Observations on the changes which have taken place in some ancient alloys of copper. By John Davy, M. D. F. R. S. In a letter to Sir Humphry Davy, Bart. P. R. S

Abstract Dr. Davy 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 consisted 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 parts 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 6 per cent, of tin, and a minute portion of arsenic.