The power and efficiency of locomotives has increased, perhaps, more since 1890, and particularly since 1895, than in any previous period. Superior materials particularly have contributed to this result, such as the substitution of cast steel for cast iron and of nickel steel for wrought iron in axles, crank pins, etc. Some of the improvements which may be mentioned are, for instance, an increase in the average heating surface from 2,000 in 1890 to nearly 3,000 square feet at the present time, and an increase in the average steam pressure from 160 pounds to 210 pounds per square inch in the same period. The maximum weight has also increased very rapidly. The average weight of a locomotive at the close of the Civil War was approximately 90,000 pounds. This has increased in somewhat the following proportions: To 1881, 102,000 lbs.; to 1893, 135,000 lbs.; to 1895, 148,000 lbs.; to 1898, 230,000 lbs.; rising in 1900 to 250,000 lbs. Passenger locomotives since 1892 have almost doubled in weight, and freight engines have more than done so. Compound and double or Mallet locomotives are also supplanting those of simpler type for peculiarly heavy service. The first compound engine was built in 1899, only one being constructed in that year. In 1900 a single locomotive works turned out 500--a number constituting two-thirds of the entire output of that company--for use in the United States. Such locomotives cost more in first instance; but the greater weight and steam capacity, together with the considerable saving in fuel, amounting to perhaps twenty per cent., more than offset this objection. The traction efficiency of these improved locomotives may be shown by the statement that in 1885 the decapod Baldwin locomotives, made to haul 3,600 tons on a level, represented the maximum capacity. Five years later the same company built locomotives to haul 4,000 tons, not only on a level, but on any ordinary grade. As indicative of late advances in locomotive construction, we may instance those built about 1900 for the Illinois Central and the Union Railroad at Pittsburg, both low-grade roads, carrying exceedingly heavy train loads. The first of these weighed, including its tender, 365,000 lbs., the Union Railroad consolidation engines weighing 334,000 lbs. Such locomotives are stated to be twice as powerful as the best which were manufactured twenty-five years ago. This record is surpassed by engines which have just been built for pusher service on the soft-coal Virginian Railway. They are of the Mallet type, weighing 540,000 pounds; with a train capacity of 4,230 tons. The evaporative surface is 6,760 square feet. As summarizing the increased efficiency of American locomotives, we may instance the figures of the Interstate Commerce Commission, showing the average performance of locomotives for the United States. Whereas in 1894 the average number of tons of freight carried per locomotive was about 32,000 tons, this rose to 46,000 tons in 1899, and to 54,600