A bombshell filled with gunpowder, a gunlock, and a small clock, have been suggested as forming the components of this invention. I am satisfied however, that several very dangerous detonating powders were well known to the alchemists; and the condensed pocket size of the machine described, would evidently require some such preparation. 'No. X.--A way from a mile off to dive and fasten a like engine to any ship so as it may punctually work the same effect either for time or execution.' Precisely the same experiment has within a week of the time at which I am now writing, been made at Washington, as it was by Mr. Fulton half a century ago with his Torpedo-harpoon. If the marquis contemplated simply human agency as the aid to apply his portable powder-machine, it must be admitted that he had at least contemplated a more effective diving bell than any known to modern times. Submarine transit was indeed a subject to which he had devoted special study. 'No. XI.--How to prevent and safeguard any ship from such an attempt by day or night. 'No. XII.--A way to make a ship not possible to be sunk, though shot at an hundred times between wood and water by cannon, and should she lose a whole plank, yet, in half an hour's time, should be made to sail as fit as before.' It is thought that a great number of airtight compartments was the secret here hinted at; but the spirit of positive confidence with which the marquis speaks, and the great number of successful shots which he defies, seems to hint at something like the Ericsson Monitor of these days. Not without interest is the following: 'No. XIII--How to make such false decks as in a moment should kill and take prisoners as many as should board the ship, without blowing the real decks up, or destroying them from being reducible; and in a quarter of an hour's time should recover their former shape, and to be made fit for any employment, _without discovering the secret_.' The words italicized set forth the startling marvel of the whole. It is said that a false deck of thick plank may be easily blown into the air, when a number of small iron boxes, open at the top, and filled with gunpowder, are placed beneath. How this could be done and yet kept secret is indeed a wonder, and we must therefore conjecture that the marquis had some other device in his mind. Certain it is, that the idea of converting vessels into traps of destruction, or of so defending them as to destroy assailants after boarding the decks, has not been very extensively developed.