42 
by the consideration of its diurnal motion, which is supposed 
to generate a centrifugal tendency, and thus originate the 
abnormal figure. And yet, with reference to this view, the 
physics of the earth show that this centrifugal tendency does 
not exist at its equator now, for the equatorial oceanic cur- 
rents, and cloud ring, are passing continuously from east to 
west, or receding upon the axial motion ; whereas they should 
be advancing upon it, or passing front west to east were 
centrifugal action in operation. Jt is held to be fully esta- 
blished by the satisfactory way in which it accounts for pre- 
cession, nutation, and recession, the very phenomena it is 
required to explain. "* In fact, it "is a necessary assumption 
with modern science, for without a protuberant equatorial 
ring, the moon, planets, and sun would have no displaced 
matter through which to exercise perturbing force ; and 
therefore precession, nutation, and recession would be un- 
accounted for. Hence, if the earth is not an oblate spheroid, 
modern science lias failed to explain the cause of these phe- 
nomena,"! or of the oceanic titles. The hypothesis of occa- 
sional change of the earth's axis, has been brought forward 
very frequently of late years by some of the first authorities 
in science. Amongst these may be mentioned Professor 
Haughton, of the Dublin University, Sir Henry James, and 
Mr. John Evans, Fellows of the Geological Society. Alleged 
astronomical difficulties, which may not bear a sifting analysis, 
have heretofore too readily quelled a thorough scrutiny of 
the question. Sir Thos. Airy, the Astronomer-Royal, in his 
report to the Board of Visitors for 1861, regarded such a con- 
tingency as not impossible, however, stating " The Transit 
circle and Collimators still present those apj)earances of 
agreement between themselves, and of change with respect 
to the stars, which seem explicable only on one of two sup- 
positions, that the ground itself shifts with respiect to the 
general earth, or that the axis of rotation changes." 
Sir J. F. Herschel asserts, as proof of the astronomical 
assumptions that the polar axis is a fixture, and that the solid 
earth participates with the fixed axis in the motion of rota- 
tion, ;ts if the axis " were really a bar of iron driven through 
it," " That the latitude of places on the earth, or their situa- 
tion, with respect to the poles, have undergone no change- 
since the earliest ages. 2nd, that the sea maintains its 
level, which could not be the case if the motion of the axis 
were not accompanied with a motion of the whole mass of 
* Dr. Pratt. "Astronomical Investigations." Loudon, 1805. 
t Ibid. 
