184 
ON THE VIBRATIONS AND STABILITY OF A GRAVITATING PLANET. 
and structure of the earth, as well as the more general questions of planetary 
evolution. 
In conclusion I have to express my indebtedness to Professor G. H. Darwix and 
Professor A. E H. Love for advice and assistance which I have received from them. 
^ OTE.~ Added Fehruary -lOth, 1903. While the above paper was in the press, 
Iiofessor W. J. Sollas read a paper before the Geological Society in which the 
Figure of the Earth was discussed from a geological standpoint. Professor Sollas 
had arrived, from an examination of the geological features of the earth, at a 
conclusion^ very similar to that to which I had been led from theoretical 
considerations : he had detected an axis of symmetry, other than the axis of rotation, 
m the earth’s figure, and expressed the opinion that “the pear-shaped form, now that 
it was pointed out, became obvious to mere inspection ; it was a geographical fact, 
and not a speculation.” 
1 he axis of Professor Sollas’ pear does not, however, coincide with that which I 
tentatively put forward m the above jiaper, and the object of this note is to accept 
the alteration suggested by his paper. The conclusion reached in his paper is that 
the axis of symmetry of the pear-shaped figure passes through a point of latitude 
and longitude about G° N. by 30° E. Thus Africa-the continent whose mean height 
aliove sea-level is greatest—must lie taken to be the centre of the “Land 
Hemisphere ” in fig. 1 ,>f my paper, wliile the protuberance which formed the stalk 
of the pear ^ IS submerged in the Pacific Ocean, which now forms the “Water 
Hemisphere. ^ Almost the only remaining evidence of the existence of this 
jiiotubeiance is the fact tliat the axis of the pear coincides with the earth’s greatest 
diameter. The great circle of earthquake-centres suggested in § 38 of my paper is 
to be leplaced by the line of Pacific folding ; this approximately forms a small circle 
(of radius about 80°) wliich almost coincides with the proposed great-circle in the 
noithein hemisplieie. Furtlier details of Professor tSoLLAs' view will he found in his 
paper (“'The Figure of fl,e Eartli,” ‘ (piart. Journ. Gcol. Soc.,’ vol. lix.. Part Lp. 
The fact tl.at Africa is .surroumled by a belt of seas, and this again by a belt of 
and Ijefore the Pacihc is reached, points jierhaps to a bodily subsidence of the blunt 
eiK of tlie pear, the circle of fracture having possibly been the line of Pacific foldin':. 
'Sucli a fracture would, of course, disiilace tlie ceiitre of gravity of the pear, and 
probably this would account not only for the feature just mentioned, hut also for the 
non-appearance of tlie protuberance. It will be noticed that the smallness of the 
latitude of the extremities of the axis (6°) agrees well with tlie theory of iilanetarv 
evolution put forward in 25-30 of the present paper ] 
PEESSIITED 
6 APR. 1903 
R 
