that the bolts might be turned and the ballast dropped, should the necessity arise.
In connection with each of the water tanks there was a sea-cock open to the sea to supply the tank for sinking; also a force pump to eject the water from the tanks in the sea for raising the boat to the surface.
There was also a bilge connection to the pump.
A mercury gauge, open to the sea, was attached to the shell near the forward tank, to indicate the depth of the boat below the surface.
A one and a quarter shaft passed through stuffing boxes on each side of the boat, just forward of the end of the propeller shaft.
On each end of this shaft, outside of the boat, castings, or later fins, five feet long and eight inches wide, were secured.
This shaft was operated by a lever amidships, and by raising or lowering the ends of these fins, operated as the fins of a fish, changing the depth of the boat below the surface at will, without disturbing the water level in the ballast tanks.
The rudder was operated by a wheel, and levers connected to rods passing through stuffing boxes in the stern castings, and operated by the captain or pilot forward.
An adjusted compass was placed in front of the forward tank.
The boat was operated by manual power, with an ordinary propeller.
On the propeller shaft there were formed eight cranks at different angles; the shaft was supported by brackets on the starboard side, the men sitting on the port side turning on the cranks.
The propeller shaft and cranks took up so much room that it was very difficult to pass fore and aft, and when the men were in their places this was next to impossible.
In operation, one half of the crew had to pass through the fore hatch, the other through the after hatchway.
The propeller revolved in a wrought iron ring or band, to guard against a line being thrown in to foul it. There were two hatchways—one fore and one aft—16 inches by 12, with a combing 8 inches high.
These hatches had hinged covers with rubber gasket, and were bolted from the inside.
In the sides and ends of these combings glasses were inserted to sight from.
There was an opening made in the top of the boat for an air box, a casting with a close top 12 by 18 by 4 inches, made to carry a hollow shaft.
This shaft passed through stuffing boxes.
On each end was an elbow with a 4-foot length of 1 1/2 inch pipe, and keyed to the hollow shaft; on the inside was a lever with a stop-cock to admit air.
The torpedo was a copper cylinder holding a charge of ninety pounds of explosive, with percussion and friction primer mechanism,