PHASES OF THE NOON. The first peculiarity about the moon is the constant and regular change of its illuminated surface from a thin crescent to a circle. and vice versa, and a cor responding change in the time of her appearance above the horizon. These changes depend upon the position of the moon relative to the earth and the sun, for it is only the half of the moon facing the sun that is illuminated by his rays, and the whole of this illuminated portion can be seen from the earth only when the sun, earth. and moon are nearly in a straight line (the line of sii=3/llics), and the earth is between the sun and moon. When the moon is in the line of syzygies, hut between the earth and the sun, no part of her illuminated disk can lie seen from the earth. In the forme• case, the moon is said to be full, and in the latter. new. A few days after `new moon' the moon appears to be a little to the east of the sun as a thin crescent, with the horns point ing to the east, and as she increases her angular distance from the sun at the rate of about 12° daily, the crescent of light becomes broader till, alto• the lapse of a little more than seven days, at which time she is 90° in advance of the sun, she presents the appearance of a semicircle of light. The moon is then said to have completed her first quarter. Continuing her course, she becomes 'gibbons': and at the 15th or 16th day from the new• moon attains a position 180° in advance of the sun, and now presents the appearance known as full moon. From this point she begins to approach the sun, again ap pearing 'gibbous,' and after a third period of inure than seven days, reaches a point 90' west of the sun and enters her la‘st, quarter. Here,
again, she appears as a semicircle of light, the illuminated portion being that which was not illuminated at the end of the first quarter. The moon, now rapidly approaching the sun, resumes the crescent form, but this time with the horns pointing westward, the crescent becoming, thinner and thinner, till the moon reaches the position of 'new• moon' and disappears. The earth as seen from the moon presents similar phases, and has consequently, at the time of new moon, the appearance of a round illinninated disk, and at full moon is invisible. This explains the peculiar phenomenon occasionally observed when the moon is near the sun (either before or after the new moon), of the part of the moon's face which is unilluminated by the sun appearing faintly visi ble, owing to the reflection upon it of strong earth-light. This phenomenon is often called the new moon in the old moon's arms. At new moon, the moon collies above the horizon about the same time as the sun, and sets with him. but rises each day about fifty minutes later than on the day previous, and at the end of the first quarter rises at midday and sets at midnight, continuing to lag behind the slim When full, she rises about sunset and sets about sunrise. and at the commencement of her last quarter she rises at midnight and sets at midday. The daily retardation of the moon's rising, just stated to be about fifty minutes. is subject to considerable variations. In the latitude of New York it may range from 23 minutes to 1 hour 17 minutes. See HARVEST M005.