Pine Bluff daily graphic., 1894-08-18
THE TIME OF mooNRlsg.
1t Is Effty-One Minutes Later on Any Day
 Than on tue DaY Before.

1t Is Fifty-One Minutes Later on Any Day
 Than the Day Before.
 The time of moonrise on any day is on the average about fifty-one minutes later than on the preceding day This retardation Is, however, by no means constant in amount, being at times very much less than the average and at times very much greater. A very marked diminution in the time of re- tardation occurs about the time of the full moon which falls in September. This moon is called the harvest moon. The same phenomenon in less degree occurs at the time of the next follow ing full moon, which is known as tho hunters moon The time of retarda- ion during the harvest moon is less than half an hour in our attitudes, in- instead of it's average value of nearly ln hour, and for several successive nights the moon seems to rise at nearly the same time
 Briefly stated, the cause of the phe- nomenon is this: At the time of the rising of the harvest moon the ap- parent path of the moon among the stars is much less inclined to the hori- zon than it is at other times, and the ordinary days motion of the moon along this path makes an unusually small change of the position of the moon with reference to it's distance from the horizon.
 A more detailed explanation may make the matter little more easily understood. In addition to the ordi- nary apparent daily motion which the moon has in common with all other heavenly bodies, it has another motion by which it completes the circuit of the heavens relatively to the sun once month, and the direction of this mo- tion is generally not parallel with the direction of the diurnal motion, it be- ing generally northward or southward as well as eastward. Anyone may see this motion by an hours watching of the relative positions of the moon and star near it. The diurnal motion is al- ways on t line at right angles to q line drawn from the body to the celestial pole, the point in the heavens approx imately indicated by the pole star. 1t is always perfectly uniform about the pole as center, and it is this which we take as our ordinary measure of time.
 Now consider the position of the moon and the sun at the time of full moon. The moon rises just as the sun sets. On the next evening at sunset he. I.a1 fIo zon, because it has moved eastward among the stars relatively to the sun, and it will not rise until the diurnal motion of the heavens brings it above the horizon. If the moons motion were uniform and always along the line of ordinary diurnal motion, this retardiation of the time of rising would always be tho same and would, as stated at the outset, be ffty-one minutes per day. But at the time of harvest moon the direction of motion of the moon among the stars is considerably north ward as well as eastward, and at the time of moonrise this line makes com paratively small angle with the hori- zon, very much less than it does at ObneT IlIneS OI luIl llOOh uuIiuk LH6 year. Therefore, at sunset on the day after the full, the noon having moved along line which is inclined to the horizon at much smaller angle than usual, it's distance below the horizon will be less than the average, and hence smaller amount of diurnaI mo- tion will bring it into view-that is, the retardation of time of rising is less than it is at other times This condi- tion continues for several days.
 Several other things, notably the in- clination of the moons orbit to that of the earth and the varying rate of mo- tion in the orbit due to variation of dis tance from the earth, tend to change the amount of daily retardation, but they do not depend on the time of the year, and they sometimes intensity and sometimes diminish the peculiar phe- nomenon of harvest moon. Latitude has strong effect, and in northern Europe the phenomenon is much more noticeable one than it is in the United States In fact, if one goes far enough north, the harvest moon may rise even earlier on any night than it did on the night preceding.- Y. Sun.