Entretiens familiers sur l'astronomie, avec des chapitres sur la géographie et l'navigaton . des planètes,notre lune est très insignifiant dans la taille. Vénus est de la taille de la terre, et si broughtas proche de nous que la lune, semble fourtimes aussi grand que la lune. Mais Vénus, thoughnearer pour nous que toute autre planète, n'est jamais 25 seront transportés des millions de milles loin de la ce earth.Compare avec les lunes de la distance et de ne pas vous étonner que ce dernier apparaît pour muchlarger et plus lumineux. Qu'entendons-nous par les phases de themoon ? Nous nous référons à l'thisbody assume différentes formes. Laissez-nous voir ce qui la cause

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Familiar talks on astronomy, with chapters on geography and navigaton . of the planets, our moon is very insignificant in size. Venus isof about the size of the earth, and if broughtas near to us as the moon, would appear fourtimes as large as the moon. But Venus, thoughnearer to us than any other planet, is never lessthan 25 millions of miles distant from the earth.Compare this with the moons distance, and youwill not wonder that the latter appears so muchlarger and brighter. What do we mean by the phases of themoon? We refer to the different shapes thisbody assumes. Let us see what causes it toappear sometimes as a crescent, and at othertimes round. Moons Phases. 6? You know that the earth, carrying with it themoon, revolves about the sun. The moon, too, revolves about the earth, though in a muchsmaller orbit. Now do you not see that themoon, in its revolution about the earth, mustsometimes be between the earth and sun, some-times at right angles to a line joining theircentres, and sometimes it must have the earthbetween the sun and itself? A very simple. Fig. 3. Note. It is to be observed that this diagram, like all othersin the book, is much exaggerated and out of scale. In pointof fact, E S is to E A nearly as 400 to I; and the orbit of themoon is an ellipse, and not a circle. 68 Familiar Talks on Astronomy, etc, diagram will serve to illustrate this; and we maysuppose the earth to be at rest—the phenomenonwill be the same. Let S (Fig. 3) represent the sun; the point Sis sufficient to indicate it. Let E be the earthin its orbit (only a portion of which is repre-sented). It may for our purpose be representedby a point. The small circle, A, B, C, D, rep-resents the orbit of the moon in its revolutionaround the earth. Let A be the position of themoon when it is between the earth and sun; Bbe its position when it has moved 90 degrees, and is at right angles to the line S E, joining thecentres of the sun and earth; C be its positionwhen it is in opposition to the sun

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