belief that spring will succeed winter,
that summer will succeed spring, that autumn will succeed summer, and
that winter will succeed autumn. But he knows still further--and this
knowledge is essential to his intellectual repose--that this
succession, besides being permanent, is, under the circumstances,
_necessary_; that the gravitating force exerted between the sun and a
revolving sphere with an axis inclined to the plane of its orbit, must
produce the observed succession of the seasons. Not until this
relation between forces and phenomena has been established, is the law
of reason rendered concentric with the law of nature; and not until
this is effected does the mind of the scientific philosopher rest in
peace.

The expectation of likeness, then, in the procession of phenomena, is
not that on which the scientific mind founds its belief in the order
of nature. If the force be _permanent_ the phenomena are _necessary_,
whether they resemble or do not resemble anything that has gone
before. Hence, in judging of the order of nature, our enquiries
eventually relate to the permanence of force. From Galileo to Newton,
from Newton to our own time, eager eyes have been scanning the
heavens, and clear heads have been pondering the phenomena of the
solar system. The same eyes and minds have been also observing,
experimenting, and reflecting on the action of gravity at the surface
of the earth. Nothing has occurred to indicate that the operation of
the law has for a moment been suspended; nothing has ever intimated
that nature has been crossed by spontaneous action, or that a state of
things at any time existed which could not be rigorously deduced from
the preceding state.

Given the distribution of matter, and the forces in operation, in the
time of Galileo, the competent mathematician of that day could predict
what is now occurring in our own. We calculate eclipses in advance,
and find our calculations true to the second. We determine the dates
of those that have occurred in the early times of history, and find
calculation and history in harmony. Anomalies and perturbations in
the planets have been over and over again observed; but these, instead
of demonstrating any inconstancy on the part of natural law, have
invariably been reduced to consequences of that law. Instead of
referring the perturbations of Uranus to any interference on the part
of the Author of nature with the law of gravitation, the question
w