Part 8

A suspension bridge would solve the problem, but in many cases not satisfactorily. The method adopted by Colonel C. Shaler Smith at the Kentucky River Bridge [p. 55] shows ingenuity and boldness worthy of special remark. The Cincinnati Southern Railroad had here to cross a cañon 1,200 feet wide and 275 feet deep. The river is subject to freshets every two months, with a range of 55 feet and a known rise of 40 feet in a single night. Twenty years before, the towers for a suspension bridge had been erected at this point. The design adopted for the railroad bridge was based upon the cantilever principle. The structure has three spans of 375 feet each, carrying a railway track at a height of 276 feet above the bed of the river. At the time of its construction this was the highest railway bridge in the world, and it is still the highest structure of the kind with spans of over 60 feet in length. The bridge is supported by the bluffs at its ends and by two intermediate iron piers resting upon bases of stone masonry. Each iron pier is 177 feet high, and consists of four legs, having a base of 71½ × 28 feet, and terminating at its top in a turned pin 12 inches in diameter under each of the two trusses. Each iron pier is a structure complete in itself, with provision for expansion and contraction in each direction through double roller beds interposed between it and the masonry, and is braced to withstand a gale of wind that would blow a loaded freight-train bodily from the bridge.

The trusses were commenced by anchoring them back to the old towers, and were then built out as cantilevers from each bluff to a distance of one-half the length of the side spans, and at this point rested upon temporary wooden supports. Thence they were again extended as cantilevers until the side spans were completed and rested upon the iron piers. This cantilever principle is simply the balancing of a portion of the structure on one side of a support by the portion on the opposite side of the same support. Similarly the halves of the middle span were built out from the piers, meeting with exactness in mid-air. The temporary support used first at the centre of one side span and then at the other, was the only scaffolding used in erecting the structure, none whatever being used for the middle span.

When the junction was made at the centre of the middle span, the trusses were continuous from bluff to bluff, and, had they been left in this condition, would have been subjected to constantly varying strains resulting from the rise and fall of the iron piers due to thermal changes. This liability was obviated by cutting the bottom chords of the side spans and converting them into sliding joints at points 75 feet distant from the iron piers. This done, the bridge consists of a continuous girder 525 feet long, covering the middle span of 375 feet, and projecting as cantilevers for 75 feet beyond each pier, each cantilever supporting one end of a 300-foot span, which completes the distance to the bluff on each side.

A most interesting example of cantilever construction is the railway bridge built several years ago at Niagara, only a few rods from the suspension bridge and a short distance below the great falls. It is shown in the illustrations above and on page 91. The floor of the bridge is 239 feet above the surface of the water, which at that point has a velocity in the centre of 16½ miles per hour and forms constant whirlpools and eddies near the shores. The total length of the structure is 910 feet, and the clear span over the river between the towers is 470 feet. The shore arms of the cantilever, that is to say, those portions of the structure which extend from the top of the bank to the top of the tower built from the foot of the bank, are firmly anchored at their shore ends to a pier built upon the solid rock. These shore-arms were constructed on wooden false works, and serve as balancing weights to the other or river arms of the lever, which project out over the stream. These river-arms were built by the addition of metal, piece by piece, the weight being always more than balanced by the shore-arms. The separate members of the river-arms were run out on the top of the completed part and then lowered from the end by an overhanging travelling derrick, and fastened in place by men working upon a platform suspended below. This work was continued, piece by piece, until the river-arm of each cantilever was complete, and the structure was then finished by connecting these river-arms by a short truss suspended from them directly over the centre of the stream. This whole structure was built in eight months, and is an example both of a bold engineering work and of the facility with which a pin-connected structure can be erected. The materials are steel and iron. The prosecution of this work by men suspended on a platform, hung by ropes from a skeleton structure projecting, without apparent support, over the rushing Niagara torrent, was always an interesting and really thrilling spectacle.

The Lachine Bridge recently built over the St. Lawrence near Montreal, illustrated below, has certain peculiar features. It has a total length of 3,514 feet. The two channel spans are each 408 feet in length and are through spans. The others are deck spans. Through spans are those where the train passes between the side trusses. Deck spans are those where the train passes over the top of the structure. These two channel spans and the two spans next them form cantilevers, and the channel spans were built out from the central pier and from the adjacent flanking spans without the use of false works in either channel. A novel method of passing from the deck to the through spans has been used, by curving the top and bottom chords of the channel spans to connect with the chords of the flanking spans. The material is steel.

This structure, light, airy, and graceful, forms a strong contrast to the dark, heavy tube of the Victoria Bridge just below.

The enormous cantilever Forth Bridge, with its two spans of 1,710 feet each, is in steady progress of construction and will when completed mark a long step in advance in the science of bridge construction.

Of entirely different design and principle from all these trusses are the beautiful steel arches of the St. Louis Bridge [p. 95], the great work of that remarkable genius, James B. Eads. This structure spans the Mississippi at St. Louis. Difficult problems were presented in the study of the design for a permanent bridge at that point. The river is subject to great changes. The variation between extreme low and high water has been over 41 feet. The current runs from 2¾ to 8½ miles per hour. It holds always much matter in suspension, but the amount so held varies greatly with the velocity. The very bed of the river is really in constant motion. Examination by Captain Eads in a diving-bell showed that there was a moving current of sand at the bottom, of at least three feet in depth. At low water, the velocity of the stream is small and the bottom rises. When the velocity increases, a "scour" results and the river-bed is deepened, sometimes with amazing rapidity. In winter the river is closed by huge cakes of ice from the north, which freeze together and form great fields of ice.

It was decided to be necessary that the foundations should go to rock, and they were so built. The general plan of the superstructure, with all its details, was elaborated gradually and carefully, and the result is a real feat of engineering. There are three steel arches, the centre one having a span of 520 feet and each side arch a span of 502 feet. Each span has four parallel arches or ribs, and each arch is composed of two cylindrical steel tubes, 18 inches in exterior diameter, one acting as the upper and the other as the lower chord of the arch. The tubes are in sections, each about twelve feet long, and connected by screw joints. The thickness of the steel forming the tubes runs from 1-3/16 to 2-1/8 inches. These upper and lower tubes are parallel and are 12 feet apart, connected by a single system of diagonal bracing. The double tracks of the railroad run through the bridge adjacent to the side arches at the elevation of the highest point of the lower tube. The carriage road and footpaths extend the full width of the bridge and are carried, by braced vertical posts, at an elevation of twenty-three feet above the railroad. The clear headway is 55 feet above ordinary high water. The approaches on each side are masonry viaducts, and the railway connects with the City Station by a tunnel nearly a mile in length. The illustration shows vividly the method of erection of these great tubular ribs. They were built out from each side of a pier, the weight on one side acting as a counterpoise for the construction on the other side of the pier. They were thus gradually and systematically projected over the river, without support from below, till they met at the middle of the span, when the last central connecting tube was put in place by an ingenious mechanical arrangement, and the arch became self-supporting.

The double arch steel viaduct recently built over the Harlem Valley in the city of New York [p. 97] has a marked difference from the St. Louis arches in the method of construction of the ribs. These are made up of immense voussoirs of plate steel, forming sections somewhat analogous to the ring stones of a masonry arch. These sections are built up in the form of great I beams, the top and bottom of the I being made by a number of parallel steel plates connected by angle pieces with the upright web, which is a single piece of steel. The vertical height of the I is 13 feet. The span of each of these arches is 510 feet. There are six such parallel ribs in each span, connected with each other by bracing. These great ribs rest upon steel pins of 18 inches diameter, placed at the springing of the arch. The arches rise from massive masonry piers, which extend up to the level of the floor of the bridge. This floor is supported by vertical posts from the arches and is a little above the highest point of the rib. It is 152 feet above the surface of the river--having an elevation fifty feet greater than the well-known High Bridge, which spans the same valley within a quarter of a mile. The approaches to these steel arches on each side are granite viaducts carried over a series of stone arches. The whole structure forms a notable example of engineering construction. It was finished within two years from the beginning of work upon its foundations, the energy of its builders being worthy of special commendation.

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In providing for the rapid transit of passengers in great cities the two types of construction successfully adopted are represented by the New York Elevated and the London Underground railways. The New York Elevated is a continuous metal viaduct, supported on columns varying in height so as to secure easy grades. The details of construction differ greatly at various parts of the elevated lines, those more recently built being able to carry much heavier trains than the earlier portions. The roads have been very successful in providing the facilities for transit so absolutely necessary in New York. The citizens of that city are alive to the present necessity of adding very soon to those facilities, and it is now only a question of the best method to be adopted to secure the largest results in a permanent manner.

The London Underground road has also been very successful. Its construction was a formidable undertaking. Its tunnels are not only under streets but under heavy buildings. Its daily traffic is enormous. The difficult question in its management is, as in all long tunnels, that of ventilation, but modern science will surely solve that, as it does so many other problems connected with the active life of man.

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Many broad questions of general policy, and innumerable matters of detail are involved in the development of railway engineering. In the determination, for instance, of the location, the relations of cost and construction to future business, the possibilities of extensions and connections, the best points for settlements and industrial enterprises, the merits and defects of alternative routes must be weighed and decided.

Where structures are to be built, the amount and delicacy of detail requisite in their design and execution can hardly be described. Final pressures upon foundations must be ascertained and provided for. Accurate calculations of strains and stresses, involving the application of difficult processes and mechanical theories, must be made. The adjustment of every part must be secured with reference to its future duty. Strength and safety must be assured and economy not forgotten. Every contingency must, if possible, be anticipated, while the emergencies which arise during every great construction demand constant watchfulness and prompt and accurate decision.

The financial success of the largest enterprises rests upon such practical application of theory and experience. Even more weighty still is the fact that the safety of thousands of human lives depends daily upon the permanency and stability of railway structures. Such are some of the deep responsibilities which are involved in the active work of the Civil Engineer.

FOOTNOTE:

[8] Reference is made to the substitution of locks in the Panama Canal for the original project of a canal at the sea-level.

AMERICAN LOCOMOTIVES AND CARS.

BY M. N. FORNEY.

The Baltimore and Ohio Railroad in 1830--Evolution of the Car from the Conestoga Wagon--Horatio Allen's Trial Trip--The First Locomotive used in the United States--Peter Cooper's Race with a Gray Horse--The "De Witt Clinton," "Planet," and other Early Types of Locomotives--Equalizing Levers--How Steam is Made and Controlled--The Boiler, Cylinder, Injector, and Valve Gear--Regulation of the Capacity of a Locomotive to Draw--Increase in the Number of Driving Wheels--Modern Types of Locomotives--Variation in the Rate of Speed--The Appliances by which an Engine is Governed--Round-houses and Shops--Development of American Cars--An Illustration from Peter Parley--The Survival of Stage Coach Bodies--Adoption of the Rectangular Shape--The Origin of Eight-wheeled Cars--Improvement in Car Coupling--A Uniform Type Recommended--The Making of Wheels--Relative Merits of Cast and Wrought Iron, and Steel--The Allen Paper Wheel--Types of Cars, with Size, Weight, and Price--The Car-Builder's Dictionary--Statistical.

Among the readers of this volume there will be some who have reached the summit of the "divide" which separates the spring and summer of life from its autumn and winter, and whose first information about railroads was received from Peter Parley's "First Book of History," which was used as a schoolbook forty or fifty years ago. In his chapter on Maryland, he says:

But the most curious thing at Baltimore is the railroad. I must tell you that there is a great trade between Baltimore and the States west of the Alleghany Mountains. The western people buy a great many goods at Baltimore, and send in return a great deal of western produce. There is, therefore, a vast deal of travelling back and forth, and hundreds of teams are constantly occupied in transporting goods and produce to and from market.[9]

Now, in order to carry on all this business more easily, the people are building what is called a railroad. This consists of iron bars laid along the ground, and made fast, so that carriages with small wheels may run along upon them with facility. In this way, one horse will be able to draw as much as ten horses on a common road. A part of this railroad is already done, and if you choose to take a ride upon it, you can do so. You will mount a car something like a stage, and then you will be drawn along by two horses, at the rate of twelve miles an hour.

The picture reproduced below (Fig. 2) of a car drawn by horses was given with the above description of the Baltimore & Ohio Railroad. The mutilated copy of the book from which the engraving and extract were copied does not give the date when it was written or published. It was probably some time between the years 1830 and 1835. That the car shown in the engraving was evolved from the Conestoga wagon is obvious from the illustrations.

This engraving and description, made for children, more than fifty years ago, will give some idea of the state of the art of railroading at that time; and it is a remarkable fact that the present wonderful development and the improvements in railroads and their equipments in this country have been made during the lives of persons still living.

In the latter part of 1827, the Delaware & Hudson Canal Company put the Carbondale Railroad under construction. The road extends from the head of the Delaware & Hudson Canal at Honesdale, Pa., to the coal mines belonging to the Delaware & Hudson Canal Company at Carbondale, a distance of about sixteen miles. This line was opened, probably in 1829, and was operated partly by stationary engines, and partly by horses. The road is noted chiefly for being the one on which a locomotive was first used in this country. This was the "Stourbridge Lion," which was built in England under the direction of Mr. Horatio Allen, who afterward was president of the Novelty Works in New York, and who is still (1889) living near New York at the ripe age of eighty-seven. Before the road was opened, he had been a civil engineer on the Carbondale line. In 1828 Mr. Allen went to England, the only place where a locomotive was then in daily operation, to study the subject in all its practical details. Before leaving this country he was intrusted by the Delaware & Hudson Canal Company with the commission to have rails made for that line, and to have three locomotives built on plans to be decided by him when in England. This, it must be remembered, was before the celebrated trial of the "Rocket" on the Liverpool & Manchester Railway, which was not made until 1829. Previous to that trial, it had not been decided what type of boiler was the best for locomotives. The result of Mr. Allen's investigations was to produce in his mind a decided confidence in the multitubular boiler which is now universally used for locomotives. Other persons of experience recommended a boiler with small riveted flues of as small diameter as could be riveted. An order was therefore given to Messrs. Foster, Rastrick & Co., at Stourbridge, for one engine whose boiler was to have riveted flues of comparatively large size, and another order was given to Messrs. Stephenson & Co., of Newcastle-on-Tyne, for two locomotives with boilers having small tubes. The engine built by Foster, Rastrick & Co. was named the "Stourbridge Lion." It was sent to this country and was tried at Honesdale, Pa., on August 9, 1829. On its trial trip it was managed by Mr. Allen, to whom belongs the distinction of having run the first locomotive that was ever used in this country. In 1884 he wrote the following account of this trip:

When the time came, and the steam was of the right pressure, and all was ready, I took my position on the platform of the locomotive alone, and with my hand on the throttle-valve handle said: "If there is any danger in this ride it is not necessary that the life and limbs of more than one should be subjected to that danger."

The locomotive, having no train behind it, answered at once to the movement of the hand; ... soon the straight line was run over, the curve was reached and passed before there was time to think as to its not being passed safely, and soon I was out of sight in the three miles' ride alone in the woods of Pennsylvania. I had never run a locomotive nor any other engine before; I have never run one since.

The two engines contracted for with Messrs. Stephenson & Co. were made by them, and Mr. Allen has informed the writer that they were built on substantially the same plans that were afterward embodied in the famous "Rocket." They were shipped to New York and for a time were stored in an iron warehouse on the east side of the city, where they were exhibited to the public. They were never sent to the Delaware & Hudson Canal Company's road, and it is not now known whatever became of them. If they had been put to work on their arrival here the use of engines of the "Rocket" type would have been anticipated on this side the Atlantic.

The first railroad which was undertaken for the transportation of freight and passengers in this country, on a comprehensive scale, was the Baltimore & Ohio. Its construction was begun in 1828. The laying of rails was commenced in 1829, and in May, 1830, the first section of fifteen miles from Baltimore to Ellicott's Mills was opened. It was probably about this time that the animated sketch of the car given by Peter Parley was made. From 1830 to 1835 many lines were projected, and at the end of that year there were over a thousand miles of road in use.

Whether the motive power on these roads should be horses or steam was for a long time an open question. The celebrated trial of locomotives on the Liverpool & Manchester Railway, in England, was made in 1829. Reports of these trials, and of the use of locomotive engines on the Stockton & Darlington line, were published in this country, and, as Mr. Charles Francis Adams says, "The country, therefore, was not only ripe to accept the results of the Rainhill contest, but it was anticipating them with eager hope." In 1829 Mr. Horatio Allen, who had been in England the year before to learn all that could then be learned about steam locomotion, reported to the South Carolina Railway Company in favor of steam instead of horse power for that line. The basis of that report, he says, "Was on the broad ground that in the future there was no reason to expect any material improvement in the breed of horses, while, in my judgment, the man was not living who knew what the breed of locomotives was to place at command."

As early as 1829 and 1830, Peter Cooper experimented with a little locomotive on the Baltimore & Ohio Railroad (Fig. 4). At a meeting of the Master Mechanics' Association in New York, in 1875--at the Institute which bears his name--he related with great glee how on the trial trip he had beaten a gray horse, attached to another car. The coincidence that one of Peter Parley's horses is a gray one might lead to the inference that it was the same horse that Peter Cooper beat, a deduction which perhaps has as sound a basis to rest on as many historical conclusions of more importance.

The undeveloped condition of the art of machine construction at that time is indicated by the fact that the flues of the boiler of this engine were made of gun-barrels, which were the only tubes that could then be obtained for the purpose. The boiler itself is described as about the size of a flour-barrel. The whole machine was no larger than a hand-car of the present day.