DEEP-SEA DEPOSITS. 551 



Mr. Kordeiiskiold, in his second expedition to Greenland, plainly- 

 recognized also tlie abundance of dusts from tLe friction of the glaciers 

 on their bottom. When this very fine clay has been dried by the sun, 

 it is put in motion by the least breeze, and the air is filled far around 

 with clouds of dust, so that the rocks and plants are covered with a 

 sort of grayish powder, wliich gives a somber appearance to the whole* 

 country. The eminent traveller saw, in transportations of this nature, 

 not only one of the elements of marine sediments, but also the probable 

 origii! of the diluvial ooze, known under the name of loess, in conformity 

 with the views of Mr. Kichthofen.* 



It nuist also be remarked that the currents of the atmosphere carry 

 across the widest seas terrestrial dust of all kinds, volcanic and other. 

 The deposits of the ocean find active collaboration in this aerial trans- 

 portation. 



Marine sediments are not composed merely of mineral debris, more 

 or less fine, pebbles, sands, and ooze. Solid reuuiins which mollusks 

 and other inhabitants of the sea leave after death, are associated 

 with this debris in large numbers, and are sometimes deposited in pre- 

 dominant proportion. Such remains often lose their characteristic 

 forms in consequence of dissolving chemical action so as to augment 

 the mass of deposits apparently inorganic. 



It is thus that these various accumulations gradually come to con- 

 stitute around continents a sort of belt which constantly increases, t 



In co-ordinating all that was known of these marginal deposits, the 

 only ones which had then been studied, Delesse published thirty years 

 ago a lithological study of the sea bottom. The hydrographic maps made 

 by naval officers and engineers served as the basis for his works.| In 

 regard to the seas bordering France, which were the j)rincipal object of 

 the author's studies, he himself examined all the specimens collected both 

 on the shores and farther out. Tables of hundreds of deposits show 

 their exact derivation, their physical, mineralogical, and organic char- 

 acteristics,§ and also their chemical composition. An atlas annexed 

 to the text gives three lithological maps, very skillfully executed, 

 representing, one, the seas of France, another the seas of Europe, and 

 the third the seas of North America. 



In certain regions of the shore the nature of the sea bottom has been 

 so completely studied in all its particulars that an idea almost as exact 



* The Second Swedish Expedition to Greenland. Trans, by Charles Rabot, 1888, pp. 

 247 and 248. 



IThe width of this belt is calculated at au average of 250 kilometers; it extends 

 often to 600 and 700 kilometers, for example on the coast of Brazil, opposite the 

 Amazon. 



\ Lithology of the Seas of France and of the principal seas of the Globe. Paris, 

 1872. 



§ Dr. Fischer, who has studied the organic character of the deposits, has already 

 recognized, among the interesting results, the importance of the bryozoa and of the 

 foraminifera as they occur in many of the ancient sedimentary layers. 



