The discovery of which I have just given an account to the reader excluded at least from the solar system the idea of the Newtonian attraction being a cause of disorder.  But might not other forces, by combining with attraction, produce gradually increasing perturbations as Newton and Euler dreaded?  Facts of a positive nature seemed to justify these fears.

A comparison of ancient with modern observations revealed the existence of a continual acceleration of the mean motions of the moon and the planet Jupiter, and an equally striking diminution of the mean motion of Saturn.  These variations led to conclusions of the most singular nature.

In accordance with the presumed cause of these perturbations, to say that the velocity of a body increased from century to century was equivalent to asserting that the body continually approached the centre of motion; on the other hand, when the velocity diminished, the body must be receding from the centre.

Thus, by a strange arrangement of nature, our planetary system seemed destined to lose Saturn, its most mysterious ornament,—­to see the planet accompanied by its ring and seven satellites, plunge gradually into unknown regions, whither the eye armed with the most powerful telescopes has never penetrated.  Jupiter, on the other hand, the planet compared with which the earth is so insignificant, appeared to be moving in the opposite direction, so as to be 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.