58 THE OCEAN FLOOR 



vestigating this point in the laboratory with original 

 sediments from the "Albatross" cruise submitted to 

 high pressures, has found considerable variation in 

 the figures for different kinds of sediments, some of 

 which give a velocity distinctly less than that of water! 

 Until more data of this kind have been obtained, it 

 seems best to accept provisionally the velocity for sea 

 water as a basis for calculations. 



Figure 24 is a diagram of information on thickness 

 gained from other parts of the ocean. This shows the 

 figures just quoted to be distinctly greater than any 

 found elsewhere. It is especially noteworthy that in 

 both the Pacific and Indian Oceans the sedimentary 

 thicknesses found were only a fraction of the record 

 thickness from the Atlantic. I shall return to this sur- 

 prising result below. 



A few words might be added concerning the two 

 advantages of WeibulFs method, namely its quickness 

 and cheapness. For recording the echoes from depth 

 charges exploding in depths as great as 20,000 feet it 

 is not necessary to keep the ship hove to for more than 

 half an hour. Generally, two or even three charges, 

 exploding at different depths, are used simultaneously. 

 The cost of the whole equipment, including hydro- 

 phones and wire recorder, is very moderate, not exceed- 

 ing $ 1 ,000. Moreover, by changing the time scale and 

 amplification at will in the transfer to the oscillograph 

 afterward, and by using electric "timeband-pass" filters, 

 one has facilities for examining the fine structure of the 



