226 
Moisture in Air . 
[April, 
with the use of ice ; in faCt it has been shown that ice itself 
may be manufactured with profit by this process in some 
localities, where transportation enhances the price of ice 
largely ; but it is preposterously expensive in apparatus and 
in cost of working as a means of cooling air in the great 
quantities demanded for ventilation, and the humidity of the 
cooled air would still be objectionable. The comparatively 
high temperature of the surface for cooling the air would 
fail to be very efficient in condensing the vapour thoroughly. 
In both the methods of cooling air, whether by ice or by 
water (of which great quantities would be needed), the 
cooling surface must be copper, brass, or tin, as the rusting 
of iron, when exposed to condensing vapour, is extremely 
rapid. 
The most probable result of cooled air would be a thunder- 
cloud in miniature. The atmosphere on one of our hottest 
and most sultry days of summer is on the verge of a tem- 
pest. Cooling of air of 85° to go 0 , to the extent of 20° or 
30°, produces a dense mist of super-saturated cooled air. 
The equilibrium of the atmosphere on a still, clear summer 
day, when every growing thing on the surface of the ground 
is supplying moisture, and the radiation of the ground itself 
is supplying heat to increase the relative levity of the strata 
of air next the ground — the equilibrium of such an atmo- 
sphere is very unstable. Let an upward flow be established 
anywhere, and the air will rush in all directions along the 
surface to supply the partial vacuum. The ascending 
column, as it reaches the region of lower barometrical 
pressure, will expand, become sensibly cooler, and in a short 
5 to 8 miles of height the region of frost and ice will be 
reached, and hailstones will be returned from the condensa- 
tion of the transparent vapour which had existed in the air 
when it left the surface of the ground. The writer once saw 
in a little ball-room, on a Christmas Eve, a miniature snow- 
storm deposit a little bank of snow, from the opening of 
windows to air the room when the dancers had retired, the 
night being a clear moonlight one, with the thermometer a 
little above zero. 
The difficulty of absence of moisture in air that is heated 
in winter is a matter to be disposed of with some happiness, 
by asserting it is not wanted, but the objection of presence 
of moisture in cooled air can be only overcome by not cooling 
the air. It does not seem that the successful cooling of our 
summer air, so as to produce a comfortable or healthful 
condition at spring temperatures, has any probability of 
accomplishment. 
