278 ANNUAL REPORT SMITHSONIAN INSTITUTION, 193 8 



faulting of the earth's crust under the sea. But the problem in 

 general remains. 



Ridges, scarps, or deeps on the sea floor have been recorded from 

 time to time, but latterly more precise information has been furnished 

 by the work of the Dutch Snellius expedition and our own John Murray 

 expedition in the Red Sea, Arabian Sea, and Indian Ocean. As the 

 investigators on the Snellius expedition emphasized, the possibility of 

 a submarine fault assuming gigantic proportions is not in accord with 

 Wegener's theory of a plastic substratum which is necessary for the 

 drift of continental masses. Thanks to Dr. Vening Meinesz's investi- 

 gations of the value of gravity at sea, made by pendulum observations 

 in submerged submarines, it has become possible to relate the deeps, 

 which are usually long and narrow depressions of the sea floor, to long 

 and narrow belts of strong negative anomalies of gravity. Thus there 

 is more than a suggestion that such deeps are of tectonic origin, and 

 consequently due to down-folding or fracturing of the crust. As has 

 long been realized, the best-known deeps, such as those south of the 

 Java-Timor arc and northeast of the Antillean arc, are situated in 

 the neighborhood of land-masses where earth-building movements 

 have recently been active. The same is probably true of the Nero 

 Trough of the Marianas, the Atacama Deep and the South Sandwich 

 Islands Deep. 



We pass to the consideration of the deposits at present being 

 laid down on this submarine surface of varied relief. We have as 

 yet no evidence of any relationship between the canyons and deeps 

 and the type of sediment deposited, but apart from these, it is gen- 

 erally true to say that the deep-sea sediments vary in character 

 according to the depths of water in which they have accumulated. 

 Several expeditions, notably the Meteor, the Carnegie, and the Discovery 

 II, have recently provided additional information about such deposits, 

 but it is a tribute to the work of the Challenger expedition that the 

 classification introduced half a century ago still stands. The various 

 expeditions of the research ship Discovery II, begun in 1925, are still 

 in progress. Organized by the colonial office with the view of acquir- 

 ing knowledge of the important economic problem of the feeding and 

 breeding of whales in the South Seas, the personnel of the expeditions 

 lost no opportunity of making scientific observations relating to the 

 depth, salinity, and temperature of ocean waters, to marine life of all 

 kinds, and to the character of sea-bottom deposits. Valuable results 

 are gradually being published in a series of volumes, but inasmuch as 

 many of the specimens must be examined by busy specialists, much 

 information is still awaited, including the detailed descriptions of 

 the floor deposits. But already results of surprising interest have 

 been announced. The classification of the deep-sea deposits intro- 



