Fig. 127.—Partial Eclipse of the Sun.
As the Moon is traveling round the Earth and the Earth is turning round on its own axis, the Moon’s shadow moves across a path or trail that is only about 100 miles wide, and it moves very fast, too, for it usually takes less than five minutes for the Moon to sweep over the face of the Sun.
There are three kinds of eclipses of the Sun. The first is called a total eclipse, and this takes place when the Moon covers the entire face of the Sun, as in [Fig. 125].
The second is called an annular eclipse and this takes place when the Moon does not completely cover the Sun but leaves a bright ring exposed, as shown in [Fig. 126]. The reason the Moon covers the Sun completely during a total eclipse and does not cover all of it during an annular eclipse is because the orbit of the Moon around the Earth is not a perfect circle, and so sometimes the Moon is nearer the Earth than at other times and this makes the Moon seem larger or smaller, as the case may be.
The third kind is called a partial eclipse. If we are not in the direct path of the shadow of the Moon we may see the Moon pass over only a part of the Sun, as shown in [Fig. 127].
The only total eclipses of the Sun which can be seen in the United States in the next 30 years are the following:
| Date of Eclipse | Time of Total Phase | Course of Moon’s Shadow |
|---|---|---|
| 1918, June 18, | 2 minutes | Oregon to Florida |
| 1922, Sept. 2, | 6 minutes | Pacific Ocean, U. S. & West Indies |
| 1923, Sept. 10, | 3 minutes | U. S. & Atlantic Ocean |
| 1930, April 28, | 2 seconds | U. S. & Canada |
| 1945, July 9, | 1 minute | U. S., Canada, Scandinavia and Russia |
| Note: The eclipse of 1930 will be an annular eclipse. | ||
Finding a Comet.—To the naked eye a great comet looks like a bright star with a long, glowing tail. In the long ago a comet was called a hairy star, for the early Greeks pictured the tail of a comet as being made of long hair and so from their language we get the word comet, which means hair.
