SUBMARINE VESSELS 



1789, and recorded in the Transactions of the American 

 Philosophical Society. In this letter Bushnell says: — 



"The external shape of the submarine vessel bore 

 some resemblance to the upper tortoise shells of equal 

 size, joined together, the place of entrance into the 

 vessel being represented by the opening made by the 

 swell of the shells at the head of the animal. The in- 

 side was capable of containing the operator and air 

 sufficient to support him thirty minutes without re- 

 ceiving fresh air. At the bottom, opposite to the en- 

 trance, was fixed a quantity of lead for ballast. At one 

 edge, which was directly before the operator, who sat 

 upright, was an oar for rowing forward and backward. 

 At the other edge was a rudder for steering. An aper- 

 ture at the bottom, with its valves, was designed to 

 admit water for the purpose of descending, and two 

 brass forcing-pumps served to eject the water within 

 when necessary for ascending. At the top there was 

 likewise an oar for ascending or descending, or con- 

 tinuing at any particular depth. A water-gauge or 

 barometer determined the depth of descent, a compass 

 directed the course, and a ventilator within supplied 

 the vessel with fresh air when on the surface. 



"The vessel was chiefly ballasted with lead fixed to 

 its bottom ; when this was not sufficient a quantity was 

 placed within, more or less according to the weight of 

 the operator; its ballast made it so stiff that there was 

 no danger of oversetting. The vessel, with all its appen- 

 dages and the operator, was of sufficient weight to settle 

 it very low in the water. About two hundred pounds 

 of lead at the bottom for ballast could be let down 



[95] 



