ON THE CHEMICAL ACTION OF THE SOLAR RADIATIONS. 



77 



uranium glass, although all the more refrangible rays are absorbed, these 

 rays, corresponding with the most luminous, still continue very energetic. 



Fig. 55. 



• 



• 



Fig. 56. 



Red Series. 

 Pale ruby, by Gold. 

 (110) 8 1 a. Thelower rays of the prismatic spectrum are but little changed; 

 the upper portion of the green rays become a dark olive, passing into a brown, 

 and having but very small illuminating power ; then the blue again comes 

 out in much brilliancy, and the violet rays are unaffected, except that the 

 red is rendered superior in intensity to the blue of those rays. 



(Ill) 82. Pale rvby, by Gold. — The action on 

 the luminous spectrum is as nearly as possible that 

 exhibited by 81a. 



(112). The chemical action of the glass 81 is 

 shown in a, fig. 56. It commences in the blue 

 rays, and extends upwards to the end of the violet, 

 and downwards by a slight neck to the yellow ray, 

 where it extends slightly in width. There are in- 

 dications of a protecting action around the entire a b r 



spectrum. The chemical actions of the rays which ~ 



permeated 82 were somewhat different, as is shown 



in fig. b. The spot corresponds with the yellow ray ; above this, over the 

 green, there is no action for a space equal to nearly -20, when it again com- 

 mences, and entirely ceases at the end of the luminous spectrum. In this the 

 protecting band is entirely wanting. 



(113) 83. Red, by Copper. — The spectrum appears reduced to red and 

 yellow, both well-marked and broadly separated by dark spaces ; beyond the 

 yellow a broad dark band appears, and then a set of green rays of slight 

 illuminating power. After long examination, some red violet rays appear 

 visible beyond the green. 



(1 14) 83. After the most prolonged exposure, it is impossible to detect any 

 evidence of chemical action. 



(115) 84. Reduces the spectrum to the red rays with a faint line of yellow, 

 and beyond this a line of a dark green, quite a dark olive. The spectrum 

 being projected on a screen having passed this glass, appeared merely as 

 one red spot. 



(116) 84. No chemical action even after the longest exposure. 



(117) 85. Red, by Copper — This glass reduces the spectrum to a band 

 of red of considerable brilliancy, and a band of yellow light ; by carefully 



