the lever is in the relation of i to 7, it produces a force of 30,800 lb. at 

 the hook. As the tubs full of ballast weigh only 12,100 lb., this force is 

 sufficient to retain them even if the swell produces a certain amount of 

 jarring. Let us here recall that during the towing, when somewhat 

 violent shocks could occur, the position of the levers is assured by the 

 pins (B in the preceding diagram). 



The windings of these magnets are insulated according to the same 

 principle as that of the magnetic valves. 



Appendix j 



Form of the Float 



The naval engineer will be surprised perhaps at the cylindrical form 

 of our float. He would have selected a shape approaching that of the 

 hull of a real ship. Let us observe, however, that the centre of gravity 

 of a ship is generally above the centre of gravity of the water displaced. 

 The stability of the vessel must be obtained by the shape of the hull. 

 This is what is called stability of form, such as we find, for example, 

 if a sheet of cork floats on the water : although the centre of gravity 

 of this sheet of cork is above the level of the water, its stability is 

 perfect. A cylinder, on the other hand, completely submerged, does not 

 possess any stability of form. But if its centre of gravity is considerably 

 below its axis, therefore below the centre of gravity of the displaced 

 water, it is perfectly stable. This is the type of stability which our 

 bathyscaphe makes use of. The heavy cabin will place the centre of 

 gravity of the whole below the axis of the float. In order that the vessel 

 should behave properly when it is on the surface and at sea, the 

 stability thus acquired must naturally not be sacrificed pointlessly by 

 placing too many heavy objects on the deck. Along with other reasons, 

 this is why the ballast receptacles were housed at the bottom of the 

 float. 



The cylindrical form has considerable advantages over all others. 

 For a given volume, weight and length, the resistance of a cylinder 

 to buckling is greater than that of a ship's hull. The smaller the 

 radius of curvature of a metal sheet, the more resistant this sheet is to 

 external pressure, and if at any point the radius is large, the rigidity of 

 the whole will be aflfected : now the cross-section of a cylinder has a 

 smaller radius than the largest radius of the cross-section of any other 



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