French Bathyscaph Program 477 
During this last dive, the bathyscaph descended to the greatest depth ever reached by 
man until the beginning of 1960, when the deepest sea floors known to this day (about 
11,000 metres off the Philippines) were reached by the TRIESTE bought by the United 
States of America. 
The U.S. Navy had acquired the TRIESTE with a view to using this powerful underwater 
research tool for oceanographic purposes. After the apparatus had undergone important 
changes: lengthening of the float, replacing the original sphere by a new one, forged by 
Krupp steelworks, in Germany, and enlarging the shot silos, it was an American bathyscaph 
which landed for the first time on the bottom of the Pacific Ocean, at the depth of 11,000 
metres. ) 
So, there are now two bathyscaphs in operation: one, the FNRS-3, is French, and the 
other, the TRIESTE, is American. Their research programs are quite similar: physical and 
biological oceanography, study of the propagation of supersonics and of electromagnetic 
radiations in sea water, and the geology of ocean bottoms. A second French bathyscaph is 
under construction in the Toulon Naval Dockyard; I shall mention it briefly at the end of 
this paper. 
As to the existence of other deep-water oceanographic vessels, we can only guess, as 
these would be Russian. The USSR has stated several times that it was building bathy- 
scaphs, but we have no information on this subject. 
PRINCIPLES 
To descend to great depths beneath the sea, man must enclose himself in a pressure 
hull that is watertight and capable of withstanding the pressure exerted upon it. To with- 
stand a uniform external pressure, the best shape is a sphere; that is why the hulls of 
bathyscaphs have, up to now, taken the form of a sphere. Allowing for the safety factor 
selected and for the inside diameter necessary to meet the accommodation requirements, 
this sphere must have a certain thickness, which is determined by the strength calculation 
of materials. Owing to this thickness, the sphere is much heavier than the volume of water 
which it displaces. It would immediately sink to the bottom if it were not suspended under- 
neath a float filled with extra-light petrol, which gives it the necessary buoyancy. 
This is the main difference between a submarine and the bathyscaph: in the case of a 
submarine, the weight of the pressure hull plus the weight of all the hull fittings and inside 
equipment must be equal to the displacement. We shall apply the term bathyscaph to the 
machine for which the weight of the pressure hull, including that of internal and external 
fittings, is greater than its displacement. Therefore, the float is necessary to ensure the 
trim. 
Vertical movement is effected by increasing or decreasing the machine’s weight. The 
increase in weight is produced by jettisoning petrol (which is replaced by sea water); the 
dischargeable petrol is contained in a special tank, which is isolated from the float itself 
whose buoyancy must not be impaired; this attitude is absolutely necessary to the lift of 
the craft. The decrease of weight is produced by shedding ballast; this consists of small 
steel shot contained in vertical silos in the center of the float. This shot is held in at the 
base of the silos by the electromagnetic field of an electromagnet called an electrochute, 
which lets the shot fall when the current is cut. In addition, there is a safety device, 
called an electrorapid-release, which enables the opening of the silo to be freed completely 
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