at the surface of the Ocean and at the bottom. 243 
grs. nearly. When the coin of 1810 had lost its covering, it 
weighed 330 grains, or 82 grains of the substance of the dollar 
had assumed the state of a sulphuret. The other weighed 
356°82 or less by 55:18 ers. By exposure during thirty-five 
years in one case, 100 parts of the coin had been destroyed 
to the extent of nearly 2U parts, the other 13-39, giving an aver- 
age of 16°52. 
These incrustations were crystallized distinctly and their com- 
position was carefully determined. Water abstracted traces of 
chlorids of sodium and magnesia, with sulphate of lime only. 
Acetic acid took up a compound of chlorine, carbonate of lime 
and oxyd of copper, in minute quantity. The investing coating 
was removed from one coin by making it the negative of a single 
galvanic circle, in dilute sulphuric acid, so as to obtain the cover- 
ing in sheets; a loss of sulphur taking place. Water acidulated 
, With nitric acid, after several days, detached the covering from 
the other, and this sample was used for determining the sulphur, 
in the form of sulphuric acid, as well as the bases. Operating 
in this way, it was found that very small portions of chlorids of 
sodium, magnesium, and sulphate and carbonate of lime adhered 
to the incrustation, while the pure portion of this consisted of 
bisulphuret of copper with sulphuret of silver and gold; even 
the minute trace of the latter metal in the silver, being mineral- 
ized by sulphur. 
Connected with this observation is another I have made on 
the corrosion of an alloy of 1 silver in 500 copper, used as 
Sheathing, in which both metals united to chlorine and oxygen, 
and were removed rapidly and largely by surface water, as a 
simple metal would have been 
_ No opportunity has yet offered for continuing these examina- 
ons on copper and other metals obtained from great depths 
®xert a most important influence. ‘These waters are never desti- 
tute of organic matter ina changing state. ‘This matter dissolved 
from the surface of the earth or from rocks in percolating the 
W. assumes a state in which it powerfully attracts oxygen. 
aters holding this matter in solution, readily decompose sul- 
