Page:Astronomy for Everybody.djvu/165

and lines of eclipses are published in the astronomical ephemerides. An eclipse may be total or annular in a region a few miles north or south of this central line, but never for so far as one hundred miles. Outside this limit an observer will see only a partial eclipse, that is, one in which the moon partly covers the sun. In yet more distant regions of the earth there will be no eclipse at all.

A total eclipse is one of the most impressive sights that nature offers to the eye of man. To see it to the best advantage one should be in an elevated position commanding the widest possible view of the surrounding country, especially in the direction from which the shadow of the moon is to come. The first indication of anything unusual is to be seen, not on the earth or in the air, but on the disk of the sun. At the predicted moment a little notch will be seen to form somewhere on the western edge of the sun's outline. It increases minute by minute, gradually eating away, as it were, the visible sun. No wonder that imperfectly civilised people, when they saw the great luminary thus diminishing in size, fancied that a dragon was devouring its substance.

For some time, perhaps an hour, nothing will be noticed but the continued progress of the advancing moon. It will be interesting if, during this time, the observer is in the neighbourhood of a tree that will permit the sun's rays to reach the ground through the small openings in its foliage. The little images of the sun which form here and there on the ground will then have