4(JS Abstract ofiyr Ho^ki's Address on 



They found, that when the solar beam was twice reflected in the 

 manner just stated, the heat and light refused simultaneously to 

 be reflected in certain positions of the second reflector. The 

 same experiment was repeated with incandescent bodies, with 

 the same result ; and even, as stated by Berard, with bodies 

 having temperatures beneath that of visible incandescence. 

 These experiments were probably discontinued in consequence 

 of the death of Malus, and the details were never published, if, 

 indeed, they were ever carried to any great extent. The result 

 has been, that Berard's conclusion seems not to have been gene* 

 rally adopted by the scientific world. The polarization of heat 

 has remained amongst the doubtful facts in science. It has 

 been adopted in scarcely any systematic works, whether British 

 or foreign ; and, of late years, direct evidence seemed to be en- 

 tirely against it. Professor Powell of Oxford, repeatedly and 

 fruitlessly, attempted to obtain Berard's result. Nobili of 

 Florence (whose recent loss science has to deplore) attempted it 

 likewise with the aid of his thermo-multiplier, an instrument ad- 

 mirably adapted for the measurement of small quantities of heat ; 

 and Melloni having failed to polarize even luminous heat by 

 tourmalines, concurs in the conclusions of Powell and Nobili. 

 The Vice-President then observed, that it was under these cir- 

 cumstances that the subject was undertaken by Professor Forbes, 

 who, by means of arrangements differing from any that had be- 

 fore been used, has succeeded in completely establishing the 

 polarization of heat under all the circumstances in which light is 

 polarized, namely, by Reflection, Transmission, and Double 

 Refraction, and that it is for the establishment of these facts 

 that the Keith Prize has been awarded by the Council. 



Dr Hope then stated that, in the ordinary case of the publica- 

 tion of papers, the Society holds itself in no degree responsible 

 for the truth of the facts stated therein ; but, in the adjudica- 

 tion of prizes, the case is different; and that, with regard to them, 

 the Council are bound to be satisfied of the truth of the state- 

 ments for which they award their prize. Several members of the 

 Council had seen and satisfied themselves of the accuracy of Mr 

 Forbes''s leading experiments before the Keith Prize was award- 

 ed ; and, some days ago, he deemed it right to request Mr 

 Forbes to shew him the more important of these experimental 



