Change in the Earth' s Axis. 
221 
maximum effect of each degree of change is tIt 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. 1 
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) many 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 irregulär 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 examination 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. 
Keferring to recent papers bearing on this subject, the author 
adds : — 
Since this paper was written, “ Le Deplacement Polaire ” of Dr. 
Jules Carret 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 inquiring 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 bis Glasgow address : “ A slow distortion of the 
earth as a whole would never produce any great angular Separation beiween the 
instantaneous axis and axis of maximum momeut of inertia for the time heilig.” 
