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46 Proceedings of the American Philosophical Society. or, 
6.29% 4=25.16, or nearly 25°F. As air at 82° F’. expands zl, for each 
‘additional degree, the difference of bulk, arising from the heat received, 
— above calculated, would be 2,°5, or 7's nearly. 
When air replete with aqueous vapor was admitted into a receiver par- 
tially exhausted, and containing liquid water, a copious precipitation of 
moisture ensued, and a rise of temperature greater than when perfectly 
dry air was allowed to enter a vessel containing rarefied air in the same 
state. In the instance first mentioned, a portion of vapor rises into the 
place of that which is withdrawn during the partial exhaustion. Hence, 
when the air, containing its fall_proportion of vapor, enters, there is an 
excess of vapor which must precipitate, causing a cloud, and an evolution 
of latent heat from the aqueous particles previously in the aériform state. 
Dr. Hare conceives that as the enlargement of the space occupied by a 
sponge, allows proportionably a larger quantity of any liquid to enter its 
cells, so any rarefaction of the air when in contact with water, conse- 
quent on increase of heat or diminution of pressure, permits a proportion- 
ably larger volume of vapor to associate itself with a given weight of the 
air. When, subsequently, by the afflux of wind replete with aqueous 
vapor, the density of the aggregate is increased, a portion of the vapor 
equivalent to the condensation must be condensed, giving out latent heat, 
excepting so far as the heat thus evolved, being retained by the air, raises 
the dew point. 
Hence, whenever a diminution of density of the air inland causes an 
influx of sea air to restore the equilibrium, there may result a condensa- 
of the Atlantic, is transferred to the soil of the United States. 
Dr. Hare proceeded to mention some additional experiments which he 
had made respecting the increase of temperature resulting from the ad- 
mission of dry air into an exhausted receiver. When the receiver was 
exhausted so as to reduce the interior pressure to one fourth of that of 
the atmosphere, and one fourth was suddenly admitted, so as to reduce @ 
gage from about 223 inches to 15 inches, heat was produced ; and how- 
ever the ratio of the entering air to the residual portion was varied, still 
there was a similar result. 
When the cavity of the receiver was supplied with the vapor of ether 
or with that of water, so as to form, according to the Daltonian hypothe- 
sis, a vacuum for the admitted air, still heat was produced by the latter, 
however small might be the quantity or rapid the readmission. When the 
receiver was exhausted, until the tension was less than that of aqueous 
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