508 



[chap. 23 



Power is provided by externally mounted lead-acid batteries operating 

 hydro jets forced at high speeds through nozzles instead of propellers. The jets 

 are said to allow great maneuverability and speeds up to 1.5 knots. The craft 

 is ballasted with 250 kg of water and iron blocks. One of the two iron weights 

 is dropped off routinely ; the other in an emergency. Trim is maintained by 

 mercury which can be pumped to various reservoirs. The weight of the diving 

 payload must be carefully controlled ; diving is commenced with a negative 

 buoyancy of 20 kg. Both still and movie cameras are installed ; mercury -vapor 

 lamps provide external lighting. A hydraulic three-fingered prehensile arm 



Fig. 6. Cousteau's "diving saucer" for plunges to 300 m. (Nat. Geog. Mag. photo.) 



permits the collection of specimens. Emergency escape is possible by donning 

 scuba (self-contained underwater breathing apparatus) and pressurizing the 

 hull to the ambient sea pressure so that the top hatch can be opened. 



The present "diving saucer" is limited to 300 m with a tested safety factor 

 of three. It is thus confined to the continental shelf and the upper portions of 

 the continental slope. Construction is underway of a new model with a spherical 

 cabin of the same volume as the prototype. This will extend the depth range to 

 1000 m. More efficient hydrojets will be used pumping a greater volume of 

 water at a lower pressure than at present. 



5. Buoyant-Hulled Deep Ships or Bathynauts 



Although the existing bathyscaphs have made a remarkable contribution 

 toward direct exploration of the deep sea, it is evident that they are somewhat 



