FOREIGN CORRESPONDENCE. 
107 
a salt wtich silver is very apt to form, and which is one of the 
most plentiful of the silver-ores. Small particles of it are constantly 
washed down by probably most rivers, and carried to the sea, where it 
is dissolved by the salt-water. 
Copper has just been discovered in the water of the Mediterranean 
by M. Septimus Piesse, whose remarks have been published by our 
Parisian contemporary, Cosmos. To the sides of a steam-vessel going from 
Marseilles to Corsica, the author attached bags filled with nails and 
iron-filings. Iron having the power of displacing copper from its com- 
binations, the iron nails and filings were found on examination to have 
extracted from the water a notable quantity of copper, which adhered 
to the nails and iron-filings. Certain soluble salts of copper, such as 
the sulphate for instance, which are not easily decomposed by 
natural agents, are probably carried down to the sea by rivers, together 
with insoluble particles, such as sulphide of copper, which, by long 
contact with sea-water, would transform itself into sulphate or chloride 
of copper, and be dissolved. M. Septimus Piesse has gone so far as to 
attribute the blue and green colours of certain parts of the ocean to salts 
of copper. But this was a rash step to take, and it would have been 
more reasonable had the author contented himself with stating simply 
the discovery of a small quantity of copper in sea-water — a discovery 
not devoid of interest — rather than attribute to this source the colora- 
tion of the waters of the ocean, which may be due to a thousand more 
likely causes. 
In searching for copper by the above means, gold, if any were in 
solution in the sea, would certainly have been found. None of this 
most precious metal has ever been discovered in sea-water ; and why ? 
The reason is obvious — salts of gold are very easily decomposed ; the 
least particle of organic matter decomposes the soluble ones, and pre- 
cipitates their gold. Hence, when gold is met with in nature, it is 
always in the metallic state. It is impossible, therefore, that it can 
ever be found in sea-water, although no doubt exists as to a million or 
two sterling being washed down now and then by the various rivers, 
and swept into the sea in different parts of the world. If we wish to 
discover maritime gold we must look for it in the sand of the sea-beaten 
shores. 
This reminds us that we have just received a sample of sand said to 
bo auriferous, and recently imported by some speculators from the 
