on.

[Illustration: Fig. 14.--Scheiner's Observations on Sun-spots.]

It often happens that a large spot divides into two or more separate
portions, and these have been sometimes seen to fly apart with a
velocity in some cases not less than a thousand miles an hour. "At
times, though very rarely" (I quote here Professor Young,[4] to whom I
am frequently indebted), "a different phenomenon of the most surprising
and startling character appears in connection with these objects:
patches of intense brightness suddenly break out, remaining visible for
a few minutes, moving, while they last, with velocities as great as one
hundred miles _a second_."

[Illustration: Fig. 15.--Zones on the Sun's Surface in which Spots
appear.]

"One of these events has become classical. It occurred on the forenoon
(Greenwich time) of September 1st, 1859, and was independently witnessed
by two well-known and reliable observers--Mr. Carrington and Mr.
Hodgson--whose accounts of the matter may be found in the Monthly
Notices of the Royal Astronomical Society for November, 1859. Mr.
Carrington at the time was making his usual daily observations upon the
position, configuration, and size of the spots by means of an image of
the solar disc upon a screen--being then engaged upon that eight years'
series of observations which lie at the foundation of so much of our
present solar science. Mr. Hodgson, at a distance of many miles, was at
the same time sketching details of sun-spot structure by means of a
solar eye-piece and shade-glass. They simultaneously saw two luminous
objects, shaped something like two new moons, each about eight thousand
miles in length and two thousand wide, at a distance of some twelve
thousand miles from each other. These burst suddenly into sight at the
edge of a great sun-spot with a dazzling brightness at least five or six
times that of the neighbouring portions of the photosphere, and moved
eastward over the spot in parallel lines, growing smaller and fainter,
until in about five minutes they disappeared, after traversing a course
of nearly thirty-six thousand miles."

The sun-spots do not occur at all parts of the sun's surface
indifferently. They are mainly found in two zones (Fig. 15) on each side
of the solar equator between the latitudes of 10 deg. and 30 deg.. On the
equator the spots are rare except, curiously enough, near the time when
there are few spots elsewhere. In high latitudes they are never seen.
Closely