850 Marvels of the Universe 
the Sun has almost, 
but not quite, blocked 
out the last trace of 
the Sun itself, just as 
it does so the forward 
edges of the two bodies 
exhibit alternate points 
of light and darkness 
which are known by 
the name of “ Baily’s 
Beads,” so-called from 
the English astronomer 
who first particularized 
them, though he was 
not actually the first 
to record them. It 
is generally considered, 
though the explanation 
is not perhaps wholly 
satisfactory, that they 
are due to the moun- 
tains of the Moon 
blocking out absolutely 
portions of the Sun’s 
surface, whilst other 
portions of that surface 
not so obstructed peep 
THE CORONA OF MAY 28th, 1900. through the valleys 
The Corona, or halo of light, usually appears a few seconds before the total extinction of the 
between the different 
Sun's light and continues visible until a few seconds after the luminary first reappears. It is 
in the nature of an atmosphere surrounding the Sun and extends outwards for several millions lunar mountains. Al- 
of miles. 9 ° 
most immediately after 
the disappearance of the Beads, which of course is very sudden, red flames flash out at 
various points round the circumference of the Moon. These “ prominences,” as they are called, 
have been dealt with in an earlier article (see page 1). But the most interesting phenomenon 
connected with these eclipses is the ‘‘ Corona,” or halo of light which can be observed surrounding 
the black disc of the Moon. It usually appears a few seconds before the total extinction of the 
Sun’s light, continuing visible during the whole period of the Sun’s absence and for a few seconds 
after its reappearance. Its nature is probably that of an atmosphere surrounding the Sun and 
stretching outwards to a distance of several diameters of the Sun; in other words, to several 
millions of miles. 
There is one peculiarity connected with the Corona too important to be ignored—it varies in 
extent and outline from time to time, seemingly dependent for some occult reason upon the pre- 
valence or absence of spots on the Sun. These, it is well known, vary in number during a clearly 
recognized period of about eleven years. If a total eclipse occurs when the spots are at or near 
a minimum the Corona extends in a marked manner right and left of the equatorial diameter of the 
Sun. If, on the other hand, an eclipse is coincident with a period of maximum spots, the Corona is 
contracted on both sides opposite to the equatorial diameter of the Sun, and is much more compact 
taken as a whole all round the Sun’s circumference. These differences seem well established, but 
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a satisfactory explanation is not yet forthcoming. 
