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The questions now arise — 1st, What becomes of the 
enormous quantity of heat given off by the vapour which is 
condensed in the atmosphere ? And 2nd, As the mois- 
ture which forms rain is not in the state of a true vapour, is 
it in the ordinary liquid state, or in some other state not 
hitherto recognised by meteorologists and chemists ? With 
regard to the first question, it may be remarked that air nearly 
saturated with vapour, has probably a greater power of 
radiating heat than dry air. The upper portion of a wind 
charged with vapour would therefore undergo a rapid cooling, 
and as the vapour which loses its latent heat does not imme- 
diately affect the transparency of the air, this process would 
go on unchecked for some time, and would gradually extend 
to the lower strata ; the vapour which had lost its latent heat 
would also gradually descend and accumulate in the lower 
atmosphere, until at a certain stage of the process clouds and 
rain were formed. This view of the subject is supported by 
the well-known fact, that the rate of decrease of the tempera- 
ture of the atmosphere with the height, is greater in rainy 
than in fine weather ; and it appears likely to lead to a 
satisfactory explanation of many important atmospherical 
phenomena. 
With respect to the second question, it is difficult to offer 
any plausible conjecture. There can, however, be little 
doubt that vapour deprived of its latent heat often exists to a 
considerable extent in the atmosphere without sensibly affect- 
ing its transparency ; and, indeed, it often happens that the 
atmosphere is unusually transparent immediately before, and 
even during showers of rain, and when, therefore, it is 
strongly charged with vapour in this peculiar state. 
Notwithstanding the cooling by radiation of the upper 
portion of a warm, moist wind, it is very probable that at a 
station on the surface of the earth, the temperature would be 
found to go on slowly increasing, in consequence of the 
