35 
Steam Engme. 
ceive 30^ of temperature ; and if the experiment be con- 
ducted with proper precautions, 90*^, the arithmetical 
mean of the temperature of the separate parts, will be the 
temperature of the mixture. If three pounds of water at 
100® be mixed with one pound at 60°, we shall have the 
same quantity of heat as before, viz, four pounds at 90°. 
Hence, if the quantity of water be multiplied by the tem- 
perature, the product will be a comparative measure of 
the quantity of caloric which the water contains, exceedr 
ing the zero of the thermometer employed. 
Thus, in the last example, 
•5 X 100 — 300 the caloric above zero in the first portion, 
lx 60 — 60 = the caloric above zero in the second do. 
The sum, 360 = the caloric above zero in the mixture. 
Dividing 360 by 4, the whole quantity of water, we ob- 
tain 90® , the temperature of the mixture. 
This method of computation may be conveniently ap- 
plied to a variety of cases. Thus, in the foregoing expe- 
riment, drachms of steam at 212° , added to 64 drachms 
of water at 50^, produced 72| drachms of water at 173 
Now, 
72i X 173 == 125421 
64 X 50 = 3200 
93421 
= whole heat of the mixture. 
_ C heat of 64 drachms, one of 
~ ^ the component parts. 
_ C heat of 8 | drachms, the other 
~ I component part. 
Therefore 93421 divided by 8| — 1099, should have 
been the temperature of the latter portion {viz, 6 1 drachms), 
had none of its heat been latent ; and 1099 — 212 = 887 
gives the latent heat of the steam. This result does not 
differ more than might be expected, owing to the unavoid- 
able inaccuracies of the experiment, from Mr. Watt’s de- 
termination, which states the latent heat of steam at 900^, 
^ from that to 950^. (Black’s Lectures, i. 174.) La^ 
