GEOLOGICAL SOCIETY OP PENNSYLVANIA. 



381 



Abraham discharges, from the depth of 1440 feet, about 

 2,092,320 gallons every twenty-four hours. Dolcoath 

 mine, from nearly the same depth, about 535,173 gallons 

 in the same time ; and Hurl Yor from the depth of 950 

 feet 1,692,660 gallons. 



In no mining district of the world has the drainage of 

 water from mines, and the machinery and power apper- 

 taining to it, received greater attention and undergone 

 such important improvements as in Cornwall. Ever since 

 the efforts of Messrs Bolton and Watt, and their high 

 talents and abilities were exerted to bring into practice 

 their improvements on the steam engine, this mode of 

 power has added greatly to the development of the mine- 

 ral resources of that district of England. Much has since 

 been effected by the practical skill and repeated experi- 

 ments of the Cornish engineers; and even within the last 

 year an extraordinary increase of power has been at- 

 tained in consequence of the improvements introduced 

 by Messrs West and Petherick, two young engineers of 

 great rising eminence; and whose engine, erected at the 

 Lanescot mine, I had much satisfaction, lately, in in- 

 specting. The increase of power, thus obtained, will be 

 seen in the annexed tables of the duty of the various 

 steam engines of the different mines of Cornwall. 



The term horse power,^^ commonly used to express 

 the power of steam engines, is never used in Cornwall, 

 but the word " duty" substituted in its place. As these 

 engines are principally employed in drawing water from 

 the mines, it is the practice to express the duty of an 

 engine by the number of pounds it raises in a given time 

 to the height of one foot. This is ascertained by multi- 

 plying the weight lifted in a stated period, by the height 

 in feet it is lifted. Thus, if 1000 pounds of water are 

 lifted 20 feet high per stroke, it would be equivalent to 

 20,000 lifted one foot high. The power of an engine, 



