We journey through space which has a temperature of 200° below zero; but we live, as it were, in a conservatory, in the midst of perpetual winter. We are roofed over by the air that treasures the heat, floored under by strata both absorptive and retentive of heat, [Page 95] and between the earth and air violets grow and grains ripen. The sun has a strange chemical power. It kisses the cold earth, and it blushes with flowers and matures the fruit and grain. We are feeble creatures, and the sun gives us force. By it the light winds move one-eighth of a mile an hour, the storm fifty miles, the hurricane one hundred. The force is as the square of the velocity. It is by means of the sun that the merchant's white-sailed ships are blown safely home. So the sun carries off the miasma of the marsh, the pollution of cities, and then sends the winds to wash and cleanse themselves in the sea-spray. The water-falls of the earth turn machinery, and make Lowells and Manchesters possible, because the sun lifted all that water to the hills. Intermingled with these currents of air are the currents of electric power, all derived from the sun. These have shown their swiftness and willingness to serve man. The sun's constant force displayed on the earth is equal to 543,000,000,000 engines of 400-horse power each, working day and night; and yet the earth receives only 1/21500000000 part of the whole force of the sun. Besides all this, the sun, with provident care, has made and given to us coal. This omnipotent worker has stored away in past ages an inexhaustible reservoir of his power which man may easily mine and direct, thus releasing himself from absorbing toil. EXPERIMENTS. Any one may see the spots on the sun who has a spy-glass. Darken the room and put the glass through an opening toward the sun, as shown in Fig. 37. The eye-piece should be drawn out about half an inch beyond [Page 96] its usual focusing for distant objects. The farther it is drawn, the nearer must we hold the screen for a perfect image. By holding a paper near the eye-piece, the proper direction of the instrument may be discovered without injury to the eyes. By this means the sun can be studied from day to day, and its spots or the transits of Mercury and Venus shown to any number of spectators. [Illustration: Fig. 37.--Holding Telescope to see the Sun's Spots.] First covering the eyes with very dark or smoked glasses, erect a disk of pasteboard four inches in diameter between you and the sun; close one eye; stand near it, and the whole sun is obscured. Withdraw from it till the sun's rays just shoot over the edge of the disk on every side. Measure the distance from the eye to the disk. You will be able to determine the distance of the sun by the rule of three: thus, as four inches is to 860,000 miles, so is distance from eye to disk to distance from disk to the sun. Take such measurements at sunrise, noon, and sunset, and see the apparently differing sizes due to refraction.