ied
not much less than one hundred years in its passage hither. It has been
suggested that the collision of two suns, or of two great masses of
matter, would create such phenomena; but, apart from the improbability
of such a catastrophe occurring among the celestial orbs, the rapid
subsidence in the luminosity of the observed objects would indicate that
the outburst was produced by causes of a more rapidly transitory nature
than what would result from the collision of two condensed masses of
matter. A collision occurring between two swarms of meteors has been
suggested as one way of accounting for the sudden appearance of those
stars; but another, and more plausible, explanation is that they are
produced by a great eruption of glowing gas from the interior of a sun,
causing an enormous increase in its luminosity, which subsides after a
time, and is succeeded by a normal condition of things. It has been
observed that all those temporary stars, with the exception of two, have
appeared in the region of the Milky Way. In this luminous zone the
condensation of small gaseous stars and nebulae is more pronounced than
in any other part of the heavens, and this would seem to indicate that
there may be cosmical changes taking place among them which need not be
associated with the occurrence of catastrophes resulting in the
conflagration of worlds, and that Nature, in accomplishing her purposes,
does not overstep the uniform working of her laws, upon which depend the
stability and existence of the universe.

PERIODICAL AND VARIABLE STARS are distinguished from other similar
objects by the fluctuations which occur in the quantity of light emitted
by them. The difference in the luminosity of some stars is at times so
marked that, in a few weeks or months, they decline from the first or
second magnitudes to invisibility, and, after the expiration of a
certain period, they again gradually regain their pristine condition.
When these changes take place with regular recurrence, they are called
'periodical;' when they occur in a variable and uncertain manner, they
are called 'irregular.' About 300 stars are known as variable, but the
majority of them are telescopic objects. Their periodical changes of
brilliancy present every degree of variety; in some stars they are
scarcely perceptible and occur at long intervals; in others, changes of
brightness occur in a few hours or days, by which the light emitted is
intensified many hundreds of ti