was not a phenomenon of perpetual occurrence,
would justly excite in the highest degree the astonishment of mankind.
What, in effect, is more extraordinary than to see an inert mass, that
is to say, a mass deprived of will, a mass which ought not to have any
propensity to advance in one direction more than in another, precipitate
itself towards the earth as soon as it ceased to be supported!

Nature engenders the gravity of bodies by a process so recondite, so
completely beyond the reach of our senses and the ordinary resources of
human intelligence, that the philosophers of antiquity, who supposed
that they could explain every thing mechanically according to the
simple evolutions of atoms, excepted gravity from their speculations.

Descartes attempted what Leucippus, Democritus, Epicurus, and their
followers thought to be impossible.

He made the fall of terrestrial bodies depend upon the action of a
vortex of very subtle matter circulating around the earth. The real
improvements which the illustrious Huyghens applied to the ingenious
conception of our countryman were far, however, from imparting to it
clearness and precision, those characteristic attributes of truth.

Those persons form a very imperfect estimate of the meaning of one of
the greatest questions which has occupied the attention of modern
inquirers, who regard Newton as having issued victorious from a struggle
in which his two immortal predecessors had failed. Newton did not
discover the cause of gravity any more than Galileo did. Two bodies
placed in juxtaposition approach each other. Newton does not inquire
into the nature of the force which produces this effect. The force
exists, he designates it by the term attraction; but, at the same time,
he warns the reader that the term as thus used by him does not imply any
definite idea of the physical process by which gravity is brought into
existence and operates.

The force of attraction being once admitted as a fact, Newton studies it
in all terrestrial phenomena, in the revolutions of the moon, the
planets, satellites, and comets; and, as we have already stated, he
deduced from this incomparable study the simple, universal, mathematical
characteristics of the forces which preside over the movements of all
the bodies of which our solar system is composed.

The applause of the scientific world did not prevent the immortal
author of the _Principia_ from hearing some persons refer the principle
of gravi