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III. Observations on the changes which have taken place in some 

 antient alloys of copper. By John Davy, M. D. F. R. S. In 

 a Letter to Sir Humphry Davy, Bart. Pres. R. S. 



Read November 17, 1825. 



Permit me through you to lay before the Royal Society, 

 the results of some experiments and observations on the 

 incrustations of certain antient alloys of copper, which I trust 

 may not be undeserving of notice, whether considered in 

 connexion with the arts of Antient Greece, or in relation to 

 the slow play of chemical affinities acting during a long^ 

 period of time. 



I shall commence with the most interesting object that 

 I have examined since I have been in the Mediterranean, for 

 which I am indebted to His Excellency Sir Frederick Adam, 

 His Majesty's Lord High Commissioner in the Ionian islands. 

 This is a bronze helmet of the antique Grecian form, recently 

 found in a shallow part of the sea, between the citadel of 

 Corfu, and the village of Castrades. Both internally and 

 externally it is partially encrusted with shells, and a deposit 

 of carbonate of lime. The surface of the helmet generally, 

 both under the incrustation, and where freed from it, is of a 

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

 and red. On minute inspection, the green and red patches 

 exhibit a crystalline structure, and the red very distinctly ; 

 and on examining them with a lens, they were found to be 



