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IX. Notes on some recent Improvements of the Steam-Engines 

 in Cornwall. By W. Jory Henwood, F.G.S. Member of 

 the Royal Geological Society of Cornwall. 



To Richard Taylor, Esq. F.S.A. F.L.S. 8fc. 



Dear Sir, 



THE same excuse which was offered by Mr. Farey for his 

 long silence on the subject of my paper* may, perhaps, 

 now serve for mine on that of hisf. I shall not attempt a 

 regular discussion of his papers, as the digressions and the 

 many objects they embrace, would, I fear, be unsuitable to 

 your pages, and tiresome to your readers. I purpose confining 

 myself to the various alterations and improvements which 

 have been made in this county since Messrs. Boullon and 

 Watt, and their agents, ceased to superintend the steam- 

 engines on our mines ; with the addition of a few incidental 

 observations on some of Mr. Farcy's statements. 



In my former communication to you on this subject, I said 

 that " variation in the elasticity of the steam employed by 

 no means affects the invention [my views would have been 

 more correctly expressed, had I said the merit or priticiple of 

 the invention] of expansive working ;" and, notwithstanding 

 Mr. Farey's indignant attempts, he has advanced nothing 

 wiiich bears the semblance of proof of the contrary. 



Mr. Farey says:^, Mr. Watt " proposed in 1782 to work 

 his engines by stopping the supply of steam when the piston 

 had only moved one-fourth of its course." Will diat gentleman 

 j)articularize the engines in this county which 7ww expand 

 more than three-fourths of their stroke? " Mr. Watt's en- 

 gines with such boilers" (which will not retain steam of more 

 than 3^ pounds per square inch above the atmosphere) "can- 

 not be made to exert a competent power to drain deep mines, 

 unless the supi)ly of steam to the cylinder is continued until the 

 piston has run through more than half its course J." This 

 I humbly apprehend will depend on the size of the engine, 

 and the weight to be lifted. I hope I shall not be charged 

 with ♦'altering" this sentence so as to make it " very indefinite." 

 In 1801-2, Captain Trevithick erected a high-pressure 

 engine of small size at Marazion, which was worked by steam 

 of at least 30 pounds on the s(|uare inch above atmospheric 

 pressure. In 1804, as Mr. Farey admits f), tiie same gentle- 

 man introduced his celebrated and valuable wrought-iron 



• Phil. Mag. and Annals, N.S. vol. vii. p. 323. 

 f Ibid. p. 421. and vol. viii. p. 30.5. J Ibid. p. 309. 



§ Ibid. p. 313. . 



N.S. Vol. 10. No. 56. Aug. 1831. O cylmdri- 



