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THE MOON’S CHANGES

invert the figure to have the daily progress of the re-ceding rim of light from “ full ” to “new.” Or we mayconstruct such a figure on a larger scale, and dividethe semicircle ABC into 59 equal parts, then the factof perpendiculars let fall from the division-pointsupon A C will correspond very nearly indeed to theprogression and retreat of the advancing illuminatedrim from “ new ” to “ full,” and thence to “ new ”again, at six-hourly-intervals.

Let us next consider the actual motions of themoon in the heavens at different times. We shallhave, in so doing, to take into account the inclinationof the moon’s path to the ecliptic, as well as theeccentricity of the lunar orbit.

So long as we regard the moon as moving in theecliptic, we can at once determine ‘the nature ofthe moon’s movements during any month of theyear, by considering where the sun is placed onthe ecliptic during that month. Thus in March thesun crosses the equator ascendingly. Hence, at thetime of new moon, the moon is near the equator, and,like the sun, is about as many hours above as belowthe horizon. As the moon passes to the first quarter,she traverses the ascending part of the ecliptic, andat the time of first quarter is near the place occupiedby the sun at the midsummer solstice. In otherwords (for we cannot too directly refer these motionsto the stellar heavens) the moon is near the placewhere the constellations Taurus and Gemini meettogether. Thus the first-quarter moon in spring is a