightly above or below the rest) would be to cause the passing weight to deflect into other than right horizontal lines, and thereby to exert a portion of its accumulated forces, as a falling body consequently striking the bridge with a weight in proportion, to the squares of the distance, through which the part so operating passed vertically. This in practice will amount to more or less in proportion to the perfectness of the machinery and the velocity of the body moving. Another condition has to be considered. The bridge is not and cannot be from the nature of its construction perfectly rigid nor is it desirable it should be. Therefore every load which passes over it will bend it, more or less; consequently, there will be a force operating, which is due to the amount of the deflection of the roadway, or in other words, if the bridge is deflected any given quantity, by the passage of a load over it, the load so passing will exert on the bridge a force equal to its static weight and an additional amount, due to the ac- cumulation of momentum, through the vertical space it has passed in according to the time it is so passing. Therefore the greater the speed the greater the effect on the bridge un- less it is perfectly rigid. The effect af the horizontally moving load on the trajec- tory caused by the flexure of the bridge in front of the load has not to be considered in proportioning the st '"'ngth of a suspension bridge, although it is an essential item in the cal- culation for determining the operation of a moving load on a metal girder, cast iron arch or tubular bridge, as any force — 29 — in the horizontal direction would not be transmitted through the suspending bars to the main cables, which are the ulti- mate strength of the bridge, but would only operate on the roadway without affecting any other part. The greatest load which is likely to be on the bridge at one time in rapid motion as before stated will not exceed four hundred tons. It has been shewn at page 26, that the bridge will bear safely 2,083 tons net weight uniformly distributed over the centre span. A' ^ough it scarcely needs demonstration, to make it appear that a weight so in- considerable a portion of that which the bridge will bear safely at rest, will not affect it in any manner, injuriously while passing over it. Still, to make the matter more clear it may be done as follows. The greatest static deflection that this weight will produce considering the bridge as a perfectly flexible catenary in equilibrium, will be equal to nine inches. That is, if the bridge is considered a series of chains with perfectly flexible joints, irrespective of any stiffness, in itself, except what arises from Us own weight merely, as any load placed in the middle before it can depress it must draw up the ends of the platform and the haunches of the cables. (See appen- dix F.) The augmentation of the vertical force of the load during its passage from the horizontal through the amount of this deflection, will carry it beyond the static quantity, cor- responding to the increase of force. I , > .i)A . The deflection produced by a train of four hundred tons moving at the rate of sixty miles per hour will be equal to about eleven inches considering the bridge as above, as perfectly flexible, and the force which it will exert equal to about 427 tons, vertical p'-cssure in which if added to the weight of the bridge, will be 7,446 tons, or less than — 30 — ono fourth of what the cables are capable of sustaining in their catenarian position. But the bridge is not perfectly flexible, but is so far rigid by means of the parapets and lower string timbers, and the deck planks and strings for the track, that if the para- pets were detached from the suspending rods, they would support their own weight held from either end a distance of 650 feet. It must therefore be evident, that where so powerful a combination exists, forming a truss over which the passing load is to travel, that any deflection which would otherwise occur will be distributed over at least one half the distance that the parapets will support themselves, and therefore the deck will deflect only one half what it would without this combination, or there abouts. With any very considerable deflection, there might be danger of fracturing the side timbers, but it is well known that combinations of timber will spring much more than this amount without injury. The steamboats on the western ri- vers, frequently spring from two to four feet when grounding, without causing a leak. In the above calculations the effect of a train of four hun- dred tons burthen, at speed of sixty miles per hour, has been estimated. This is a much greater weight and higher speed than necessary. The loss of time in slacking up to a speed of nine miles per hour while croi^sing the bridge will be three minutes only, should it be thought advisable to do so, but the effects of the maximum load as above, at the high speed cannot possibly injure the work. DURABILITY. The masonry of the towers, revetments, retaining walls, &c., being built with the best material and in the most — 31 — substantial manner} may be considered almost indistruc- tible. The iron work of the anchors and attachments is all so ar- ranged that a free circulation of air will be about these parts ; they can also all be inspected and painted, and although underground, will not be subject co any damp- ness or corroding influences, that cannot be guarded against. The wires of the cables being each separately varnished and collectively coated with suitable annealed wire, wound round them and covered with prepared (a) Franklinite and linseed oil and afterwards painted, if kept so will never rust ; and the wood work being so arranged that it is well drained and kept from standing water the joints being pit- ched and caulked will last for years. The atmosphere, too of Quebec, is particularly well adap- ted to iron structures, as may be evinced in the manner that the plated tin roofs resist the attacks oi the weather, where they are left unprotected, as is the case on most of the buil- dings. On the whole if well taken care of, and painted at in .ervals, there is no reason why the entire work will not last for centuries, with the exception of the deck which will re- quire renewing, when worn out by travel (b). LIGHTNING. It may be supposed by some that the lightening will in- juriously affect a work where there is so much iron exposed as there will be here. No danger however need be apprehended from this cause as similar works testify. There appear to be distinct electric currents, constantly passing and repassing through the different parts of the (a) A native mineral composed of oxide of iron i zinc and manganese. (b) See that part of this report which refers to the Cbineese Bridges. — 32 — work, and the number of points, such as the heads of bolts, angles &c., of the small pieces, which will be presen- ted, will be so many conductors of the electric fluid, that no very severe shock will be experienced anywhere, even while the bridge is a medium between differently charged electric bodies. r I am not aware that any iron ship has ever met with severe accident from the effects of lightening while many wooden ones are known to have been entirely destroyed. This fact may perhaps be explained satisfactorily by the same reason- ing as will apply to the bridge, namely the number of points which act as conductors ol the fluid. . Time alone can determine the effect produced upon the ultimate particles of the material, by the constantly recur- ring changes in the electric and magnetic currents ; but evi- dence is not wanting to prove that centuries may elapse be- fore any very decided change takes place by these agencies, while operating under, and circulating by slightly exciting causes, even where the material is under continuous heavy strains. (See for example the chain bridges of China, dis- cribed hereafter.) OF THE ESTIMATES, ETC. ^1 In making the estimates of cost I have borne in mind the request of his honor the mayor, that every thing should be " thoroughly considered as to cost " and for this reason have more fully developed the details of the work than is usual in similar cases ; in consequence of which I am able to assure you that the prices here named are such as will actually build the work in the manner proposed. . I am also authorized in stating that there are some of the most reliable contractors ready to contract for the work above water at these prices, ^i ..^.v v ,...,. ;: I have sought from them very definite information respec'^ — 33 — ting the prices of materials, labor, &c., and the means of getting supplies and workmen, and you may I confidently believe, depend on the results. The work below water, that isthecoflFcrdamsand founda- tions to the towers, including the ice breakers, is usually the subject of special contract. The estimate, I believe, will fully cover any expenditure necessary for this part of the undertaking. ' '' ' The plans here proposed contemplate a structure capable of carrying safely a train of cars of maximum load, at great velocity, and two lines of public road each ten and one half feet wide, filled from end to end with people, the most severe load which it can ever be called upon by accidental circumstances to carry. Should it however be thought advisable to incur a less considerable outlay than is required for the proposed work, a bridge of smaller dimensions and less strength designed for lighter travel may be constructed. It may be thought best, financially, to dispense with the line of rails across the bridge and to have it lighter and less costly, and to use waggons from the railways, on the south side connecting again with a railway into the City, or to have a bridge intended only for light trains to be drawn by stationary steam or by horse power. Or, again, it mrfy be well to build such a bridge as can be enlarged and strengthened and at first use it for light travel if it is thought that facilities will exist in future for obtaining means which are not now available. As however all these questions are subject to many con- tingencies, I have not entered into the merits of any of them, more particularly as I am of opinion that the bridge here proposed is the best suited to the wants of the city and as there appears to be but little difficulty in the way finan. Cially. '■■■'''' >-="--f/f_- .... »rfv?v ••>■,'•••?- ^;- ;; — 34 — It will however be borae in mind that any change in Provincial Tariff affecting the price of materials, will make the work more or less costly. SUMMARY OF ESTIMATE OP COST. All the timber including the X 8 d I| 0* Kaces in the deck of the Bridge 11,693 10 7 46,774. 12 Suspending rods, refined iron. 4,180 16,720. 00 Cable rings and cross cables with attachments to main cables 1,000 4,000. 00 Small iron castings 600 2.400. 00 Small forgings, bolts, nuts &c. 5,820 23,280. 00 Annealed wire best quality.. 30,000 120,000. 00 Cable wire,(average strength) 1500 lbs strand 188,100 752,400. 00 Masonry in the two towers and foundations, including hydraulic ciment, and pumping cofferdams 195,134 10 780,538. 00 Large cast iron work, inclu- ding the saddles, anchor plates and fitting same. .. . 5,255 21,020. 00 The large forgings, consisting of anchor bars, saddle bars ' *. and attachments 46,300 185,200. 00 The masonry in the revet- ments, including the offices . &c., the foundations to be s laid in ciment 5,842 23,368. 00 Machinery, Engineering, &c. 15,000 60,000. 00 Building and sinking coffer- dams and ice breakers. .. • 45,413 2 181,653. 40 Amount carried forward. •• • £554,338 2 7 $2,217,352. 52 — 3ft — Amount brought forward... £554>,338 2 7 $2,217,352. 52 ' -d -■■^-..•:.;. - Building cables and putting same up. 6,300 25,200. 00 Carpenter's work on roadway 4,525 18,100. 00 Putting on deck and vampets. 2,425 9,700. CO Guies and machinery for same 2,000 8,000. 00 The adits, anchor shafts and chambers 4,400 17,600. 00 de573,9S8 2 7 $2,295,952. 52 Add for contingencies 10 per cent, and for negotiations of bonds, interest during construction and profits to contractors 23| per cent 191,329 7 6^ 765,317. 51 Total amount for Bridge complete ^6765,3 17 10 IJ $3,061,270.03 Note.— The £ signifies pound Halifax currency. OF SUSPENSION BBIDOES GENERALLY. Having now discribed the nature of the sites proposed to be built upon, the bridge itself proposed to be built, with its strength, the loads which will come on it and its capacity to bear these loads, and having submitted with the same the estimated cost of the completed structure ; it is now pro- posed to oflFer a few general remarks on the subject of this class of bridges, and to compare the one proposed with other works for similar purpose, in existence, and to reply to the objections which are usually urged against suspension bridges for railway traffic. I deem it due to your honorable body, to lay before you all — 36 — ill the supposed difficulties, resting assured there is no good to be gained by shrinking from the most scrupulous enquiries. If the premises arc correct and the deductions rightly made the results must be certain even though we have no prece- dent. Suspension bridges are no new method of construction. The general principle upon which their strength de- pends, was known and in use before the historic period. It is supposed the ancient Peruvians were amongst the first who used this kind of structure in any thing like the form now employed ; but if we may believe the traditions of the Chineese and the channels through which the informa- tion comes, suspension bridges built of iron wire were in use at the formation of the present dynasty of the empire, and how much before we are not told ; in Kirchers' China illustrated is as follows, translated by Mr. Fordham, (Drewry). " In the province of Junnan over a valley of great depth and through which a torrent of water runs with great force and rapidity, a bridge is to be seen said to have been built by the Emperor Mingus of the family of the Hamae, in the year of Christ sixty-five ; it is of chains of iron put together with hooks so secured to rings on both sides of the Chasm> that it forms a bridge by planks placed upon them. There are twenty chains each of which is twenty perches or three hundred palms in length (330 feet), i Iron suspension bridges are probably of Asiatic Origin. The bridge of Chouka , is so ancient that the inhabitants are ignorant of the date of its erection and attribute to it a fabulous origin. (Drewry on suspension bridges). The suspension bridges of Peru were built of ropes made from the bark of the trees of the country and the fibres ol the Agara Americana. ■ . u-> , . Rope suspension bridges were used in France as early as — 37 tho icign oi Charles the ninth. In Davilas, Ilistoria dcl^ Guiore, civil dc Francia, (Vol. 1. p. 204), may be found an account of u rope bridge which waH used at the siege of Poicticrs, to cross the river chain. Douglas, in his work on military bridges, says that rope suspension bridges were used in Italy in 1742. It is difficult to determine when the first European perma- nent suspension bridges were built ; some years ago, Mr. Stephenson published an account of a suspension biidge built across the Tees near Middleton, which is supposed to be the first one built in Europe. ■ The date is set at 1741, but it is uncertain. It is only a foot bridge and is intended i ^^ the use of the miners. Mr. Navier speaks of a chain stretched between two rocks near the town of Moustiers in the department des basses Alpes. It is six hundred and fifty-six ieet long. It is made of rods, about I inch diameter linked together. It is suppo- sed to have been erected in the thirteenth century. For what purpose is not known. The traditions of some assign it as an offering to the Virgin Mary, others suppose it to have been constructed by tht knights of Rliodes. The most im" portant fact however connected with it in a scientific point of view, is that it has hung so long, uninjured by rust, which is distinctly stated by Drewry. It is to be regretted that exact dimensions are not given by which the strain ou the points of suspension, could be determined, as such would materially assist to demons- trate the effect of loads on matter subject to vibration under strain, during great lengths of time, evidence which is much wanted in the scientific world. In the United States, Mr. Finley, in 1796, built a sus- pension bridge of chain cables, near Greenbush, on the road to Uniontown,(See Pope's bridge architecture) ; and between 38 -' then and 1810, several suspension bridges of considerable span were built on his plan. i •- ^ ^' '• In the year 1814, in England, i^^^ attention of engineers, was directed to this subject. Mr. Durabell, of Warringtou, suggested plans for a road from Kuncom in Chester to Liverpool. It was proposed to cross the valley of the Kun- com, by a web of metalic rings, one opening of one thousand, and two of £ve hundred each were thought necessary to ac- commodate the navigation. 1 V ••: • :>>;;>, >/ .?r Mr. Telford suggested for this place a bridge of iron bars made in links^ and made many experiments relative to if J which are given in the appendix of Prof. Barlow's work on the strength and stress of timber. (Third edition 1826). Up to !819, several small suspension bridges were made in England, some of bars, some of rods and some of wire cables. The first large bridge in England, on the suspension prin- ciple, 'Tas built across the Tweed, near Berwick. It was de- signed and erected by capt. Samuel Brown, R. N. It was begun in 1819, and finished the next year. The span is four hundred and forty-nine feet. The same year that the bridge above referred to was began, Mr. Telford commenced operations at the Menai Straits^ and in seven years completed the work now standing as a monument to his exalted talents. Since then to the present time,suspension bridges, more or less modified iii form, have been constructed throughout tha civilized world, some of them of very great magnitude. On the folloving pages Trill be fouLd a table of some of the largest suspension and fixed bridges, now completed and in course of erection. — 39 — ^ e i It n a e il § « I i o H S -J r I gp gPfiQPP SPQ P w ^ *i 6 o ^ pp ^4 (U 11 Q OS S fflg IH i gona 0) t3 a t« o < 53 e< CO is ^ 18 o ^ ^ 00 O "O 00 '^ cu '^ 0) •• <* i£ •« w o o o in o ct t« o -^ ct (o o CO t« o o» tJi o SSSS;: « ;;;; >• 93 3 S?S°o 2 CO O CO o «o t* »rt C3 C" ^ to t3 I a o IS CO •B V n O Q ii 0} CO V't* S .2 (D bp; d 1 •>-< s g) a ^^:S oj S ?> 9> g @ a ^ -S js 3 ® ^ ,0 i£ 10 — Pi^ 41 — ^ The Britannia and Conway Tubular Bridges were built by Mr. Robert Stephenson. The Britannia cross the Menai Straits at the Britannia Rock. As for the Chester and Holyhead Railway bridge, it consists of four spans ; two of 230 feet each and one of 458 feet, nine inches, and one of 459 feet, three irches. The roadways of either bridges are sustained ic rectangu- lar tubes of wrought iron plates riveted together. The Britannia bridge is 103 feet above high water. The entire length is frora out to out of the abutments 1832 feet eight inches. The estimated cost of this work before completed wag i£602,00O sterling, with the experiments to proportion it by, it cost many thousand of pounds more j it was finished in 1850. ■ ■ ■ " " ' ■ ■ '-■■''■ ■- - The Conway bridge is one span of 400 feet ; it cost com- plete JE 146,000 sterling. ^ : ^ fT J The ultimate strength of one of the large tubes' of the Britannia bridge is equal to 78 tons per foot run (E. Clark, Brit, and Con. Tub. Bridges, Vol. II, p. 760), while that pro- posed at Quebec is 1427 tons per foot run, the difference being necessary to ensure safety to travel on the side roads ofthebridge. ^ ' » n :^ Tho cost per foot run for the Britannia and Conway bridges within the abutments is equal to about ^397 ster- ling; while the bridge at Quebec will cost only £195 ster- ling per foot run within the abutments, or if estimated per foot run at the same price as the tubular bridges, the plan here proposed affects a savir^ of J6791,061 currency, while it is an admitted fact that the greater the span, the greater proportionally should be the cost, for a similar construction. A tubular bridge, if it could be built at all, at this site, would not cost less than £4,600,000 currency. * From the foregoing remarks and tables, it be mjfy obser- _ 42 — T«d that the longest suspension bridge now finished, is five and one fifth times as large as any stone arch in exis< tence. It is also four and one third times as large as the largest cast iron arch, and twice and one third times as larf^e nearly as the span of the Great Britannia Tubular Bridge. Mr. Robert Stephenson, when before a parliamentary committee, gave it as his deliberate opinion that cast iron ar- ches could not be carried beyond spans of three hundred and sixty feet with safety. Sir John Rennie, thought they might be made somewhat larger, bv; ' '^^.s not prepared then to discuss the question. (See Edwin k, History, Brit. Tub. Bridge). I am of opinion that cast iron arches may be made much larger than to span 360 feet, notwithstanding the difficul- ties arising from the expansion and contraction of the me- tal, not however any thing like the span required at Quebec. Although the Britannia and Conway Tubular Bridges are very large works, yet they are but little over one quarter of the span required. These are. the largest railway bridges yet built. The largest cast iron arches are about one 0.149, the span required, and the largest stone arch is less than one eighth what is wanted. We are then forced to something diflferent, something yet to be tried, new for the object, but after all older in applica- tion and much longer known scientifically but for purposes slightly different. The Britannia bridge and the great cast iron arches and in fact every great work in existence were experiments until tried ; we must then suit the application of principles to the work required, nothing more is necessary. — 43 — THE SUPPOSED OBJECTIONS TO SUSPENSION BRIDGES FOB RAILWAY PURPOSES. It might appear almost presumptuous to suggest a plan for a work of such great magnitude as is required at Que- hec, in principle the same as that which has heen condem- ned in such unqualified terms by those standing high in the profession, if it had not within itself such evidences of its appropriateness, as may be easely discussed in general terms without the din of abstruce technicalities, and if the question had not its warm advocates in the highest ranks of science. In the calculations and description of the proposed brid- ges it has been demonstrated mathematically, that the weight of the bridge will be a certain quantity, that this quantity is in equilibrium, and that there is a certain iner- tia due to this amount of i.uitter so disposed. That a train of cars and the other loads which will be on the bridge, at any time constituting a maximum, will bear a given propor- tion to the bridge, the eflFect of which, in motion or at rest will be a given quantity. This amount, it is shewn, is not likely under the most unfavorable circumstances to injure the structure or i-» produce any unlocked for results. Similarly favorable results have not been met with, when trials have been made with railways on bridges of this kind for the following reasons. ' Mr. E. Clark, in the work before referred to, states that the experiments on the Stockton and Darlington railway, upon which it appears the only trials were made with loco- motives on a suspension bridge in England, and upon which the sweeping conclusions are formed against this class of structure, (Vol. 1. p. 41.) " Mr. Stephenson had practically " seen the difficulty of employing the ordinary suspension " bridge for railway purposes, on the Stockton and Darling- " ton railway, where he was called in to erect a new bridge — 44 — iV'i I? ■ •• " across the river Tees, in consequence of the failure of a bridge of this discription which had been constructed «c it ti ft there. This was a case in which an attempt was made to render the roadway rigid by ordinary trussing. " It is remarkable in this case that after the roadway was strengthened and rendered rigid by piles driven into the " bed of the river the chains only affording partial support) their vibration literally destroying the framework under the platform, and drew the piles out of the ground. These considerations led Mr. Stephenson to abandon the at- tempt to render an ordinary suspension bridge, rigid " and to resort to an independent beam." From what is here remarked it is evident that Mr. Ste- phenson made yp his mind and came to the conclusions which he has since persisted in with regard to suspension bridges for railway travel, from his experiments on the bridge built on the Stockton and Darlington line, near Middleton. As I am unable to learn the precise dimensions of the bridge in question, it is not in my power to make an ana- lytical comparison of its capacity and the conclusion arrived at. I have sought in allmost all the scientific periodicals of the time when the experiments were made for the neces- sary data, and although frequent mention is made of it in general terms, but few dimensions are given, probably be- cause the result was a failure and was expected to be so by many. According to the statements made before the parliamen- tary committee, where the Britannia Tubular Bridge was under consideration, the Middleton bridge must have been very disproportionately built (E. Clark's, work, page 63). ,. " The platform of the bridge, says Mr. Stephenson, rose up three feet before a locomotive at ordinary speed." J After the trial which it appears nearly proved destructive It — 45 — to the work, piles were driven into the bed of the river, and the bridge secured to them. This must necessarily have made a bad business worse* Independently of the effects of passing loads on such a structure, which must have been to depress one end of the bridge and by so doing to raise the other, alternately drawing the piles out and pressing them into their places again ; the expansion and contraction of the cables would be such that as they shortened by a decrease of temperature the platform would rise and with it the piles would be drawn out correspondingly. When the cables again become elongated by an increase of heat they would have nothing to support, as the pil<^s would remain as the cold had left them, the weight of the platform being insufficient to drive them to their places again ; (such changes might easily occur from midnight to noon) and when any load in addition, sufficiently heavy to press the piles down again, was brought on to the platform, the heaving and throwing so destructive to the bridge was necessarily produced. Yet upon these insufficient premises the important ques- tion of the applicability of suspension bridges for railways, mainly depended. — An experiment differently terminating, would probably have entirely changed this very impoitant branch of railway construction. The inertia of the bridge or the weight in equilibrium com- pared to the weight of the load to pass over it, appears to have been entirely foregotten or neglected. This is however the principal data upon which the entire calculation should rest. If the load to be moved upon any body in equilibrium bears such a proportion to the body upon which it is to move, thn *- its momentum will readily overcome the inertia of the quiescent body, a disturbance will ensue, and in a proportion — 40 — of one body to the other, out when the momentum of the moving body is small compared to the inertia of the body in equilibrium, the effect will be little to such a degree that it may in many cases be imperceptible. • •• Theoretically a pound weight placed on the bridge pro- posed will actually depress the part under the weight, but the quantity will be imperceptible, r ; • The Fribourg bridge, with a span of eight hundred and seventy feet weighing only 190'ton8, had upon it a body of troof'S marching numbering 500 men these would weigh 31^ tons, the load was therefore nearly one sixth, the sus- pended weight of the bridge, and yet the deflections or heav- ings were very inconsiderable. At the Fairmount bridge, Mr. Ellet, the engineer, writes, that the suspended weight of the bridge is 115 tons. " I had, says he, upwards of 70 tons on it in motion at one time, the deflections were about four inches. This was before any trusses were put on." - At Queenston, when the platform of the bridge was so far finished that loaded waggons might pass over it, but before any truss of any kind, (not even a hand railing) was put on it, a very considerable load was allowed to go over. The bridge in this unfinished condition might be conside- red as flexible as the cables, which supported it, no condi- tion rendering it rigid but its own weight, and the slight stiffness of the floor planks, which were three and one half inches pine laid lengthwise. The two chords one 3J x 9 inches laid flat and the other 5x8 inches of pine, were In place, but they are not screwed wp and consequently for- med no part of the truss which they afterwards carried. In this condition the suspended weight of the bridge was about 160. It was desired to demonstrate io the judges appointed by the rei^[)ective legislatures of New- York and Canada, (the — 47 — Honorable Judge Millet, of Buffalo and Gilbert McMiclien esquire, of Niagara Co., who were then present), that the bridge was in all respects competent to carry more than was likely at any time to come upon it, under ordinary circum- stances, and accordingly a number of waggons were loaded with gravel and stones which with their horses were estima- ted at from seventy to seventy-five tons weight. This load evenly divided on either side of the river, at a signal, accom- panied by between two and three hundred persons, several light waggons and some persons on horseback, moved simultaneously on to the bridge and passed over,the two lines crossing in th^ centre. The deflections although observable were not considerable, certainly not enough to have preven- ted a locomotive from over coming them. They were not determined while the load was passing but by comparing the load with the weight of the bridge, and that with the weight of the proposed bridge at Quebec, we shall find that it will require the enormous sum of 3,509 tons to deflect the Quebec bridge as much as the Queenston bridge was deflected. So far as opinions are concerned, itmay be remarked that Mr. Robert Stephenson of England when before a parlia- mentary committee, (See E. Clark's works, on Britannia Tubular bridge. Vol. 1. p. 63), distinctly stated that it is fea- sable to carry a railway across the old Menai Suspension bridge, and that it was not used for the railway because the government objected. This bridge is merely a common suspension bridge inten- ded for the travel of ordinary roads merely, and was built before railways were in use. ' ' ' General Sir Charles Pai&ley, Inspector General of rail- ways m England, also stated before the same committee, that he believed suspension bridges entirely practicable iov rail- I' I" — 48 ~ ways if rightly constructed : Sir John Rennie, also coincided with these opinions. See the same work, page 71. This it must be remembered was after the failure of the bridge, which for the time being decided the question ; and which it can only be presumed both these eminent engineers were acquainted with. ' •' m .<• As to the expansion and contraction of the cables, I need only remark, that the wires being in such near proximity to each other any change of temperature experienced will act on them all, and so produce a uniform strain. r > - The saddles before described will allow these changes to operate without disturbint^ the equilibrium of the bridge, and the alteration in the line of the roadway will be so slight as not to impede the passage of a train, while to ordi- nary road travel it will be inappreciable. I have estimated the eflFects due to a change of tempera- ture equal to one hundred and eighty degrees Farenheit. I am indebted to the principal of the City Academy for ta- bles of mean temperature, at your city, prepared by himself for many years past, upon which these calculations have been based. ., . • THE OPERATIONS OF THE WIND. : Independently of the fact that a suspension bridge has less wind surface than any other kind of structure for the same purpose, in order to assure you that no apprehension for the safety of the work from this cause need be fear, I desire to state that in proportion to the main span this will be the heaviest suspension bridge ever constructed. The Menai Strait, the Wheeling and the Queenston bridges are all of them in situations quite as much exposed as the Quebec bridge will be, yet while the wind surface is only twelve times that of an average obtained from these works the weight of the bridge or the body to be moved by the — 49 — wind is thirty-nine times as much as a corresponding ave- rage. • • . I . :' . , Besides this the guies, as specified in the description, are to be added capable of sustaining a lateral strain equal to fifty pounds per square foot of the wind surface. OF THE EFFECTS OF VIBRATION. In the previous pages will be found descriptions of some bridges in principle the same as that here proposed, which have withstood the operations of vibrations for several cen- turies. It is however a question of very great interest to ascertain precisely what changes take place in the ultimate particles of metal affecting their cohesive force during long con- tinued vibrations and pulsations, and for this reason the Royal Commissioners appointed by Her Majesty to enquire into the application of iron to railway structures, instituted a very elaborate and carefully made set of experiments, and in their report to the Queen, which was presented to the Houses of Parliament, they state (page X), that by inge- nious contrivances, worked by steam power they bent cast iron bars upwards of one hundred thousand times successi- vely, at the rate of four depressions per minute, and that each of these depressions was one third of what would have caused the bar to break, but thai the bars were not at all in- jured by this process, which they afterwards proved by breaking them in the ordinary way, with stationary loads placed in the centre. In a second experiment with the bars laid hoiizontally one half of the breaking weight was drawn lowly backwards and forwards over the bars bending them each time ninety- six thousand times, without apparently affecting it in any manner. • .^ ■ Wrought iron bars were subjected to ten thousand perio- G — 50 — r> > die deflections, through luilf the space which wouUl produce a large permanent flexure, which did not in any manner in- jure them. At Quchec, any flexure that the cublcH may receive duo to the passage of the greatest loads or to the wind, will not be more than the two hundredth part of what would produce a permanent bend in good wire. ' The commissioners though have taken but little notice of the subject of suspension bridges for railways, stating that they have generally been condemned for such uses. The objections which they urge, in reference to loads moving on beams, only apply to the suspension bridge as far as stated in the article on the " effects of loads." The experiments they made bore more particularly on the subject of cast iron as applied to girders, and to beams and tubular bridges. As before shewn the effect of the horizontally moving body on the trajectory in front of the load is not transr^t- ted to the main cables, but is confined to the roadway ^ at least so far as any direct vertical pressure is concer- ned. I am unable to reconcile the conclusions arrived at by the commissioners, with regard to the operations of loads, moving at ordinary or very high speeds, with the usually received theories or with experiments made by myself to determine this question. They state they have determined (see page XII) that a body in motion, actually presses heavier on that which supports it than when at re«/. The apparatus they used for this purpose is discribed in the report and consisted of two bars supported at either end over which from an inclined plane which terminated at them, a car loaded atpleasure was projected. It is not stated that any horizontal plane intervened bet- — 51 — wccn the inclined plane and the flexible bars, and consc* qucntly if the load descended directly unto the barn, it must have operated impart as a falling body,and would pro- duce a greater effect in so doing than if at rest. In order to determine this question more satisfactorily to myself, I requested Mr. G ran t, of Frederic ton N.B., in Janua- ry last, who was then in charge of the bridge being built un- der my directions over the Saint-John river, at the city of Saint-John, to have the necessary machinery prepared and the experiments made. They resulted in furnishing very different data to what had been obtained by the commissioners. In this case the apparatus used was similar to that i^^ed by them, except that instead of the inclined plane termina- ting at the flexible bars it ended with a curve having a tan- gent in a horizontal rigid platfoim, made stationary and ins- tead of flexible bars an almost rigid platform, was used upon which the rails for tht cars to run upon were laid. This plane was supported by four levers, in the manner of a platform scale, so that the plane would descend the same distance, with any weight on it whether placed at either end or in the middle. The levers being connected at the middle a helical spring ballance was used to determine the depressions, and the quantities were measured by sliding verniers. ^ • By these means it was shown that there was no more ver. tical force due to the passage of a load than to the same load at restf except that which resulted from the accumulation of momentum in the space the weight passed through verti- cally. This the machinery was made to determine by lifting the platform to the same position with the weight upon it as when it received the car from the incline, in motion, and then suddenly releasing it. ..,.,, f.'i 1 i i ' W' I — 52 - Hence the deduction that had the plane been perfectly ri- gid and without vertical motio*^, there would have been no more pressure exerted by the load in motion than at rest, but without the vertical motion, the amount of the pressure could not have been determined. ^^.. /^; There w<«s no more deflection, when the car passed at the rate of twenty-five miles per hour, which was nearly the greatest speed attained, than when the same load passtd at miles per hour. -. i At the highest speed a slight vibration was perceptible that did not occur at the lowrer speeds. This constituted the only apparent difference, and probably arose from ine- qualities in the machinery. On the other hand, I cannot agree with those engineers who have maintained, that a degree ci velocity might practi- cally be attained, which should diminish the pressure on the plane or bridge that the load was passing over. Those holding the views frequently cite examples of per- sons having skated safely over ice upon which if they remained stationary for an instant would have broken with them. In this instance the deductions have been erroneously made. It is not that the person skating over the ice actually pressed with less foice on it when moving swiftly than when standing still, but that it takes a certain time to com- municate motion to the particles of the ice and for them to tr^usmit the motion |to those contiguouL^ to them, before which the mass cannot break, which time in the example before 'us is not allowed on account of the velocity of the Skaten Y .;V,;,;;,i. ii .::Ms '.,_.'■ Pi 'f'^ ■ Illustrations, modifications of this principle have occured in several instances, whore small cast iron bridges have — 53 — been broken by the passage of train? but had not time to fall until the cars had passed over in safety. At the Fairmount bridge, experiments were made with loaded carts to determine this question and the results were recorded. &v:.-A''iy>^.\:ihm/' ■-.^■'..■^^■.^■■^.i^y.ii It is stated (a) that the depressions were less while the load was in motion than when the same weight was at rest on the bridge. ,? - , - % , ?; .'■ , i ; , - I am of opinion that some of the conditions were over- looked. ■^•■-' '■• ;'■ ' -^•:" ' '■'■'■: -■' ^ 'M---"-'- --' • - . *» ■ I know of no law which will lead to the conclusion that a body weights more or less, while in motion than when at rest ; velocity cannot augment or diminish the force of gra- vity on a body moving in a right horizontal line in free space. ■^-- «'■ --■•.^" ■ •■ , If the surrounding medium was composed of strata of va- riable density with the lower part most dtnse, a body at very high speed would rise in it and consequently press less heavely on what supported it than when at rest. This law of projectiles is well understood in connection with gunnery. In the atmosphere with the moving body a train of cars the differences are too small to be appreciable. Hence I am distinctly of opinion that the same effect is due to a load in motion over a biidge as while at rest on it, if the machinery could be perfect and the bridge perfectly rigid. The other conditions applying as before stated. Several estimates and offers has^*^ been made at various times in the United States, for constructing suspension bridges for railway purposes. (a) Se3 a report made by Mr. Ellet, to a coiamittee of the citizens of Hart- ord on the crossing of the Connecticut river, tit Middleton. — 64 — Mr. Ellet, who has built some of the largest and best sus< pension bridges in the world, recently proposed to the citi- zens of Hartford, a railway bridge for the crossing of the Connecticut river, near Middletown, and oflfered to construct the work for a given sum, furnishing security for the perfor- mance of the contract. The bridge proposed was to have one span of eight hun- dred feet, to be built in conformity to the principles of the work proposed at Quebec. It has not yet been built owing probably to the policy of the company being somewhat at variance with the wishes of the people of Hartford, and because the line of railway con- necting with it is not so far completed as to require it. Several engineers of eminence have proposed a lailway suspension bridge to cross the Niagara River,near the Falls, among them Mr. Robeling, who has built the largest sus- pension aqueducts, has ofiTered for this work. I trust that your honorable body will consider that what I have remarked, relative to the views and opinions of others has not been said with any desire to disparage the efforts of those who are entitled to the plaudits of the civilized world, particularly of those who have launched out on new and untried paths, where unusual difficulties have had to be encountered, vhich they have successfully surmounted, my only regret is, in reference to this matter, that t>o many have labored to prove the insufficiency y instead of endeavoring to overcome the difficulties of a combination, which it is believed will ultimately be the only system suited to the very great spans which are frequently to be met with in railway constructions, particularly on the American Con- tinent. Should any objection arise as to the height of the bridge above the river, it may be increased at least twenty-five feet without materially affecting any thing but the cost of the — 56 — masonry in the towers below the roadway and in the revet- ments and embankments, r- > •. The gradients of the railways, and every other condition remaining the same. -, - , m , , 'u A good example in practice of the strength of wire is found at Fort Washington on the Hudson river, where the wire for the telegraph makes a span of upward s of 4000 feet. This wire has stood for a great length of time and is, I understand, only renewed, when rusted away. / .. - . At Quebec, the provisions made against rust will effec- tually prevent any action from it, and the greatest span is only two fifths of what practically is here shewn wire is capable of attaining, 'v; - DREDGERS PLAN. A plan of suspension bridges known on account of a patent for the same having been issued to Mr. Dredge, the designer as Dredges suspension bridge has of late been much commented upon. It may not therefore be out of place here to refer to this design as if proved useful it should be adopted. It is claimed for the plan in q^eneral terms, that by placing the suspending rods diagona the main supporting cables may be made much lighter than when the suspending rods hung vertically. Some of the advocates of this plan have gone so far as to assert that if the chains were sundered at the middle, aie bridge would sustain itself as well as if they were con- nected. Admetting these premises for the sake of iliust tion^ it will be seen that the resultants of the forces so act that the semi-bridge may be considered a bracket, projecting from one side of the tower, the apex of the: tower being the — 56 — point of suspension and the line of the roadway being the point of compression ; the neutrial axis, will be on the face of the tower, now the forces which will operate here do not need any fornular to make them perfectly plain. If the chains were parted at the middle the crushing force upon the ends of the roadway would at once be in propor- tion to the angle of direction of the chains, and the load, ei- ther of the bridge itself or any weight upon it. In any of these bridges which I have yet seen the designs for, the end of the roadway is not so proportioned as to receive this strain without flexure and crushing, and if this takes place by the mechanical distribution of the suspen- ding rods it must prove an injury. Besides if the combina- tions in the flooring &c., were so made as to resist perma- Eently these strains,there wouldbe greater weight suspended and more material employed than in the ordinary suspension bridge of the same effective strength. I am therefore constrained to the same opinion as the edi- tor of the Mechanic's Magazine, (Vol. 3, page 407), "that the obliquity of the suspending rods is positively injurious." SOCIAL INTERESTS, ETC. A very large portion cf the mechanical work of the bridge can be done within the city by its own irhabitants. I have taken particular pains to ascertain the condition of the foundaries, machine shops, quarries, &c., &c. All the castings both heavy and light can be made at Quebec. ' * It may cost a trifle more to do so, but the tax payers ^if the bridge is built as here suggested^ will have the advan- tage of reimbursements, in their ovm line of business. The masonry and woodwork, and in fact every thing used in the construction of the bridge, may be either the direct product or the legitimate merchandize of the city. -■ - ■ ' • '- — 5^ — A very considerable part of the cost of the work will be labor from which an immediate return will be made to the city through the supplies required, and although the cost of the work will be very considerable, it is by no means large when compared with other undertakings. Some idea of the comparative magnitude of the underta- king may be formed from Inspector Generals Hincks* work on Trade and Navigation,in which it is stated that the custom entry value of the exports and imports of the City of Quebec for 185C, were £l,4fll,863, or nearly twice as much as the entire cost of the work, or about 56 times as much as will be required to pay principal and interest on the proposed work if built as here suggested. That the port of Quebec must grow in importance com- mercially, socially, and in every other manner, cannot be doubted, if once connected with the Atlantic coast by means of such lines of cu*. imunication as will not be closed by the revolving seasons. Major Robinson has reported that from Quebec to Hali- fax a railway may be built, on which the business of a very large country may be earned on at all times of the year j my own examination!? verify these assertions. If then this railway is constructed, and there is no doubt it will be, sooner or later, suitable and adequate means must be provided for connecting with it. The entire trade of the great upper country for nearly one half the year, must go over it. From the nature of the country and the width of the river, the railway cannot cross the St.-Lawrence below Quebec. If then it does not cross here what is the altemative ? H — 58 — where is Quebec ? The entire trade with allits concomitant advantages gives your city the " go by." For half the year the river is almost impassible, masses of ice deny the stoutest boat a passage, and frequently the pas- senger who is compelled to cross is many hours and some- times a whole day doing so. At the best oi times it will be difficult and expensive to transport goods and merchandize across the river in boats and lighters, and to load and unload from cars to carts and carts to boats and to carts again before reaching the ware- houses, while in the winter time, no marchandize at all can cross in sufficient quantities to be worthy of remark. While by means of the bridge and the railway as here proposed, the cars may be loaded in Halifax, Boston or New- York, and not unloaded until they are under the roofs of warehouses in your city. It appears to me there is no alternative, Quebec must be connected to the southern shore of the river by some perma- nent means, by something upon which communication can be kept up at all times without reference to time or season, something that the wind, the waves, the cold or heat will not impair. Gentlemen of Quebec, you must either build a bridge or a New City. , » Without suitable means of crossing, rival communities to Quebec will spring up on the south shore, and the trade of the ancient capital will leave it. It is no parallel case at New- York. There although to a great extent the business of the city on railways is carried on by ferries crossing to the island from the main land, they run uninteiuptedly or nearly so at all seasons, for it is near fifty years since the harbor of New- York has been closed and almost as long since the rivers at the lower part of the — 60 — • island have been so frozen as to impede steam navigation except for a few hours together. % - . . ^ ^'^v^ju Three great lines of railway however cross directly on to the island from the north by means of bridges, and come immediately into the heart of the city and the Erie railway Co., which in summer runs boats from Piermont twenty- seven miles up the river, find it to their advantage to send the passengers in winter over the Patterson Railway, in or- der that they may cross the river at the city to avoid the in- convenience and delay attendant at the upper terminus where ^herc is usually more ice. As regards the distance of the bridge from the present city proper, it may be remarked, that should the city in- crease as rapidly as there is every reason to suppose, it will when the railways and other great contemplated improve- ments are completed, not be a generation hence when the bridge will be within its limits. New- York has grown over as much distance in thirty-five years as from Victoria Cove to Saint- John Gate. OF THE PLAN AT SITE N°. 2. Owing to the considerable length of time, which would necessarily be occupied and the additional cost I have not prepared plans in detail for any proposed bridge at the Palais Saint-Louis, but estimates have been made by which it has been determined that a bridge suitable for railways of pro- portionate strength with the one proposed, cannot be cons- tructed for lesb Ihan nine millions of dollars while it would most likely cost from eleven to twelve millions. ' The very great height of the towers required here and the considerable addition to the main span makes this great difference in cost. The towers should be 444 feet high and 210 by IG feet . .- 60 — •quare at the base, to be in proportion with those pro- posed at site N<>. 1, and of sufficient strength for the work> The other parts would be in nearly the same ratio. With considerations of respect, I am your, &c., &c. EDW. W. SERRELL, Engineer. Dated at New- York, March 1852. In relation to the means of obtaining the necessary funds to construct a bridge for railways and common road travel to cross the Saint-Lawrence at Quebec, with the probable revenue from the same predicated on the accompanying esti- mates of cost. The bridge as proposed will cost dE765,S17 currency or $3,061,270. It is for the purpose of connecting the city of Quebec with the Halifax and Quebec railway, the Quebec and Richmond railway, or any other great trunkline of railway through this part of the Province, and with any overland means of transit on the south side of the Saint-Lawrence, and will be if there should ever be a railway on the north shore from Quebec to Montreal, a part of the main trunk line from the Atlantic coast to the interior of the country, . — 61 — Presuming then that it is necessary to connect the rail- ways with the city to moke them the Halifax and Quebec and the Quebec and Richmond^ etc., railways or to resort to a change of name and change of purpose corresponding to any change of terminus, it is thought that at least one half the cost of the bridge should be appropriated from the three and one half per cent, Imperial loan to be employed in the construction of the great trunk line of railways. The remaining half to be paid by the city of Quebec in order to insure the terminus within itself with its concomi- tant advantages. The city of Quebec will then have to pay J£d82,658 cur- rency, or $1,530,634. By obtaining a loan at four per cent on the credit of the city, which can no doubt be easely done, which loan shall be paid of? in annual sums divided over a period of twenty years, the equated amount to be paid per year including the interest on the part unpaid will be equal to $108,280 or dE27,070 currency. The value ol the real property of the city of Quebec, ac- cording to the official statement of the treasurer, supposing that the assessments made on the rental are in proportion, uniformly as twenty-five is to forty of their value (which is about what he supposes them to be) is equal to ^£5,992,089 currency or $23,968,356. ? Therefore if every citizen and the corporation were to pay for this purpose, upon the value of their respective real pro- perty within the city a sum equal to $0,45 per year on each $100 value, equal to 1 2[25 pence per pound,the bridge may be built and the city enjoy its advantages, and thus pay for the work in twenty years. These calculations have been based on the supposition % — fl2 — that tho bridg-c would not contribute any revenue towards paying for itself, while the result will be very much more favorable. Among the many sources of direct revenue from the bridge, may be estimated the following, the indirect advantages to the city it is impossible to calculate. It has been calculated by those who thoroughly luulors- tand the subject, that about forty thousand persons annually visit Quebec on pleasure for the purpose of sight seeing. Each of these persons would no doubt pay twenty-fivo cents to see the bridge and cross over; this is equal to J^IO,000. The districts on the southerly side of the river which would keep up a constant communication with the city by means of the bridge, contain 13J),077 inhabitants. While the towns lying beyond the Saint-Charles river, from which the inhabitants cross the Saint-Charles river bridge to reach the city, contain 22,180 inhabitants only. The very large number of ferry boats and small steamers which cross the river irom the city to the south side, running a short distance up or down, is evidence that there is a very considerable business done in this way, from which a large revenue must be derived. Most of those who now cross in boats will when the bridge is finished, cross on it and if any estimate was obtained of the revenue from the boats it must fall far short of what would be realized at the bridge for the same purpose, for many reasons, among which may be mentioned that the bridge will be open at all times of the year and day and night, while the boats can run but little more than half the year. Waggons and heavy articles will also be taken over on the bridge, which never are taken over in small boats or in — m — the winter time, in any manner except when the river is fro- zen over. From these sources of revenue, and that which the work will create, independently of the railways, and many others that cannot be enumerated, it may be safely calculated that the bridge will earn enough to pay the cost of repairs, atten- dants, and a very considerable o;:m besides which when the bridge is paid for as here proposed, will bo direct revenue or profit to the city. ' ; r,- MAPS AND PLANS. Map a. — A general outline map, shewing the vicinity of Quebec and so much of the river Saint-Lawrence as to determine the narrowest parts near the city, compiled from Major Hollands and other surveys. Sheet 1. — The general side elevations and plan of the pro- posed bridge, shewing the embankments, revet- ments, &c. Sheet 2. — The towers for the same in side and front eleva- tion and section. Sheet 3. — The revetments shewing the adits. The segmen- tal masonry, and the elevation of the ofl&ce, &c. Sheet 4. — Represents the details of the woodwork. The cross section of the bridge at the roadway, with the side elevation of the trusses, &c., &c. -*> <■ ' > '. ■■> ,'-' Sheet 5.— The plan and details of the cofferdams. ' ' ' ' . — ni — APPENDICE A. The strain on the cables, resulting from their posiUon. A C. B.,is aeatenary. The curve is in equilibrium ; there- fore the part B. C, wainot be disturbed by supposing the point C. feed regarding it and the point B. as the point of — 65 — suspctiHion. (The curve A C H represents the centre npan, and B C cither of the land spans). G denotes the centre of gravity of the part 13 C. The tangents B I and C I will intersect at I on u vertical line drawn through the point G. Denote by T the tension at B ; by K the tension at C ; and by p the weight of the portion B C. Because the three forces p, T and K are in equilibrium about the point I, we have p : K : : B H : II I r T : : B H : B I Whence H I K = /;. > B H B I T ^ p. , B H Denote the versed sine by jT, and where this docs not exceed 0,07 of the span A B, the space H I may be without sensible error regarded as half the semi-span B D, which denote by I, and we have : T B H+ IH = ▼ , TT 4 BI = TBH+IH = ▼/* + Substituting these quantities in the above equations, we have 1^ __ p I or the horizontal tension or thrust. 2/ I T = f V I 2 vr; / 2 4/2 or the tension at the points of suspension, which being determi- ned, proportion the cables accordingly. t ^ 66 — B. By reference to the first j,art of Appendix A, it will be seen that the strains remain the same, whether the catenary is complete or divided in the centre, with the apex as one of the fixed points. Therefore iLe semi or land spans may in every respect be considered the same as the entire catenary, so far as applied to the direction of forces and their quantity. c. THE STRAIN ON THE TOPS OF THE TOWERS. The angle of direction of the cables of the land spans being the same as that of the centre spans, the resultant of the forces becomes vertical pressure only. Where the backstays of a single span, or the cables of a Bridge of more than one span, leave the towers at different angles, the pressure becomes more or less horizontal or side- ways, tending to press the towers inwards or outwards, but when the angles arc the same the horizontal forces neutra- lize each other, u d the pressure becomes only vertical. D. • The vertical pressure of the cables is = T x Nat. Cos. of the angle of direction of the cables x % because the land spans and centre spans wrl counterbalance each other. The pressures calculated in the text are the breaking for- ces of the Bridge. E, Any two catenaries are similar when their points of sus- pension are on the horizontal plane, whether the elements and other dimensions coustiwUting them are proportionately increased or decreased indefinitely. — 67 — Hence the tension in similar catenaries are directly as their weights. Therefore when any weight is uniformly distrihutcd on any cntcnary, an increase or decrease will only produce dif- ferent tensions on the parts, without altering the figure of the curve. When a platform or deck is hung (as in the case of a Bridge) to the catenaries hy means of the vertical suspen- ding rods, their conditions remain very nearly the same, as if the weight was uniformly distributed on the catenary. F. As an excess of weight upon any part of a catenary will tend to depress that part, it follows necessarily that unless the catenary changes its length, one part cannot sink without raising some other part a corresponding quantity. Therefore when the centre is depressed the haunches are raised, and when the haunches are depressed that portion opposite to it will be raised, and will grivitate on the centre. ERRATA. pflg c 6 Una 18 between its, read between it (1 SI 13 K IC 28 26 abeying such " obeying " sunk tc 14 « 2 ramened " rammed it (< 9 constructeed " constructed >1 (1 15 19 te 30 6 hundredths by pound bare " hundredths pounds " base 1( 19 << 31 case " base (1 2t) II 6 lands " sands « 21 « 18 bounded " bonded 22 34 (1 5 6 apix races " apex ** knees (( 34 i( i9( it 30 ciment " cement << 38 << 5 et 6 Kuncorn " Runcorn (1 39 <( 14 Fairwount " Fairmount n 39