most important. It is, indeed, interesting to consider how much poorer
modern astronomy would be but for the extraordinary coincidence which
makes a total solar eclipse just possible. The sun is about 400 times
farther off from us than the moon, and enormously greater than her in
bulk. Yet the two are relatively so distanced from us as to look about
the same size. The result of this is that the moon, as has been seen,
can often blot out the sun entirely from our view for a short time. When
this takes place the great blaze of sunlight which ordinarily dazzles
our eyes is completely cut off, and we are thus enabled, unimpeded, to
note what is going on in the immediate vicinity of the sun itself.

In a total solar eclipse, the time which elapses from the moment when
the moon's disc first begins to impinge upon that of the sun at his
western edge until the eclipse becomes total, lasts about an hour.
During all this time the black lunar disc may be watched making its way
steadily across the solar face. Notwithstanding the gradual obscuration
of the sun, one does not notice much diminution of light until about
three-quarters of his disc are covered. Then a wan, unearthly appearance
begins to pervade all things, the temperature falls noticeably, and
nature seems to halt in expectation of the coming of something unusual.
The decreasing portion of sun becomes more and more narrow, until at
length it is reduced to a crescent-shaped strip of exceeding fineness.
Strange, ill-defined, flickering shadows (known as "Shadow Bands") may
at this moment be seen chasing each other across any white expanse such
as a wall, a building, or a sheet stretched upon the ground. The western
side of the sky has now assumed an appearance dark and lowering, as if a
rainstorm of great violence were approaching. This is caused by the
mighty mass of the lunar shadow sweeping rapidly along. It flies onward
at the terrific velocity of about half a mile a second.

If the gradually diminishing crescent of sun be now watched through a
telescope, the observer will notice that it does not eventually vanish
all at once, as he might have expected. Rather, it breaks up first of
all along its length into a series of brilliant dots, known as "Baily's
Beads." The reason of this phenomenon is perhaps not entirely agreed
upon, but the majority of astronomers incline to the opinion that the
so-called "beads" are merely the last remnants of sunlight peeping
between those