Changes in the Sea-level. 209 



group of terms 



| { -03046 - -00673 + -00145 - -00333 \ , 



after which the terms become so small and so nearly balanced 

 as not to be worth setting down. The result for fifty terms is 

 ft x -01127, or near upon as much again as the quantity obtained 

 for northern elevation. 



The general result, then, of the disturbance of the earth's sur- 

 face is not such as was anticipated by those who first started this 

 speculation, though it cannot surprise those who are familiar 

 w T ith the theory of the tides. The solid nucleus of our ideal 

 earth remaining central, as we have seen, there is an accumula- 

 tion of water towards the two opposite regions where the differ- 

 ence between the extraneous attraction on the surface and on the 

 centre, which is the true disturbing force, is greatest. In the 

 tidal theory, owing to the great distance of the luminary, these 

 differences follow the same law, sensibly, under and opposite 

 to the disturbing body '; but in our case the changes are very 

 rapid under and near the ice, which lies close to the surface, 

 while they are gradual in the opposite hemisphere. Hence 

 results an egg-shaped form of sea surface, with a comparatively 

 sharp little end at the north, balanced by a big-end or broad- 

 spread mass at the south, both ends combining to rob the equa- 

 torial region. 



As I said at the beginning of this paper, the failure to account 

 for the special facts of the glacial epoch does not deprive this 

 theory of a certain positive value. If it cannot explain elevations 

 or depressions of 1000 feet, it does teach us there is an agency 

 at work in nature, which had perhaps been overlooked, which 

 must be borne in mind in all speculations where- tens of feet are 

 material. The existing world, with its irregular continents and 

 scooped-out seas, cannot have its water-surfaces level (regularly 

 spherical or elliptical I mean); and with secular changes in the 

 disposition of the solid parts, there must be local changes in the 

 fluids, manifesting themselves in submersions or "raised beaches," 

 which, when arising from this cause, must be in long and regular 

 lines. 



For a continent composed of matter between two and three 

 times the density of water, and rising above its level, represents 

 a sea over the same area with the addition of an attracting mass 

 of more than the average depth and more than the density of 

 this sea; and a hollow scooped out of a supposed level sea-bot- 

 tom in like manner represents an abstraction of previously exist- 

 ing attractive force there. And these disturbances in the force 

 will produce corresponding elevations or depressions of mean level 



