For some years after this his first great triumph, George Stephenson gave his whole time to the building of railroads and the improvement of the engine. He was assisted by his son Robert, to whom he gradually surrendered his business, and retired to Tapton House, on the Midland Railway, and led a busy but pleasant life during the remaining years of his existence. Even as early as 1840, he seems to have projected many improvements which were only generally adopted many years later. He proposed self-acting and continuous systems of brake, and considered a good system of brake of so great importance, that he advocated their compulsory introduction by State legislation. He advised moderate speeds, from considerations both of safety and of expense. A few years after the opening of the Liverpool & Manchester road, great numbers of schemes were proposed by ignorant or designing men, which had for their object the filling of the pockets of their proposers rather than the benefit of the stockholders and the public; and the Stephensons were often called upon to combat these crude and ill-digested plans. Among these was the pneumatic system of propulsion, already referred to as first proposed by Papin, in combination with his double-acting air-pump, in 1687. It had been again proposed in the early part of the present century by Medhurst, who proposed a method of pneumatic transmission of small parcels and of letters, which is now in use, and, 15 years later, a railroad to take the place of that of Stephenson and his coadjutors. The most successful of several attempts to introduce this method was that of Clegg & Samuda, at West London, and on the London & Croydon road, and again in Ireland, between Kingstown and Dalkey. A line of pipe, _B B_, seen in Fig. 56, two feet in diameter, was laid between the rails, _A A_, of the road. This pipe was fitted with a nicely-packed piston, carrying a strong arm, which rose through a slit made along the top of the pipe, and covered by a flexible strip of leather, _E E_. This arm was attached to the carriage, _C C_, to be propelled. The pressure of the atmosphere being removed, by the action of a powerful pump, from the side toward which the train was to advance, the pressure of the atmosphere on the opposite side drove the piston forward, carrying the train with it. Stephenson was convinced, after examining the plans of the projectors, that the scheme would fail, and so expressed himself. Those who favored it, however, had sufficient influence with capitalists to secure repeated trials, although each was followed by failure, and it was several years before the last was heard of this system. [Illustration: FIG. 56.--The Atmospheric Railroad.]