tities of matter.

Having established this universal law, Newton was able not only to
determine the weight which the same body would have at the surface of
the sun and the planets, but even to calculate the quantity of matter in
the sun and in all the planets that had satellites, and also to
determine their density or specific gravity.

With wonderful sagacity Newton traced the consequences of the law of
gravitation. He showed that the earth must be an oblate spheroid, formed
by the revolution of an ellipse round its lesser axis. He showed how the
tides were caused by the moon, and how the effect of the moon's action
upon the earth is to draw its fluid parts into the form of an oblate
spheroid, the axis of which passes through the moon. He also applied the
law of gravitation to explain irregularities in the lunar motions, the
precession of the equinoctial points, and the orbits of comets.

In the "Principia" Newton published for the first time the fundamental
principle of the fluxionary calculus which he had discovered about
twenty years before; but not till 1693 was his whole work communicated
to the mathematical world. This delay in publication led to the
historical controversy between him and Leibnitz as to priority of
discovery.

In 1676 Newton had communicated to Leibnitz the fact that he had
discovered a general method of drawing tangents, concealing the method
in two sentences of transposed characters. In the following year
Leibnitz mentioned in a letter to Oldenburg (to be communicated to
Newton) that he had been for some time in possession of a method for
drawing tangents, and explains the method, which was no other than the
differential calculus. Before Newton had published a single word upon
fluxions the differential calculus had made rapid advances on the
Continent.

In 1704 a reviewer of Newton's "Optics" insinuated that Newton had
merely improved the method of Leibnitz, and had indeed stolen Leibnitz's
discovery; and this started a controversy which raged for years.
Finally, in 1713, a committee of the Royal Society investigated the
matter, and decided that Newton was the first inventor.

_IV.--Later Years of Newton's Life_

In 1692, when Newton was attending divine service, his dog Diamond upset
a lighted taper on his desk and destroyed some papers representing the
work of years. Newton is reported merely to have exclaimed: "O Diamond,
Diamond, little do you know the mischief you have done me!