The beautiful little earth-ball, with its precious freight of human beings, softly flies about the sun. Amply protected in a transparent case of atmosphere, it completes its tremendous journey of 576,000,000 miles once every year. During this year its temperature is varied by four seasons which are caused by the earth being inclined 23½ degrees on its axis.
"Some say, he bid his angels turn askance
The poles of earth twice ten degrees or more
From the sun's axle; they with labor push'd
Oblique the centric globe."
—Milton's Paradise Lost.
During this journey around the sun, the earth rotates 366¼ times on its axis, making one revolution every 23 hours, 56 minutes and 4.09 seconds. This causes each side to be alternately warmed and lighted every few hours. Cupped close to the darkened hemisphere lies a huge cone of shadow which extends out in space past the moon. When the moon rolls through this shadow it is eclipsed for it has come into our night.
This cone of the earth's shadow is our personal night and ours alone, and, although the stars seem enmeshed in its velvet sides, it is not the night of earth that holds the stars,—its darkness merely shuts out the glare of the sun and the stars of the universe therefore become visible. This remarkable view gave to man a science set in beauty so keen that in the world's young days it was thought that it was music too sweet to be heard by any but the gods. But now we know that all Nature is like that, and there is not a cliff, rock, shell, mountain, valley, water, land or any living thing in the botanical or zoological kingdom, no matter how common or how lowly, which does not carry, even as the stars, its quota of science and song.
[1]Le Conte.
[2]De Greer, Bulletin of the Geological Society of America, vol. III, 1892.
