ON THE THEORIES OF ELEVATION AND EARTHQUAKES. 43 
order of magnitude as the excess itself. Without dwelling, however, on in¬ 
ferences which have not received the sanction of accurate analysis, we may 
observe that whatever influence we allow to centrifugal force and that of 
gravity acting on a mass of great dimensions, we cannot still consider the 
present form of the earth as a modification of any very difl’erent form result¬ 
ing from the action of those force* on a mass originally solid, without having 
recourse to particular hypotheses. It would seem necessary, for instance, that 
axis of rotation in tl>e initial motion sbonld have h*?en at least nearly co¬ 
incident with a permanent axis of rotation; and also that U»erc should be 
wine particular law of density of the mas* in its original form, to insure in 
its fin^ form a density which should have a certain symmetrical relation to 
the axis of rotation, such as doubtless exists in the actual density of the globe. 
It i» the absence of the necessity for all such additional restrictive assump¬ 
tions that constitutes the great rccomineodation of the hypothesis of the earth « 
former fiiiidity, and which enables us to account, on that hypothesis, in so 
simple and satisfactory a maimer, for the present fonn and' density of the 
earth, as the results of mechanical causes. 
13. Another mode has also been suggested of accounting for the sphe¬ 
roidal form of the earth, independently of the hypothesis of its former fluidity *. 
Suppose, for instance, its original form to have been spherical, and the period* 
of its rotation the same as at present The equatorial region wotiM form one 
continuous ocean, while the laud In the polar regions would rise above the 
level of tlie ocean, attaining its greatest lu-ight at either pole. But these 
polar tracts of land would bo slowly rcmoverl by that constant opomtion on 
its shores by which the ocean is now wearing away the laud which protrudes 
above Its surface, and an approximation to the spheroidal form would doubt¬ 
less thus be produced if sufficient lime wore allowed for the operation. 
I am not aware that any one has advocated this view of the Mjbjpct as a 
probable one, and the dUtinguislipd author of the work just referred to, in 
stigg^diig It, has inade the following remark“We are far from meaning 
here to trace the process In/ which the earth really assumed its actual form¬ 
al! wc intend is, to sJiow that this is tho form to which, under (lie condition 
01 a rotation on its axis, it must tend; nnrl which it would attain even if ori¬ 
ginally and (so (o speak) perversely eoiistilutcd otherwise." It may also be 
Observed that geological observation has afforded no indication, as I conceive, 
01 any greater accumulation of sedimentary deposiU in the enuatorial than 
>n e polar regions. .Still this mode of accounting for the earth s spheroidal 
orm might be appealed to (as, in fact, it has been by a dl8tinguislu*d geolo¬ 
gist; as one not inconsistcm with physical principle.s and admissible condi- 
ons, and therefore as tending to diminish our confidence in the theory which 
presents the spheroidal form of the earth os a proof of iu former fluidity. It 
M*i f tlt^irablo to KubmiT this idea of the possible origin «f the sphe- 
roiaal form to as accurate a test as we are able. But for tilth pun> 09 e it will 
e necessary to make some hypothesis respecting the internal eonstiiution of 
toe earth as well as its external form. It may perhaps bo ileemcl the sim- 
p Ch supi^itinn, that the primitive matter of the earth would hare been of 
unitorm density undera unifonn pre^isure. Adopting tiiis hypothesis in con¬ 
junction with that ol the earth's primitive sphericity, it wouhl follow that the 
•b rioi surfaces of equal density wouhl bo spherical, having for their com¬ 
mon centre tho centre of tho earth. AiYor the earth had been thus consti- 
u ea, we must suppose it to have received its spheroidal form by the denu- 
a *on of Its polar regions, and tho deposition of the transported matter to 
• Uerschel’s Astronomy, page 120. 
