Familiar talks on astronomy, with chapters on geography and navigaton . degrees from thepoles, and the tropics of Cancer and Capri-corn 23^ degrees from the equator. WhenI was a boy I used to wonder why geogra-phers did not place these imaginary circles at23 or 24 degrees, and not bother us with thefraction. The axis of the earth points always in thesame direction. Hence, at our summer solstice,June 21, it is inclined toward the sun to itsgreatest possible extent; and at our wintersolstice, December 21, it is inclined from thesun to its greatest possible extent. On the 21stof June, then, the N
Familiar talks on astronomy, with chapters on geography and navigaton . degrees from thepoles, and the tropics of Cancer and Capri-corn 23^ degrees from the equator. WhenI was a boy I used to wonder why geogra-phers did not place these imaginary circles at23 or 24 degrees, and not bother us with thefraction. The axis of the earth points always in thesame direction. Hence, at our summer solstice,June 21, it is inclined toward the sun to itsgreatest possible extent; and at our wintersolstice, December 21, it is inclined from thesun to its greatest possible extent. On the 21stof June, then, the North Frigid zone is entirelyilluminated, and it is constant day; the SouthFrigid zone receives no light from the sun, andit is constant night. The Seasons. 4i On the 21 st of December the North Frigidzone receives no light, and it is constant night;while the South Frigid zone is entirely illumin-ated, and it has continual day. At the equinoxes, March 21 and September21 (that is, when the sun crosses the equator),one half of the earth is illuminated from poleto Fig. 2. Note. It is to be noted that this figure, like all others inthe book, is out of scale, and very much exaggerated. Theearths orbit, for example, is represented as a circle, though weknow it to be an ellipse. 42 Familiar Talks on Astronomy\ etc. In the diagram (Fig. 2), let S be the sun, andA, B, C, D, the earth in four positions in itsorbit; P P the axis of the earth, and E Q theequator. A represents it on the 21st of June,C on the 21st of December, B on the 21st ofSeptember, and D on the 21st of March. Let,also, a b and a b be the Arctic and Antarcticcircles. At A, the summer solstice, the NorthFrigid zone is entirely illuminated, and the daysare evidently longer than the nights everywherein the northern hemisphere. At C, the wintersolstice, the North Frigid zone will receive nolight from the sun, and the days in the northernhemisphere are shorter than the nights. At B,the autumnal equinox, and at D, the ve
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