This is an addition to the dome more curious than useful; it is a mode of sending up a note and bringing down an answer while the Vessel is under water, Figure the first _A_ is a cock with the cavity _B_ in which there is a small reel; _C_ the handle of which runs to _D_.... _E_ is a piece of Cork, the note is to be written on a piece of parchment, tied round the cork or put into it, the cock is them turned by the handle _F_ to face the opening _G_; the reel is then turned off and the cork mounts to the surface attached to a small silk line, when the answer is fixed to the cork the man below wind it down into the cock which being turned towards the inside of the Vessel the answer may be taken out. [Illustration: PLATE THE SEVENTH ] Figure the second is an end View. Figure the Third shews a man operating & the cork mounting, this may be useful in making experiments; _Plate the Seventh one quarter of an inch to a foot_ This shews the submarine vessel under sail and at anchor under water with her plunging anchor out, These seven drawings with this discription will enable any able mechanician to construct and perform the experiments of a submarine Vessel; It is not intended that she should go under or near the vessels which are to be attacked, her use is to enable the weaker maritime nations to attack the stronger without being detected or interrupted in their operations, hence She is contrived to hide under water when pursued, where she may continue the whole day and approach the fleets and harbours of the enemy in the night, there anchor her cargo of submarine bombs under water, or leave them to the tide, or use them in any other way which time and practice may point out; and retire unperceived for another cargo and deposit them in like manner on the coast, in the mouths of rivers in harbours or among fleets at anchor, and thus place Such numbers as would render it impossible for any Vessel to move through them without the imminent danger of being blown up and totally annihilated; Of the submarine Bombs and modes of Using them. * * * * * As Government are in possession of the real locks and Bombs with the modes of arranging them for action it will not be necessary to make detailed drawings of the several parts. _Plate the 8th_