DIASTROPHISM AND THE FORMATIVE PROCESSES 137 



But these prudential considerations do not affect the general 

 diagnostic nature of the oceanic deposits. They only bear on 

 certain special bathymetrical inferences. 



It appears from all the considerations that bear upon the case 

 that the diagnostic character of the abysmal deposits is of a most 

 declared and convincing type when broadly applied with due cir- 

 cumspection. Grounds for a critical attitude only arise in respect 

 to ultra-inferences based on small remnants of ancient deposits 

 in limited areas. 



Now the broad facts are these : At the present time nearly two- 

 thirds of the area of the earth's surface is covered by deep-sea 

 deposits of recent origin. About one-half of the present surface 

 is covered by truly abysmal deposits. What lies below these 

 abysmal deposits, representing earlier periods, is unknown, because 

 inaccessible. There is a strong presumption that similar deposits 

 lie below the recent ones representing the earlier ages. This pre- 

 sumption rests on the more primary assumption that oceans of 

 great volume existed all through those earlier ages and were giving 

 rise to oceanic deposits, since the requisite forms of life and of debris 

 are known to have then existed, and this, taken in connection with 

 the even more significant fact that such abysmal deposits do not 

 form appreciable members of the terranes of the continents, leaves 

 no other presumption available. Sir John Murray says: "With 

 some doubtful exceptions, it has been impossible to recognize in 

 the rocks of the continents formations identical with those of 

 the pelagic deposits."^ And again he remarks: "It seems doubt- 

 ful if the deposits of the abysmal areas have in the past taken any 

 part in the formation of the existing continental masses."^ With 

 few exceptions, the marine members of the continental deposits 

 belong to the shelf-sea series and to deposits of the foreset terrige- 

 nous type. These are facts of the first order of moment, and in 

 them lies strong evidence of the permanence of the continents. 

 The marine deposits of the continents are either epi-continental or 

 terrigenous, the deposits of the ocean basins are oceanic and prob- 

 ably always have been as far back as the record permits us to go. 



' Murray and Renard, ''Challenger" Report on Deep Sea Deposits (1891), p. 189. 

 ' Op. cit., Introduction, p. xxix. 



