Although Evans' distinct contribution to the problem of steam locomotion on the common roads was not particularly practical it was at least important as being the first suggestion of anything of the kind in the United States. Road conditions in this country at that time were worse than they were in England and yet under more discouraging circumstances he was as far advanced in ideas and plans as his great contemporaries, Trevithick and others across the water. To Evans must be given the credit of perfecting the high-pressure, non-condensing engine, and even Trevithick, "the father of the locomotive," was largely indebted to him for his progress in the lines he was working on in England, his plans and specifications having been sent abroad for the English engineers to inspect in 1784.
Born at Leadhills, Scotland, October, 1783. Died in London, March 22, 1831.
More fortunate than most of the English inventors of the seventeenth and eighteenth centuries, with whom he was associated, William Symington came of a family that was able to give him a good education. His father was a mechanic who had charge of the engines and machinery at the Warlockhead lead mines, and the son gained his first knowledge of mechanics and engineering in the shops with his father. Intended for the ministry, he was sent to the University of Glasgow and the University of Dublin to pursue his studies. But the ministry had slight attractions for him, and when the time came for him to choose a profession, he adopted that of civil engineering.
In 1786 he worked out a model for a steam road-car. This was regarded very highly by all who saw it. It is said that Mr. Meason, manager of the lead mines at Warlockhead, was so pleased with the model, the merit of which principally belonged to young Symington, that he sent him into Edinburgh for the purpose of exhibiting it before the professors of the University, and other scientific gentlemen of the city, in the hope that it might lead in some way to his future advancement in life. Mr. Meason became the patron and friend of Symington, allowed the model to be exhibited at his own house, and invited many persons of distinction to inspect it. The carriage supported on four wheels had a locomotive behind, the front wheels being arranged with steering-gear. A cylindrical boiler was used for generating steam, which communicated by a steam-pipe with the two horizontal cylinders, one on each side of the firebox of the boiler. When steam was turned into the cylinder, the piston made an outward stroke; a vacuum was then formed, the steam being condensed in a cold water tank placed beneath the cylinders, and the piston was forced back by the pressure of the atmosphere. The piston rods communicated their motion to the driving-axle and wheels through rack rods, which worked toothed wheels placed on the hind axle on both sides of the engine, and the alternate action of the rack rods upon the tooth and ratchet wheels, with which the drums were provided, produced the rotary motion. The boiler was fitted with a lever and weight safety valve. Symington's locomotive was abandoned, the inventor considering that the scheme of steam travel on the common roads was impracticable.