98 Mr. W. J. Henwood's Notes on some recent Jmproveme?its 



cylindrical boilers*, now universally used in this county. To 

 these, every one at all acquainted with the Cornish improve- 

 ments ascribes a great part of the saving we have obtained. 

 This will further appear from an extract from a valuable work 

 edited by John Taylor, Esq. F.R.S. + : the monthly con- 

 sumption of coal in Dolcoath mine was in 



« 1 Rn7 f; 1 1 9 S 'bushels, and the mine was > 1 60 fath. level under 



' \ being sunk below the ^ adit: adit 42 f. deep. 



1808,5184- 170 fathom level. 



1809, 5688 



1810, 6840 180 fathom level 



1811, 6912 



18121,4752 190 fathom level. 



1813, 4536 



1814, 5413 



1815, 5954 . 



181 6§, 5322 



1817, 3102 



The alteration in the boilers, was the introduction of Capt. 

 Trevithick's cylindrical boilers in place of the common waggon 

 boilers, which had until then been there in use. 



In J811-12, Capt. Trevithick erected a single acting en- 

 gine of 25-inches cylinder, working with but two valves (the 

 exhausting valve being wanting) at Huel Prosper Mine in 

 the parish of Gwithian, which of course had a cylindrical 

 boiler, in which the pressure of steam was more than 40 

 pounds on the square inch above atmospheric pressure ; and 

 the engine was so loaded that it worked full seven-eighths of 

 the stroke expansively. Mr. Woolf, as Mr, Farey states ||, 

 came to reside in Cornwall about the year 1813, and his " first 

 engines for pumping water from mines were set up by him in 

 1814, at Wheal Abraham and at Wheal Vor mines in Corn- 

 wall ; they had each two cylinders." 



If the use of high-pressure steam acting expansively were 

 a part of Mr. Woolfs patent, to which he could establish a 

 legal and exclusive right ; why did he not prefer a claim on 

 Capt. Trevithick, or the adventurers in Huel Prosper Mine, 

 who were using an engine of that description before that gen- 

 tleman's arrival in Cornwall? The answer is obvious. Mr. 

 Taylor remarks 1[, " During the whole of this year (1814), 



• Phil. Mag. and Annals, N.S. vol. i. p. 127- f Records of Mining, 



p. 163. X Alteration in the boilers this year. 



§ In this year the old engine was replaced by a new one ; — of this more 

 hereafter. || Phil. Mag. and Annals, vol, viii. p. 308, 



K Records of Mining, p. 156. 



Jeffery 



