On the Chemically Active Rays in the Sun's Atmosphere. 345 

 the polar equation of the path is 



np 



cos nd' 



(42) 



Hence the nearest approach to the axis attained by the globule 

 is np, and the whole change of direction which it experiences is 



ir( 1J. The case of- =2'3 is represented in the annexed 



diagram, copied from Tait and Steele's book [§ 149 (15), 

 Species V.]. 



XLII. On the Absorption of the Chemically Active Rays in the 

 Sun's Atmosphere. By H. C. VogeiA 



IT has been observed by Bouguer that the light emitted by 

 the sun is less intense near the edges of the solar disk than 

 in the middle,, in consequence of the absorption in the atmo- 

 sphere surrounding the sun. Photometric measurements showed 

 that the intensity of the light emitted by a point situated in the 

 centre of the solar disk is to that emitted by a point situated at 

 a distance of three fourths of the solar radius from the centre as 

 48 is to 35. Observations to this effect have been made lately 

 by Secchif and Liais J. Secchi has extended these observations 

 to the heat-rays, the absorption of which he tried to determine. 

 It might be of interest to extend the observations to the che- 

 mically active and more refrangible rays. Although every pho- 

 tographic image of the sun shows a very strong decrease of 

 light towards the border of the sun's disk, the absorbing-power 

 of the sun's atmosphere for chemically active rays has never been 



* Translated by Arthur Schuster, Ph.D., from Poggenclorff 's Annalm, 

 1873, No. 1. 



t Le Soleil, p. 121. 



% "Sur Fintensite relative de la Lumiere dans les divers points du 

 disque du Soleil," Mem. Cherbourg, vol. xii. (1866) pp. 277-342, 



