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Reports ancl Proceedings — 
approximate numbers seera to be sufficiently exact for every useful purpose. The 
conclusions arrived at are as follows : — 
(1) The displacement of the earth’s axis of figure frora the axis of rotation that 
would be effected by the elevations and depressions suggested in the question above 
referred to, would be less than 10’ of angle. 
(2) A displacement of as much as 20“ could be effected by the elevations and 
depressions of the kind suggested only if their heights and depths exceeded by many 
times the height of the highest mountains. 
(3) Under no circumstances could a displacement of 20° be effected by a transfer of 
matter of less amount than about a sixth part of the whole equatorial bulge. 
(4) Even if a transfer of this quantity of matter were to take place, it need not 
produce any effect, or only a small effect, on the position of the axis of figure, e.g. if 
it took place in a way resembling that suggested in the question, it would produce a 
displacement amounting to but a small part of 20°. 
(5) If, however, we suppose a deviation of the axis of figure from the axis of 
rotation amounting to as much as 20° to have bcen by any means brought about. the 
effect would be to cause a sort of tidal motion in the ocean, the greatest height of 
which would tend to be about twice the depth of the ocean. The author suggests as 
probable that the effect of this tendency would be to cause tbe ocean to sweep over 
the continents in much the same way that a rising tide sweeps over a low bank on a 
level shore. 
(6) The notion that a large deviation of the earth’s axis of figure from its axis of 
revolution may be effected by elevations and accompanying depressions is at first sight 
an inviting way of bringing polar lands into lower latitudes, and thereby accounting 
for the more genial climate that is believed to have once prevailed in such countriesas 
Greenland. The investigation by wliieh the above results have been obtained seems 
to show that the desired explanation is not to be sought in the direction indicated by 
Mr. Evans’s question. Whether there is any other agency by which a gradual 
displacement of the pole geographically could be effected is a question of far wider 
scope than that discussed in the present paper, and one which the author does not 
profess to determine. 1 
Discussion. — Mr. Evans was willing to admit that in his Address he had some- 
what overstated the araount of ebange in the position of the polar axis which was 
likely to result from the supposed belts of elevation and depression. When, however, 
be was told that the displacement would not exceed ten miles, notwithstanding his 
implicit faith in mathematics, there arose an inward feeling- of disbelief as to the 
conditions of the problem having been accurately stated in order to obtain such a 
result. It seemed to him that the author had treated the globe as an absolutely solid 
spheroid instead of a terraqueous globe, with the proportions of land and sea upon its 
surface as at present existing, which were important elements in the case. 
The depth of the ocean in equatorial and polar regions ought surely to be taken 
into account, as it was quite possible to conceive of the irregularly-shaped solid 
portion of the globe projecting in places through a sphcroidal coating of water, so as 
to form large tracts of land, and yet on the average forming a sphere. Such a sphere, 
from disturbances of its equilibrium, he believed would be much more liable to 
changes in its axis than a spheroid, and the nearer a spheroid approached a sphere, 
the more sensible it would become to such disturbances. 
Ile had never intended to suggest that the hypothetical beit was to be suddenly 
elevated so as to produce the enormous tidal movements of which the author spoke. 
On the contrary, he believed that all such disturbances of equilibrium were gradual, 
and that the axis of rotation and that of figure were never at any great distance frora 
each other. There was one portion of the paper which he found difficult to com- 
prehend. He could not conceive why so enormous a protuberance as 125 miles over 
a beit 20° in width should be necessary in Order to displace the polar axis by 20°, 
when the present equatorial protuberance was only about one-tenth of that height. 
Moreover, the probability is that tbe earth, instead of being a rigid solid, is to a 
certain extent viscous or plastic, and that such should be the case seeras quite in 
accordance with geological facts. If the globe were a viscous body, with a solid crust 
1 The first draught of the paper, of which the above is an account, was drawn up last August, 
and was shortly after sent to Mr. Evans. It was written independently of the wider view of the 
subject taken by Sir W. Thomson in his Address delivered at the last Meeting of the British 
Association, and by Mr. G. Darwin in his paper, of which an abstract has been published in 
No. 175 of the Proceedings of the Royal Society. 
