Walther — Origin and Peopling of the Deep Sea. 59 



But the salty sea water has the peculiar property of clarify- 

 ing muddy river water in a short time and of precipitating all 

 ooze to the bottom. In this way all the river mud is deposited 

 in the shallow sea region and no fragment of quartz reaches 

 the abyss. 



Sir John Murray, after the completion of the Challenger 

 expedition, examined all the known samples of deep-sea bot- 

 tom and showed that in these depths sediments of a very pecu- 

 liar character exist. The mightiest role in their composition 

 is played by the floating organisms of the sea. The chalky 

 shells of frail Globigerina cement together the main mass of 

 the so-called Globigerina ooze, which covers about half of the 

 entire deep sea bottom.' This cream-yellow when fresh, soft, 

 liquid lime-ooze is connected with the continental muds of the 

 coast zones by transition stages, and passes, by decrease of its 

 chalk content, into the so-called Red Clay of the deep sea, 

 which covers about one-fourth of the earth's surface. To it 

 are joined isolated areas which are completely strewn over by 

 the delicate microscopic siliceous tests of Radiolaria. The 

 Red Clay of the deep sea originates from transformed vol- 

 canic ashes and through the solution of organic calcareous 

 skeletons. 



With certain exceptions the above named deep sea sedi- 

 ments and other associated deposits of the abyssal regions are 

 distinguished by the following characteristics : 



1. They contain neither quartz nor other fragments of 

 continental rocks. 



2. They contain no plant residue which is brown or black 

 in color. 



3. They are piled in horizontal layers and are spread over 

 marvelous distances. 



4. They contain no remains of shallow sea animals or 

 plant-eaters. 



5. By very slow and gradual transitions they are connected 

 with the shallow water sediments of another origin. 



The geologic examination of the continental masses has 

 given the remarkable result that from the oldest times of earth 

 history to the present day almost every part was repeatedly 

 sea bottom. The present position and limits of the ocean are 

 a transitory appearance, and while it was formerly believed 

 that it was possible to measure and gauge the height of the land 

 by the fixed level of the sea surface, it has been known for 

 twenty-five years that the sea level is variable. Now, if each 

 part of the present dry land was one or more times sea bottom, 

 we must first ask whether we know deposits in the earth crust 

 which by their lithologic and faunal character can be con- 

 sidered as formerly sea bottom. 



