
348 Mr. Watt's Thoughts on the conftituent 
és tary or latent heat which that water had ‘contained, both aaa 
‘air and as {team 3; and if from that quantity we deduét the . 
i, latent heat of the fteam, the remainder will be the latent or. 
‘¢ elementary heat contained more in air than in fteam.” This © 
experiment may be made more compleatly by means of the ex- 
cellent apparatus which Mefl. Lavorsier and De La Prace 
have contrived for fimilar purpofes. 
Until direct experiments- are made, we may conclude, from: 
thofe which have been made by the gentlemen juft named, on 
the decompofitions of air by burning phofphorus and char- 
coal, that the heat extricated during the combuftion of inflam- 
mable and dephlogifticated air is much greater than it appears 
to be; for they found that one Paris ounce (= 576 Parifian 
grains) of dephlogifticated air, when decompofed by burning 
phofphorus, melted 68,634 ounces of ice; andas, according to 
another of their experiments, ice, upon being melted, abforbs 
135° of heat, by FAHRENHEIT’s {cale, each ounce of air gave 
out 68,634 x 135°=9265°,590; that is to fay, a quantity of — 
heat which would have heated an ounce of water, or any other 
matter which has the fame capacity for receiving heat as water 
has, from 32° to 9265%°: a furprifing quantity! (It is to be 
underftood, that all the latent heats mentioned herein are com-_ 
pared with the capacity of water). And when an ounce of — 
dephlogifticated air was changed into fixed air, by burning } 
charcoal, or by the breathing of animals, it melted 29,547 oz. 4 
of ice; confequently we have 29,547 x 135°= 3988°,845. the 3 
quantity of heat which an ounce ef dephlogifticated air lofes” 4 
when it is changed into fixed air. By the heat extricated dur- 
ing the detonation of one ounce of nitre with one ounce of 
fulphur, 32 ounces of ice were melted ; and, by the experiment 
1 haye mentioned of Dr, PriesTLEy’s (6), it appears that 
nitre 
SS) 
