46 A TEXTBOOK OF OCEANOGRAPHY 



other hâve been put forward from time to time — is beyond the 

 scope of this work. Really we know very little of the older 

 sedimentary rocks of extra-European locaHties, and conse- 

 quently until thèse hâve been more thoroughly investigated 

 and submitted to microscopical examination it is hardly 

 possible to arrive at a definite opinion. The chief points put 

 forward in favour of the theory of the permanence of the great 

 oceanic areas may be summarised as follows : 



1. Tlie relative distribution of land and water is against 

 any great change. For any new large mass of land to rise out 

 of the ocean-bed would mean a gênerai submergence, since 

 the volume of the oceanic water greatly exceeds that of the 

 land above sea-level (p. i6). 



2. The contours of the ocean-bed show great uniformity 

 of level (p. 17). There is no évidence of geological faults or 

 of subaerial denudation. 



"The compression which has caused the thickening, 

 accompanied by corrugation, such as characterises most 

 elevated tracts, is a continental phenomenon and has no 

 analogue beneath the océan." 



3. AU continents and continental islands présent the same 

 range of geological formations, and such formations are 

 indicative of the near présence of land. 



4. There is no true abyssal deposit represented in the 

 geological strata. The chalk is not really a représentative of 

 the globigerina ooze. 



5. According to Dana, the great oceanic dépressions are 

 régions of the maximum radial contraction of the earth, and 

 therefore permanent, 



Probably oceanic depths of 2,000 fathoms and over are of 

 great antiquity. For a fuU account of spéculations on this 

 subject the works of Suess, Dana, and Osmund Fisher should 

 be consulted. 



