Note 207 — Chapter XV · Watt again visits Cornwall—Invention of the Rotary Motion—The Patent Right again assailed.

Boulton and Watt were by this time employing their engine for a like purpose, as appears from a letter of Boulton to S. Wyatt, dated 28th February, 1781, in which he says,—“We are now applying our engines to all kinds of mills, such as corn mills, rolling iron and copper, winding coals out of the pit, and every other purpose to which the wind or water mill is applicable. In such applications, one hundred weight of coals will produce as much mechanical power as is equal to the work of ten men for ten hours, and these mills may be made very much more powerful than any water-mills in England.” To Mr. Henderson he wrote at the same date:—“I make no scruple to say but that I could readily build a more powerful and in every respect better copper-rolling mill by steam than any water-mill now in England. As soon as the Cornish engines are at work, I intend to turn millwright and make our steam-mills universally known.”