PROFESSOR OLMSTED'S OBJECTIONS. 441 



is the only phenomenon which the Professor mentioned as 

 being better accounted for by the supposition of a whirling 

 motion than by my theory ; in this there was a manifest 

 failure, unless the air went out at the sides below, and 

 down in the middle, and inwards above. But besides the 

 positive evidence furnished by the Professor himself, that 

 this is not the fact in tornadoes, it is certain that if the air 

 came down in the centre, it would not only not form cloud, 

 but it would dissolve any cloud which it might have con- 

 tained in the upper regions, from which it is supposed to 

 descend. The Professor knew that I had asserted, if air 

 should descend from a height sufficiently great to be con- 

 densed into half the space by the increased pressure, it 

 would, by the heat of condensation, then be 90 warmer, 

 and be able to hold eight times as much vapor as it could 

 before it began to descend. This was proved by experiment, 

 and was not contradicted by the Professor. It may, then, 

 very fairly be inferred, that he has abandoned the doctrine 

 which he formerly taught, " that a sudden production of 

 cold would follow, of course, from the descent of such large 

 quantities of air from the regions of perpetual frost, as 

 would be driven down by the meteors of the 13th of No- 

 vember, 1833, falling into our atmosphere with immense 

 velocity," as he said they did. [Silliman's Jour., vol. 18, 

 p. 160.] 



The Professor accuses me of making hypotheses, and 

 founding my explanations on them; he attempted to point 

 out but one, and that is already answered. Let us see for 

 a moment how the old theory stands in this respect. It 

 first supposes that large quantities of cold air from northern 

 latitudes can be brought to meet and mingle with large 

 quantities of warm air from southern latitudes, without 

 assigning any cause of this meeting and mingling which 

 is not only an hypothesis, but one, if granted, that would 

 not explain the phenomena. It supposes that on mingling, 



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