Translations and abstracts from the French. 265 
a certain continued electric tension, — invincibly opposes 
the combination of oxygen with the metal, none that ac- 
tion is so strongly manifested on ae occasions. 
I assured myself that a certain duration of achat of the 
metal is necessary to effect this state of things, for when I 
interrupted the contact in a similar apparatus, which had 
een in operation but a few days, the copper was speedily 
oxidated. Iam engaged in new researches to ascertain the 
limit of time necessary to effect - this preserving power, and 
also the limits of the iecetiog | tself.* 
1e copper of the apparatus whose contact was inter- 
rupted after forty seven days, still continues, (now more than 
twenty days,) perfectly Art and no jadice ons of OXi- 
dation appear in the vess 
the etnkeoe, has been made by G. rmann, Jr 
his question, the author observes, depends necessarily 
and exclusively on the solution of another, that is whether the 
water of the sea, like fresh water, attains its maximum of 
density before it arrives at the aes of congelation. 
our methods of trial were pursued. 
1, By taking the specific cael of the some at different 
temperatures by an excellent hydrostatic balanc 
-7 Nicholson’s areometer 
. By the method of Dr. Hope, in determining the tem- 
raters * prs i and descending currents 
‘ mple and elegant method su ggested by the 
other, viz. 2 determination of the intervals of time in the 
cooling of the water under examination, through every suc- 
cessive half degree, from 15° or 20° I’. above, to the freez- 
&P 
* My eee tee eh led me to perceive that Sir H. Davy, in the Bake- 
rian Lectu ot ig tae mitted a serious error in recommending the use 
of zine or tn tion lers in which sea water is used 
I have tound pew th that tin, far from preserving iron, is on contrary 
aa boiler, instead of 
preserved a 8 it. Hence a piece of tin introduced into 
diminishing the danger of ee by preserving the boiler, would power- 
full ee to its des 
t. XVI.—No. "2. 7 
