TI1K WATT AND THE TREVITHICK ENGINES. 



181 



in 1811, (>912 bushels; in 1812, 4752 bushels. 1 The alteration 

 in the boilers was the introduction of Captain Trevithick's cylin- 

 drical boilers in the place of the common waggon boilers, which 

 had until then been there in use. 



" 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.' " 2 



The foregoing was read at the Philosophical Society 

 in 1831, to refute erroneous statements on the Watt 

 and Trevithick engines. My fn'end Mr. Henwood had 

 at that time made official experiments in conjunction 

 with Mr. John Rennie on the detail, working, and duty 

 of high-pressure steam Cornish engines, the Watt low- 

 pressure steam principle having been wholly given 

 up. Bees's ' Cyclopaedia ' 3 also bears the following 

 similar testimony to date of the increased duty : 



" Trevithick's high-pressure engine was erected in Wales in 

 1804 to ascertain its powers to raise water. The duty was 

 seventeen millions and a half pounds raised one foot high for 

 each bushel of coals. 



" The high-pressure steam-engines require a greater quantity 

 of coals, in proportion to the force exerted, than the engine of 

 Mr. Watt, and consequently are not worked with advantage in 

 a situation where coals are dear. 



" From the reports of the engines now working in the mines 

 of Cornwall, which, with the exception of a few of Woolf 's 

 engines, are all on Mr. Watt's principle, and most of them con- 

 structed by Messrs. Boulton and Watt, taking the average of 

 nine engines bad, good, and indifferent together they were 

 found in August, 1811, to raise only thirteen millions and a half. 

 But when it was known by the engine keepers that their engines 

 were under examination, they took so much pains to improve the 



1 Alteration in the boilers that 

 year. 



2 ' Phil. Mag. and Annals,' vol. x., 

 p. 97, " Xotes on Some Recent Im- 

 provements of the Stcam-Engine in 



Cornwall," by W. Jory Henwood, 

 F.G.S. 



3 See Rees * On the Steam-Engine,' 

 published 1819. 



