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TRANSACTIONS OF THE 



therefore, is expressed by the number of pounds it can 

 lift one foot high in a given time; and its expenditure of 

 fuel and consequent efficiency, by the number of pounds 

 it lifts to the height of one foot with one bushel of coals. 

 The comparative merits of different engines, therefore, 

 (whatever be their power, or depth of the mines, are 

 easily ascertained by this simple process. Therefore, if 

 an engine lift 100 millions of pounds one foot high per 

 hour, we ascertain its power; and if it lifts 100 millions 

 one foot high whilst it consumes two bushels of coal, the 

 work done with one bushel of coal is ascertained : and 

 by comparing that performance with another engine with 

 the consumption of the same quantity of fuel, we thus 

 ascertain the comparative efficiency of the two engines. 



The term horse power,'' however vague at first, 

 has, from long use, become as expressive as any other, 

 and conveys to those who understand it, as definite an 

 idea of the power of an engine, as the more intelligible 

 mode adopted by the Cornish mining engineers. It is 

 only necessary to know that the power of a horse is esti- 

 mated at 150 pounds lifted 220 feet per minute, or 33,000 

 pounds lifted one foot high per minute, and we can in- 

 stantly compare the power of an engine estimated by 

 horse power, with the power of one estimated by the 

 Cornish method. 



It would appear, from authentic experiments, that the 

 best engines, by Bolton and Watt, are estimated as capa- 

 ble of raising 19,800,000 pounds per bushel of coals, 

 while that of Messrs West and Peth crick raises 

 97,856,382 pounds per bushel of coals, being 80 inch 

 cylinder, single. 



The improvements generally, in the Cornish steam 

 engines, without including the additional ones introduced 

 by Messrs W. and P., would appear to be, in the opi- 

 nion of competent judges, as follows: — 



