ultimately absorbed in the
incandescent matter of the sun. Finally, the moon seemed as if it would
one day precipitate itself upon the earth.

There was nothing doubtful or speculative in these sinister forebodings.
The precise dates of the approaching catastrophes were alone uncertain.
It was known, however, that they were very distant. Accordingly, neither
the learned dissertations of men of science nor the animated
descriptions of certain poets produced any impression upon the public
mind.

It was not so with our scientific societies, the members of which
regarded with regret the approaching destruction of our planetary
system. The Academy of Sciences called the attention of geometers of all
countries to these menacing perturbations. Euler and Lagrange descended
into the arena. Never did their mathematical genius shine with a
brighter lustre. Still, the question remained undecided. The inutility
of such efforts seemed to suggest only a feeling of resignation on the
subject, when from two disdained corners of the theories of analysis,
the author of the _Mecanique Celeste_ caused the laws of these great
phenomena clearly to emerge. The variations of velocity of Jupiter,
Saturn, and the Moon flowed then from evident physical causes, and
entered into the category of ordinary periodic perturbations depending
upon the principle of attraction. The variations in the dimensions of
the orbits which were so much dreaded resolved themselves into simple
oscillations included within narrow limits. Finally, by the powerful
instrumentality of mathematical analysis, the physical universe was
again established on a firm foundation.

I cannot quit this subject without at least alluding to the
circumstances in the solar system upon which depend the so long
unexplained variations of velocity of the Moon, Jupiter, and Saturn.

The motion of the earth around the sun is mainly effected in an ellipse,
the form of which is liable to vary from the effects of planetary
perturbation. These alterations of form are periodic; sometimes the
curve, without ceasing to be elliptic, approaches the form of a circle,
while at other times it deviates more and more from that form. From the
epoch of the earliest recorded observations, the eccentricity of the
terrestrial orbit has been diminishing from year to year; at some future
epoch the orbit, on the contrary, will begin to deviate from the form of
a circle, and the eccentricity will increase to the s