[ 542 ] 



LXXVII. Letter to Richard Taylor, Esq., one of the Editors 

 of the Loud, and Edinb. Philosophical Magazine, occasioned 

 by M. Melloni's paper on the Polarization of Heat in the 

 Annates cte Chimiejfor May 1837. By James D. Forbes, 

 Esq., Prof, of Nat. Phil, in the University of Edinburgh. 

 My dear Sir, 

 ^VTOU may recollect last year at Bristol your having men- 

 -*- tioned to me your intention of translating a paper of M. 

 Melloni's in which my experiments on polarized heat were 

 referred to, and having wished to know whether I chose that 

 any remarks from me should accompany it in the " Scientific 

 Memoirs* ;" I replied that though I conceived that M. Melloni 

 had not dealt quite fairly by me or my experiments, yet such 

 was my abhorrence of scientific controversy that nothing short 

 of necessity should ever cause me to enter into it. I still re- 

 tain the same sentiments ; I still think that the opinion of 

 those whose opinion is alone worth having on such abstract 

 and unfamiliar points, will be decided by an examination of 

 the original memoirs in which the experiments are contained ; 

 to which memoirs I have given as extensive a circulation as I 

 conveniently could. In their hands I very willingly leave my 

 claim to the establishment of the chief facts of the polarization 

 of heat as far as yet known; and it happens, fortunately for 

 me, that the hostility with which my results were at first re- 

 ceived by those who have since taken the trouble to examine 

 and confirm them, prevents any, even the slightest, question 

 respecting priority in any part of the inquiry. 



I have, however, more than once taken the liberty of using 

 your journal as a vehicle for combating any definite objection 

 urged to the accuracy of my experiments. This is all that I 

 mean to do in the present letter. 



In the Annates de Chimie for May 1837 (but which has 

 only very recently appeared) M. Melloni states the results at 

 which he has arrived by the use of my methods of polarizing 

 heat, which he seems to have applied with great skill and with 

 his usual attention to minute accuracy. Whilst he amply con- 

 firms my results as to phenomena generally, he finds a marked 

 difference in the quantitative measures made on the amount of 

 heat from different sources polarized by a given pile of mica. 

 He endeavours to explain the difference in our results by 

 pointing out a source of error in mine. That this supposed 

 source of error has no recognisable existence, but is one of 

 those infinitesimal objections with which my experiments have 

 been from the first assailed, I shall now endeavour to show. 

 M. Melloni supposes that the secondary heat radiated from 

 * Scientific Memoirs, vol. i. p. 325. 



