thousand
times greater than that we experience at the summer solstice; and
that this heat being two thousand times greater than that of red-hot
iron, an iron globe of the same dimensions would be fifty thousand
years entirely losing its heat. Newton added that in the end comets
will approach so near the Sun that they will not be able to escape the
preponderance of its attraction, and that they will fall one after the
other into this brilliant body, thus keeping up the heat which it
perpetually pours out into space. Such is the deplorable end assigned
to comets by the author of the "Principia," an end which makes De la
Bretonne say to Retif: "An immense comet, already larger than Jupiter,
was again increased in its path by being blended with six other dying
comets. Thus displaced from its ordinary route by these slight shocks,
it did not pursue its true elliptical orbit; so that the unfortunate
thing was precipitated into the devouring centre of the Sun." "It is
said," added he, "that the poor comet, thus burned alive, sent forth
dreadful cries!"

[Illustration: A COMET]

It will be interesting, then, in a double point of view, to follow a
comet in its different passages in sight of the Earth. Let us take the
most important in astronomical history--the one whose orbit has been
calculated by Edmund Halley, and which was named after him. It was in
1682 that this comet appeared in its greatest brilliancy, accompanied
with a tail which did not measure less than thirty-two millions of
miles. By the observation of the path which it described in the
heavens, and the time it occupied in describing it, this astronomer
calculated its orbit, and recognized that the comet was the same as
that which was admired in 1531 and 1607, and which ought to have
reappeared in 1759. Never did scientific prediction excite a more
lively interest. The comet returned at the appointed time; and on the
12th of March, 1759, reached its perihelion. Since the year 12 before
the Christian era, it had presented itself twenty-four times to the
Earth. It was principally from the astronomical annals of China that
it was possible to follow it up to this period.

Its first memorable appearance in the history of France is that of
837, in the reign of Louis le Debonnaire. An anonymous writer of
chronicles of that time, named "The Astronomer," gave the following
details of this appearance, relative to the influence of the comet on
the imperial imagination: