"Sir,--I received your favour of the 12th February, but did not answer it in due course, because I was then erecting an engine on the new plan, which is now at work, and performs exceedingly well. It is equal in power to a 72-inch diameter cylinder, double power of B. and Watt's. The expense of erection, and the consumption of coals in this engine, are not one-third of a B. and Watt's to perform the same work. I am the same Trevithick that invented the high-pressure engine. I have sent out nine steam-engines to the gold and silver mines of Peru. I intend to sail for that place in about a month or six weeks, but shall appoint agents in England to erect these engines. "No publication or description whatever has been in circulation, neither is it required, for I have a great many more orders than I can execute. "I have not seen anything of Mr. Losh's patent engine, or Mr. Collins'. "If you should go to London I advise you to call on Mr. Jas. Smith, Limekiln Lane, Greenwich, who is an agent for me, and will soon be able to show you an engine on this plan at work. "I remain, &c., "R. TREVITHICK." Unless the foregoing letters are based on error, the only conclusion to be drawn is that Watt, on the expiry of his patent right and of twenty-eight years of labour, having erected his masterpiece in Cornwall, was within a few years so beaten that Trevithick, in his challenge to Woolf, offered to throw in the Watt engine as a make-*weight, and with such odds to bet him two to one that his comparatively small and cheap high-pressure engine should beat the two big ones, both in power, in first cost, and in economical working. The Watt engine was one of his largest, with a 72-inch cylinder. Its power was equal to Trevithick's 33-inch pole-engine, when worked with steam of 34 lbs. to the inch; but the latter also worked with three times that pressure of steam, whereby its power was increased threefold. The first cost of these engines was probably in inverse proportion to their power. Trevithick's cost 700_l._, while three times that sum would not pay for the Watt engine. The reported duty of Watt's Herland engine was twenty-seven millions; and if the trial was with his ordinary bushel of 112 lbs. of coal, the duty would only be equal to twenty millions with 84 lbs. of coal, which constituted the Cornish bushel. Trevithick's pole high-pressure steam-engine did fifty-seven millions; in other words, performed the same work as the Watt engine with less than half of the daily coal. This large economy led to orders for many engines, on his promise that they should cost much less than those of Watt of equal power, and should perform the work with one-third of the coal. Some believed him, though others were stony-hearted, and as obstinate as donkeys. [Rough draft.] "MR. PHILLIP, "PENZANCE, _8th March, 1816_.