He continued to be the "right hand man" of the concern in Cornwall. Boulton wrote to Watt, towards the end of 1782: "Murdock hath been indefatigable ever since he began. He has scarcely been in bed or taken necessary food. After slaving night and day on Thursday and Friday, a letter came from Wheal Virgin that he must go instantly to set their engine to work, or they would let out the fire. He went and set the engine to work; it worked well for the five or six hours he remained. He left it, and returned to the Consolidated Mines about eleven at night, and was employed about the engines till four this morning, and then went to bed. I found him at ten this morning in Poldice Cistern, seeking for pins and castors that had jumped out, when I insisted on his going home to bed." On one occasion, when an engine superintended by Murdock stopped through some accident, the water rose in the mine, and the workmen were "drowned out." Upon this occurring, the miners went "roaring at him" for throwing them out of work, and threatened to tear him to pieces. Nothing daunted, he went through the midst of the men, repaired the invalided engine, and started it afresh. When he came out of the engine-house, the miners cheered him vociferously and insisted upon carrying him home upon their shoulders in triumph! Steam was now asserting its power everywhere. It was pumping water from the mines in Cornwall and driving the mills of the manufacturers in Lancashire. Speculative mechanics began to consider whether it might not be employed as a means of land locomotion. The comprehensive mind of Sir Isaac Newton had long before, in his 'Explanation of the Newtonian Philosophy,' thrown out the idea of employing steam for this purpose; but no practical experiment was made. Benjamin Franklin, while agent in London for the United Provinces of America, had a correspondence with Matthew Boulton, of Birmingham, and Dr. Darwin, of Lichfield, on the same subject. Boulton sent a model of a fire-engine to London for Franklin's inspection; but Franklin was too much occupied at the time by grave political questions to pursue the subject further. Erasmus Darwin's speculative mind was inflamed by the idea of a "fiery chariot," and he urged his friend Boulton to prosecute the contrivance of the necessary steam machinery.[6] Other minds were at work. Watt, when only twenty-three years old, at the instigation of his friend Robison, made a model locomotive, provided with two cylinders of tin plate; but the project was laid aside, and was never again taken up by the inventor. Yet, in his patent of 1784, Watt included an arrangement by means of which steam-power might be employed for the purposes of locomotion. But no further model of the contrivance was made.