“Now it is upon this variation that the phenomenon of the ‘Harvest’ and the ‘Hunter’s Moon’ depends. If I had a celestial globe here I could show you that at the time of the Autumn Equinox, September 22d, when the sun crosses the equator moving southward, the apparent path of the moon in the sky intersects the eastern horizon at a comparatively small inclination. In other words the moon at that time instead of rising steeply from the horizon rises on a long slope almost parallel with the horizon. The consequence is that for several evenings in succession the Full Moon near the time of the Autumn Equinox may be seen rising just after sunset at almost the same hour. Look at this second diagram and you will see why this is so. [Illustration: Diagram Illustrating the Harvest Moon. ] “The little circles M show the moon at several successive positions in her orbit, just twenty-four hours apart. You perceive that in consequence of the slight inclination to the eastern horizon the sinking of the latter caused by the earth’s rotation will bring the moon into view night after night at almost the same hour. In fact, in high northern latitudes like those of Norway and Sweden the moon’s path at this time of the year may actually coincide with the horizon, so that for several evenings she will rise at exactly the same hour. The name ‘Harvest Moon’ explains itself, since it always occurs at the time of the autumn harvests and the vintage, and seems to supplement the fading daylight for the benefit of late laborers in the fields. The ‘Harvest Moon’ does not occur every year at precisely the same date. It is very rare that Full Moon happens to fall just on September 22d. It usually either precedes or follows that date. The ‘Harvest Moon’ is the Full Moon which occurs nearest to the Autumn Equinox, either before or after. The ‘Hunter’s Moon’ is the first Full Moon which follows the ‘Harvest Moon.’ Like the former it rises for several successive evenings near the same hour, but this phenomenon is less marked in the case of the ‘Hunter’s Moon,’ because it is farther from the Equinox.” “Thank you, again,” said my friend. “I shall never henceforth look at the moon without thinking of circles, straight lines, and arrows as well as of ‘ring mountains’ and ‘seas.’”