. Africa . * 111 s=. THE SEASONS. 5 of the ellipse. Hence, when the Earth reaches thesepoints in its annual course, the sun is vertically over theequator, and day and night are equal everywhere on thesurface of the globe. This takes place once in spring andonce in autumn, hence we speak of the vernal andautumnal equinoxes, which occur about the 20th of Marchand the 22d of September. The accompanying diagramrepresents four positions of the Earth in its orbit, each 9 0°apart. Since the sun can only enlighten one half of thesurface at once, viz. that which is turned towards it, theshaded portions
. Africa . * 111 s=. THE SEASONS. 5 of the ellipse. Hence, when the Earth reaches thesepoints in its annual course, the sun is vertically over theequator, and day and night are equal everywhere on thesurface of the globe. This takes place once in spring andonce in autumn, hence we speak of the vernal andautumnal equinoxes, which occur about the 20th of Marchand the 22d of September. The accompanying diagramrepresents four positions of the Earth in its orbit, each 9 0°apart. Since the sun can only enlighten one half of thesurface at once, viz. that which is turned towards it, theshaded portions of the globe here represent the dark,and the bright the enlightened halves of the Earth. Inthe positions A and C the sun is vertically over the inter-section of the equator and ecliptic. In these positions thepoles of the Earth are on the extreme borders of theenlightened hemispheres, and it is day over half thenorthern and half the southern hemisphere at point of the Earths surface describes half its da
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Keywords: ., bookauthorkeaneaha, bookcentury1800, bookdecade1870, bookyear1878
