Dr. Black continued to take a lively interest in Watt’s experiments, and lent him occasional sums of money from time to time to enable him to prosecute them to an issue. But the Doctor’s means were too limited to permit him to do more than supply Watt’s more pressing necessities. Meanwhile, the debts which the latter had already incurred, small though they were in amount, hung like a millstone round his neck. Black then bethought him whether it would not be possible to associate Watt with some person possessed of sufficient means, and of an active commercial spirit, who should join as a partner in the risk, and share in the profits of the enterprise. Such a person, he thought, was Dr. Roebuck, the founder of the Carron Iron Works, an enterprising man, of undaunted spirit, not scared by difficulties, nor a niggard of expense when he saw before him any reasonable prospect of advantage.[81] [81] For Memoir of Roebuck, see ‘Industrial Biography,’ p. 133. Roebuck was at that time engaged in sinking for coal on a large scale near Boroughstoness, where he experienced considerable difficulty in keeping the shafts clear of water. The Newcomen engine, which he had erected, was found comparatively useless, and he was ready to embrace any other scheme which held out a reasonable prospect of success. Accordingly, when his friend Dr. Black informed him of an ingenious young mechanic at Glasgow who had invented a steam-engine, capable of working with increased power, speed, and economy, Roebuck immediately felt interested, and entered into correspondence with Watt on the subject. He was at first somewhat sceptical as to the practicability of the new engine, so different in its action from that of Newcomen; and he freely stated his doubts to Dr. Black. He was under the impression that condensation might in some way be effected in the cylinder without injection; and he urged Watt to try whether this might not be done. Contrary to his own judgment, Watt tried a series of experiments with this object, and at last abandoned them, Roebuck himself admitting his error. Up to this time Watt and Roebuck had not met, though they carried on a long correspondence on the subject of the engine. In September, 1765, we find Roebuck inviting Watt to come over with Dr. Black to Kinneil (where Roebuck lived), and discuss with him the subject of the engine. Watt wrote to say that “if his foot allowed him” he would visit Carron on a certain day, from which we infer that he intended to walk. But the way was long and the road miry, and Watt could not then leave his instrument shop, so the visit was postponed. In the mean time Roebuck urged Watt to press forward his invention with all speed, “whether he pursued it as a philosopher or as a man of business.”