On the corrosion of Copper and Silver in Sea-water. 325 
Copper of this:kind, is frequently met with in commerce and 
is derived from the Chilian ores of copper, which although ar- 
gentiferous, do not yield enough silver, to render its separation 
economical. 
An occasion offered for again examining this subject, when 
the argentiferous native copper of Lake Superior was first refined 
and rolled by the Revere Copper Company, more than five years 
since, and the results have lately been obtained. oa 
Four suits of sheathing, for large merchant vessels, formed the 
subjects for observations, the metal being of uniform composition, 
as determined by assay of the clipping from many sheets. Two 
thousand parts of the alloy contained 4 parts of pure silver, or 
the standard ton of this country contained 4 Ibs. of silver. 
A proximate analysis of this metal was also made, and it 
“proved to be pure copper, throughout the mass of which, an alloy 
of silver and copper was evenly distributed, so as to form either 
@ mixture, or a compound alloy, iu which one part of the copper 
1s truly combined with the silver and the other larger part, simply 
combines with the alloy. This is a very common constitution of 
alloys, in which two metals exist, without any metalloid occur- 
- ever, corrosion should take place, it was in accordance with ob- 
Served cases that the silver alloy would act as a negative ele- 
ment, and the copper alone would be removed. How erroneous 
ese inferences proved, will be seen in the detail of the results. 
The “Chicora” was coppered Jan. 9, 1847, taking 7,392 Ibs. 
metal, which was fastened by bronze nails. She was employed 
in trade to China and wore her copper so rapidly, that it was re- 
moved in March, 1849, 2,628 Ibs. only remaining. In this case 
the sheets after the usual operations, had been consolidated by 
“cold rolling.” Be 
The ‘Serampore” was coppered January 18, 1847, requiring 
8.447 lbs. of “cold rolled” metal, secured by bronze nails. 
sailed to China and home, via Cape of Good Hope, and to the 
Pacific and home, via Cape Horn, requiring new copper in March, 
1850. The weight of the remaining copper, was not ascertained. 
The “ Hamilton’. was coppered October 22, 1847, requiring 
7,706 Ibs. metal, secured by bronze nails. The sheets used were 
in the ordinary or annealed state. This vessel was employed in 
the India trade and wore out her copper in August, 1849. The 
Weight of the copper remaining was 3,086 lbs. = 
_ ‘The “ Carthage” w red November 26, 1847, he gat: 
% Hos 
‘ ae 
; Be as coppe 
_ * 8727 Ibs. “cold rolled” metal fastened by bronze nails. 
