248 THE BOTTOM OF THE SEA. 



air, the pressure of it against the moveable lid keeps 

 the valve closed. 



The entire apparatus, when under water, works as 

 follows. By drawing in his breath, the workman re- 

 moves a certain part of the air from the chamber ; 

 exterior pressure is then immediately exerted on the 

 moveable lid, v/liich falls, and through the intermediate 

 rod causes the valve to open. Air issues from the 

 reservoir, and re-establishes the equilibrium between 

 the interior of the air-chamber and the surrounding 

 medium ; tlie lid rises, and the conical valve, returning 

 to its former position, again intercepts the communi- 

 cation between the reservoir and the air-chamber, 

 until another aspiration brings about a repetition of 

 these phenomena. When the workman respires, the 

 valve, which we have already mentioned as existing 

 in the respiratory tube, permits the air expelled from 

 the lungs to escape into the water. 



This apparatus works automatically ; whatever be 

 the irregularity in the working of the air-pump, its 

 action is as regular as that of the steam-engine. The 

 workman receives exactly the quantity of air necessary 

 for respiration ; this air reaches him at a pressure equi- 

 valent to that to which the rest of his body is submitted, 

 and- he is able to breathe without attention or effort. 



MM. Eouquayrol and Denayrouze, not content with 

 having enabled the workman to breathe independently 



