80 



Intelligence and Miscellaneous Articles. 



The observations of the 12th were divided into two series. In the 

 second, the moon being very near a misty horizon, the results un- 

 derwent a very rapid diminution. 



On the '20th Mr. Wolf was good enough to take part in the ob- 

 servations, and undertook the readings of the galvanometer. The 

 following are the details of this series, during which the needle was 

 comparatively quiet. I cite it as an example, because, neglecting 

 the first number, obtained before the galvanometer was well in place, 

 it corresponds to the maximum effect observed : — 



October 20, 1869. (The scale is inverted.) 









Mean difference 



Times. 



Stop. 



Uncorrected 



between the effects 



deflection. 



of the stop on 









and off. 



h m 









9 53 



On. 



161-5 





56 



Off. 



120-3 



31-5 



59 



On. 



1421 



25-8 



10 2 



Off. 



112-4 



23-4 



5 



On. 



131-5 



22-8 



8 



Off. 



1050 



26-6 



11 



On. 



131-8 



260 



14 



Off. 



106-7 



19-2 



17 



On. 



1200 



21-2 



20 



Off. 



910 



23 



23 



On. 



108-2 



225 



26 



Off. 



80-0 



22-4 



29 



On. 



96-7 









Mean ... 



221 



The ratio of the surface of the object-glass to the illuminated sur- 

 face of the pile was about 230. If we assume that three-fourths of 

 the light which falls on the object-glass reaches the pile, the power 

 of concentration of the telescope is equal to about 247. The deflec- 

 tion obtained on the 20th would then correspond to twelve millionths 

 of a degree for the direct luminous rays of the moon. This is about 

 the sixtieth part of the result obtained by Mr. Piazzi Smyth on the 

 Peak of Teneriffe, working with the whole of the lunar rays. 



The luminous heat of the moon increases rapidly with the phase ; 

 but its height and the condition of the sky, even without cloud, 

 greatly affect its intensity. — Comptes Rendus, October 25, 1869. 



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