206 Proceedings of the Royal Physical Society. 



in accounting for their preservation on any hypothesis, until 

 an accidental phenomenon enabled me satisfactorily to account 

 for it. 



While preparing chloride of gold, I had occasion to expose 

 to the action of nitro-muriatic acid many small articles of 

 jewellery which had been chased and variously-fashioned. 

 After exposing them for many hours in the usual bath at the 

 proper temperature, I was astonished to find that none of the 

 articles had changed either in shape or size, although the 

 solution showed the proper quantity of gold had been dis- 

 solved. After decanting the acid, and washing well the 

 jewellery with distilled water, and again adding a fresh quan- 

 tity of aqua regia, I found that no further portions of gold 

 were dissolved, but that the articles still retained their form 

 and size. Some of the rings, which were chased in high re- 

 lief, exhibited, as when put into the flask, every mark of the 

 workman's tool. The mystery was soon unriddled; the jewellery 

 had all been alloyed largely with silver, every atom of which 

 had been changed into a chloride, and as each atom of gold 

 was dissolved, it was replaced by an atom of the worn silver, 

 and so the form of each article was retained as when first put 

 into the flask. On analysis, it was found that no particle of 

 gold was left — all was converted into chloride of silver. This 

 fortunate experiment at once enabled me to perceive, that when 

 a ligneous atom was removed from a fossilising tree, an atom 

 of silica was deposited, and hence the perfection with which 

 the most minute structure was preserved. 



This being the last meeting of the Session, the Society 

 adjourned to the commencement of next Winter Session, 



