444 PHILOSOPHY OF STORMS. 



cold air above, in this case too the cloud would be hollow, 

 for only the external parts of the ascending current could 

 mingle with the air through which it passed. And if dif- 

 ferent currents on the same horizontal plane are supposed 

 to mingle, it is an hypothesis contrary to nature, to suppose 

 they would be of such different temperatures as to produce 

 those very dense clouds which we see formed, by hundreds, 

 almost every day in the summer, when the air to the north 

 of one cloud is as warm as the air to the south. When 

 gentlemen make hypotheses they ought to be careful not to 

 make them contrary to known laws of nature, and when 

 made they ought to explain at least some of the phenomena 

 for which they are deduced. The Professor concluded 

 his strictures, by reading me a lecture on monomania, with- 

 out, however, directly mentioning that term, acknowledging 

 " there was magnanimity in the course I was pursuing, but 

 warning me of the danger of letting my mind dwell too 

 much on one subject, and expressing regret that I had 

 provoked this discussion." He declared he " had no in- 

 terest but his desire for truth, in demolishing his opponent's 

 theory ; nor could he indeed expect to do so to the satisfac- 

 tion of that gentleman, for he knew he had now become so 

 enthusiastic in the opinions he advocated, in opposition to 

 nearly the whole world of science, that he was blind to all 

 evidence, and deaf to all arguments." 



These observations were made, and this persevering te- 

 nacity to the old theory manifested in the face of the follow- 

 ing demonstration of its incompetence to explain the phe- 

 nomena which had been published in the Journal of the 

 Franklin Institute, in 1836. Let the candid reader judge 

 who is " blind to evidence, and deaf to argument." 



Here it may be worth while to turn aside for a moment, 

 to examine the efficiency of the most plausible theory of 

 rain that has ever been given to the world. I mean that of 



