The two combined, when well seen, make a
spectacle without parallel among the marvels of the sky. Although many
attempts have been made to render the corona visible when there is no
eclipse, all have failed, and it is to the moon alone that we owe its
revelation. To cover the sun's disk with a circular screen will not
answer the purpose because of the illumination of the air all about
the observer. When the moon hides the sun, on the other hand, the
sunlight is withdrawn from a great cylinder of air extending to the
top of the atmosphere and spreading many miles around the observer.
There is then no glare to interfere with the spectacle, and the corona
appears in all its surprising beauty. The prominences, however,
although they were discovered during an eclipse, can now, with the aid
of the spectroscope, be seen at any time. But the prominences are
rarely large enough to be noticed by the naked eye, while the
streamers of the corona, stretching far away in space, like ghostly
banners blown out from the black circle of the obscuring moon, attract
every eye, and to this weird apparition much of the fear inspired by
eclipses has been due. But if the corona has been a cause of terror in
the past it has become a source of growing knowledge in our time.
The story of the first scientific observation of the corona and the
prominences is thrillingly interesting, and in fact dramatic.
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