. 1825.] Proceedings of Philosophical Societies, 465 



• IX. A?i Eocperimentcl Impiiry into the Nature of the Radiant 

 Heating Eff eels from Terrestrial Sources, By Baden Powell, 

 MA. FRS.^ (See Annals for March, 1825, p. 224 ; and for May, 

 1825, p. 360.) E. W. B. 



Article XL 



Proceedings of Philosophical Societies, 



ROYAL SOCIETY. 



The Royal Society resumed its sittings on the 17th of Nov. 

 when the name of Major-Gen. Sir Benjamin D'Urban, Lieut.- 

 . Governor of Demerara, who had been elected a Fellow in the 

 course of the last session, was ordered to be inserted in its 

 printed hsts ; and the following papers were read : — 



On the Changes that have taken place in some ancient Alloys 

 of Copper, in a letter from John Davy, MD. FRS. to Sir Hum- 

 phry Davy, Bart. Pres. RS. In this letter, Dr. Davy, who is 

 pursuing a train of scientific researches in the Mediterranean, 

 describes the effects which time and the elements have produced 

 on various Grecian antiquities. The first he examined was a 

 helmet of the antique form found in a shallow part of the sea 

 between the citadel of Corfu and the village of Castrartis, which 

 was partly covered with shells and with an incrustation of car^ 

 bonate of lime. Its entire surface, as well where invested with 

 these bodies as where they were absent, presented a mottled 

 appearance of green, white, and red. The green portions con- 

 sisted of the submuriate and the carbonate of copper, the white 

 chiefly of oxide of tin, and the red of protoxide of copper in 

 octahedral crystals, mingled with octahedrons of pure metallic 

 copper. Beneath these substances the metal was quite bright, 

 and it was found by analysis to consist of copper, and 18*5 per 

 cent, of tin. A nail of a similar alloy from a tomb at Ithaca, 

 and a mirror from a tomb at Samos, in Cephalonia, presented 

 the same appearances, but in less distinct crystallization : the 

 mirror was composed of copper alloyed with about six per cent, 

 of tin, and minute portions of arsenic and zinc. A variety of 

 ancient coins, from the cabinet of a celebrated collector at 

 Santa Maura, presented similar appearances, and afforded corre- 

 sponding results ; the white incrustations being oxide of tin, the 

 green consisting of carbonate and submuriate of copper, and the 

 red of the protoxide of the same metal ; some having a dingy 

 appearance arising from the presence of black oxide of copper 

 mingled with portions of the protoxide. Dr. Davy was unable 

 to detect any relation between the composition of the respective 

 coins and their state of preservation, the variations in this 

 respect which they presented appearing to arise rather from the 

 circumstances under which they had been exposed to the raine- 

 Neio Series, vol. x. 2 h 



