It would be difficult to find a form of mechanical construction in America which bears more strongly the imprint of our national characteristics than the American locomotive. In its general appearance, constructive details, and unquestionable convenience of operation, it stands entirely distinct as a type among the hundred-and-one styles of locomotives that are manufactured in the shops of the world. This national individuality is seen even more strongly in the great industrial establishments in which our locomotives are made, where labor-saving machinery and carefully-thought-out methods of shop management have enabled us to build at a speed and price which cannot be approached by any other nation. The magnitude of the locomotive industry in this country was emphasized in the festivities which attended the recent completion of their 20,000th locomotive by one of the locomotive works of this country, an event which occurred in the spring of the present year. The early founding of the Baldwin Locomotive Works, its rapid growth, the many standard types of locomotives which have been originated in the shops of the company, and the fact that its locomotives have been for years finding their way to the four corners of the earth render the works thoroughly representative of the locomotive industry in this country.

Mathias W. Baldwin, who founded the establishment, started in business as a jeweler in a small shop in Philadelphia in the year 1819. In 1830 the steam railroad was beginning to make its appearance and establishing itself in this country, and to gratify public interest the proprietor of a Philadelphia museum gave an order to Baldwin for the construction of a miniature locomotive for exhibition. In the spring of 1831 the work was completed and the toy was set in motion on a circular railroad track at the museum. The success of the model brought an order to Baldwin for a locomotive from the Philadelphia, Germantown & Norristown Railroad Company. Guided by his experience with the little model, and by some memoranda which he had taken of a locomotive recently imported from England by the Camden & Amboy Railroad Company, Baldwin completed the curious and historical locomotive known as "Old Ironsides," of which we give an illustration on our front page. The engine was tried November 23, 1832, and did duty on the Germantown road and, later, on other roads for a period of over twenty years. The "Ironsides" was a four-wheeled engine, modeled after the English pattern of those days, and it weighed in running order something over five tons. The cylinders were placed beneath the smokebox and connected to a pair of cranks on the rear axle, which was placed in front of the firebox. The driving wheels were 54 inches in diameter, and the front, wheels 45 inches in diameter. The cylinders were 9½ inches in diameter by 18 inches stroke, and they were carried beneath the smokebox, as is done today with modern inside-connected engines. The wheels had cast-iron hubs, wooden spokes and rims, and wrought-iron tires. The frame was of wood. The boiler was 30 inches in diameter and contained seventy-two copper flues 1½ inches in diameter. The valve motion was given by a single loose eccentric to each cylinder, and the engine was reversed by changing the position of the eccentric on the axle by a lever operated from the firebox. The contract price was $3,000.

The second engine, built in 1834 for the Charleston & Hamburg Railroad Company, was a six-wheeled engine with a single pair of drivers, 4½ feet in diameter, carried behind the firebox, with a half-crank axle of Baldwin's design. The wood and iron wheels used on the "Ironsides" having proved faulty, the driving-wheels in this case were cast in solid bell metal. The "Miller" had cylinders 10 inches in diameter by 16 inches stroke, and weighed in working order about 8 tons. The boiler was constructed with a high circular dome over the firebox, a form of construction which was consistently followed for many years afterward. The next engine, the "Lancaster," built in 1834, weighed about 8½ tons, and in that year five locomotives were completed. In the following year, the business having outgrown the works, a location was found on Broad and Hamilton Streets, the site of the present works, then in the suburbs of the city. From that time on the growth of the plant was rapid, fourteen engines being built in 1835 and forty in 1836. Without attempting to go into the details of the progress of the works, it is sufficient to state that several standard American types had their origin in the Baldwin shops, and of these, perhaps the most notable are the "Consolidation," the "Mogul" and the "Atlantic" types. The Consolidation," from which the type of this name was named, was built in July, 1866, for the Lehigh Valley Railway. She was a remarkably powerful engine for that day, with cylinders 20 by 24; four pairs of drivers connected, and a Bissell pony truck equalized with the front drivers. The engine in working order weighed 90,000 pounds. The "Mogul" class took its rise from an engine built for the Louisville & Nashville Railroad in 1861. The "Mogul" had three pairs of drivers connected, and a swinging pony truck, which was later equalized with the forward drivers. The first "Atlantic" type of locomotive was built in 1895 for the Atlantic Coast Line, which was followed by engines of the same type for the Atlantic City trains of the Philadelphia & Reading Railroad. The 1,000th locomotive was built in 1861. The 5,000th locomotive, built in 1880, was designed for fast passenger service between Philadelphia and New York, and to run with a light train at a speed of 60 miles per hour; its cylinders were 18 by 24, and it was carried on a four-wheel truck, one pair of 6½-foot driving wheels, and a pair of 45-inch trailing wheels equalized with the drivers. The 10,000th locomotive was completed in 1889; the 15,000th in 1896; and the 20,000th in 1902.

A banner year in the history of these works was the season of 1889, when the first of the now celebrated compound locomotives was completed and placed on the Baltimore & Ohio Railroad. It was of the four-cylinder type designed by S. M. Vauclain, the general superintendent, a high and a low-pressure cylinder being carried on either side of the smokebox, the high-pressure above and the low-pressure below, although in some later engines the positions are, for convenience, reversed. The two pistons on either side are connected to a common crosshead, and each pair of cylinders is cast in one piece with the piston, steam-chest and one-half of the saddle. The arrangement is shown very clearly in the accompanying perspective view of the cylinders. The valve, which is double and hollow, controls the steam admission and exhaust of both cylinders. The exhaust steam on the high-pressure cylinder becomes the supply steam for the low-pressure cylinder; and as the steam for the high-pressure cylinder enters the steam-chest at both ends the valve is in practically perfect balance. A by-pass valve is provided to admit live steam to the low-pressure cylinder in starting.

In view of the fact that there is, even to-day, a rather widespread, although mistaken, idea among railroad men that the superiority of the compound to the single-expansion locomotive is doubtful, it is well to draw attention here to two facts: First, that the scientific tests which have been made in experimental engineering laboratories, such as those at Purdue University and Columbia University, have shown that the compound locomotive is decidedly more economical than the single-expansion; and, second, that where the management, engineers and firemen of a railroad have taken hold of the compound with the determination to give it a perfectly fair trial, it has not proved more costly in repairs and has maintained what we might call its laboratorial reputation for economy. We quote from a paper on the performance of a four-cylinder Baldwin, compound locomotive, by Richard A. Smart, Assistant Professor of Experimental Engineering at Purdue University, in which he draws the following conclusions: First, that there was with an increase of speed an increase of horse power and economy up to 270 revolutions per minute; second, the indications were that the power would increase for speeds considerably above 270 revolutions per minute; third, the increase in economy with increase of speed was chiefly due to a decrease of cylinder condensation; fourth, the average steam consumption of the compound was much lower than the lowest consumption shown by the single-expansion engine; fifth, the saving in steam shown by the compound locomotive would result in a saving in coal of from 18 per cent to 33 per cent.

Perhaps the most celebrated locomotives turned out by these works are those which have been built to haul the extremely fast trains which are running between Camden, across the Delaware River from Philadelphia, and Atlantic City. These are of the celebrated "Atlantic" type in which the cylinders drive the rear pair of four-coupled drivers and the weight of the firebox is carried by a pair of trailers. Engine 1027 was built under guarantee to haul a train of eight cars (four coaches and four Pullmans) to Atlantic City, a distance of 55.5 miles, in sixty minutes; or to haul six cars over the same distance in fifty minutes, with a development of an estimated horse power of 1,400. In practice, however, this locomotive exceeded the guarantee by about 10 per cent. Another of the "Atlantic" type was built for the Chicago, Milwaukee & St. Paul Railroad, under contract to haul nine cars between Milwaukee and Chicago in one hour and forty-five minutes, with an estimated development of maximum horse power of 1,600. One of the latter engines exceeded the guarantee by four cars, hauling thirteen cars, in the specified time, the train and locomotive together weighing 600 tons. Following on these excellent results the company proceeded to make accurate tests of 1027 to determine just what the locomotive was capable of. It was found that with an experimental train of twelve coaches the horse power increased directly with the speed until it reached 1,450 horse power at 70 miles an hour, and even at this speed the locomotive had a reserve of power to overcome grade resistance or to enable it to accelerate the train to a higher speed.

It is a well-known fact that at the higher speeds the single-expansion locomotive is subject to drawbacks in the shape of wire drawing of the steam, back pressure in the cylinders and overforcing of the fire, which are absent in the compound with its wider range of expansion and its milder exhaust. Careful tests have shown over and over again that there is about 25 per cent economy in a compound as compared with a single-expansion locomotive doing the same work. This is due to the less evaporation required to develop the necessary energy, together with the slower rate of combustion of fuel resulting from exhausting the steam at lower tension. Of course, it is understood that these results are only obtained, as we have before remarked, where the management and operatives of the road are in thorough sympathy with the compound, and are desirous of giving it every facility to show its best results.

The 20,000th locomotive, of which we present an illustration, is a further improvement in which it is sought to secure a more perfect balance of the reciprocating parts than is possible on the ordinary type. The high and low-pressure cylinders, instead of being arranged above one another in a vertical plane, are all carried in one horizontal plane, the high-pressure cylinders within the frames beneath the smokebox and the low-pressure cylinders on the outside of the frames. The low-pressure crossheads are connected with the main driving wheels by outside connecting rods as in ordinary practice. The main driving axle has two cranks, which are set at right angles to each other on each side of the center of the locomotive, and each crank is coupled to the crosshead of one of the high-pressure pistons. The crank on the axle and the crank-pin in the wheel for the corresponding high and low-pressure cylinders are set at an angle of 180 degrees, and the two axle cranks being set at 90 degrees results in the action of each high and low-pressure cylinder, on one side of the locomotive quartering with the equivalent cylinders on the opposite side. As a consequence, an almost perfectly balanced engine is secured, and the amount of counter-balance required is reduced to a very low limit. The arrangement is the same as was used by Strong in his locomotive that attracted so much attention a dozen or more years ago, and it has lately been adopted with very good results on two or three of the English roads. Other special features of No. 20,000 are that it carries the Vanderbilt boiler and tender. In the former the firebox is cylindrical and corrugated, and in the tender the water tank is cylindrical, and the coal box is built at the front end of the tender and is, therefore, very conveniently placed for the fireman. The locomotive weighs in working order 176,510 pounds, of which 127,010 pounds are on the driving wheels. The weight of the tender loaded is 99,000 pounds. The driving wheels are 73 inches in diameter and the cylinders are 15 and 25 in diameter by 26 inches stroke. The boiler has a total heating surface of 2,793 square feet, of which 128 square feet are in the firebox.