"Sir,--In consequence of the conversation that has passed between you and West Wheal Tin Croft adventurers, the said adventurers have resolved to put an engine on that mine, agreeable to the proposals offered by you; that is, the engine shall be capable of lifting a 5-inch bucket, 50 fathoms, 4-feet stroke, 15 strokes per minute, or a duty equal thereto; for which they will pay you 50 guineas one month after the engine shall be at work, and 50 guineas more at four months after that, and 50 guineas more at four months from that time, making the full payment of 150 guineas in nine months from the time the engine shall set at work, the adventurers paying all expense, except the engine materials, which shall be delivered on the mine. But in case the engine not performing the above duty, the adventurers to be at liberty to return the same engine, and you to pay back all the money that you had received for the said engine. "Signed by GABL. BLEWETT, "in behalf of the Adventurers and Company." Trevithick was willing to spend more than his last penny in establishing the superiority of his high-pressure steam expansive engines, but the selfishness of adventurers retarded their progress. The atmospheric, mentioned by Watt as working in Dolcoath in 1777,[88] did five or six millions of duty, yet in Trevithick's hands, about 1798 to 1800, when he erected his globular boiler with internal tube, one of them was tested with the 63-inch Watt low-pressure vacuum engine, when the latter did sixteen millions to ten millions by the atmospheric engine, being nearly double the duty it performed in its original form; and we shall still trace this same engine as Bonze or Gons until it increased to six times its first duty under the name of Stray Park 63-inch. [Footnote 88: See vol. i., pp. 30, 57; vol. ii., p. 115.] Trevithick having erected a high-pressure steam condensing whim-engine at Cook's Kitchen,[89] and in Dolcoath[90] a high-pressure puffer whim-engine, pleaded hard in 1806[91] to be allowed to supply the large pumping engines of Newcomen and Watt with higher pressure steam from his cylindrical boiler, which after years of consideration Dolcoath, in 1811, agreed to. In 1813 he wrote:--"That new engine you saw near the sea-side with me is now lifting forty millions, one foot high, with one bushel of coal, which is very nearly double the duty that is done by any other engine in the county. A few days since I altered a 64-inch cylinder engine at Wheal Alfred to the same plan, and I think she will do equally as much duty. I have a notice to attend a mine meeting to erect a new engine, equal in power to a 63-inch cylinder single."[92] [Footnote 89: See vol. i., p. 91.] [Footnote 90: See vol. i., p. 91.] [Footnote 91: See vol. ii., p. 142.] [Footnote 92: See Trevithick's letter, January 26th, 1813, vol. ii., p. 55.]