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Art. X. Proceedings of the Royal Society. 



The sittings of the Royal Society were resumed for the season 

 on Thursday, the 17th of November, at which meeting a paper was 

 communicated by Dr. Davy, entitled, Observations on the Changes 

 which have taken place in some ancient alloys of Copper. 



The author first describes the nature of an incrustation upon an 

 ancient helmet found in a shallow part of the sea between the 

 citadel of Corfu and the village of Castrades ; the surface was of 

 a variegated colour, mottled with spots of green, dirty white, and 

 red : the red and green patches exhibited minute crystals of red 

 oxide of copper and metallic copper, and were further composed 

 of its green submuriate and carbonate ; the dirty white parts con_ 

 sisted chiefly of oxide of tin. 



These new combinations are only superficially produced : the 

 metal was found bright beneath, and consisted of copper alloyed 

 with 18.5 per cent, of tin. 



An ancient nail from a tomb in Ithaca, and a mirror from a 

 tomb at Samos, in Cephalonia, afforded nearly similar, but less 

 distinctly, crystalline results. The copper in the mirror was 

 alloyed with G per cent, of tin, and a minute portion of arsenic. 



The examination of the incrustation upon ancient coins, con- 

 sisted of oxide of tin, and of carbonate, and submuriate of copper ; 

 it, in some cases, acquires a dingy hue, from the prevalence of 

 black oxide of copper, mixed with a little of its protoxide. 



The author could discover no connexion between the perfect 

 state of preservation of ancient coins, and their composition ; but 

 he observes, that the manner in which the crystalline structure of 

 the incrustation is acquired, is a peculiarly interesting question. 

 There being no reason to suspect deposition from solution, u are 

 we not," says the author, " under the necessity of inferring that 

 the mineralizing process witnessed in its effects depends on a slow 

 motion and separation of the particles of the original compound ; 

 and must we not conclude that this motion is connected with the 

 operation of attractions of different kinds, as chemical-affinity, 

 electro-chemical attraction, and attraction of aggregation ? " If 



