To Watt, pressing pecuniary cares were never absent, and debt added to these made him the most afflicted of men. Besides this, he says, he had been cheated and was "unlucky enough to know." Wise man! ignorance in such cases is indeed bliss. We should almost be content to be cheated as long as we do not find it out. It was at such a crisis as this that another cloud, and a dark one, came. The sanguine, enterprising, kindly Roebuck was in financial straits. His pits had been much troubled by water, which no existing machinery could pump out. He had hoped that the new engine would prove successful and sufficiently powerful in time to avert the drowning of the pits, but this hope had failed. His embarrassments were so pressing that he was unable to pay the cost of the engine patent, according to agreement, and Watt had to borrow the money for this from that never-failing friend, Professor Black. Long may his memory be gratefully remembered. Watt had the delightful qualities which attracted friends, and those of the highest and best character, but among them all, though more than one might have been willing, none were both able and willing to sustain him in days of trouble except the famous discoverer of latent heat. When we think of Watt, we picture him holding Black by the one hand and Small by the other, repeating to them "I think myself in nothing else so happy As in a soul remembering my dear friends." The patent was secured--so much to the good--but Watt had already spent too much time upon profitless work, at least more time than he could afford. His duty to provide for the frugal wants of his family became imperative. "I had," he said, "a wife and children, and I saw myself growing gray without having any settled way of providing for them." He turned again to surveying and prospered, for few such men as Watt were to be found in those days, or in any day. With a record of Watt's work as surveyor, engineer, councillor, etc., our readers need not be troubled in detail. It should, however, be recorded that the chief canal schemes in Scotland in this, the day of canals for internal commerce, preceding the day of railroads that was to come, were entrusted to Watt, who continued to act as engineer for the Monkland Canal. While Watt was acting as engineer for this (1770-72), Dr. Small wrote him that he and Boulton had been talking of moving canal boats by the steam engine on the high-pressure principle. In his reply, September 30, 1770, Watt asks, "Have you ever considered a spiral oar for that purpose, or are you for two wheels?" To make his meaning quite plain, he gives a rough sketch of the screw propeller, with four turns as used to-day. Thus the idea of the screw propeller to be worked by his own improved engine was propounded by Watt one hundred and thirty-five years ago. This is a remarkable letter, and a still more remarkable sketch, and adds another to the many true forecasts of future development made by this teeming brain.