HORSE-POWERS OF A STEAM-ENGINE. 215 



Report concerning the Power of a Steam-Engine ereBed bi/ Cori" 

 traa at * ^**. 



IT is required to determine whether the fteam-engine ere6led Steam engine aC 

 g^t ♦ * ♦ * lyy j^r. — ^, be equal to the power of fixteen ***** 

 horfes. The fame has a cylinder of 21| inches diameter, and 

 gives 23 doable ftrokes per minute, of four feet each. 



In anfwer to this quefiion it muft be previoufly remarked, Reafon why 



that fleam-eniiines havins: ori<rinally been recommended and f ^^"™, ^"S'n« 



" o o y ^ have been com* 



fubflituted inftead of horfes, the method of computing by the pared with 



number of thofe animals intended to be fupplied by means of ^°'^^"' 

 this invention, has been generally applied, though it is much 

 lefs certain and accurate than other methods well known to 

 mechanical men. The uncertainty of calculating by horfe-Itlsanuncertaijj 

 powers arifes from various caufes ; fuch as the great differ.-"^ 

 ences of ability between the flrong and heavy horfes ufed in Lon- 

 don, and thofe of not half the flrength ufed in various parts of 

 the country ; the greater or lefs degree of fpeed during work ; 

 the quantity of re-aftion agalnfl: which they are urged to pull; 

 the (horter or longer time of work ; their food, fiabling, &c. 

 &c. And this uncertainty, as may eafily be conceived, is (o 

 great, that the words horfe^poiver cannot pradically be ap- 

 plied, otherwife than to denote a certain quantity of mechanic 

 effed agreed upon and underftood between engineers, and 

 muft not be underftood to denote any elementary meafure, ^ 

 capable of being worked out or inferred within any reafonable 

 or ufeful limits, from the real power of the horfe hlmfelC 



It therefore follows of neceffity, that the engine muft be Words horfe- 

 iexamined by firft ftating its mechanic effea; that is to %, Jo^e^an'^arbicrarr 

 how many pounds weight it is capable of raiting through a quantity of 

 given fpace in a given time, that is to fay, through the height ^^^^' 

 of one foot during one minute, and then dividing this fum by 

 the like effeQ producible by one horfe, according to the ftate- 

 ments and pradice of engineers of the firft reputation. I con- 

 fine myfelf to MelT. Boulton and Watt, Dr. Defaguliers and 

 Mr. Smeaton, 



The pradice of MelT. Boulton and Watt is, to con fider a Quantities of 



horfe as capable of raifing a certain weight, which is ftated to ^^"^^ P^*^ ^°^^^» 

 . r^ 1 • 1 • r X 1 • 1 • . by Boulton and 



be ot 32000 pounds avoirdupois, one toot high m one minute, -vvatt, Defagu- 



Pefaguliers' refults brought to the fame form, give 27500 lie« and Smca* 



' , tO£U 



pounds i 



