thickness only, they would meet the impact first and their damage 

 would not result in any loss of petrol. 



THE CONTROL VALVE 



The bathyscaphe, derived from the free balloon, is, like the balloon, 

 equipped with a control valve: by 'pulling' the valve the aeronaut 

 allows gas to escape, thus diminishing the speed of ascent or beginning 

 the descent. In the same way the pilot of the bathyscaphe must be able, 

 by opening the control valve, to sacrifice the petrol to check the rate 

 of ascent, to stabilize his machine or even to make it go down. 



The valve of the balloon is placed at the top of the single gas 

 envelope. If it remains jammed in its open position, the pilot cannot 

 avoid a return to earth. This happened when the first American 

 stratospheric balloon, the Century of Progress, took off; instead of 

 going up into the stratosphere, the balloon, after having reached a 

 height of only a few hundred feet, landed in the middle of Chicago 

 railway station. Some weeks later, the valve having been modified, it 

 went up again, and this time brought the altitude record from Europe 

 to America. To eliminate dangers of this type, obviously more 

 serious for a bathyscaphe than for a balloon, it is sufficient to 

 place the valve on the top of a small, independent reservoir. I chose 

 the central ,tube of our hull (from which the cabin was to be suspended) 

 to store the stabilizing petrol. Its small volume of 153-5 cu. ft. 

 represents a static lift of the order of 3300 lb. 



The manipulation of the valve, very simple in the conventional free 

 balloon, more complex in the stratospheric balloon, here became a 

 difficult problem. It is described in the Appendix. 



UNBALLASTING 



It is difficult to say which is the most important part of the bathy- 

 scaphe : just as the strength of a chain depends upon that of each link, 

 each of the components of our submarine was of vital importance : 

 numerous problems had to be resolved before it was possible to plunge 

 into the construction of the whole. 



The problem of unballasting, however, is among the most interest- 

 ing : it is one of those which occupied our thought from the beginning. 



In describing the FNRS 2 we mentioned different systems of 

 unballasting, all based upon the utilization of a magnetic field whose 

 action ceases as soon as the current which feeds it is cut off. 



[79] 



