.8,,. THE PERMANENCE OF OCEANIC BASINS. 425 



definite horizon has been anywhere detected, though such a deposit 

 must have been formed and largely preserved if the whole or any 

 considerable part of a continent had risen from ocean depths at any 

 period of its history, constitutes of itself a very strong argument against 

 any such interchange of oceanic and continental areas having 

 occurred. 



I have now shown that there are three distinct groups of 

 phenomena which are either altogether inconsistent with any general 

 interchange of oceanic and continental areas, or which render it 

 exceedingly difficult to understand how such interchange could have 

 been brought about. These phenomena are: — (i) The enormous 

 disproportion between the mean height of the land and the mean 

 depth of the ocean, which would render it very difficult for new land 

 to reach the surface till long after the total submergence of the 

 sinking continent. (2) The wonderful uniformity of level over by far 

 the greater part of the ocean floor, which indicates that it is not 

 subject to the same disturbing agencies which throughout all 

 geological time have been creating irregularities in the land-surface, 

 irregularities which would be far greater than they are were they not 

 continually counteracted by the lowering and equalising effects of 

 subaerial denudation. (3) The remarkable parallelism and com- 

 pleteness of the series of geological formations in all the best known 

 continents and larger continental islands, indicating that none of them 

 have risen from the ocean floor during any portion of known geological 

 history, a conclusion enforced by the absence from any of them of that 

 general deposit of oceanic ooze at some definite horizon, which would 

 be at once the result and proof of any such tremendous episode in 

 their past history. 



I submit that these facts, and the conclusions to be logically deduced 

 from them, form a very powerful a pylori argument as against those 

 who maintain the interchange of continents and oceans as a means 

 of explaining certain isolated geological or biological phenomena ; 

 such, for instance, as the much-disputed origin of the chalk, or the 

 supposed necessity for land-communication to explain the distribution 

 of certain groups of reptiles or fishes in remote geological times. 

 Before postulating such vast revolutions of the terrestrial surface in 

 order to cut the gordian knot of difficulties which may be mainly due 

 to imperfect knowledge, it will be necessary to show that the con- 

 siderations here adduced, as well as the great body of facts which 

 have caused many eminent geologists, naturalists, and physicists to 

 hold the doctrine of oceanic permanence, are either illogical or 

 founded on incorrect data. For, surely, no one will suggest that so 

 vast a problem of terrestrial physics can be held to be solved till we 

 have exhausted all the evidence at our command, and have shown 

 that it largely preponderates on one side or the other. 



The present article is intended to supply a hitherto unnoticed 

 class of arguments for oceanic permanence, and these must of course 



