TEERACES AND KIVEE VALLEYS OE WESTERN EUROPE. 275 



ocean stretches gradually away westwards to depths of 

 2,600 fathoms and upwards. The material of which it is 

 composed is mainly of or2:anic origin. In the Bay of Biscay 

 the depth descends to 3,000 fathoms, and the floor consists of 

 " blue and green mud " varieties of the Globigerina-ooze, with 

 percentages of carbonate of lime, ranging from 53 to 75 ; 



.Fidl 



W 



Ocean, Surface 



EuropB 



ConHize?ilal 

 PldZ/orm 



Abyssal Region ^/^^^^^^^^^ 



mms%;/M///mM 



N.America 



Ocean Surface 





V/////////^///////X./// . , 



Figs. 1 and 2, To illustrate the difference of outline between 

 the European Continental Terminal Slope and that of the N. 

 American Continent. 



the residue consisting of minute particles of quartz, felspar, 

 augite and volcanic matter.* 



III. Slopes of the Great Declivity. — Exception has 

 been taken to the views here advanced regarding the nature 

 and origin of the Great Declivity on the ground that the 

 slopes are extreme!}^ shght. This view does not appear to 

 be borne out by the results of actual measurement — which 



* Eeport " Challenger " Expedition, p. 48. 



