314 Royal Society: — 



to the advantage of the current ; but as the metalloid radical 

 SO 4 which attacks the zinc is not solely taken from the sulphuric 

 acid but comes partially from the dissolved sulphate of zinc, it 

 follows that the electromotive force, and therefore the power of 

 the battery, diminishes proportionally to the quantity of heat 

 necessary for the electrolysis of this latter salt. 



To the electrolysis of zinc, therefore, we must principally at- 

 tribute the want of constancy in the intensity of the current 

 furnished by a Smee's couple*. 



VII. Substituting amalgamated cadmium for zinc in the for- 

 mation of the couples, I observed perfectly similar results. 



VIIL Finally I introduced into the part of the circuit exterior 

 to the calorimeter which contained the pile a rheostat, in some cases 

 at the ordinarytemperature, and in some heated to bright redness. 

 In the latter case the resistance was almost doubled, and the 

 quantity of heat furnished by the battery was that which would 

 have been taken from it by a rheostat of double the length and 

 kept at the ordinary temperature. I shall soon revert to this 

 subject. 



XXXVII. Proceedings of Learned Societies. 



ROYAL SOCIETY. 



[Continued from p. 162.] 



May 27, 1869.— Lieut. -General Sabine, President, in the Chair. 



T^HE following communication was read : — 



A "On the Radiation of Heat from the Moon." By the Earl 

 of Rosse, F.R.S. 



The following experiments on Lunar Radiant Heat were under- 

 taken with the view of ascertaining whether with more powerful and 

 more suitable means than those previously employed by others, with 

 little or no success, it would be possible to detect and estimate the 

 amount of heat which reaches the earth's surface from the moon. 



Professor Piazzi Smyth had conducted a series of experiments on 

 the Peak of Teneriffe with a thermopile, but apparently without 

 any means of concentrating the moon's heat beyond the ordinary 

 polished metal cone. 



Melloni had employed a glass lens of considerable diameter (I be- 

 lieve about three feet) ; but as glass absorbs rays of low refrangibility, 

 it was not so well adapted to concentrate heat as a metallic mirror. 



In the following experiments the point sought to be determined 

 was, in what proportions the moon's heat consists of: — ■ 



(1) That coming from the interior of the moon, which will not 

 vary with the phase : — 



* I preferred the use of Sniee's battery in my researches, because I was 

 not concerned with the constancy of the current, and it is both rapid and 

 easy to work with. 



