﻿Change in the Earth's Axis. 221 



maximum effect of each degree of change is -^l-^ of the weight of the 

 bulge, and the possibility of a redistribution of land and sea prevent- 

 ing a change in an opposite direction of the motion of the poles was 

 pointed out. 



The astronomical objections are that any such movement of the 

 axis would be discoverable from the earth's and moon's motions, 

 that is, by precession and nutation of the equinoxes, which are 

 caused by the attraction of the sun and moon on the equatorial bulge. 

 It is from no sufficient change in these motions that we have been 

 told the figure of rotation has not altered in 3000 years (the limit of 

 known observation), but this has been based upon a preternatural 

 rigidity of the earth which is not now maintained by all physicists.^ 



It has been seen how the forces under consideration may have 

 acted in opposite directions, and a consideration of recent geological 

 phenomena shows that while large areas have been elevated it has 

 not taken place steadily and uninterruptedly, but that there have 

 been elevations and subsidences (or kindred phenomena) man}' times 

 repeated, so that, if we turn to the north of Europe, to Belgium, or 

 to Italy, we find, for a general elevation of a few hundred feet to 

 have taken place since the middle of the Tertiaries, there have been 

 subsidences and elevations of many thousand feet in each direction. 

 Now, with the number of forces at work, and the irregular distribu- 

 tion of land and sea, it may be said that a reversal of conditions in 

 one part could not take the axis back to exactly the same place; 

 in other words, the axis might tack. 



The great changes in the Tertiary period were briefly considered, 

 showing how much change of level has taken place. 



Mr. Waters said the points he wished to bring forward are, that a 

 change of the position of the axis would elucidate many facts which 

 have not yielded to any other explanation, and that a change of the 

 position must take place, but that only a small amount could be 

 directly proved ; but if there is a cumulative effect, then it may be 

 explained. The idea thrown out for exauiination by physicists was 

 whether the frequent changes in direction which are caused by 

 forces working in various parts of the world would not thus give a 

 sufficient increase to the amount calculated. 



Referring to recent papers bearing on this subject, the author 

 adds : — 



Since this paper was written, " Le Deplacement Polaire " of Dr. 

 Jules Garret has come into my hands. This little work is written 

 to demonstrate from various grounds that the position of the axis 

 has changed, but without inquii-ing into the cause. The greater 

 part of the book is devoted to proving that the present distribution 

 of land and sea can only be accounted for by such a change, and this 

 he thinks explains the polar land area and the antipodal position of 

 nearly all the land to water areas. He shows that the effect of 

 a change of position of the axis with the unequal diameters of the 



1 Sir William Thomson says in his Glasgow address : " A slow distortion of the 

 , earth as a ivhole would never produce any great angular separation between the 

 instantaneous axis and axis of maximum moment of inertia for the time beiusr." 



