q 46 Sir Humphry Davy’s additional experiments, &c. 
combinations. If copper in contact with cast iron be placed 
in a vessel half full of sea water, and having its surface par- 
tially above that of the water, it will become coated with 
carbonate of lime, carbonate of magnesia, and carbonate of 
soda ; and the carbonate of soda will gradually accumulate 
till the whole surface in the air is covered with its crystals : — 
and if the iron is in one vessel, and the copper forming an 
arc with it in another ; and a third vessel of sea water in 
electrical connection by asbestos or cotton is intermediate, 
the water in this intermediate vessel continually becomes less 
saline ; and undoubtedly, by a continuance of the process, 
might be rendered fresh. 
I shall not take up the time of the Society, by referring to 
some obvious practical applications of these researches, to the 
preservation of finely divided astronomical instruments of 
brass by iron, of instruments of steel by iron, or zinc : my 
friend Mr. Pepys has already ingeniously taken advantage of 
this last circumstance, in inclosing finely cutting instruments 
in handles or cases lined with zinc, and many other such ap- 
plications will occur. I cannot conclude, without mentioning 
particularly my obligations to Sir By am Martin, the Comp- 
troller, and Sir Robert Seppings, the Surveyor of the Navy, 
for the interest they have taken, and the zeal they have 
shown in promoting these researches ; and without stating 
how much I owe to the care, attention, and accuracy of Mr. 
Nolloth, Master Ship-wright, and Mr. Goodrich, Mecha- 
nist in the Dock-yard at Portsmouth, in superintending the 
execution of many of the experiments. 
