

Ch. XII.] 



GREAT DEPTH OF SEA 



2G5 



be en an unbroken continuity of land at one and the same 



at depth of the sea as compared to the mean height of 



time . 



>f 



I shall 



tlian 



perM the climate of the globe was much wanner or colder 

 »„ it is now, it would have a tendency to retain that higher 

 or lower temperature for a succession of geological epochs. 

 That tendency would usually be in favour of warmer climates 

 because these would be consistent with a normal state of 

 L>2raphy • but, if once abnormal conditions like the present 

 Lvailed, they would be persistent for an indefinite lapse of 



ages. 



Tlie slowness of climatal 



change 



would arise from the great depth of the sea as compared to 

 the height of the land, and the consequent lapse of time re- 

 quired to alter the position of continents and great oceanic 



basins. , „ , . , 



To one who contemplates the vast amount of geographical 



change which has occurred in Post-tertiary, and still more 



Pliocene and Miocene times, it 



might at 



first sight 



appear that in the course of such a period as might corre- 

 spond with the disappearance of one set of organic beings 

 and the coming in of another, there would be a complete 

 revolution in the outward form of the earth's crust. But 

 such an opinion would not be in harmony with the 

 which have come to our knowledge of late years in regard 

 to the average height of the continents as contrasted with 

 the enormous depth of the sea, both as inferred theoretically 

 from observations on the tidal wave, and proved practically 



iM A * I Mw 1 I- I _ j^J 



facts 



by deep sea soundings. 



The mean height of the land is 



only 1,000 feet, the depth of the sea 15,000 feet. The effect 



-« -* * — < f~\ /~\ /\ I _ « ^i— -« -a 



therefore, of vertical movements, 



equalling 



1,000 feet in 



both directions, upward and downward, is to cause a vast 

 transposition of land and sea in those areas which are 

 now continental, and adjoining to which there is much 



M 



sea 



not exceeding 1,000 feet in depth. 





of equal amount would have no tendency to produce a sen- 

 sible alteration in the Atlantic or Pacific oceans, or to cause 

 the oceanic and continental areas to change places. De- 



