418 Reports and Proceedings — 



Instead of a fixed dogma as to the impossibility of cliaBge, we find a 

 divergence of mathematical opinion, and variations of the pole, differ- 

 ing in extent, allowed by different mathematicians who have of late 

 gone into the question, as for instance the Eev. J. F. Twisden,^ Mr. 

 George Darwin,- Professor Haughton,^ the Eev. E. Hill,* and Sir 

 William Thomson.* All agree in the theoretical possibility of a 

 change in the geographical position of the earth's axis of rotation 

 being effected by a redistribution of matter on the surface, but they 

 do not appear to be all in accord as to the extent of such changes. 

 Mr. Twisden, for instance, arrives at the conclusion that the elevation 

 of a belt twenty degrees in width, such as that which I suggested in 

 my Presidential Address to the Geological Society in 1876, would 

 displace the axis by about ten miles only, while Professor Haughton 

 maintains that the elevation of two such continents as Europe and 

 Asia would displace it by about sixty-nine miles, and Sir W. Thomson 

 has not only admitted, but asserted as highly probable, that the poles 

 may have been in ancient times " very far from their present geo- 

 graphical position, and may have gradually shifted through ten, 

 twenty, thirty, forty, or more degrees without at any time any 

 perceptible sudden disturbance of either land or water." 



I am glad to think that this question, to which I to some extent 

 assisted to direct attention, has been so fully discussed, but I can 

 hardly regard its discussion as being now finally closed. It appears 

 to me doubtful whether eventually it will be found possible to con- 

 cede to this globe that amount of solidity and rigidity which at 

 present it is held to possess, and which to my mind at all events 

 seems to be in entire disaccordance with many geological phenomena. 

 Yet this, as the Kev. 0. Fisher'' has remarked, is presupposed in all 

 the numerical calculations which have been made. I am also doubtful 

 whether, in the calculations which have been made, sufficient regard 

 has been shown to the fact that a great part of the exterior of our 

 spheroidal globe consists of fluid which, though of course connected 

 with the more solid part of the globe by gravity, is readily capable 

 of readjusting itself upon its surface, and may, to a great extent, be 

 left out of the account in considering what changes might arise from 

 the disturbance of the equilibrium of the irregular spherical or sphe- 

 roidal body which it partially covers. It appears to me also possible 

 that some disturbances of equilibrium may take place in a mysterious 

 manner by the redistribution of matter or otherwise in the interior of 

 the globe. Captain F. J. Evans,'' arguing from the changes now 

 going on in terrestrial magnetism, has suggested the possibility of 

 some secular changes being due to internal, and not to external 

 causes ; and if it be really true that there is a difference between the 

 longest and shortest equatorial radii of the earth, amounting to six 

 thousand three hundred and seventy-eight feet,^ such a fact would 



1 Quart. Journ. Geol Soc, 1878, p. 35. 



2 Proc. R. S., vol. XXV. p. 328. Phil. Trans., vol. clxvii. p. 271. 



3 Proc. R. S., 1-877, 1878. ^ Geol. Mag., July, 1878. 

 * Geol. Mag., June, 1878. '' Nature, May 16, 1878. 



5 Rep. Brit. Assoc, 1876, p. 11. 8 Thomson and Tait, Phil. p. 648. 



