iSz THE OCEAN 



foundations are laid and other submarine 

 work is carried on and much is done under 

 water which could never be accomplished in 

 any other manner. But even with a diving- 

 suit man is still limited in his work beneath 

 the sea, for the pressure of the water affects the 

 man in the suit just as it affects the men in the 

 diving bell or the naked diver of the tropics. 

 In order to force the air down to the diver in 

 his suit the pressure at the pump must be 

 greater than the pressure of the water where 

 the diver stands, and hence a point is soon 

 reached where the pressure is so great that 

 human flesh and lungs cannot stand it and 

 death would result if it should be maintained. 



Some men are able to withstand far greater 

 pressures than others and are sufficiently ac- 

 customed to diving to remain under water for 

 longer periods than their fellows, but the best 

 and most experienced diver in the world can 

 only remain below for a comparatively short 

 time and can only penetrate to depths of 

 twelve to twenty fathoms with safety. 



With the construction of successful sub- 

 marine boats man made a marvellous advance 



