The first locomotive came into practical use in 1804. Twenty years before, Watt had patented—but had not constructed—a locomotive engine, the application of steam to drive carriages having first been suggested by Robinson in 1759. The first locomotives were very imperfect, and could draw loads only by means of toothed driving-wheels, which engaged teeth in rack-work rails. The teeth were very liable to break off, and the rails to be torn up by the pull of the engine. In 1813, the important discovery was made that such aids are unnecessary, for it was found that the “bite” of a smooth wheel upon a smooth rail was sufficient for all ordinary purposes of traction. But for this discovery, the locomotive might never have emerged from the humble duty of slowly dragging coal-laden waggons along the tramways of obscure collieries. The progress of the locomotive in the path of improvement was, however, slow, until about 1825, when George Stephenson applied the blast-pipe, and a few years later adopted the tubular boiler. These are the capital improvements which, at the famous trial of locomotives, on the 6th of October, 1829, enabled Stephenson’s “Rocket” to win the prize offered by the directors of the Liverpool and Manchester Railway. The “Rocket” weighed 4½ tons, and at the trial drew a load of tenders and carriages weighing 12¾ tons. Its average speed was 14 miles an hour, and its greatest, 29 miles an hour. This engine, the parent of the powerful locomotives of the present day, may now be seen in the Patent Museum at South Kensington. Since 1829, numberless variations and improvements have been made in the details of the locomotive. In weight, dimensions, tractive power and speed, the later locomotives vastly surpass the earlier types. [Illustration: FIG. 9.—_Section of Locomotive_ (A.D. 1837). ]