EARLY APPLICATION OF THE ECCENTRIC.
On the early forms of locomotives, a single eccentric was used to operate the valve for forward and back motion. The eccentric was made with a half circular slot, on which it could be turned to the position needed for forward or back motion. It was held in the required position by a stop-stud fastened on the axle. Several forms of movable eccentrics were invented, and received considerable application during the first decade of railroad operating; but the best of them provided an extremely defective reversing motion. The first engineer to apply two fixed eccentrics as a reversible gear was William T. James of New York, who made a steam carriage in 1829, and worked the engine with four eccentrics,—two for each side. The eccentrics were connected with a link, but the merits of that form of connection were not then recognized here; for it was not applied to locomotives till it became popular in England, and was re-introduced to this country by Rogers. The advantage of the double fixed eccentrics seemed, however, to be recognized from the time James used them; for the plan was adopted by our first locomotive builders. The first locomotive built by Long, who started in 1833 what was afterwards known as the Norris Locomotive Works, Philadelphia, had four fixed eccentrics.