64 



HISTORY OF THE SEA. 



rubber so as to be air-tight. It yields to both interior and ex- 

 terior pressure, rising and falling as the ease may be. When 

 exterior pressure is exerted on it, the valve is affected, com- 

 munication is opened between the air-chamber and the reservoir 

 and a portion of the compressed air from the latter flows into 

 the chamber. Should there be too much air in the chamber 

 its pressure against the movable lid keeps the valve closed. 



When in use under water its operation is thus: The 

 diver by drawing his breath takes air from the chamber : ex- 



DIVERS DRESSED IN THE APPARATUS DESCRIBED. 



terior pressure is exerted on the movable lid, it falls, causes 

 the valve to open, and air comes from the reservoir to estab- 

 lish the equilibrium, when the lid rises and shuts off the com- 

 munication between the air-chamber and the reservoir until 

 another inspiration on the part of the diver repeats the action 

 past described. When the workman expires, the valve in the 

 respiratory tube allows the expelled air to escape into the 

 water. This apparatus works automatically ; though the air 

 pump may be worked irregularly, its action is regular. The 

 \li ver -ec^ : ves just the quantity of air enough for a respiration. 



