(The details of the construction of the double valve F and of the 

 control valve E are given in the Appendices.) 



Another danger, namely, the stopping up of all this piping by ice, is 

 also guarded against. If the bathyscaphe stays a certain time at the 

 bottom, the petrol gradually takes on the temperature of the ambient 

 water, which in the Atlantic, even in the tropics, can be close to freezing 

 point. Let us suppose that now it begins a rapid rise: on account of 

 the adiabatic expansion, the temperature of the petrol will go still 

 lower, falling to 1 5° or even 5° F. As a result the water contained in 

 the pipes will freeze along the walls. The cross-section of these pipes 

 must then be of a size such that in no case can the ice formed prevent 

 the free circulation of water, otherwise the float could burst. Taking 

 into account the thermal conductivity of the ice, and of the time during 

 which the low temperature of the petrol could continue, we calculated 

 the cross-section that these tubes must have and, as a measure of pre- 

 caution, these calculations were verified by tests carried out at the 

 Glacières de Bruxelles (Brussels Refrigerating Works) and at the ice- 

 works of E. Burgin of Basle. 



Finally, the drain-cocks B are covered with caps which protect 

 them against all damage. These caps also prevent a loss of petrol in 

 case the straight-through taps should leak. To avoid the caps, which 

 naturally contain air, being crushed under great pressure, they are 

 connected to rubber vessels filled with water, placed in the float: in 

 the depths the petrol compresses the rubber sacks and causes the water 

 to pass into the caps, to replace the air, the volume of which will have 

 been reduced to almost nothing. 



THE AIR TANKS 



The extremities of the float are air- tanks (Nos. i and 14, Fig. 8). 

 Their purpose is to give buoyancy to the bathyscaphe during all the 

 surface operations. When full of air, they increase the lifting force of the 

 float by 12 tons. Before the dive is begun, the valves A are opened, and 

 sea water enters at the bottom of the tanks. After the dive, compressed 

 air, supplied from the towing vessels by means of a flexible tube, is used 

 to expel the water in these tanks : the deck can then be seen to emerge 

 more and more above the level of the sea. If necessary, the float can also 

 be trimmed by filling the two tanks unequally. They also assure a certain 

 protection in case of collision : being built in metal sheeting of o-i 18 in. 



[78] 



