1"6 ON THE IDENTITY OF LIGHT, HEAT, 



with condensed vapour internally, and prevents the action of 

 the rays ; galvanometer at zero. 



2h. 15m. The needle is now deflected towards the left 1°. 



The whole of the helix (save the extremity) was now 

 shaded from the rays, and the immediate result was 4' to the 

 left. The shade was removed, and the needle declined to 

 21°. Replaced the shade, and the result was 3^° to the left. 



2h. 35m. Needle P. Shaded the whole of the helix ex- 

 cept the south illuminated end, and the result to the left hand 

 was3^ 



January 31st. — The greater part of the helix being covered 

 by the shade of the window frame, the needle began to vibrate, 

 and continued its vibrations for some time. Shortly after- 

 wards two-thirds of the extremity of the helix being 

 illuminated, the needle deflected 4>° to left. 



llh. 35m. Sun clouded, galvanometer 3° to left. Helix 

 shaded, declined to 0°. 



2h. 20m. Shaded the helix, 0°. On removing shade, 3=^ to 

 the left hand. 



February 14th, 1851. — Sun much clouded. 



9h. 40m. No deflexion ; afterwards shaded the lower half 

 of the extremity of the helix, result, 1° towards the right. 

 A cloud intervened, and it declined to 0°. 



llh. 20m. GsilyanometeT marks 21° to left. Shaded upper 

 half, no deflexion ; shaded whole helix, and no deflexion ; 

 shaded lower half, and galvanometer indicated 5°. This was 

 repeated several times, with similar results. 



Covered the whole length of the silk line supporting the 

 needle with a paper shade, lest there might be any results 

 from the action of the rays upon it. The shade was fre- 

 quently removed and replaced during deflections of the 

 needle, but no influence appeared to result from these 

 changes. 



12\\. 50m. Galvanometer marks 2i° to the left hand. 

 The sun becomes bright, and the deflection that ensued was 



