Pacific Ocean the position or the existence of which ie etill doubt- 

 ful. 



Mapping the topography of the regions that have as yet been only 

 plumbed here and there, added to more detailed examination of other 

 parts of the ocean, \^ll bring to light many ridges, troughs, es- 

 carpments, and other irregularities of the bottom such as have ac- 

 tually been revealed by the Panama-Australian profile just mentioned, 

 by the Meteor^ s traverses of the South Atlantic, and by those of the 

 Carnegie in the southeastern Pacific. 



Now we have at hand a new tool for the purpose, in the recently 

 developed method of sounding by timing the echo sent back by the 

 bottom, by which any ship equipped with the necessary gear can take 

 almost continuous soundings in any depth of water throughout her 

 voyages, and while running full speed. There is no longer any doubt 

 as to the accuracy of the method, and it has been tried often enough 

 to prove its entire practicability. We may, therefore, look forward 

 to a very rapid development of our knowledge of the shapes of the 

 ocean basins along all the commercial routes, and on the routes 

 followed by naval ships. All that is needed is to arouse interest, 

 and to procure the funds necessary for equipping ships with the sonic 

 gear. Here it is the task of the oceanographer to accumulate and 

 tabulate the data, for the geologist to interpret it in terms of the 

 earth's history, 



2. Sub^aarine Sedimentation 



Study of the marine sediments has three chief objects; 

 (a) it throws light on the cycle of matter within the sea, (b) a 

 knowledge of the sediments now being laid down under the sea is pre- 

 requisite for interpretation of sedimentary rocks on land; and 

 (c) better knowledge of the nature of the sediments, and of the rate 

 at which they are now being laid down, will clarify our ideas as to 

 the permanence of the ocean basins. 



To the geologist a study of sediments and of sedimentation is 

 essential, because the development of stratigraphy depends upon a 

 knowledge of the environi-nent of deposition; and this development is 

 necessary for a correct understanding of the sequence of events in 

 the earth's history. Furthermore, sedimentary rocks that were 

 originally laid down under water now cover some 75fo of the surface of 

 the lands. It is also probable that areas overlayed by igneus rocke 

 are m nany places underlayed by sedimentary. In fact, there are 

 probably no large parts of the continental areas that were not under 

 salt water^at some time in the geologic past. Sedimentary rocks 

 also contain a majority of our mineral resources. They are, thus, 

 the most important element in the earth's outer shell as they affect 

 man's undertakings. If we can safely reconstruct the ecological 

 relationships of the fossil remains they enclose from analogy with 

 their closest living relatives in the modern seas, the study of 

 sediments will tell us much about the climates of the past; will also 

 give clues to the character of the earth's atmosphere, and to the 

 chemistry and physics of the sea bottom, during past ages. 



The task of the sedimentary geologist, therefore, includes, not 



