It will be observed from these explanations that Watt's views as to road locomotion were still crude and undefined; and, indeed, he never carried them farther. While he was thus discussing the subject with Boulton, William Murdock, one of the most skilled and ingenious workmen of the Soho firm--then living at Redruth, in Cornwall--was occupying himself during his leisure hours, which were but few, in constructing a model locomotive after a design of his own. He had doubtless heard of the proposal to apply steam to locomotion, and, being a clever inventor, he forthwith set himself to work out the problem. The plan he pursued was very simple and yet efficient. His model was of small dimensions, standing little more than a foot high, but it was sufficiently large to demonstrate the soundness of the principle on which it was constructed. It was supported on three wheels, and carried a small copper boiler, heated by a spirit-lamp, with a flue passing obliquely through it. The cylinder, of 3/4 in. diameter and 2 in. stroke, was fixed in the top of the boiler, the piston-rod being connected with the vibrating beam attached to the connecting-rod which worked the crank of the driving-wheel. This little engine worked by the expansive force of the steam only, which was discharged into the atmosphere after it had done its work of alternately raising and depressing the piston in the cylinder.
[Illustration: SECTION OF MURDOCK'S MODEL.]
Mr. Murdock's son informed the author that this model was invented and constructed in 1781, but, from the correspondence of Boulton and Watt, we infer that it was not ready for trial until 1784. The first experiment with it was made in Murdock's own house at Redruth, when it successfully hauled a model wagon round the room--the single wheel placed in front of the engine, and working in a swivel frame, enabling it to run round in a circle.
Another experiment was made out of doors, on which occasion, small though the engine was, it fairly outran the speed of its inventor. It seems that one night, after returning from his duties at the Redruth mine, Murdock determined to try the working of his model locomotive. For this purpose he had recourse to the walk leading to the church, about a mile from the town. It was rather narrow, and was bounded on each side by high hedges. The night was dark, and Murdock set out alone to try his experiment. Having lit his lamp, the water soon boiled, when off started the engine, with the inventor after it. Shortly after he heard distant shouts of terror. It was too dark to perceive objects; but he found, on following up the machine, that the cries proceeded from the worthy pastor of the parish, who, going toward the town, was met on this lonely road by the hissing and fiery little monster, which he subsequently declared he had taken to be the Evil One in _propria persona_!