34 THE OCEAN FLOOR 



and the author used a pressure-tight spherical container, 

 evacuated before immersion, into which the water in the 

 long coring tube was admitted through a valve, released 

 at the moment of impact on the bottom."^ In 1942 with 

 this "vacuum corer" an undistorted core nearly 50 feet 

 long was raised from the depths of the Gullmar Fjord, 

 on the west coast of Sweden. Shortly afterward Kullen- 

 berg, who also utilized high water pressure but with a 

 simpler and more effective contrivance without any 

 vacuum container, obtained a core of 65 feet from the 

 same fjord. ^ Where great length of core is essential, this 

 "piston core-sampler" (Figure 14) has become the 

 standard tool of deep-sea coring, not only in Sweden 

 but also in other countries. Figure 15 shows the 

 development which coring apparatus has undergone. 



At the same time the foremost Swedish authority on 

 explosives, Waloddi Weibull of the Bofors armament 

 works, at the author's suggestion developed a new 

 method for measuring the totally unknown thickness of 

 the sediment carpet in great ocean depths. Utilizing 

 depth charges, so constructed that they could be 

 detonated at any desired depth between 1,500 and 

 20,000 feet, and recording by means of an oscillograph 

 the echoes thrown back against the bottom and from the 

 "bottom below the bottom," Weibull got a measure of 

 the thickness of the sediment, traversed twice by the 

 fainter and deeper echoes. 



In the spring of 1946, in order to test these and other 

 new tools of deep-sea research, the Swedish research 



