with him a reserve of compressed air which permits him, according 

 to the supply he has at his disposal, to breathe during fifteen, thirty 

 and even forty-five minutes.^ 



At the same time the impediments of the 'diving-suit' and the 

 heavy 'helmet' have been dispensed with. Thus instead of walking 

 with difficulty on the sea-floor, the modern diver moves freely in 

 three dimensions. His speed has been increased by rubber flippers 

 affixed to his feet : thanks to this invention of Corlieu, the diver has 

 become a 'frogman'. This sport, which arose before the war in France, 

 is now spreading through 'the entire world. We know the role played 

 by frogmen-divers at the time when the Allies landed in Normandy. 



Readers interested in the history of diving will find a quantity of 

 little-known details in the book of Pierre de Latil and Jean Rivoire, 

 A la recherche du monde marin ('In Search of the Undersea World'), 

 Plon (Paris), 1954. The authors, with extraordinary patience, have 

 examined everything to be found in ancient documents on the subject 

 of marine exploration. 



What depths can man reach with these various methods } Whether 

 he uses the classic diving-suit or the equipment of the frogman, the 

 diver will still be subject to the pressure of the water, which adds 

 14-2 lb. per sq. in. to the atmospheric pressure each time he goes down 

 another 33 ft. This pressure enters the thorax and the entire body. 

 Contrary to what is often believed, it is not the mechanical effects 

 of this pressure which limit the depths accessible to man. The serious 

 or mortal accidents which occur are due to physico-chemical reaction 

 in our bodies. Under heavy pressure, the nitrogen of the air breathed 

 in is dissolved in the blood and even in the tissues, thus setting off 

 various disturbances, of which the most dangerous is a feeling of 

 sleepy well-being. In this state the diver, losing consciousness little 

 by little, can be led to make false moves and even to remain beyond 

 the safety limit, when a few minutes earlier he knew perfectly well that 

 he was running a mortal danger in staying submerged any longer. 



In rising to the surface, a new risk is incurred: the nitrogen, dis- 

 solved in the blood and in the tissues, is affected by the lower pressures 

 and released just like carbon dioxide in a bottle of champagne or 

 mineral water when it is opened. Thus the blood vessels may be 

 obstructed by bubbles of nitrogen : this leads to ' gaseous embolism ' 

 and produces paralysis or death, either during the ascent, or even a 



1 For example, the Cousteau-Gagnan device. 



[20] 



