It will be observed that the principal new features in this engine were the two cylinders and the toothed-wheel working into a rack-rail. Mr. Blenkinsop contrived the latter expedient in order to insure sufficient adhesion between the wheel and the road, supposing that smooth wheels and smooth rails would be insufficient for the purpose. Clumsy and slow though the engine was compared with modern locomotives, it was nevertheless a success. It was the first engine that plied regularly upon any railway, doing useful work; and it continued so employed for more than twenty years. What was more, it was a commercial success, for its employment was found to be economical compared with horse-power. In a letter to Sir John Sinclair, Mr. Blenkinsop stated that his engine weighed five tons; consumed two thirds of a hundred weight of coals and fifty gallons of water per hour; drew twenty-seven wagons, weighing ninety-four tons, on a dead level, at three and a half miles an hour, or fifteen tons up an ascent of 2 in. in the yard; that when "lightly loaded" it traveled at a speed of ten miles an hour; that it did the work of sixteen horses in twelve hours; and that its cost was £400. Such was Mr. Blenkinsop's own account of the performances of his engine, which was for a long time regarded as one of the wonders of the neighborhood.[33] The Messrs. Chapman, of Newcastle, in 1812 endeavored to overcome the same fictitious difficulty of the want of adhesion between the wheel and the rail by patenting a locomotive to work along the road by means of a chain stretched from one end of it to the other. This chain was passed once round a grooved barrel-wheel under the centre of the engine, so that when the wheel turned, the locomotive, as it were, dragged itself along the railway. An engine constructed after this plan was tried on the Heaton Railway, near Newcastle; but it was so clumsy in action, there was so great a loss of power by friction, and it was found to be so expensive and difficult to keep in repair, that it was very soon abandoned. Another remarkable expedient was adopted by Mr. Brunton, of the Butterley Works, Derbyshire, who in 1813 patented his Mechanical Traveler, to go _upon legs_ working alternately like those of a horse.[34] But this engine never got beyond the experimental state, for, at its very first trial, the driver, to make sure of a good start, overloaded the safety-valve, when the boiler burst and killed a number of the by-standers, wounding many more. These, and other contrivances with the same object, projected about the same time, show that invention was busily at work, and that many minds were anxiously laboring to solve the problem of steam locomotion on railways.