56 Dr. Davy’s observations on the changes which have 
formed of octohedrons of the red oxide of copper, intermixed 
with crystals of the same form of metallic copper. These 
crystals are most distinct at the surface ; they even adhere 
to the calcareous crust, and may he detached with it, pre- 
senting well-formed facets towards the part from which they 
have been separated. Chemical examination shows that 
they are actually composed of metallic copper, without the 
least tarnish, and of the pure ruby protoxide of copper ; and 
that the green rust consists principally of carbonate and sub- 
muriate of copper, and the dirty white chiefly of oxide of 
tin. The mineralizing process (if I may be allowed the 
expression) which has produced these new combinations, in 
general has penetrated very little into the substance of the 
helmet. The incrustation and rust removed, the metal is 
found bright beneath ; in some places considerably corroded, 
in others very slightly. It proves on analysis to be copper 
alloyed with 18.5 per cent, of tin. Its colour is that of our 
common brass, and it possesses a considerable degree of 
flexibility. 
An antient nail from a tomb in Ithaca, and an antient 
mirror from a tomb at Samos, in Cephalonia, have afforded 
me results very similar to the preceding, excepting that the 
mineralized part, consisting of oxide of tin, submuriate, 
carbonate, and protoxide of copper, each more or less col- 
lected apart from the others into little masses, has exhibited 
rather a crystalline structure than distinct well-formed 
crystals, and has been without any appearance of crystals of 
metallic copper. The copper in the mirror I have found 
alloyed with about 6 per cent, of tin, and a very minute 
quantity of arsenic and zinc. 
