MEMOIR XXL] INFLUENCE OF LIGHT UPON CHLORINE. 



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 the Franklin In- 

 stitute. 



Though this experiment, and several modifications of 

 it which I might relate, fail to establish any permanent 

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

 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 

 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. 



