162 Intelligence and Miscellaneous Articles.. 



employed for such thermo-electric piles ; in that state, however, it 

 can be easily worked into any required form. 



Pyifolu site, combined with platinum, also gives a pile whose electro- 

 motive force can be easily raised to one-tenth of that of a Daniell's 

 element, without fear of the heat thereby required decomposing the 

 mineral. The upper and lower ends of a small cylinder, 6 millims. in 

 diameter and 50 millims. long, easily cut from a complicated fibrous 

 variety of pyrolusite, were enveloped with platinum wire ; and the 

 upper junction, in a cover of mica, was heated directly in a non-lumi- 

 nous flame, whilst the lower one was immersed in water. An expe- 

 riment therewith, in which, as already remarked, d was equal to 0*25 

 of a metre, gave 1 = 74*0 and 2=68*2; whence result the values 

 L= 183*6 and E = 217*5. The electromotive force, therefore, 



amounted again to not less than — of that of a Daniell's element ; 



y o 

 the resistance, however, was 18*4 times that in the Daniell's ele- 

 ment above described.— Poggendorff's Annalen, vol. cxxiii. p. 505. 



ON THE RADIANT HEAT OF THE MOON. 



To Professor Tyndall,F.B.S., 8(C. 

 Sir, ' Utrecht, January 6, 1865. 



Allow me to trouble you for your duly and highly esteemed opinion 

 on a subject to which I have given considerable time and care, as 

 you may know from my Chang ements periodiques de temperature de- 

 pendants du Soleil et de la Lime, and from the Annalen of Poggendorff. 

 I remember your having written in the Philosophical Magazine*, 

 first, that you could not, as Melloni did, find a heating effect from 

 the full moon's rays by means of your thermoscope, but that, at 

 the same time, you were of opinion that the smoke of London was 

 an obstacle ; and secondly, that you supposed that the moon's rays 

 cleared the sky, and that from that cause the earth lost more heat 

 than it gained by the direct action of the moon. I want to know 

 whether this was a lapsus calami, or your real opinion. 



It is very improbable to me that a source of heat should be in any 

 way a source of cold, even if I could admit Sir John Herschel's 

 opinion to be a true one — that the moon does clear the sky. I 

 could not find, from many years' observations, that the sky is more 

 serene when the moon is above than when she is beneath the hori- 

 zon — in other words, that it is clearer about the time of full moon 

 than it is about the time of new moon. 



As for the influence on the temperature, I have added together all 

 the observations taken on the first day of the moon, from 1729 till 

 now, as well as all the observations taken on the second, third, fourth, 

 and so on. 



The result is not the same from 1729 to 1789 as it is from 1789 



to now. In the first period I found a greater sum of temperatures 



for the days between the 12th and 26th than for the 27th, 28th, 



29th, 30th, and the eleven first days. In the second period I find 



* Vol. xxii. p. 470. 



