j: The Principle of the Bathyscaphe 



STATIC LIFT 



TO understand how the bathyscaphe functions, it is sufficient to 

 compare it to a free balloon. 



In spite of the difference of surroundings in which they move and 

 of the quite opposed ends in view, the principle in question is the same : 

 that of Archimedes. If the weight of an immersed body is lighter than 

 the weight of the ambient fluid corresponding to its volume, the body 

 will rise : if it is greater, that is to say, if the body is heavier than the 

 fluid which it displaces, it will descend. The balloon moves about in 

 the air, where it must at first rise and then descend. The bathyscaphe 

 moves about in the water. Leaving the surface, it must go down to the 

 depths, then rise. The balloon rises because its envelope, inflated by a 

 gas lighter than the ambient air (hot air, town gas, hydrogen or 

 helium), is voluminous enough to support the weight of the car hanging 

 from it. In the same way the bathyscaphe is, in its principle, lighter 

 than water: a float filled with a light substance sustains a watertight 

 sphere which is fastened to it. 



What is the substance with a specific gravity less than that of water 

 which is suitable for filling the float } 



We must straightway exclude the use of gases : they are much too 

 compressible. The pressures prevailing at great depths would reduce 

 their volume and their supporting power in such proportions that it 

 is not possible to consider their use, unless the effects of this compres- 

 sion can be avoided. To obtain this result it would be necessary to 

 enclose the gas in a vessel with rigid walls, the more resistant and heavy 

 the deeper the dives in prospect. It is the principle adopted for con- 

 ventional submarines, the hull of which is filled with air : but we know 

 that they cannot dive beyond loo fathoms or so without the risk of 

 their light hulls being crushed. But for the bathyscaphe which 

 must be able to go down some thousands of fathoms, we must seek 

 another solution, since this requires a considerable thickening of the 

 walls, and hence a prohibitive weight. 



I turned from gases and looked for a less compressible substance. 

 A solid lighter than water would suit and would have the advantage 

 of not flowing away if the float became damaged. Because of the fact 



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