In pursuance of this call upon American genius, three locomotives were produced, but only one of these was made to answer any useful purpose. This engine, the "York," was built at York, Pa., and was brought to Baltimore over the turnpike on wagons. It was built by Davis & Gartner, and was designed by Phineas Davis, of that firm, whose trade and business was that of a watch and clock maker. After undergoing certain modifications, it was found capable of performing what was required by the company. After thoroughly testing this engine, Mr. Davis built others, which were the progenitors of the "grasshopper" engines (Fig. 7) which were used for so many years on the Baltimore & Ohio Railroad. It is a remarkable fact that three of these are still in use on that road, and have been in continuous service for over fifty years. Probably there is no locomotive in existence which has had so long an _active_ life. [Illustration: Fig. 7.--"Grasshopper" Locomotive. (From an old photograph.)] In August, 1831, the locomotive "John Bull," which was built by George & Robert Stephenson & Company, of Newcastle-upon-Tyne, was received in Philadelphia, for the Camden & Amboy Railroad & Transportation Company. This is the old engine which was exhibited by the Pennsylvania Railroad Company at the Centennial Exhibition in 1876. After the arrival of the "John Bull" a very considerable number of locomotives which were built by the Stephensons were imported from England. Most of them were probably of what was known as the "Planet" class (Fig. 8), which was a form of engine that succeeded the famous "Rocket." The following quotation is from "The Early History of Locomotives in this Country," issued by the Rogers Locomotive & Machine Works: These locomotives, which were imported from England, doubtless to a very considerable extent, furnished the types and patterns from which those which were afterward built here were fashioned. But American designs very soon began to depart from their British prototypes, and a process of adaptation to the existing conditions of the railroads in this country followed, which afterward "differentiated" the American locomotives more and more from those built in Great Britain. A marked feature of difference between American and English locomotives has been the use of a "truck" under the former. [Illustration: Fig. 8.--The "Planet."]