C 304 ) 



which flujt water tight upon the iron band: the crown was- 

 liuns^ to the iron band with hinges fo as to turn over fide- 

 uile, when opcneu'. To make it perfedly fccure when 

 fliut, it might be icrewed down upon the band by the ope- 

 rator, or by a perfon without. 



There were in the brafs crown, three round doors, one 

 diredtly in front, and one on each fide, large enough to put 

 the hand through — when open they admitted frefh air; theif 

 Ihutters were ground perfedly tight into their places with 

 emery, hung with hinges and iecured in their places when 

 fliut. There were likewife feveral fraall glals v/indows in 

 the crown, for looking through, and for admitting light in 

 the day time, with covers to fecure them. There were 

 tv,'o air pipes in the crown. A ventilator within drew 

 frefhair through one of the air pipes, and dilcharged it in- 

 to the lower part of the veffel ; the frefh air introduced by 

 the ventilator, expelled the impure light air through the 

 other air pipe. Both air pipes were fo conftruded, that 

 they fhut themfelves whenever the water rofe near their 

 tops, fo that no water could enter through them, and open- 

 ed themfelves immediately after they rofe above the water. 



The veflel was chiefly ballafted with lead fixed to its 

 bottom ; when this was not fufficient, a quantity was plac- 

 ed within, more or lefs, according to the weight of the ope- 

 rator ; its ballaft made it fo ftiff, that there was no dan- 

 ger of ovcrfetting. 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, would be let down forty or fifty 

 feet below the vefl^elj this enabled the operator to rife in- 

 llantly to the furface of the water, in cafe of accident. 



When the operator w^ould dcfcend, he placed his foot 

 upon the top ot a brafs valve, deprefllng it, by which he 

 opened a large aperture in the bottom of the vefl^el, through 

 which the water entered at his pleafure ; when he had ad- 

 mitted 



