ELECTRICITY, MAGNETISM, AND GRAVITATION. 



163 



Interposed a screen, and the galvanometer declined to 

 zero. 



p.m., 2 , Sun clouded, galvanometer 2i°. 



" " « more clouded, " 2°. 



" " " still more clouded, " 1°. 



8^ in the evening. Galvanometer had returned to 0°, as 

 usual. 



January 6th, — One half the extremity of the helix shaded 

 by a pillar, 



a.m., lOh.Om. Galvanometer deflected to S°. 



" 11 . 50. Sun clear, unshaded, galvanometer 7i°. 

 " " Interposed a screen, and in i min. " 5°. 



" " Removed " " " Ti". 



Repeated, with like results, several times. 

 ** 12 . 0. Sun unclouded, galvanometer 9^, 



p.m., 12 . 1. Galvanometer 10°; 1 min. more 11°. 

 " 12 . 3. Window and apparatus very clean, 12°, 

 ** 12 . 5, Galvanometer 15°. 



" 12 . 7i. Ditto 15°. 



The instrument had been cleaned and might not have 

 been correctly adjusted — and probably the last stated degrees 

 are overrated. The wires at the south extremity of the 

 , helix, which were originally green, were now inked, so as 

 to produce a greater facility for the absorption of the rays. 

 The galvanometer ultimately settled in the evening at 5°, 

 which would reduce the stated indication of the galvanometer 

 from 15° to 10°, as before. 



January 18th,* a.m., llh. Om. Sun clouded, galva- 

 nometer lk°, 



A little more obscured, 5° ; sun brighter, but 



not free from clouds 7^°, 



Now 8° ; sun more obscured, galvanometer de- 

 clined to 4°. 



In i a min. 5°; 1 min., sun yet clouded 6°. 



