5o6 5UB-MARINE VESSEL. 



outfide end, which commanded the rudder, by means of 

 a rod extendhig from the end of the crank to a kind of tiller, 

 fixed upon the left hand of the rudder. Raifing and de- 

 preffing the firft mentioned tiller turned the rudder as the 

 cafe required. 



A compafs marked with phofphorus diredted the courfe, 

 both above and under the water ; and a line and lead 

 founded the depth when neceflary. 



The internal fhape of the vefTel, in every poffible fedtion 

 of it, verged towards an ellipfis, as near as the defign 

 would allow, but every horizontal fe£tion, although ellip- 

 tical, yet as near to a circle, as could be admitted. The body 

 of the veflel was made exceedingly ftrong; and to ftrengthen 

 it as much as poflible, a firm piece of wood was framed, 

 parallel to the conjugate diameter, to prevent the fides 

 from yielding to the great prefTure of the incumbent watei', 

 in a deep immerfion. This piece of wood was alfo a feat 

 for the operator. 



Every opening was well fecured. The pumps had two 

 fets of valves. The aperture at the bottom, for admitting 

 water, was covered with a plate, perforated full of holes 

 to receive the water, and prevent any thing from choaking 

 the paflage, or flopping the valve from fhutting. The 

 brafs valve might likewife be forced into its place with a 

 fcrew, if neceffary. The air pipes had a kind of hollovr 

 fphere, fixed round the top of each, to fecure the air-pipe 

 valves from injury : thefe hollow fpheres were perforated 

 full of holes for the paflage of the air through the pipes : 

 within the air-pipes were fhutters to fecure them, fhould 

 any accident happen to the pipes, or the valves on their tops. 



Wherever the external apparatus pafled through the bo- 

 dy of the veflel, the joints were round, and formed by 

 brafs pipes, which were driven into the wood of the veflel, 

 the holes through the pipes were very exactly made, and 

 the iron rods, which pafled through them, were turned in 



a 



