A Key to the Knowledge of Nature Author:Robert Taylor Purchase of this book includes free trial access to www.million-books.com where you can read more than a million books for free. This is an OCR edition with typos. Excerpt from book: 2. DAY AND NIGHT. Besides the revolutions already described in Chap. I. the planets have another motion, each turning round on its own axis, which is called t... more »heir diurnal motion. This compound motion may be illustrated, by running an orange round in contact with the out edge of the plane of a round table. Let the place of the stalk and the opposite point, represent the poles of the earth; at half way between them, draw a line round representing the equator, and cutting the orange into two parts or hemispheres. The plane of the table will represent the plane of the earth's orbit : the sun being supposed at the centre, half above and half below the surface. Then, placing the finger and thumb upon the two opposite points of the orange, and applying the equator to the edge of the table ; so, that one half of the orange, or the northern hemisphere may be above the table's surface, and the other half or southern hemisphere below; in this position roll it round from the west by the south to the east. Once round the table will represent a year. But in performing this, the orange will have made several revolutions on its own axis. The earth makes 365J; and each of them affords us a day and a night; for, as the sun is the source of light, and only one half of the earth is towards him at once, the cause of what we term Day and Night is very evident. But another circumstance will here attract the attention of the young experimenter. He will perceive, when the orange has made one revolution on its own axis, that the same place will not be towards the sun: he must push it a little farther. So the earth completes a revolution on its axis in about 23hrs. 5G miii.; but requires 4 minutes more before the same place is exactly towards the sun, making a day and night to consist of 24 hours. ...« less