296 PROF. E. HULL, LL.D., ETC., ON THE SUB-OCEANIC 



are evidently taken at relatively distant intervals, such being 

 amply sufficient for all practical purposes. Were the same 

 minuteness or detail to be expended in mapping the Great 

 Declivity as is needed for topographical surveys, based on contour 

 lines, we should doubtless learn that the ancient, now submerged, 

 coast-line also presented a well marked curvilinear irregular 

 outline similar to such as those with which we are familiar. 



It is not easy to assign, or understand, the determining cause 

 of this great change of level of the North Atlantic Ocean, but it is 

 quite illogical to suppose that such cause, of whatever nature it 

 might have been, should have acted in the same direction all over 

 the globe. 



We might attribute the change to the submergence of a vast 

 region of the Northern Hemisphere. If so, as I should conceive 

 to be plausible, it is reasonable to conceive the simultaneous 

 emergence elsewhere of a region of somewhat comparable extent 

 — probably in the Southern Hemisphere. This problem may be 

 elucidated during the course of next centuiy, especially during the 

 Antarctic polar expeditions. 



We might also conceive that in consequence of a regular, slow, 

 progressive change in the axis of rotation of our globe — were that 

 theory to be admitted as tenable — the region under consideration 

 was once situated nearer the then tropical zone, and far nearer 

 the former equator than at present. Need I remind the members 

 that the equatorial diameter of the globe, or any other diameter 

 supposed to be drawn within the tropics, greatly exceeds in length 

 any drawn in higher latitudes, and that it is about 20 miles in 

 excess of the axis of rotation, that is to say the polar diameter ? 



As a general rule the most lofty mountains in the world are 

 situated between the equator and 36°, lesser eminences are met 

 with as high as 43° ; Mont Blanc is 46°. This I attribute to 

 centrifugal force. If so, similar results would have been 

 produced in correlation to the axis of rotation, whatever it might 

 have been at the given period. A submergence of 1,000 fathoms 

 having been established as a certainty, it only remains to add that 

 the great regularity of the submerged tract bespeaks the abso- 

 lutely logical conclusion that it must been the result of an 

 enormously long, sloio action, excluding all notion of paroxysms or 

 other disturbances. 



