should, indeed, expect to see, under such
exceptionally favourable atmospheric conditions as Professor Langley
enjoyed on Pike's Peak, the _roots_ of the zodiacal light presenting
near the sun just such an appearance as he witnessed; but we can imagine
no reason why their visibility should be associated with a low state of
solar activity. Nevertheless this seems to be the case with the
streamers which astonished astronomers in 1878. For in August, 1867,
when similar equatorial emanations, accompanied by similar symptoms of
polar excitement, were described and depicted by Grosch[538] of the
Santiago Observatory, sun-spots were at a minimum; while the corona of
1715, which appears from the record of it by Roger Cotes[539] to have
been of the same type, preceded by three years the ensuing maximum. The
eclipsed sun was seen by him at Cambridge, May 2, 1715, encompassed with
a ring of light about one-sixth of the moon's diameter in breadth, upon
which was superposed a luminous cross formed of long bright branches
lying very nearly in the plane of the ecliptic, and shorter polar arms
so faint as to be only intermittently visible. The resemblance between
his sketch and Cleveland Abbe's drawing of the corona of 1878 is
extremely striking. It should, nevertheless, be noted that some
conspicuous spots were visible on the sun's disc at the time of Cotes's
eclipse, and that the preceding minimum (according to Wolf) occurred in
1712. Thus, the coincidence of epochs is imperfect.

Professor Cleveland Abbe was fully persuaded that the long rays
carefully observed by him from Pike's Peak were nothing else than
streams of meteorites rushing towards or from perihelion; and it is
quite certain that the solar neighbourhood must be crowded with such
bodies. But the peculiar structure at the base of the streamers
displayed in the photographs, the curved rays meeting in pointed arches
like Gothic windows, the visible upspringing tendency, the filamentous
texture,[540] speak unmistakably of the action of forces proceeding
_from_ the sun, not of extraneous matter circling round him.

A further proof of sympathetic change in the corona is afforded by the
analysis of its light. In 1878 the bright line so conspicuous in the
coronal spectrum in 1870 and 1871 had faded to the very limit of
visibility. Several skilled observers failed to see it at all; but Young
and Eastman succeeded in tracing the green "coronium" ray all round the
sun, to a heigh