taken place in some antient alloys of copper. 59 



phasnomena, which often seem to» occur in the mineral 



kingdom ? These facts offer an obvious practical application, 



both in determining the antiquity and genuineness of ancient 



works of art ; for aerugo of the kind which I have described 



could not be successfully imitated by any artificial processes ; 



and a very slight chemical examination, or even one by the 



lens, would be sufficient to expose any fraud attempted to be 



practised by substituting modem imitations for ancient 



works. 



I am, most truly yours, 



J. DAVY. 



To Sir H. Davy, Bart, 

 Pres. R. S. 



