aj© Central Principles and ConJi)u8ion of a Suh-tnarine Vejfd. 



rudder for (leering. An aperture, at the bottom, with its valve, was defigned to admit 

 ■water, for the purpofe of defcending ; and two brafs forcing pumps ferved to ejedl: the 

 water within, when neceflary for afcending. At the top, there was likewife an oar for 

 afcending or defcending, or eontinuing at any particular depth — A water gauge or baro- 

 meter, determined the depth of defcent, a compafs diredled the courfe, and a vent;;lator 

 within, fupplied the veflel with frefh air, when on the furface. 



The entrance into the veflel was elliptical, and fo fmall as barely to admit a perfon. 

 This entrance was furrounded with a broad elliptical iron band, the lower edge of which 

 was let into the wood of which the body of the veflel was made, in fuch a manner, as to 

 give its utmofl fupport to the body of the veflel againfl; the prcflure of the water. Above 

 the upper edge of this iron band, there was a brafs crown, or cover, refembling a hat 

 with its crown and brim, which flmt water tight upon the iron band: the crown was hung 

 to the iron band with hinges fo as to turn over fidewife, when opened. To make it per- 

 fedlly fecure when fliut, it might be fcrewed down upon the band by the operator, or by 

 a perfon without. 



There were in the brafs crown, three round doors, one direftly in front, and one on 

 ■each fide, large enough to put the hand through — when open they admitted frefliair; 

 their fliutters were ground perfeftly tight into their places with emery, hung with hinges 

 and fecured in their places when fliut. There were likewife feveral fmall glafs windows 

 in the crown, for looking through, and for admitting light in the day time, with covers 

 to fecure them. There were two air pipes in the crown. A ventilator within drew freCi 

 air through one of the air pipes, and difcharged it into the lower pait of the vefl"el ; the 

 frefli air introduced by the ventilator, expelled the impure light air through the other air 

 pipe. Both air pipes were fo conflirudled, that they (hut themfelves whenever the water 

 rofe near their tops, fo that no water could enter through them, and opened themfelves 

 immediately after they rofe above the water. 



The veflel was chiefly ballafted with lead fixed to its bottom ; when this was not fufii- 

 cient, a quantity was placed within, more or lefs, according to the weight of the operator ; 

 its ballafl: made it fo ftifi", that there was no danger of overfetting. The veflel with all its 

 appendages, and the operator, was of fufficient weight to fettle it very low in the water. 

 About two hundred pounds of the lead, at the bottom, for ballaft, could be let down 

 forty or fifty feet below the veflfel; this enabled the operator to rife infl;antly to the furface 

 of the water, in cafe of accident. 



When the operator would defcend, he placed his foot upon the top of a brafs valve, 

 deprefling it, by which he opened a large aperture in the bottom of the veflel, through which 

 the water entered at his pleafure ; when he had admitted a fufficient quantity, he defcended 

 very gradually ; if he admitted too much, he ejefted as much as was neceflary to obtain 

 an equilibrium, by the two brafs forcing; pumps, which were placed at each hand. When- 

 cv- "he veflel leaked, or he would afcend to the furface, he alfo made ufe of thefe forcing 

 pur-^o. When the fltilful operator had obtained an equilibrium, he could row upward, or 



downward 



