Mercury is brightest this date, and furthest from the sun August 13. Venus will be at her descending node August 17. Jupiter will be near the moon August 17, 4h. 20m. morning, being the moon's apparent diameter north; this will be an occultation south of the equator. Saturn will be near the moon August 16, being about 7° south. There will be a partial eclipse of the moon August 16, in the evening. The moon will rise more or less eclipsed east of Kansas, west of which no eclipse will be visible. Middle. End. H.M. H.M. Boston 7 24 eve. 8 50 eve. New York 7 12 eve. 8 38 eve. Washington 7 00 eve. 8 26 eve. Charleston 6 48 eve. 8 14 eve. Chicago --------- 7 44 eve. St. Louis --------- 7 33 eve. New Orleans --------- 7 34 eve. The following shows the appearance of the moon when the eclipse is greatest--7·1 digits, or 0·596 of the moon's diameter. [Illustration] The size of the eclipse will be the same for all places. The time of middle and end for any other places may be obtained by applying the difference of longitude from Washington, converted into time, to the Washington time of middle and end, adding if east of Washington, and subtracting if west. * * * * * =An Interesting Astronomical Observation.= _To the Editor of the Scientific American:_ While viewing the planet Jupiter, at about 5 minutes past 10 o'clock P.M., a very strange sight presented itself to the observers, who were looking for a transit of one of the satellites. A very dark spot much larger than a satellite was seen on the eastern edge of the disk, as shown in the above diagram. It moved rapidly westward along the upper margin of the northern belt and passed off at 1 o'clock 24 minutes A.M. (12th). From its first internal contact till its last external contact was just 3h. 19m., Pittsburg time. It appeared to be a solid opaque body, truly spherical, very sharply defined, and most intensely black. The transit of the satellite occurred at 15 minutes after 11 o'clock, and had no unusual appearance. Now what was that dark body? We are constant observers of the heavenly bodies, though not deeply versed in the science of astronomy, and are anxious to know if any one can give us some light on the subject. The telescopes used were a 2½ inch and 5 inch achromatic, magnifying 154 and 216 diameters, but the 154 was chiefly used. JOSEPH WAMPLER. JAMES R. GEMMILL. McKeesport, Pa., July 11, 1878. [Illustration] * * * * * =Some of Professor Marsh's Recent Discoveries.=