496 PHILOSOPHY OF STORMS. 



as a dense fog, or drop in small rain all day long, scarcely 

 clearing once ; the country, at a little distance, having very 

 little rain." 



The bad philosophy of supposing the air so light on these 

 occasions as to let the clouds on passing sink down in it 

 over London, does not invalidate the evidence of the prin- 

 cipal fact. 



From these remarkable facts alone, I think it will be ac- 

 knowledged that there is some connection between great 

 fires and rains other than mere coincidence, even if that 

 connection remained a mystery. Humboldt acknowledged 

 this in the case of volcanoes, when he speaks of the myste- 

 rious connection between volcanoes and rain, and says that 

 when a volcano bursts out in South America in a dry season, 

 it sometimes changes it to a rainy one. But now, when it 

 is demonstrated by the most decisive evidence, the evidence 

 of experiment, that air, in ascending into the atmosphere in 

 a column, as it must do over a great fire, will cool by di- 

 minished pressure, so much that it will begin to condense 

 its vapor into cloud as soon as it shall rise about as many 

 hundred yards -as the temperature of the air is above the 

 dew point in degrees of Fahr., it amounts to a very high 

 probability that great fires have sometim.es produced rain. 

 That great fires and even volcanoes should not always pro- 

 duce rain is manifest from the circumstance that, as they 

 break out accidentally, they may sometimes occur when 

 the state of the atmosphere is unfavorable, and even ad- 

 verse to rain. First, if they should break out when there 

 is a current of air, either near the surface of the earth, or 

 at a considerable distance above, of some strength, the up- 

 moving column would be swept by it, out of the perpen- 

 dicular, before a cloud of great density could be formed, 

 and thus rain would be prevented. 



Second, they might break out when the dew point was 

 too low to produce rain at all ; and, third, there may some- 



