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XTI.— ON DE. EDDY'S HYPOTHESIS THAT RADIANT HEAT 

 IS AN EXCEPTION TO THE SECOND LAW OE THER- 

 MODYNAMICS. Br GEORGE E. EITZGERALD, M.A., 

 . E.T.C.D. 



[Eead, December 18, 1882.] 



In the Scientific Proceedings of the Ohio Mechanics' Institute for 

 July, 1882, and at the meeting of the American Association for 

 the Advancement of Science in Montreal, Dr. Eddy proposed an 

 exceedingly ingenious experiment, by which he expected that it 

 would he -possiMe to get radiant heat to pass from a ^cooler to a 

 hotter body. I had the pleasure of hearing his Paper at Montreal, 

 and though I then saw no flaw in his reasoning, I pointed out to 

 him that he had only taken two of the bodies concerned into con- 

 sideration, yet I dared not express a decided opinion on the matter 

 without further consideration. The further consideration has re- 

 sulted in my thinking that the reasoning is not valid, as I hope to 

 be able to point out. 



•I shall take what seems to me an experiment somewhat simpler 

 in theory, though one that would be harder to carry out in practice, 

 than Dr. Eddy's. 



Suppose that two regions A and B, separated by three parallel 

 screens /, m, and n, having apertures in them x, y, z, capable of 



I in 



L |l 



a; • I «/ 



being opened and closed from the centre, so as to make everything 

 perfectly symmetrical 'round the line AB perpendicular to the 

 screens. Now, if x be opened for a very short time, a certain quan- 

 tity of radiant energy will escape out of A into the region between 

 ? and m; and Up be opened when this heat reaches m it can cer- 

 tainly be let on into the region mn ; and if z be similarly opened 



SCIEN. PliOC, K.D.S. — VOL. I\. PT. I. 



