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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 
