66 connection between him and Roebuck, had formed a great esteem for his new acquaintance, had pressed him to settle at Birmingham, and had engaged, (which in any case he said they would most certainly do), that Mr. Boulton and he should both assist him in every possible way. "I have no "kind of doubt of your success," says Dr. S., "nor of your acquiring fortune, if you proceed upon a proper plan as to "the manner of doing business, which if you do you will be "sole possessor of the affair, even after your patent has expired. Whether it would be possible to manage "the wheel and reciprocating engines by separate partnerships, without their interfering, I am not certain; if it is, "Boulton and I would engage with you in either, provided you will live here. I am, in haste, dear Watt, your affec"tionate humble servant, W. SMALL." 66 66 66 They were evidently in greater doubt as to the expediency of forming any intimate business connection with Roebuck, some rumours of the dangerous extent of whose enterprises had probably reached Birmingham; although of him also, it is proper to add, Dr. Small writes, at the same date, "his integrity and generosity, everybody agrees, are "great." In the earlier part of 1768, Mr. Watt, "close-working," as he terms it, actively renewed his experimental alterations and trials of both the wheel or circulating engine, and the reciprocating or condensing one. Putty and other lutings, intended to keep the complicated valves of the former tight, in reality hindered them from shutting, by being metamorphosed into "the form of little balls;" and contributed to make the completion of that machine,-what it always remained,—a sort of labour of Sisyphus. But in the latter, great progress was made; for, although "the mercury" (with which the piston was packed), "by an unforeseen accident "found its way into the cylinder, and played the devil with "the solder," yet the piston was made to act by steam above it, as well as by the vacuum below it; the cylinder was set wholly in a steam-case; the piston was "extremely tight, and might easily be made tighter still; made of pasteboard, 66 "baked with linseed oil, and put on like the leather of a e 66 pump-box." He further proposed making two exhausting barrels instead of one, and giving them each half of its stroke, thereby producing a more perfect vacuum; "making the engine go of itself, "that the strokes may be counted, and the water measured "that is boiled away. These things are in hand, and will 66 soon be done." This was on the 29th of April, and by the 10th of May he had got the two new exhausting cylinders cast, bored, and partly turned, as well as new condensers made, and expected to have them going again by the end of the week. 66 "The two cylinders stand side for side; the pipe sat bottom "communicate with two condensers, which, by the pipe c, "communicate with the large cylinder. There is a valve at e "that prevents the air and water in the condenser from going "into the big cylinder at the return of the piston of the exhauster, but obliges them to go out at the top of the con"denser through the pipe e, having a valve at bottom to "prevent their return. This pipe e has another use, viz., to "measure accurately the quantity of water condensed [at] "each stroke, by observing what space it occupies in this tube. "I take this to be the best way of determining that article, "if we can make the pistons of the exhausters tight, so that none may be introduced that way. As soon as I have got "it completed I will write you, that I may either come to 66 you and give you account of the success, or you come here "and see the machine go. I am uneasy till I know the "exact quantity of steam consumed; though from several "circumstances I think it will answer hopes. At any rate "the vacuum is good and sudden; the consumption un"doubtedly the least possible." After one or two trials which gave good promise, but left "several motions to adjust still," on the 24th of May he was at last able to send the following satisfactory report to Dr. Roebuck: |