" Phan 
Quantity of Heat evolved from Atmospheric Air. 219 
proves that heat is generated by friction ; and Rumford has shown 
that the quantity is very considerable. According to an experi- 
this cause, he found that a mechanical force of one horse power 
evolved heat enough to raise the temperature of 263 pounds of 
water 90° EF’. in 24 hours; which, it may be easily calculated, is 
sufficient to melt 63 pounds of ice per hour. I consider that upon 
the principle on which the friction of the steam engine and simi- 
ar machines is usually calculated, the condensing pump, used in 
this experiment, consumed nearly one-half of a horse power. If 
this assumption be correct, and Rumford’s experiment be consid- 
ered a standard formula for such calculations, the heat generated 
by the piston and piston rod must have been equivalent to the 
fusion of about eighty pounds of ice per day; or was equal to an 
increase of temperature of (80—5000 = 8°-—-625) -125 of a degree. 
Applied to the data of the preceding table, these’ corrections 
will make the whole amount of heat evolved by air, compressed 
with a force of six atmospheres, as follows: 
Heat as shown by the water of injection,. .  . 8° 
added, for correction 1, _ . : ; : ‘ge Neti hs 
6c ce ce “ec 2 r 125 
“ pe we 3 : estimated at ‘ hes og 
3 vi 8°-500 
“deducted, for correction 4, eg Set gO 
dee ss : : ¢ x # x cf 80875 
es ae i ~ . re + x 
g the heat evolved: by the .co 
it ari@eorrét, 8 
