1% of this gas is quite innocuous; a person would only begin to be 

 affected at 2%. Our apparatus was thus more than satisfactory for 

 the two occupants planned for from the beginning : it would allow the 

 presence of three persons without difficulty. 



We could also, if needed, reduce the intake of oxygen. With i -76 

 pints (i 1.) a minute, for example, the quantity of air regenerated would 

 be nearly 9 gallons a minute and the concentration of the carbon 

 dioxide would rise by degrees to 0-85%. 



In any case, the apparatus would furnish more oxygen than two 

 men consume and the concentration of this gas would rise bit by bit. 

 In the stratospheric balloon that was of no importance since the excess 

 air could always be allowed to escape and in the cabin there could even 

 be established a pressure less than one atmosphere. In the bathyscaphe 

 the excess of oxygen must be remedied in another way. This was 

 very simple: as soon as the oxygen became in excess, we closed 

 the bottle of this gas and the air was sent through the alkaline car- 

 tridges by means of an electric fan. Its rate of feed being 52-8 gallons a 

 minute, it had only to operate a quarter of the time during which the 

 bottle of oxygen was closed. 



In passing, it may be noted that, contrary to an opinion commonly 

 held, it is much more important to absorb the carbon dioxide from the 

 air than to add oxygen to it. 



What about the water vapour? A man expels from his lungs in 

 twenty-four hours about 2 lb. of water : the quantity of water given out 

 by perspiration depends much upon the circumstances, but it can 

 easily reach from 2 to over 4 lb. a day. The crew of the bathyscaphe 

 might then give off over 12 lb. of water vapour in twenty-four hours, 

 which represents 10 pints of water vapour a minute! As the wall of 

 the cabin of the stratospheric balloon became extremely cold on the 

 side opposed to the sun, the water vapour condensed sufficiently 

 there. In the bathyscaphe, however, it would be worth while to absorb 

 the humidity by means of a hygroscopic substance, in the present 

 case, silicagel: this substance has the great advantage over sulphuric 

 acid, phosphoric acid and calcium chloride, which are usually employed 

 in the circumstances, that it never liberates a corrosive liquid. ^ 



Unforeseen circumstances could result in the crew remaining shut 



1 During the expedition to the Cape Verde Islands, I used silicagel manu- 

 factured by the Uetikon factory (Switzerland). For the Trieste it was the 

 Baslini Company (Milan) which furnished us with this absorbent. 



[93] 



