43 
the earth ; local changes of the sea level, arising from purely 
geological causes, being easily distinguished from that general 
and systematic alteration which a shifting of the axis of 
rotation would give rise to. " But our investigations demon- 
strate the untenable character of these assumptions ; for, 
1st, Herschel elsewhere indirectly admits that existing 
calculations of latitude may be proved erroneous, that a 
" more exact knowledge of the physical structure and figure 
of the earth will render a different manner of considering it 
necessary." And, 2nd, The level of the sea, or the position 
of its surface at quiescence with reference to elevation of 
lands "standing in the water and out of the water," we 
demonstrate by the phenomena disclosed by Geology, to be 
subject to just such alterations as change of the centre of 
gravity of the globe itself, and consequent "shifting of the 
axis of rotation, would, give rise to." Observations in 
astronomy appear to indicate that, while the magnetic pole may 
continue to point to, or retain the same direction with 
reference to the celestial sphere, there is an inherent motion 
pertaining to the earth itself, as mere inert matter controlled 
by the law of nature, — termed terrestrial gravitation, and 
hence that its retention of its position of inclination upon 
the plane of its orbit, or its aspect relatively to the 
sim's path, depends on the continuance of its component 
matter throughout its whole structure in a state of absolute 
and perfect equilibrium. If, however, changes recur from 
time to time, either of external symmetry, or in the density 
of large portions of its volume internally, or by unequal 
prolongation of a section of its contour by deposit thereon of 
dense material, the over-weighted apex of a finely poised 
sphere must over-balance it, when it must proceed to 
re-adjust itself in equilibrio, assuming, as to its equator, a 
new angle of lean, or tilt, towards the plane of its previous 
position. Thus celestial points, such as the Pole Star, and 
other constellations, will consecutively appear to relatively 
increase or decrease in longitude as computed heretofore, 
and tropical time will vary accordingly. Astronomers 
recognize these changes under one grand chain of phenomena 
termed the Precession of the Equinoxes, whereby the 
equinoctial intersects the ecliptic with a progressively varying 
angle, yielding a result of a continuous change of time of the 
sun's apparent altitude. Such time lessening, or, rather 
hastening, in the northern hemisphere, but being protracted 
or retarded in the southern hemisphere, relatively, though 
not affecting the actual or sidereal time, so that when the 
phenomena of the Precession of the Equinoxes shall be read 
