These undulations were noticed by Airy in 1842
about 6 minutes before totality. Blake, in America in 1869, observed the
same phenomenon 8 minutes before totality. In other cases the interval
would seem to have been very much shorter--a mere matter of seconds. A
very singular observation was made in 1858 by Mr. J. D. Smith at Laycock
Abbey, Wiltshire, on the occasion of the annular eclipse of that year.
He says[13]:--"Both my brother and myself were distinctly impressed with
the conviction that the withdrawal of light was not continuous, but by
pulsations, or, as it were, waves of obscuration, the darkness
increasing by strokes which sensibly smote the eye, and were repeated
distinctly some five or seven times after we had remarked the phenomenon
and before the time of greatest obscuration. This did not occur on the
return of light, which came back continuously and without shock or
break." Ruemker mentions that though this phenomenon was very apparent to
the naked eye it was not visible in the telescope.

Faint rays or brushes of light sometimes seem to spring from the
diminishing crescent of the Sun. These rays generally are very transient
and not very conspicuous, and perhaps must be distinguished as regards
both their appearance and their origin from the more striking rays
which are usually seen a few minutes before or after totality, and which
are generally associated with, or even deemed to belong to, the Corona.
Fig. 7 represents these rays as seen in Spain on July 18, 1860, some
minutes after totality. They are described as having been well defined,
but at some moments more marked than at others, and though well-defined
yet constantly varying. Radiations of light more or less of the
character just described may probably be regarded as a standing feature
of every total eclipse.

[Illustration: FIG. 7.--RAYS OF LIGHT SEEN NEAR THE TIME OF TOTALITY.]

THE APPROACH OF TOTALITY.

The next thing to think about and to look out for is the approach of the
Moon's shadow. I have mentioned this already,[14] and also the
appalling velocity with which it seems to approach. By this time the
coming darkness, which characterises every total phase, will have
reached an advanced stage of development. The darkness begins to be
felt. The events which manifest themselves at this juncture on the Earth
(rather than in the sky around the Sun) are so graphically described by
the American writer whom I have alrea