"Mr. Marsh of Woolwich gave me some musket balls, which had been taken out of Shrapnell's shells. The shells had lain in the bottoms of ships, and probably had sea-water amongst them. When the bullets are put in, the aperture is merely closed by a common cork. These bullets were variously acted upon: some were affected only superficially, others more deeply, and some were entirely changed. The substance produced is hard and brittle; it splits on the ball, and presents an appearance like some hard varieties of hæmatite; its colour is brown, becoming, when heated, red; it fuses on platinum foil into a yellow flaky substance like litharge. Powdered and boiled in water, no muriatic acid or lead was found in solution. It dissolved in nitric acid without leaving any residuum, and the solution gave very faint indications only of muriatic acid. It is a _protoxide of lead_, perhaps formed, in some way, by the galvanic action of the iron shell and the leaden ball, assisted probably by the sea-water. It would be very interesting to know the state of the shells in which a change like this has taken place to any extent. _It might have been expected, that as long as any iron remained, the lead would have been preserved in the metallic state._" In one experiment, I found that a piece of lead protected by iron underwent solution in water containing nitrate of potash, while it resisted the action of very dilute nitric acid: upon this point, however, farther enquiry is necessary; for I subsequently failed in producing the same effect, owing, no doubt, to having employed too strong an acid. Let us return from this digression to the subject of Sir Humphry Davy's Protectors. It only remains for me to relate the results which followed the practical application of the Voltaic principles which his various experiments had developed. In the month of May 1824, directions were issued by the Lords of the Admiralty to protect, in future, the copper sheathing of all his Majesty's ships which might be taken into dock, upon the plan proposed by Sir Humphry Davy. The protectors were bars of iron six inches wide at their base, three inches in thickness in their centre, and, in outward form, the segment of an extended circle. They were usually placed on each side of the ship in a horizontal position, viz. in midships about three feet under water--on the keel in a line with these--and the remainder in the fore and afterparts of the ship (about three feet under the line of fluitation), as far forward and abaft as the curvatures of their respective bodies would allow of their lying flat upon the surface of the copper. As it is difficult by verbal description alone to convey a sufficiently distinct idea of this subject to persons unacquainted with naval architecture, I have introduced a sketch, exhibiting the _general_ position of the _Protectors_, although they are necessarily exaggerated in size, or they would have appeared as mere specks upon the drawing.