one which is on top of tlie tower, on the left in the diagram. Then, 

 through this last opening, we continue to introduce the petrol. During 

 this filling operation the air in the compartments goes out by the 

 drain-cocks B. (These consist of two straight-through cocks with a 

 bore of 0-49 in.) As each compartment becomes full the petrol is seen 

 to rise through the drain-cock, and this must then be closed. When all 

 the drain-cocks are closed, we know that there is no more air in the 

 float. This is very important because, in the deep sea, any air in the 

 float would be compressed to a very small volume and an equivalent 

 quantity of water would enter the float. From this there would result 

 an overload of about 10 lb. per gallon. 



It is thus essential to make sure that all air is excluded before each 

 dive ; but we must also be able to determine the quantity of water 

 present in each compartment. For this purpose we constructed a very 

 simple instrument : a metallic tube 13-2 ft. long and 0*394 in. in external 

 diameter, which is traversed from end to end by an insulated copper 

 wire which projects 0-394 in. beyond the lower end, this last part 

 being bare. The top of the tube and the wire are cemented to a dry 

 battery and a little bulb. If it is in contact with the base of the tube, 

 the sea water (a conductor) closes the electric circuit, and the lamp 

 lights up. The drain-cocks, in the open position, give free passage to 

 the tube ; it is thus easy to sound each compartment and to determine 

 the quantity of water present in it. 



Compartments 2, 3, 4 and 5 as well as 10, 11, 12 and 13 are inter- 

 communicating at their lower ends by the openings H, while the 

 compartments 5, 6, 7, 9 and 10 communicate by the tubes G. The 

 purpose of these tubes is always to conduct the water towards the 

 central reservoir 7. This prevents losses of petrol by way of the re- 

 ciprocating valve and also improves the longitudinal stability of the 

 bathyscaphe. The reservoir 8 contains the stabilizing petrol. It is 

 equipped with a valve E operated electro-magnetically and with a 

 hole K by which the water enters to replace petrol that has been 

 jettisoned. 



When, after the filling, all the openings B and C are closed, the float 

 breathes through the double valve F to compensate the variations of 

 volume of the petrol. The U-shaped tube J should avert catastrope if 

 by some accident the double valve F becomes blocked. It contains 

 mercury, and its dimensions are such that it allows water to pass in 

 either direction if a difference of pressure of 0-15 atmospheres occurs. 



[77] 



