By F. A. Talbot 
ONE of the most remarkable features of railway operation during recent years has been the development of the mammoth locomotive. The era may be said to have commenced in France, but it is the Americans who have brought this movement to its highest pitch of perfection. The issue was forced upon the United States and Canadian railways. The necessity to haul immense loads, such as coal, ores, grain, etc., over long distances without breaking bulk, often struggling against heavy grades, presented peculiar difficulties. The eight, ten, or twelveton wagon common to the British railways became absolutely useless, because therewith, owing to the immense volume of the traffic to be handled, the lines would have become choked throughout the twentyfour hours with unwieldy long trains. During the year the United States railways have to handle over 1,500,000,000 tons of goods, which is about onesixth more than that moved on the combined railways of the United Kingdom, Germany, France, and Russia in the same period. Under such circumstances the futility of the small wagon may be appreciated. But there was another factor which influenced the situation very vitally. With the small wagon the proportion of "live" or paying tonnage in a train is small in comparison with the "dead" or nonpaying train tonnage, while more trainmiles have to be run in order to cope with the transportation of a certain volume of traffic. The point was to reduce both the number of trainmiles and the proportion of the dead load. This could be accomplished only by introducing larger vehicles. Accordingly there came the 30ton wagon, which enabled the train to be shortened very appreciably.
Once this development started it went ahead rapidly. The vehicles were increased in capacity, until today there are cars on the American and Canadian lines capable of carrying 75 tons. This means that when 5,000 tons of coal, ore, grain, or what not have to be moved a matter of ten or fifteen hundred miles, a single American train of 40 vehicles will handle what would require 300 British 10ton trucks. The operating expenses thus are decreased, as well as the trainmiles, while the income per train is increased. But the augmentation of the load per train precipitated another problem. The hauling power of a locomotive became overtaxed, so that it was necessary to utilise two engines to a train ; while for the negotiation of long steep banks through the mountains additional power had to be taken on, to push and haul the load over the hump, or else the train had to be divided and run in sections over the obstacle. The locomotive engineers were urged to evolve larger and more powerful engines to dispense with "doubleheading" and division of trains. This problem was not easy to solve, owing to the designer being cramped by the comparative narrowness of the standard gauge. The engineer increased the length and diameter of his boiler until he was unable to go another inch in either direction. Even then he encountered harassing difficulties in connection with his firebox and the complete combustion of his fuel. Additional driving wheels were introduced to secure the maximum adhesion and tractive effort, and remarkable ingenuity was displayed in order to secure efficient steaming qualities. In this search for greater locomotive power many striking and interesting types of engines were evolved, some of which are foreign to British working. Among these were such huge creations as the "Consolidation," the "Mastodon," and the "Mikado," with eight large drivers, the distinction between the types being attributable to the arrangement and number of the leading, trailing and driving wheels. Here it may be as well to describe how locomotive types are classified. The colloquial descriptions such as "Atlantic," "Pacific," "Baltic," "Consolidation," and so on are somewhat confusing, inasmuch as they convey no idea of the arrangement and number of the wheels. So the Whyte numerical system has come into general vogue as conveying the wheel disposition most satisfactorily. In this classification the wheels are divided into three groups, viz.—leading, bogie, or pony truck ; drivers ; and trailers. Thus an engine set out as of the 442 class indicates that there is a fourwheeled pony truck, followed by four drivers, and two trailing wheels, forming the familiar "Atlantic" type. If there are no leading or trailing wheels, or if one or the other be omitted, the absence is indicated by a cipher. Thus the numerical classification of a "Consolidation" locomotive is 280, signifying a twowheeled bogie, eight drivers, and no trailing wheels ; the "Mastodon" 480, with a fourwheeled bogie, eight drivers, and no trailing wheels; the "Mikado" as 282, representing a twowheeled pony truck, eight drivers, and twowheeled trailer. In view of the manner in which the locomotive engineers "have rung the changes" on the arrangement of the wheels, the Whyte numerical classification offers the simplest and most comprehensive method of nomenclature.
It was conceded generally that the ten driving wheel locomotive represented the limitations of design with a rigid wheel base. While engineers were racking their brains as to how to obtain greater power there appeared an invention which changed completely the whole problem of locomotive design. This was the articulated engine, as evolved by M. Anatole Mallet, of Paris. Its appearance on the French railways created a sensation. American engineers, realising its advantages, and the fact that therewith it was possible to obtain that increase in power which was demanded so urgently, embraced the idea forthwith. The outstanding feature of the Mallet locomotive is the division of the frame into two parts, which are connected together by a hinged joint. Each section of the frame carries a set of driving wheels and a pair of cylinders. In this way it is possible to obtain an engine having as many as twenty driving wheels—in two groups of ten each—and no more resistance is encountered in rounding curves than with an Atlantic engine. Compound working is adopted, the high pressure cylinders driving the inner, while the lower pressure cylinders drive the foremost group of wheels. These monster engines for the most part are utilised for three distinct services—express ; pusher, to assist trains over steep grades ; and the haulage of long, heavy freight trains. They are giants in the fullest sense of the word. For instance, the Great Northern "Big Bull Moosers " used on the Rocky and Cascade mountain divisions turn the scale, engine and tender complete ready for the road, at 300 tons, while the wheel base is 83 feet 1 inch. The high pressure cylinders have a diameter of 28 inches, while the low pressure cylinders are 42 inches diameter, the stroke being 32 inches. The Belpaire conical boiler has a diameter of 90 inches ; the firebox a length of 1171/4 inches by 961/4 inches wide, and 871/4 inches deep in front and 761/4 inches at the back. There are 832 tubes, each 24 feet in length, 21/4 and 51/2 inches in diameter. The firebox has a heating surface of 245 square feet ; the combustion chamber 81 square feet ; tubes 6,120 square feet ; giving a total heating surface of 6,446 square feet. The grate area is 78.4 square feet. The driving wheels are 63 inches, and the truck wheels 331/2 inches in diameter respectively. The driving wheel base is 433/4 feet in length, with 161/2 feet for the rigid base, bringing the wheel base of the total engine to 521/2 feet. The weight on the drivers is 210 tons, and on the front truck 15 tons. The tender, mounted on eight wheels, each of 36 inches diameter, carries 8,000 gallons of water and 13 tons of soft coal which is used as fuel. The engine is also fitted with an Emerson superheater, having a surface of 1,368 square feet. The working pressure of the steam is 210 pounds per square inch. It exerts a tractive force of 100,000 pounds.
This articulated Mallet engine, built by the Baldwin Locomotive Works at Philadelphia, has proved highly successful in the heaviest class of mountain service. The Pennsylvania Company also have designed a very powerful locomotive, classified by the company as the H8b type, for its heaviest freight service. This engine has four pairs of 62inch driving wheels, with a twowheeled pony truck, 280 class. The total length of the drivingwheel base of the engine is 17 feet 01/2 inch, of the engine 25 feet 91/2 inches, and of the engine and tender 59 feet 55/8 inches. The cylinders have a diameter of 24 inches with a stroke of 28 inches. The Belpaire wide firebox is used, being 1101/4 inches long by a width of 72 inches, the total heating surface being 187 square feet. The boiler has a minimum internal diameter of 763/4 inches ; there are 465 tubes of 2 inches outside diameter, the total heating surface of the tubes being 3,652 square feet. Steam is used at a pressure of 205 pounds per square inch. The weight of the engine in working order is 119.15 tons, of which 105.5 are upon the driving wheels. In working order the 8wheel tender weighs 79 tons, the complete weight of the locomotive therefore being 198.15 tons. An interesting experiment was carried out with this engine in order to ascertain. the precise freightcarrying possibilities of the 127 miles between Altoona and Enola Yard, opposite Harrisburg, Pennsylvania. This section of the system has been overhauled and reconstructed so as to secure no heavier rise than 12 feet per mile. Engine No. 1221 of the H8b type was attached to a train of 120 steel gondola cars laden with coal. Each wagon carried 521/2 tons of mineral, so that the total consignment represented 6,300 tons. The complete weight of the train, including engine, cars, and brakevan, or caboose, was no less than 8,850 tons. From end to end this train measured 4,888 feet—more than ninetenths of a mile. Despite the huge load the one engine, having a tractive power of 42,661 pounds, hauled the train over the distance of 127 miles unaided, occupying 9 hours 36 minutes on the journey, giving an average speed of 13 miles an hour. As, however, this time included delays aggregating some three hours, the actual running speed averaged 19 miles an hour. In making the trip the engine consumed over 13 tons of coal. A unique feature of the train was a telephone connection between the brakesman in the rear van and the driver of the locomotive, the wires being carried along the sides of the vehicles. While the Pennsylvania Railway Company has no intention of operating such trains regularly, yet from time to time it embarks upon such tests to determine the capacity of its freight locomotives over the improved lines, where grades have been removed and Curves compensated. Recently some very powerful "Mikados," among the largest and most powerful of the 282 type, have been constructed. The Baldwin Locomotive Works have supplied some of the largest of this class yet built for the Chicago, Rock Island, and Pacific Railway, for service upon its system where no excessively steep grades are encountered. The characteristic feature of this design is the boiler, which is constructed with a wide and deep firebox, 84 inches wide by 90 inches deep at back, and 77 inches deep at the front. The grate is placed behind the driving wheels and above the trailers, thus obtaining a large amount of grate area and furnace volume. The boiler is 86 inches in diameter, the tubes 21 feet long, having a total heating surface of 4,004 square feet. The driving wheels are 63 inches in diameter. The engine has a length of 35 feet 2 inches, the overall length of the locomotive being 67 feet 21/2 inches. The weight imposed on the drivers is 121.6 tons, while the total weight of the engine and 8wheel tender, the latter loaded with 16 tons of soft coal and 9,000 gallons of water, is 240 tons. Another wellknown system, the Delaware, Lackawanna, and Western Railroad, has also introduced fifteen Mikados of much greater sustained capacity than those hitherto used in its service. They have been constructed by the American Locomotive Company, and are being employed in the slow and fast goods service between Elmira and Buffalo. The boiler, 861/8 inches in diameter, has a total heating surface of 4,592.8 square feet, and works at a pressure of 180 pounds per square inch. The firebox is 108 feet long by 741/4 inches wide. The cylinders are of 28 inches diameter and 30 inches stroke. The grate area is 63.1 square feet, and the total heating surface 4,854.1 square feet with 1,085 square feet of superheater. The drivers, 63 inches in diameter, carry a weight of 118.75 tons, the total weight of the engine in working order being 156 tons. The 8wheel tender, loaded with 14 tons of soft coal and 8,000 gallons of water, weighs 79.85 tons, bringing the complete weight of the locomotive to 235.85 tons. These engines, with a maximum tractive power of 57,000 pounds, are superseding Consolidation locomotives, having cylinders of 26 inches diameter by 30 inches stroke, and a theoretical maximum tractive power of 51,400 pounds, in the slow freight traffic, while in the express goods service they are replacing Mogul—260 class—with cylinders 201/2 inches diameter and 26 inches stroke, and a maximum tractive power of 29,480 pounds. Although these Mikados have the same cylinder stroke as the superseded Consolidation engines, they have drivers of 63 inches instead of 57 inches. So far as the Moguls are concerned, these Mikados have almost 100 per cent. greater capacity. Among the most impressive, and largest, as well as the most powerful engines yet constructed, the Mallet compounds built by the Atchison, Topeka, and Santa Fe Railway, forming what are known as the "3000" class in the railway's service, stand preeminent. The engine alone weighs 308 tons, of which 275 tons are distributed over the twenty driving wheels, the articulated classification being 2100+0102. The tender weighs 117 tons, bringing the total weight of the locomotive in running order up to 425 tons. Its length over all is 120 feet 71/2 inches. The high and low pressure cylinders respectively are of 28 and 38 inches diameter, with a common stroke of 32 inches. The firebox, 1495/8 inches long by 78 inches wide and 76 inches deep, has 294.5 square feet of heating surface. The 377 fire tubes have a heating surface of 3,625 square feet, while the superheater has a surface of 2,318.4 square feet. There is also the reheater, and finally the feedwater heater, the tubes of which have a heating surface of 2,659.4 square feet. The introduction of the superheater, reheater and feedwater heater represents the latest development in locomotive engineering, the functions of which are described later. The driving wheels have a diameter of 57 inches, while that of the truck wheels is 341/4 inches. The tender is carried on twelve wheels, and has capacity for 12,000 gallons of water and 4,000 gallons of oil, liquid fuel being used, while the working pressure of the steam is 225 pounds per square inch. This huge locomotive has a maximum. drawbar pull of 111,600 pounds, and in an experimental run to ascertain its hauling capacity one of its class drew a train of 100 loaded freight cars, representing a live weight of 4,341 tons, from Emporia to Argentine, a distance of 111.5 miles, where the maximum grade is 21 feet per mile, in 6 hours 20 minutes. It has hauled a load of 1,911 tons at a speed of 12 miles per hour over a grade rising 79.2 feet per mile. At a speed of 10 miles per hour the engine develops some 3,000 horse power. At present these engines are being utilised for the most part in territory served by the Atchison, Topeka and Santa Fe Railway, where the ruling grade is 90 feet per mile, the trainloads upon this division averaging 1,900 tons, and the speed ranging between 12 and 15 miles per hour. Other locomotives of this class are reserved for pusher service, to assist the regular trains over Cajon Mountain in California, where the grade runs as high as 180 feet per mile. These Santa Fe giants have aroused worldwide interest.

