ho would undertake the destruction of
the Pope and the house of Austria, even venturing to prophesy that
Cromwell, Gustavus Adolphus, and Rakoczy, prince of Transylvania, would
perform the task. He also wrote to Louis XIV., informing him that the
empire of the world should be his reward if he would overthrow the
enemies of God.

Comenius also wrote against the Socinians, and published three
historical works--_Ratio disciplinae ordinisque in unitate fratrum
Bohemorum_, which was republished with remarks by Buddaeus, _Historia
persecutionum ecclesiae Bohemicae_ (1648), and _Martyrologium
Bohemicum_. See Raumer's _Geschichte der Padogogik_, and Carpzov's
_Religionsuntersuchung der bohmischen und mahrischen Bruder_.

COMET (Gr. [Greek: kometes], long-haired), in astronomy, one of a class
of seemingly nebulous bodies, moving under the influence of the sun's
attraction in very eccentric orbits. A comet is visible only in a small
arc of its orbit near perihelion, differing but slightly from the arc
of a parabola. An obvious but not sharp classification of comets is into
bright comets visible to the naked eye, and telescopic comets which can
be seen only with a telescope. The telescopic class is much the more
numerous of the two, only from 20 to 30 bright comets usually appearing
in any one century, while several telescopic comets, frequently 6 or 8,
are generally observed in the course of a year.

A bright comet consists of (1) a star-like nucleus; (2) a nebulous haze,
called the _coma_, surrounding this nucleus, the latter fading into the
haze by insensible gradations; (3) a tail or luminous stream flowing
from the coma in a direction opposite to that of the sun. The nuclei and
comae of different comets exhibit few peculiarities to the unaided
vision except in respect to brightness; but the tails of comets differ
widely, both in brightness and in extent. They range from a barely
visible brush or feather of light to a phenomenon extending over a
considerable arc of the heavens, which, comparatively bright near the
head of the comet, becomes gradually fainter and more diffuse towards
its end, fading out by gradations so insensible that a precise length
cannot be assigned to it. When a telescopic comet is first discovered
the nucleus is frequently invisible, the object presenting the
appearance of a faint nebulous haze, scarcely distinguishable in aspect
from a nebula. When the nucleus appears it may at first