175 
It was shown also in the same Paper, that the density of 
saturated vapour was to be obtained more accurately from 
this equation, and Regnault’s experiments on the latent heat 
of a stated weight of vapour, than from any direct experi- 
ments on the density of vapour made up to that time. This 
conclusion has been verified by the recent experiments of 
Messrs. Fairbairn and Tate. With the assistance of some 
excellent tables in Rankine’s “ Steam Engine and other 
Prime Movers,” calculated on these principles, the Author 
has obtained the following results : — 
Temperature 
centigrade, or 
< — 273-7. 
Volume of 1 lb. of 
air at pressure 
2,117 lb. per 
square foot. 
Dynamical 
value of latent 
heat of 1 lb. 
of saturated 
vapour. 
Proportionate 
diminution of bulk 
of saturated vapour 
per 1° cent, of any 
wanted 
temperature. 
Augmentation of 
volume of 1 lb. o' 
moist air required to 
cool it 1° cent. 
Elevation 
from earth’s 
surface re- 
quired to cool 
moist air by 
1° cent. 
J L 
d log s 
dv 
dx 
t— 273 7 
V. 
-dt 
—dt 
-dt 
0° 
12 - 38 cubic ft. 
249 ft. lbs. 
•0698 
T905 of a cubic ft. 
499 feet. 
5 
12-61 
348 
•0671 
•2150 
551 
10 
12-83 
481 
•0644 
•2434 
611 
15 
13.06 
655 
•0617 
•2753 
678 
20 
13-29 
881 
•0592 
•3096 
751 
25 
13-52 
1171 
•0569 
•3455 
827 
30 
13-74 
1538 
•0546 
•3800 
900 
35 
13-97 
1999 
•0524 
•3950 
932 
Tfie 
di) 
from the column headed by the following 
dx 
-=df=r 
V 
1 
) 
which shows the height, dx, that must be reached to get a 
lowering of temperature, — dt, when air saturated with 
moisture ascends. The pressure,^, is taken as 21 17 lbs. per 
V • 
square foot ; and the value of — , which is the name for the 
L 
