﻿220 Notice of Memoirs — A. W. Waters. 



It was suggested tliat there are three causes which might change 

 the position of the axis, viz. distortion of the earth by continental 

 and local upheaval altering the centre of gravity, and thus changing 

 the position of the axis ; the removal of water by elevation of land 

 displacing the ocean : and the removal of matter in solution ; and 

 these two last, though not considered to be the most important 

 in amount, were considered more in detail. 



According to Mr. T. Mellard Eeade,^ about one ton of solid matter 

 is removed in solution by the drainage of each square mile, so that 

 about 5000 million tons are removed from the land surface each 

 year ; thus in ten years a weight equal to that of Vesuvius 

 is removed from the land to the oceanic area by this means ; 

 and as there is more land in the northern hemisphere, this 

 gives a gain for the southern hemisphere of 3230 million tons 

 over the northern. If the earth is divided into a land and water 

 hemisphere, with England as a centre, the gain of the weight of 

 the water hemisphere is about 4300 million tons, or one Vesuvius 

 in twelve years, the place of greatest gain being about 45° S. and the 

 greatest loss 45° N. in antipodal positions. 



A statement by Sir G. B. Airy in the AtJienceum, 1860, was 

 considered in order to see what effect special alteration would have. 

 Eemoving a weight equal to that of Asia 1000 feet high from the 

 centre of the land hemisphere, and adding a similar weight at the 

 antipodes in a sinking Pacific Ocean, leaving the remaining portion 

 in each hemisphere balanced hj the natural configuration, would 

 give an alteration of from 18-27 miles. This alone would require 

 13 million years at the present rate of denudation, but there are 

 many causes, some of which were mentioned, which would very 

 much reduce the time required for this amount of " soluble denuda- 

 tion," so that it might be reduced to one or two million years, and 

 the vast thickness of calcareous rocks, which are only the record of 

 others from which they were partly formed, shows how many times 

 such areas must have been transported from land to sea. 



The sinking of an area equal to the continent of Asia to the mean 

 depth of the ocean would bring a weight of water sufficient, if the 

 antipodes were a suboceanic rising area, to displace the position 

 of the axis 40 — 60 miles by the same method of calculation. It is 

 thus seen that these may be disturbing or starting forces, but do 

 not give a large amount of change directly, and that the one to three 

 degrees which Mr. George H. Darwin, M.A.,' allows is all that we 

 should expect in recent geological times, unless there is some cumu- 

 lative effect. 



Mr. Waters maintained that if the change was caused by addition 

 of weight, then the earth in re-adjustment would cause phenomena 

 equivalent to an elevation in those semi -hemispheres from which the 

 maximum bulge has been removed, displacing, if it should be an 

 oceanic area, an amount of water to be placed in another region ; the 



' In a paper on Geological Time, read as a presidential address to the Liverpool 

 Geol. Soc. 1876-77. 



2 Proc. Roy. Soc, No. 175, 187G. 



