Represents the anchored Torpedo, so arranged as to blow up a vessel which should run against it; B is a copper case two feet long, twelve inches diameter, capable of containing one hundred pounds of powder. A is a brass box, in which there is a lock similar to a common gun-lock, with a barrel two inches long, to contain a musket charge of powder: the box, with the lock cocked and barrel charged, is screwed to the copper case B. H is a lever which has a communication to the lock inside of the box, and in its present state holds the lock cocked and ready to fire. C is a deal box filled with cork, and tied to the case B. The object of the cork is to render the Torpedo about fifteen or twenty pounds specifically lighter than water, and give it a tendency to rise to the surface. It is held down to any given depth under water by a weight of fifty or sixty pounds as at F: there is also a small anchor G, to prevent a strong tide moving it from its position. With Torpedoes prepared, and knowing the depth of water in all our bays and harbours, it is only necessary to fix the weight F at such a distance from the Torpedo, as when thrown into the water, F will hold it ten, twelve, or fifteen feet below the surface at low water, it will then be more or less below the surface at high water, or at different times of the tide; but it should never be so deep as the usual draught of a frigate or ship of the line. When anchored, it will, during the flood tide, stand in its present position; at slack water it will stand perpendicular to the weight F, as at D; during the ebb it will be at E. At ten feet under water the waves, in boisterous weather, would have little or no tendency to disturb the Torpedo; for that if the hollow of a wave should sink ten feet below what would be the calm surface, the wave would run twenty feet high, which I believe is never the case in any of our bays or harbours. All the experience which I have on this kind of Torpedo is, that in the month of October 1805, I had one of them anchored nine feet under water, in the British Channel near Dover; the weather was severe, the waves ran high, it kept its position for twenty-four hours, and, when taken up, the powder was dry and the lock in good order. The Torpedo thus anchored, it is obvious, that if a ship in sailing should strike the lever H, the explosion would be instantaneous, and she be immediately destroyed; hence, to defend our bays or harbours, let a hundred, or more if necessary, of these engines be anchored in the channel, as for example, the Narrows, to defend New-York. [Illustration: PLATE II.] The figure to the right of the plate is an end view of the Torpedo H. H shews its lever forked, to give the better chance of being struck.