PNEUMATICS. 267 



360. In steam-engines of similar construction, 

 the effects are nearly as the quantity of fuel con- 

 sumed. 



In this estimate time is necessarily involved, as, in or- 

 der to derive the greatest advantage from a given 

 quantity of fuel, the combustion must neither be 

 too quick nor too slow. 



It is computed, that an engine of the best construc- 

 tion, will raise 20,000 cubic feet of water to the 

 height of twenty-four feet for every hundred weight 

 of good pit-coal. An engine with a cylinder of 

 thirty-one inches diameter, and making twelve 

 strokes in a minute, will do the work of forty 

 horses, and will burn 11,000 Ib. of the best Staf- 

 fordshire coal in a day. See Encyclopedia Britan- 

 nica, article Steam, p. 769. PHONY, Arch. Hyd. 

 1499, vol. ii. 



Motion produced by Gunpowder. 



361. When gunpowder is fired, a permanently 

 elastic fluid is generated, which being very dense, 

 and much heated, begins to expand with a force 

 at least 1000 times greater than that of air under 

 the ordinary pressure of the atmosphere. 



ROBINS' Tracts, New Principles of Gunnery, Prop. vi. 

 HUTTON'S Mathematical Dictionary, art. Gunpow- 

 der. 



1 In 



