The science of Astronomy occupies a pre-eminent rank in the physical
circle, not only on account of that dignity conferred upon it in the
most remote antiquity, or as being the grand starting point--the
earliest born of science--from whence we must contemplate the visible
creation, if we would reduce its numerous details into one harmonious
whole; but also on account of its practical fruits, of the value of
which modern commerce is an instance. Accordingly we will glance at its
past history. In the earliest ages there was no doubt a rational view
entertained of the movements of the planets in space. From the Chaldeans
to the Arabs, a belief prevailed, that space was filled with a pure
ethereal fluid, whose existence probably did not rest on any more solid
foundation than analogy or tradition. One hundred years after Copernicus
had given to the world the true arrangements of our planetary system,
Descartes advanced his theory of vortices in the ethereal medium, in
which the planets were borne in orbits around the sun, and the
satellites around their primaries. This idea retained its ground with
various additions, until the Geometry of Newton reconciled the laws of
Kepler with the existence of a power pertaining to matter, varying
inversely as the squares of the distances, to which power he showed the
weight of terrestrial bodies was owing, and also the revolution of
the moon about the earth. Since Newton's day, those deviations from the
strict wording of Kepler's laws, have been referred to the same law,
and the avowed object of the author of the "Mechanique Celeste," was to
bring all the great phenomena of nature within the grasp of analysis, by
referring them to one single principle, and one simple law. And in his
Introduction to the Theory of the Moon, he remarks: "Hence it
incontestibly follows, that the law of gravitation is the sole cause of
the lunar inequalities."