sent position of matters
appears to be this: that there is a real connection between the general
form of the Corona and disturbances on the Sun, taking Sun-spots as an
indication of solar activity. When Sun-spots are at or near their
maximum, the Corona has generally been somewhat symmetrical, with
synclinal groups of rays making angles of 45 deg. with its general axis. On
the other hand, at the epochs of minimum Sun-spots, the Corona shows
polar rifts much more widely open, with synclinal zones making larger
angles with the axis, and being, therefore, more depressed towards the
equatorial regions, in which, moreover, there is usually a very marked
extension of Coronal matter in the form of elongated streamers reaching
to several diameters of the Sun.

[Illustration: FIG. 11.--CORONA OF 1867. (SUN-SPOT MINIMUM.)]

This generalisation is well borne out by the maximum-epoch Coronas of
1870 and 1871, and the minimum-epoch Coronas of 1867, 1874, 1875, 1878,
and perhaps 1887, and certainly 1889. On the other hand, the eclipses of
1883, 1885 and 1886 do not strikingly confirm this theory. The eclipse
of 1883 was at a time of rapidly decreasing solar activity, yet the
Corona had the features of a Sun-spot maximum. The same, though in a
somewhat less degree, may be said of the eclipses of 1885 and 1886. At
the times of both of these eclipses the solar activity was decreasing.

The forthcoming eclipse of 1900 will nearly coincide with a Sun-spot
minimum, and if the above conclusions are well founded the Corona in
1900 should resemble that of 1889, and be characterised by, amongst
other things, some very elongated groups of rays extending in nearly
opposite directions.

We are still a long way off from being able to state with perfect
confidence what the Corona is. It is certainly a complex phenomenon, and
the various streamers which we see are not, as was at one time imagined,
a simple manifestation of one radiant light. Mrs. Todd thus conveniently
summarises the present state of our knowledge:--"The true corona appears
to be a triple phenomenon. First, there are the polar rays, nearly
straight throughout their visible extent. Gradually, as these rays start
out from points on the solar disc farther and farther removed from the
poles, they acquire increasing curvature, and very probably extend into
the equatorial regions, but are with great difficulty traceable there,
because projected upon and confused with the filaments havi