To obtain mean time from apparent time we apply to apparent time a correction called the equation of time. Thus, at noon, on October 1st, in Washington, the equation of time is _minus_ 10 minutes 34.58s., which means that if from 12 hours we subtract 10m. 34.58s. we shall have 11h. 49m. 25.42s., the mean time of apparent noon, or noon as indicated by the north shadow of the vertical rod. Or, if at 10m. 34.58s. after the sun crosses the meridian we set our watch at 12 o’clock, we shall have exact mean time. On the 31st of October the real sun will be 16m. 17.56s. ahead of the mean sun, while on the 31st of December it will be 3m. 38.11s. behind the mean; that is, will reach the meridian at 12h. 3m. 38.11s. p. m. mean time. Beside the ordinary clocks, the chronometers used by navigators keep mean solar time, and family almanacs usually in some form give the “equation of time” under the headings, “clock slow” or “fast,” or “sun south.” Astronomers use also another kind of time called “sidereal,” of which we may have something to say in the future. On the 1st, 16th and 31st of this month the sun rises at 5:57, 6:13 and 6:30 a. m., and sets on the same days at 5:42, 5:18 and 4:58 p. m. respectively, showing a decrease of one hour and seventeen minutes in thirty days, or at an average rate of 2m. 34s. per day. On the 18th and 19th the sun will be eclipsed, entering the moon’s shadow at 10:20 p. m. on the 18th in longitude 132° 0.6′ east, and in latitude 63° 30.5′ north; and leaving it at 2:15 a. m. on the 19th in longitude 134° 22.7′ west, and in latitude 33° 25′ north. Greatest eclipse occurs at 12:18 a. m. on the 19th. Magnitude, 0.638. As the entire eclipse is during our night, it will of course be invisible to us, but can be seen by the inhabitants of the northeastern part of Asia and the northwestern portion of North America. THE MOON Will be eclipsed on the 4th, beginning at 3:07 p. m. and ending at 6:41 p. m., Washington mean time. The beginning of totality will be at 4:07 p. m., and the ending at 5:40 p. m.; the middle at 4:53 p. m. Magnitude, 1.533. As the moon in this section does not rise till about 5:20, only the latter half of the eclipse will be visible. On the 16th, the moon rises at 3:45 a. m.; on the 1st, sets at 2:21 a. m., and on the 31st at 3:11 a. m. On the 4th, at 4:52 p. m., full; on the 11th, at 9:21 a. m., enters upon its last quarter; on the 18th, at 7:23 p. m., new moon; and on the 26th, at 11:46 p. m., enters upon its first quarter. Is nearest to the earth on the 7th, at 8:48 a. m., and farthest away on the 23d, at 7:48 a. m. MERCURY