Proceedings of the Royal Society. 253 
result: the results obtained by other observers are also placed in 
the order in which they were made; but there is one circumstance 
to which they solicit attention, namely, that as far as Sir William 
Herschel’s observations are concerned, the dates and results will 
not accord with those published by Sir William in the Trans- 
actions, for reasons given in a former part of the paper. 
As an Appendix, measures of a few stars less perfectly observed 
are added, which, although not entitled to equal confidence with 
the others, the authors think may, perhaps, still have their use. 
Thursday, January 22. 
Dr. Scudamore was admitted a Fellow of the Society. 
The following paper was read : ; 
On a Mode of preventing the Corrosion of Copper Sheeting by Sea 
Water, in Ships of War, and other Ships. By Sir H. Davy, 
Bart., P.R.S. 
When copper sheeting, however pure the metal may be, is exposed 
to sea water, a green rust is formed upon it, which, when washed 
off, is replaced by a similar substance, till the whole of the metal 
is thus destroyed by corrosion. To prevent this effect, the Presi- 
dent avails himself of the modification of chemical affinities, derived 
from electrical powers; and in pursuing his researches in relation 
to this subject, he found the above-mentioned action upon copper 
counteracted by very weak negative electricity easily excited in it by 
the contact of a surface of tin, not exceeding ;4, that of the cop- 
per, and made part of an electric circuit in sea-water. Other 
metals may be substituted, but the ease with which a perfect 
contact is made by solder with tin, and the facility with which its 
submuriate detaches from the metal, induced Sir H. to regard it as 
best adapted to the purpose. He observes further, that the cause 
_ which prevents the oxidation of the copper, will also probably pre- 
vent the adhesion of marine animals, and of vegetables. After 
adverting to the unequivocal and satisfactory results of his experi- 
ments made upon a small scale, the author states that the Lords 
Vou, XVII. e 
