242 Chemical Conditions of the Water 
the points where the water contains the most dissolved air, have 
attempted an explanation, on mechanical principles. They have 
on those parts of the coppered surface, really exposed to the 
greatest friction. 
If we assume that the oxygen of sea-water is almost wholly 
derived from solution of one part of the atmosphere, then the 
surface under existing conditions should contain the largest . 
amount. The organized beings of the ocean, consuming the oxy- 
gen as diffused, would constantly diminish the quantity below 
composition of hydrochlorates, under the presence of oxygen 
etal; a very common change, resulting in the production 
of oxyds and chlorids. 
While pursuing the subject of copper corrosion at the surface, 
as some years since led to examine samples of copper, which 
had remained some time at the bottom of the ocean. In these 
different depths, and in one instance from clean sand below 4 
powerful rapid, have given thick layers of sulphurets of copper; 
or copper and tin. 
These observations have been lately extended, and as they 
include other materials, I shall state them more particularly. 
The Spanish vessel San Pedro de Alcantaro, was blown up off 
men, from a depth between fifty and eighty feet. The coit 
reposed in mud and was sometimes covered by a stratum of coral, 
from six to twelve inches thick. ae 
wo pieces of the coinage of 1810 and 1812 were taken for 
'y The weight of such dollars, slightly worn, was 412 
