312 Geological Society: — 



Evans, Esq., on the 18th February, 1876. The treatment of the 

 question is kinematical ; the forces by which the elevations and de- 

 pressions might be effected do not come under discussion. In de- 

 termining numerically the amount of the deviation from the formulas 

 investigated, approximate numbers seem 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 from 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 resem- 

 bling that suggested in the question, it would produce a displace- 

 ment 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 been 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 pro- 

 bable that the effect of this tendency would be to cause the 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 accom- 

 panying 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 

 countries as Greenland. The investigation by which the above re- 

 sults 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 displace- 

 ment 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 *. 



2. " Note on a Specimen of Diploxylon, from the Coal-formation 

 of Nova Scotia." By J. W. Dawson, LL.D., E.E.S., E.G.S. 



* 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. Gr. Darwin in his paper, of which an abstract has been published in 

 No. 175 of the Proceedings of the Royal Society. 



