(Vol. iv., pp. 129. 177. 235.)
It would have been more courteous in H. C. K. to have requested me to
exhibit my authority for the assertion that the pendulum phenomenon had
been latterly attributed to differences in the earth's superficial
velocity, than to have assumed that explanation as having originated
with myself. There is certainly nothing to justify H. C. K. in calling
it "A. E. B.'s theory;" on the contrary, my avowed object was to suggest
objections to it, and even my approval of it was limited to this, that,
providing certain difficulties in it could be removed, it would then
become the most reasonable explanation as yet offered of the alleged
phenomenon,--the only one, I might have added, that I had the slightest
hope of comprehending.
I can understand what is meant by the parallelism of the earth's axis;
and, with the slight exceptions caused by precession and nutation, I
take _that_ to be the standard of _fixity of direction in space_. When,
therefore, I am told that the plane of a pendulum's oscillation is also
fixed in direction, and yet that it is continually changing its relative
position with respect to the other fixity, the axis of the earth, not
only does it not present to my mind a comprehensible idea, but it does
present to it a palpable contradiction of the commonest axiom of
philosophy.
I am therefore in a disposition of mind the reverse of H. C. K.'s; that
which to him is only "hard enough to credit," to me is wholly
incomprehensible; while that which to him is "utterly impossible to
conceive," appears to me a rational hypothesis in which I can understand
at least the ground of assertion.
H. C. K. asks me to "reduce to paper" the assertion of the difference of
velocity between two parallels of latitude ten feet apart. He is not
surely so unphilosophical as to imagine that a theory, to be true, must
necessarily be palpable to the senses. If the element of increase exist
at all, however minute and imperceptible it may be in a single
oscillation, repetition of effect must eventually render it observable.
But I shall even gratify H. C. K., and inform him that the difference in
linear circumference between two such parallels in the latitude of
London would be about fifty feet, so that the northern end of a ten-feet
rod, placed horizontally in the meridian, would travel less by that
number of feet in twenty-four hours than the southern end. This, so far
from being inadequate, is greatly _in excess_ of the alleged apparent
motion in the plane of a pendulum's vibration.
In the remarks of another correspondent, E. H. Y. (Vol. iv., p. 177.),
there is but one point that seems to require observation from me; it is
his assertion that "there is no force by which a body unconnected with
the earth would have any tendency to rotate with it!" Is then the
rotation of forty miles of atmosphere, "and all that it inherit," due to
friction alone? And even so, can any object, immersed in that
atmosphere, be said to be "_unconnected with the earth_"?