It seems to have been felt that unless the road were entirely reconstructed so as to bear the heavy weight of the locomotive—so much greater than that of the tram-waggons, to carry which the original rails had been laid down—the regular employment of Trevithick’s high-pressure tram-engine was altogether impracticable; and as the owners of the works were not prepared to incur so serious a cost, it was determined to take the locomotive off the road, and employ it as an engine for other purposes. It was accordingly dismounted, and used for some time after as a pumping-engine, for which purpose it was found well adapted. Trevithick himself seems from this time to have taken no further steps to bring the locomotive into general use. We find him, shortly after, engaged upon schemes of a more promising character, abandoning the engine to other mechanical inventors, though little improvement was made in it for several years. An imaginary difficulty seems to have tended, amongst other obstacles, to prevent its adoption; viz., the idea that, if a heavy weight were placed behind the engine, the “grip” or “bite” of its smooth wheels upon the equally smooth iron rail, must necessarily be so slight that they would whirl round upon it, and, consequently, that the machine would not make progress. Hence Trevithick, in his patent, provided that the periphery of the driving-wheels should be made rough by the projection of bolts or cross-grooves, so that the adhesion of the wheels to the road might be secured. Following up the presumed necessity for a more effectual adhesion between the wheels and the rails, Mr. Blenkinsop of Leeds, in 1811, took out a patent for a racked or tooth-rail laid along one side of the road, into which the toothed-wheel of his locomotive worked as pinions work into a rack. The boiler of his engine was supported by a carriage with four wheels without teeth, and rested immediately upon the axles. These wheels were entirely independent of the working parts of the engine, and therefore merely supported its weight upon the rails, the progress being effected by means of the cogged-wheel working into the cogged-rail. The engine had two cylinders, instead of one as in Trevithick’s engine. The invention of the double cylinder was due to Matthew Murray, of Leeds, one of the best mechanical engineers of his time; Mr. Blenkinsop, who was not a mechanic, having consulted him as to all the practical arrangements. The connecting-rods gave the motion to two pinions by cranks at right angles to each other; these pinions communicating the motion to the wheel which worked into the cogged-rail.