128 Mr. Grant on protecting Iron from the Action of Salt Water. 
the enlargement of the electrodes, and their approximation, 
should be especially attended to in volta-electrometers. The 
principles upon which their utility depend are so evident that 
there can be no occasion for further development of them 
here. Me: 
Royal Institution, Oct. 11, 1834. 
XXIV. Experiments on the Protection of Iron from the 
Action of Salt-Water. By 'T. Tassert Grant, Esq. 
To the Editors of the Philosophical Magazine and Journal. 
GENTLEMEN, 
wits reference to the interesting papers which appear 
in your Journal of the present month (November 1835, 
vol. vii. pp. 389, 391.) giving an account of som eexperiments 
recently made with the view of protecting iron from the action 
of salt water, &c., I beg leave to communicate, that for some 
months past I have myself been engaged in a series of very si- 
milar experiments. My attention was drawn to the subject with 
the view of obtaining a remedy for the great wear and tear arising 
from the oxidation of the iron tanks at present generally used in 
the Navy for the stowage of fresh water. I first fitted a small 
plate of zinc, 3 inches square, ;';th of an inch thick, with iron 
rivets, to a piece of sheet iron 6 inches square, the two metals 
being completely in contact, and immersed the same into six 
gallons of spring water ; at the same time I also immersed a 
piece of sheet iron of the same dimensions, without the zinc, 
into the same quantity and quality of water: at the expiration 
of thirty days the two pieces of iron presented nearly the 
same appearance, viz. oxidation was perceivable, and to the 
same extent in both. I repeated the experiment with pro- 
tectors of larger dimensions, still without any satisfactory re- 
sult; and I have other experiments still in progress, in which 
the two metals bear a more equal proportion, but sufficient 
time has. not yet elapsed to form a correct opinion as to the 
result. Experiments with the two metals in contact in salt 
water, for the purpose of substituting iron sheathing for ships’ 
bottoms instead of copper, have also engaged my attention, 
and have been attended with various results. As far as these 
experiments have proceeded, I fear they are not likely to be 
productive of the great benefit I at first anticipated. Although 
no doubt can exist as to the zinc protecting the iron from 
oxidation, as the simple electrical action arising by the con- 
tact of the two metals in presence of the fluid will produce 
that effect, yet I have found in all instances that the cor- 
