20 of plumbago, or percarburet of iron, 6 of matter soluble in water, hydrochlorate of magnesia, hydrochlorate of iron, hydrochlorate of soda, hydrochlorate of magnesia, and organic matter, and 10 of water; as in fragments pulverised and heated for half an hour at a temperature of 100°, they lost 1-10th of their weight. "As to the reddish yellow matter, with small protuberances like nipples, which formed a thick layer on the surface of the protectors, it was formed of 75 parts of oxide of iron at the most, and 25 parts of water, besides some atoms of hydrochlorate of iron, hydrochlorate of soda, and hydrochlorate of magnesia." * * * * * Had not the health of Davy unfortunately declined at the very period when his energies were most required, such is the unbounded confidence which all must feel in his unrivalled powers of vanquishing practical difficulties, and of removing the obstacles which so constantly thwart the applications of theory, that little doubt can be entertained but he would soon have discovered some plan by which the adhesion of marine bodies to the copper sheathing might have been prevented, and his principle of Voltaic protection thus rendered available. An experiment indeed, altogether founded upon this same principle, has been already proposed, and will be shortly tried in the British navy, by building a schooner, and fastening its materials together with copper bolts, and afterwards sheathing the bottom with thin plates of iron, which are to be protected by bands of zinc. At the same time, another schooner is to be built, in which the fastenings are to consist entirely of iron bolts and nails, the former to be protected by a zinc ring under each head or clench, and the latter to have a small piece of zinc soldered under its head. This plan of protection was first adopted in America, at the recommendation of Dr. Revere; and upon its successful issue, that gentleman was lately induced to take out letters patent not only in England, but in all the maritime countries of Europe, for the sole right of manufacturing iron sheathing, bolts, and nails, thus protected.