are devoted to
terrestrial phenomena, the physical condition of the sun determines
the course of all the more important events which take place on the
surface of the earth. It is therefore fit that in this preliminary
study of the celestial bodies, which is especially designed to make
the earth more interpretable to us, we should give a somewhat special
attention to what is known under the title of "Solar Physics."

The reader has already been told that the sun is one of many million
similar bodies which exist in space, and, furthermore, that these
aggregations of matter have been developed from an original nebulous
condition. The facts indicate that the natural history of the sun, as
well as that of its attendant spheres, exhibits three momentous
stages: First, that of vapour; second, that of igneous fluidity;
third, that in which the sphere is so far congealed that it becomes
dark. Neither of these states is sharply separated from the other; a
mass may be partly nebulous and partly fluid; even when it has been
converted into fluid, or possibly into the solid state, it may still
retain on the exterior some share of its original vaporous condition.
In our sun the concentration has long since passed beyond the limits
of the nebulous state; the last of the successively developed rings
has broken, and has formed itself into the smallest of the planets,
which by its distance from the sun seems to indicate that the process
of division by rings long ago attained in our solar system its end,
the remainder of its nebulous material concentrating on its centre
without sign of any remaining tendency to produce these planet-making
circles.

THE CONSTITUTION OF THE SUN.

Before the use of the telescope in astronomical work, which was begun
by the illustrious Galileo in 1608, astronomers were unable to
approach the problem of the structure of the sun. They could discern
no more than can be seen by any one who looks at the great sphere
through a bit of smoked glass, as we know this reveals a disklike body
of very uniform appearance. The only variation in this simple aspect
occurs at the time of a total eclipse, when for a minute or two the
moon hides the whole body of the sun. On such occasions even the
unaided eye can see that there is about the sphere a broad, rather
bright field, of an aspect like a very thin cloud or fog, which rises
in streamer like projections at points to a quarter of a million miles
or