314 INFLUENCE OF LIGHT UPON CHLORINE. [MEMOIK XXI. 



trum, and found that it turned to a dark-brown color in 

 those spaces on which the more refrangible rays fell, the 

 effect reaching a maximum under the indigo ray. The 

 fixed lines of Fraunhofer were very prettily depicted, as 

 white streaks, particularly the large ones at H. I kept 

 the sample of phosphorus for several years without its 

 showing any disposition to resume the active state. 



Professor Bunseu and Dr. Roscoe dwell very appro- 

 priately on the disturbing effects of minute quantities of 

 extraneous gases mingled with chlorine on photo-chem- 

 ical induction. No one who has used a chlor-hydrogen 

 photometer can have failed to make a similar remark. 

 My attention has been directed to that subject in its 

 more general aspect, and I will ingenuously confess that 

 I have made several attempts at the transmutation of 

 metals, on the principle of compelling them, by the aid 

 of solar light, to be disengaged from states of combina- 

 tion in the midst of resisting or disturbing media. 



The following is a description of one of these alchem- 

 ical attempts: In the focus of a burning -lens, twelve 

 inches in diameter, was placed a glass flask, two inches 

 in diameter, containing nitric acid diluted with its own 

 volume of water. Into the nitric acid were poured alter- 

 nately small quantities of a solution of nitrate of silver 

 and of hydrochloric acid, the object being to cause the 

 chloride of silver to form in a minutely divided state, so 

 as to produce a milky liquid, into the interior of which 

 the brilliant converging cone of light might pass, and the 

 currents generated in the flask by the heat might drift 

 all the chloride successively through the light. The 

 chloride, if otherwise exposed to the sun, blackens mere- 

 ly upon the surface, the interior parts undergoing no 

 change ; this difficulty I therefore hoped to avoid. The 

 burning-glass promptly brings on a decomposition of the 

 salt, evolving on the one hand chlorine, and disengaging 



