2l6f HORSE-POWERS OF A ST^AM ENGINE. 



poimds; and Smeaton's 229] & pounds, under the fame clr- 

 curaftances. The lowed of thefe performances are more than 

 equal to the average power of a horfe employed in hufbandry 

 for eight hours per day. 

 A fteam engine If the diameter of the cylinder be multiplied by ilfelf (2l| 

 compute . x2l|), the produ6l will give 446;^ round inches for the whole 



furface : and Smeaton reckons the eflf;^6live or working pref* 

 fure per round inch on the atmofpheric engine, at feven 

 pounds avoirdupois. It is ufual to reckon the^ working pref* 

 fure on a clofe engine (like that in queftion), at 10 pounds 

 the round inch ; but I (hall firft take the feven pounds as 

 being againft the builder: So that, by multiplying the round 

 inches 446^: by 7, we have 3l23| pounds for the weight 

 raifed. But the ftrokes are 23 of four feet double per minute, 

 that is to fay, 184 feet. JVluUiply the weight 3I'23|: by the 

 height 184, and the produ6l 574760 will be-the mechanic 

 efFecl of the engine, or the number of pounds it will raife one 

 foot high in one minute. Laftly, Divide this by Boulton and 

 Watt*s horfe-power (5|*^|o), and the quotient 17 ^, or 

 Very nearly 18, will exprefs the power of the engine in 

 horfes. 



If we follow Defaguliers, the engine will prove equal to 21 

 horfes. 



And, according to Smeaton, its power will bfe equal to 25 

 horfes. 



If we had taken the prefiure at 10 pounds per round 

 inch,' the powers would have proved much greater, as 

 below. 

 Steam engine I" *-^^ above calculations the horfes are fuppofed to be 



can work ticble fairlv worked, and the engine is fuppofed to be flopped as 

 ^^'^* foon as the horfes leave off. But an engine can work the 



whole 24 hours ; and Smeaton, conHdering that three fetts of 

 horfes muft be kept to work conftantly for the fame time, 

 reckoned a fleam engine to be equivalent to three times as 

 many horfes as could equal its rate of working. The follow- 

 ing table will (hew the powers of this engine, according to all 

 thefe feveral methods : 



7lb. 



