there were no dates fixed, and
should know that nine kings had reigned over a nation; such an historian
would commit a great error should he allow three hundred years to these
nine monarchs. Every generation takes about thirty-six years; every
reign is, one with the other, about twenty. Thirty kings of England have
swayed the sceptre from William the Conqueror to George I., the years of
whose reigns added together amount to six hundred and forty-eight years;
which, being divided equally among the thirty kings, give to every one a
reign of twenty-one years and a half very near. Sixty-three kings of
France have sat upon the throne; these have, one with another, reigned
about twenty years each. This is the usual course of Nature. The
ancients, therefore, were mistaken when they supposed the durations in
general of reigns to equal that of generations. They, therefore, allowed
too great a number of years, and consequently some years must be
subtracted from their computation.

Astronomical observations seem to have lent a still greater assistance to
our philosopher. He appears to us stronger when he fights upon his own
ground.

You know that the earth, besides its annual motion which carries it round
the sun from west to east in the space of a year, has also a singular
revolution which was quite unknown till within these late years. Its
poles have a very slow retrograde motion from east to west, whence it
happens that their position every day does not correspond exactly with
the same point of the heavens. This difference, which is so insensible
in a year, becomes pretty considerable in time; and in threescore and
twelve years the difference is found to be of one degree, that is to say,
the three hundred and sixtieth part of the circumference of the whole
heaven. Thus after seventy-two years the colure of the vernal equinox
which passed through a fixed star, corresponds with another fixed star.
Hence it is that the sun, instead of being in that part of the heavens in
which the Ram was situated in the time of Hipparchus, is found to
correspond with that part of the heavens in which the Bull was situated;
and the Twins are placed where the Bull then stood. All the signs have
changed their situation, and yet we still retain the same manner of
speaking as the ancients did. In this age we say that the sun is in the
Ram in the spring, from the same principle of condescension that we say
that the sun turns round.

Hip