MEMOIR XXL] INFLUENCE OF LIGHT UPON CHLORINE. 315 



a metal on the other. In one experiment the exposure 

 lasted from 1 1 A.M. to 1 P.M. ; this was, therefore, equal 

 to a continuous mid-day sun of seventy-two hours. The 

 metal was disengaged readily. But what is it ? It 

 cannot be silver, since nitric acid has no action upon it. 

 It burnished in an agate mortar, but its reflection is not 

 like the reflection of silver: it is yellow. The light 

 must, therefore, have so transmuted the original silver 

 as to enable it to exist in the presence of nitric acid. In 

 1837 I published some experiments on the nature of 

 this decomposition in the Journal of tlie Franklin In- 

 stitute. 



Though this experiment, and several modifications of 

 it which I might relate, fail to establish any permanent 

 chancre in the metal under trial, in the sense of an actual 



D 



transmutation, it does not follow that we should despair 

 of final success. It is not likely that Nature has made 

 fifty elementary substances of a metallic form, many of 

 them so closely resembling each other as to be with dif- 

 ficulty distinguished. Moreover, chlorine and other ele- 

 mentary substances can be changed by the sunlight in 

 some respects permanently ; and if silver has not thus far 

 been transmuted into a more noble metal, as platinum 

 or gold, it has at all events been made transiently into 

 something which is not silver. Those who will reflect 



O 



a little on the matter cannot fail to observe that the 

 sun-rays really possess many of the powers once fabu- 

 lously imputed to the powder of projection and the phi- 

 losopher's stone. 



