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by Phineas Davis, of that firm, whose trade and business was that of a watch and clock maker. After undergoing certain modifications, it was found capable of performing what was required by the company. After thoroughly testing this engine, Mr. Davis built others, which were the progenitors of the " grasshopper" engines [p. 182] which were used for so many years on the Baltimore & Ohio Railroad. It is a remarkable fact that some of these are still in use on that road, and have been in continuous service for over fifty years, which is probably the longest active life of all existing locomotives.

In August, 1831, the locomotive "John Bull," which was built by George & Robert Stephenson & Company, of Newcastle-upon-Tyne, was received in Philadelphia, for the Camden & Amboy Railroad & Transportation Company. This is the old engine which was exhibited by the Pennsylvania Railroad Company at the Centennial Exhibition in 1876. After the arrival of the John Bull" a very considerable number of locomotives which were built by the Stephensons were imported from England. Most of them were probably of what was known as the "Planet" class, which was a form of engine that succeeded the famous "Rocket."

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I quote from "The Early History of Locomotives in this Country," issued by the Rogers Locomotive & Machine Works:

These locomotives, which were imported from England, doubtless to a very considerable extent, furnished the types and patterns from which those which were afterward built here were fashioned. But American designs very soon began to depart from their British prototypes, and a process of adaptation to the existing conditions of the railroads in this country followed, which afterward "differentiated" the American locomotives more and more from those built in Great Britain. A marked feature of difference between American and English locomotives has been the use of a "truck under the former.

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In all of the locomotives which have been illustrated, excepting the "South Carolina," the axles were held by the frames so that they were always parallel to each other. In going around curves, therefore, there was somewhat the same

VOL. IV.-18

difficulty that there would be in turning a corner with an ordinary wagon if both its axles were held parallel, and the front one could not turn on the kingbolt. The plan of the wheels and running gear of the "South Carolina," shows the position that they assumed on a curved track. It will be seen that, by reason of their connection to the boiler by king-bolts, K K', the two pairs of wheels could adjust themselves to the curvature of the rails. This principle was afterward applied to cars, and nearly all the rolling-stock in this country is now constructed on this plan, which was proposed by Mr. Allen in a report dated May 16, 1831, made to the South Carolina Canal & Railroad Company, and an engine constructed on this principle was completed the same year.

In the latter part of the year 1831, the late John B. Jervis invented what he called "a new plan of frame, with a bearing-carriage for a locomotive engine," for the use of the Mohawk &

ThePlanet."

Hudson Railroad. Jervis's engine is shown on page 178. In a letter published in the "American Railroad Journal" of July 27, 1833, he described the objects aimed at in the use of the truck as follows:

The leading objects I had in view, in the general arrangement of the plan of the engine, did not contemplate any improvement in the power over those heretofore constructed by Stephenson & Company,* but to make an engine that would be better adapted to railroads of less strength than are common in England; that would travel with more ease to itself and to the rail on curved roads; that would be less

*The truck was first applied by Mr. Jervis to an engine built by R. Stephenson & Co., of England.

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for the defendants has said, “it was at one time a question of millions, to be assured by a verdict of a jury."

In 1836, Henry R. Campbell, of Philadelphia, patented the use of two pairs of driving-wheels and a truck, as shown on the opposite page. The driving-wheels were coupled together by rods, as may be seen. This plan has since been so generally adopted in this country that it is now known as the "American type" of locomotive, and is the one almost universally used here for

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The position of its wheels on a curve, and the capacity of the truck, or "bearing-carriage, to adapt itself to the sinuosities of the track are shown in the plan. The effectiveness of the single truck for locomotives, in accomplishing what Mr. Jervis intended it for, was at once recognized, and its almost general adoption on American locomotives followed.

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John B. Jervis's Locomotive, 1831, and Plan of its Running Gear.

In 1834, Ross Winans, of Baltimore, patented the application of the principle which Mr. Allen had adopted for locomotives "to passenger and other cars."

He afterward brought a number of actions at law against railroads for infringement of his patent, which was a subject of legal controversy for twenty years. Winans claimed that his invention originated as far back as 1831, and was completed and reduced to practice in 1834. The dispute was finally carried to the Supreme Court of the United States, and was decided against the plaintiff, after an expenditure of as much as $200,000 by both sides. It involved the principle on which nearly all cars in this country are now and were then built; and, as one of the counsel

passenger, and to a considerable extent for freight, service.

From these comparatively small beginnings, the magnificent equipment of our railroad has grown. From Peter Cooper's locomotive, which weighed less than a ton, with a boiler the size of a flour barrel, and which had difficulty in beating a gray horse, we now have locomotives which will easily run sixty and can exceed seventy miles an hour, and others which weigh seventy-five tons and over. A comparison of the engraving of Peter Cooper's engine with that of the modern standard express passenger locomotive [p. 192] shows vividly the progress which has been made since that first experiment was tried-little more than half a century ago. In that period there have been many modifications in the design of locomotives to adapt them to the changed conditions of the various kinds of traffic of to-day. An express train travelling at a high rate of speed requires a locomotive very different from one which is designed for handling heavy freight trains up steep mountain grades. A special class of engines is built for

light trains making frequent stops, as on the elevated railroads in New York, and those provided for suburban traffic --and still others for street railroads, for switching cars at stations, etc. The process of differentiation has gone on until there are now as many different kinds of these machines as there are breeds of dogs or horses.

Campbell's Locomotive.

Nearly all the early locomotives had only four wheels. In some cases one pair alone was used to drive the engine, and in others the two pairs were coupled together, so that the adhesion of all four could be utilized to draw loads. The four-wheeled type [p. 183] is still used a great deal for moving cars at stations, and other purposes where the speed is comparatively slow. But to run around sharp curves the wheels of such engines must be placed near together, just as they are under an ordinary street car. This makes the wheel-base very short, and such engines are therefore very unsteady at high speeds, so that they are unsuited for any excepting slow service. They have the advantage, though, that the whole weight of the machine may be carried on the driving wheels, and can thus be useful for increasing their friction, or adhesion to the rails. This gives such engines an advantage for starting and moving heavy trains, at stations or elsewhere, which is the kind of service in which they are usually employed.

If the front end of the engine is carried on a truck, as in Campbell's planwhich is the one that has been very generally adopted in this country-the wheel-base can be extended and at the

same time the front wheels can adjust themselves to the curvature of the track. This gives the running gear lateral flexibility. But as the tractive power of a locomotive is dependent upon the friction, or adhesion of the wheels to the rails, it is of the utmost importance that the pressure of the wheels on the rails should be uniform. For this reason the wheels must be able to adjust themselves to the vertical as well as the horizontal inequalities of the track.

The axles are therefore arranged so that they can move up and down in the frames, and the weight of the engine rests on springs which bear on the axles. The ends of the springs are connected together by levers, so that the weight on one of them is transferred to the other. The front end of the locomotive rests on the centre of the truck, and the back end on the fulcrums of the equalizing levers, and it therefore is in the condition of a three-legged stool, which will stand firm on any surface, no matter how irregular, though if it has four or more legs it will not.

When more than four driving-wheels are used the springs are connected together by equalizing levers, as shown in the illustration on p. 186, which represents a consolidation engine as it appears before the wheels are put under it.

Having a vehicle which is adapted to running on a railroad track, it remains to supply the motive power. This, in all but some very few exceptional cases, is the expansive power of steam. What the infant electricity has in store for us it would be rash to predict, but for locomotives its steps have been thus far weak and uncertain, and when we want a giant of steel or a race-horse of iron our only sure reliance is steam. This is the breath of life to the locomotive, which is inhaled and exhaled to and from the cylinders, which act as lungs, while the boiler fulfils functions analogous to the digestive organs of an animal. A locomotive is as dependent on the action of its boiler for its capacity for doing work as a human being on that of his stomach. The mechanical appliances of the one and the mental and physical equipment of the other are nugatory without a good digestive apparatus.

A locomotive boiler consists of a rectangular fire-place or fire-box with double sides. The spaces between the sides

count of the large amount of water which must be evaporated in such boilers. To create a strong draught, the steam which

Longitudinal and Transverse Sections of a Locomotive Boiler.

and over the top are filled with water. The front end of the boiler has another chamber called the smoke-box. The firebox is connected with the smoke-box by a large number of small tubes, through which the smoke and products of combustion pass from the fire-box to the smoke-box; and from the latter they escape up the chimney. The tubes are all

Section of a Locomotive Cylinder.

surrounded with water, so that as much surface as possible is exposed to the action of the fire. This is essential on ac

is exhausted from the cylinders is discharged up the chimney. This produces a partial vacuum in the smoke-box, which causes a current of air to flow through the fire on the grate, into the fire-box, through the tubes, and thence to the smoke-box and up the chimney. Probably many readers have noticed that in late years the smoke-boxes of locomotives have been extended forward in front of the chimneys. This has been done to give room for deflectors and wire netting inside of the smoke boxes to arrest sparks and cinders, which are collected in the extended front and are removed by a door or spout below.

Formerly force-pumps were used to get water into the boiler against the pressure of steam, but now a very curious instrument called an injector is used for that purpose. In it a jet of steam acts on a current of water and imparts sufficient momentum to it to force it into the boiler.

Having explained how the steam is generated, it remains to explain how it propels a locomotive. It does this very much as a person on a bicycle propels it-that is, by means of two cranks the driving-wheels are made to revolve, and either the latter must then slip or the vehicle will move. In a locomotive the wheels are turned by means of two cylinders and pistons, which are connected

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