426 CHEMICAL FORCE IN THE SPECTRUM. [MEMOIR XXIX. 



very much of their chemical force. It was not totally 

 extinct, but the actinometer showed that it had under- 

 gone a very great diminution. 



From this it follows that, on its passage through a 

 mixture of chlorine and hydrogen, the radiation had suf- 

 fered absorption, and as respects the mixture under trial 

 had become deactiuized. Simultaneously the mixture 

 itself had been affected, its constituent gases uniting. 

 And thus it appears that the radiation had undergone a 

 change in producing a change in the ponderable matter. 



The following modification of this experiment shows 

 the part played by the chlorine and hydrogen respective- 

 ly when they are in the act of uniting : 



() The glass absorption vessel above described was 

 filled with atmospheric air, and the chemical force of the 

 radiation passing from the lamp through it was deter- 

 mined. It was measured by the time required to cause 

 the index of the actinometer to descend through one di- 



o 



vision. This was 12 seconds. 



(I) The absorption vessel was now half filled with 

 chlorine, obtained from hydrochloric acid and peroxide 

 of manganese. The chemical force of the ray after pass- 

 ing through it was determined as before. It was now 

 represented by 25 seconds. 



(<?) To the chlorine an equal volume of hydrogen was 

 added, the absorption vessel being consequently full of 

 the mixture. The radiation was now passing through a 

 stratum of chlorine diluted with hydrogen, and the point 

 to be determined was whether it had undergone the 

 same, or a greater, or less loss than in the preceding case, 

 since the chlorine was now uniting with the hydrogen. 

 On measuring the force, it was found to be represented 

 by 19 seconds. 



(d) Lastly, the first (a) of these measures was re- 

 peated with a view of ascertaining whether the inten- 



