‘Sxor. III] STABILITY OF EARTH'S AXIS. tPe 
each elevated area should have an area of depression corresponding 
‘in size and diametrically opposite to it, that they should lie on the 
same complete meridian, and that they should both be situated in 
lat. 45°. With all these coincident favourable circumstances, an 
effective elevation of =, of the earth’s surface to the extent of 
10,000 feet would shift the pole 111’; a similar elevation of = 
would move it 1° 461’; of 4, 3° 17; and of 4,8° 42’... Mr. Darwin 
admits these to be superior limits to what is possible, and that, on 
the supposition of intumescence or contraction under the regions in 
question, the deflection of the pole might be reduced to a quite 
insignificant amount.’ 
Under the most favourable conditions, therefore, the possible 
amount of deviation of the pole from its first position would appear 
to have been too small to have seriously influenced the climates of 
the globe within geological history. If we grant that these changes 
were cumulative, and that the superior limit of deflection was 
reached only after a long series of concurrent elevations and depres- 
sions, we must suppose that no movements took place elsewhere to 
counteract the effect of those about lat. 45° in the two hemispheres. 
But this is hardly credible. A glance at a geographical globe 
suffices to show how large a mass of land exists now both to the 
north and south of that latitude, especially in the northern hemi- 
sphere, and that the deepest parts of the ocean are not antipodal to 
the greatest heights of the land. These features of the earth’s 
surface are of old standing. There seems, indeed, to be no geo- 
logical evidence in favour of any such geographical changes as could 
have produced even the comparatively small displacement of the 
axis considered possible by Mr. G. Darwin. 
In an ingenious suggestion, Dr. John Evans contended that, even 
without any sensible change in the position of the axis of rotation of 
the nucleus of the globe, there might be very considerable changes 
of latitude due to disturbance of the equilibrium of the shell by the 
upheaval or removal of masses of land between the equator and 
the poles, and to the consequent sliding of the shell over the nucleus 
until the equilibrium was restored.* In a recent address he has 
precisely formulated his hypothesis as a question to be determined 
mathematically. The solution of the problem has been worked 
out by the Rey. J. F. Twisden, who arrives at the conclusion that 
even the large amount of geographical change postulated by Dr. 
‘Evans could only displace the earth’s axis of figure to the extent 
of less than 10’ of angle, that a displacement of as much as 10° or 
15° could be effected only if the heights and depths of the areas 
elevated and depressed exceeded by many times the heights of 
the highest mountains, that under no circumstances could a dis- 
placement of 20° be effected by a transfer of matter of less amount 
than about a sixth part of the whole equatorial bulge, and that even 
1 Phil. Trans. Nov. 1876. 2 Proc. Roy. Soc. xv. p. 46 (1867). 
3 Q. J. Geol. Soc. (1876) p. 62. 

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