The locomotive which we illustrate this week is unquestionably the most powerful ever constructed. As we have shown elsewhere, the continually increasing size of American engines is due to the desire to secure the most economical results in operation. As between the policy of hauling a heavy train with a single engine or two light trains with light engines, there is, in the former case, a saving of the expense of a complete train crew. Further advantages, at least on tracks where the traffic is heavy, result from the reduction of the number of separate trains in operation.

The two locomotives of the type shown have recently been built by the Pittsburg Locomotive and Car Works for the Union Railroad Company, Pittsburg. They are at work on a short stretch of line between Munhall and North Bessemer, Pa., which forms part of the Carnegie system and connects the Duquesne Furnaces, Homestead Steel Works and the Edgar Thomson Steel Works. Four miles of the line are built on a grade of 70 feet to the mile and another stretch of the road (about 2,000 feet) is built on the unusually heavy grade of 2.7 per cent.

We are informed by Mr. D. A. Wightman, the general manager of the Pittsburg Locomotive and Car Works, to whom we are indebted for the photographs from which our engravings were prepared, that, owing to the great amount of wet weather since these locomotives went into service, the company have been unable to secure any reliable data of their performance in actual service on the various grades of the road.

The estimated tractive force, however, is 53,280 pounds and the estimated hauling capacity on a practically level track is about 6,650 tons. Now, just what these figures mean can perhaps be best understood by expressing them in other terms. The accompanying sketch, which is, of course, purely imaginary, shows what an engine with a drawbar pull of 26½ tons could accomplish in the way of lifting dead weight. The locomotive slung in chains represents a passenger engine of the average size used in this country thirty to forty years ago. If a cable were passed from the slings over a pulley and carried to the drawhead of the tender of one of these Pittsburg consolidations, she would be able to raise the smaller locomotive by direct pull without the use of any kind of purchase.

The hauling capacity on a level of 6,650 tons represents a train of 166 box cars loaded with wheat. The total length of such a train would be 5,700 feet, or considerably over a mile, and the wheat would represent, at an average of 15 bushels to the acre, the product of 9,000 acres, or over 14 square miles of land. And this enormous load could be taken over the road, or rather the level portions of it, at a comfortable speed of 10 miles an hour.

He would have seemed a bold prophet to our forefathers who would have dared to foretell that at the close of this century we should have steam horses that could cart away the products of 14 square miles of the countryside at a load, and do it at a gait faster than that of the local mail coach.

The very remarkable photograph which is reproduced on the front page serves excellently well the purpose for which it was taken, namely, to give an impressive idea of the great size of the parts of the locomotive. The little engine was lifted to its perch by the shop crane. It is standing on the cylinder casting, which weighs 8¾ tons, as against a weight of 6¼ tons for the yard engine. The other particulars of the yard engine are: Cylinders, 6 by 10 inches; gage, 24 inches; diameter of boiler, 24 inches; driving wheels, 26½ inches; tractive force, 1,883 pounds.

It will thus be seen that the cylinders of the big engine, which are 23 inches in diameter, are only 1 inch less than the diameter of the yard engine boiler.

The cylinders of the consolidation are of the half-saddle type, made heavy, and have great depth longitudinally. A steel plate 1-and-three-eighths inches thick, and of the same width as the bottom of the saddle, extends across and is bolted to the lower frames, and to this plate, as well as to the frames, the cylinders are securely fastened. Heavy bolts passing through the top frame bars at the front and back of the saddle form additional transverse ties, and relieve the saddle casting from all tensile strains. The longitudinal strains usually transmitted to cylinders through frames are largely absorbed by the use of a casting extended from the buffer beam well up to the saddle, and securely bolted to the top and bottom frames. This casting also acts as a guide for the bolster pin of the truck. The above method of relieving cylinders of longitudinal stress was introduced by the Pittsburg Locomotive Works nearly two years ago and has proved in practical use on a large number of locomotives to be of great value in reducing the breakage of saddle castings. The frames are 4½ inches wide. They were cut front rolled steel slabs made by the Carnegie Steel Company and weigh 8½ tons per pair, finished.

In the accompanying table we give a comparison of some of the most notable of the recent big freight locomotives, from which it will be seen that the latest is considerably the largest of the big fellows. They are arranged in the order of their construction.

The tender is of the standard type and weighs, loaded, 52 tons, so that the weight of the engine and tender in working order is 167 tons. The total length over all of engine and tender is 63 feet 3½ inches. The center of the boiler is 9 feet 3-and-three-eighths inches above the rails, the top of the boiler is 13 feet and the smokestack 15½ feet above the rails. The driving axle journals are 9 by 12 inches, and the main crank-pin is 7 by 7 inches. The steam ports are 1-and-three-eighths inches wide by 20 inches long, while the exhaust ports are 3¼ inches by 20 inches. The tender has a capacity of 5,000 gallons of water and 10 tons of coal.