the rotation of Venus if the period is as short as a day; in fact the persistent failure to find evidence of rotation has perhaps come to be regarded as evidence on the side of those who contend for a period of 225 days. If the planet rotates in a day the velocity would be about a third of a mile per second. The effective velocity at time of superior conjunction would be two-thirds of a mile per second, or, as near conjunction as observations could be taken, perhaps half a mile per second; a quantity at present measurable. For the present the announcement of Belopolsky's results goes no further than the bare statement that the period of the planet's rotation is found to be short.

In Astronomische Nachrichten No. 3633 Mr. Epsin publishes a further liberal list of stars with remarkable spectra. The stars are with one exception fainter than the seventh magnitude, and most of them are more or less striking examples of type III. A large majority of the stars of the present list are situated in the Milky Way near Cygnus.

At the meeting of the Royal Astronomical Society, March 9, Mr. Shackleton (Monthly Notices, March; Observatory, April) read a paper describing his apparatus for examining the distribution of matter in the sun's corona. A photograph was exhibited, taken near the middle of totality in the eclipse of 1896, showing the continuous spectrum to a distance of 15' from the moon's limb, while the coronium line at λ 5303 reached a height of only 5'. Mr. Shackleton described a combination of color screens admitting a narrow band of green light in the neghborhood of λ 5303 and suppressing the rest of the spectrum. If coronium is confined to the inner corona, photographs taken through such a screen chiefly by the coronium radiation should be less extended and less irregular in form than ordinary photographs in which the entire continuous spectrum of the outer corona is active.

Prof. FitzGerald contributes to Nature of May 3 a short note in support of the idea that the sun's corona is of the nature of a solar aurora. He cites, to explain the absence of a dark line of coronium in the sun's spectrum, recent experiments by Herr Cantor which seems to show that when the radiation of a gas is due to electric discharge there is no corresponding absorption.

Mr. Newall contributes to the Monthly Notices of the Royal Astronomical Society for March some results of his study of the spectroscopic binary Capella. His former period of 104 days is confirmed. The observations show that the two components of different types of spectrum are nearly equal in mass, and are not very different in brightness. The radius of the relative orbit if it is seen edgewise is about 52,000,000 miles, or if seen inclined at an angle of 60° to the line of visior. 104,000,000. Assuming as accurate Elkin's rather uncertain value of 0".08 for the parallax, the actual brightness is about 500 times that of the Sun; for the orbit assumed to be seen edgewise the angular separation is 0".04 and the mass 1.7 that of the Sun; for the orbit assumed to be seen under an angle of 60° the angular separation is 0".08 and the mass 14 that of the Sun.

PLANET NOTES FOR JUNE AND JULY.

H. C. WILSON.

Mercury is evening star with Venus and will be visible to the naked eye at least during the first week in July. On June 22 in the morning Mercury will be in conjunction with Venus, Mercury being then 2°19' north of Venus. Mercury

and the new moon will be near each other on the night of June 28, and again
on July 26. On the morning of July 4 Mercury will be at greatest elongation
east from the Sun, 26° 1'. Toward the end of the month Mercury will ap
proach the Sun, coming to inferior conjunction on the morning of August 1.

Venus will be visible as evening star only a few days more, since she will be at inferior conjunction on the morning of July 8. A few days after that one may look for the planet in the north-east in the morning.

Mars crosses the meridian between nine and half past nine and can only be studied now in the morning twilight. He is so nearly keeping pace with the earth in his orbit around the Sun that the relative positions change slowly.

Jupiter is at his best for this year, visible toward the south in Scorpio in the early evening. He will be stationary in right ascension July 28 and after that move eastward among the stars.

Saturn will be at opposition June 23 in the constellation Sagittarius. You see this planet every evening now, toward the southeast after nine o'clock, a golden star with steady light. It is a pity that, now that the rings are turned as open to us as they ever are, the altitude of the planet should be so low that observations are always unsatisfactory. Our loss, however, is gain to those in the southern hemisphere and they ought to have their turn at this splendid planet. Uranus is in Scorpio and about 7° east and 2° south of Jupiter and may be seen at the same hours.

NOTE.-In. denotes ingress; Eg., egress; Dis., disappearance; Re., reappearance; Ec., Eclipse; Oc., occultation; Tr., transit of the satellite; Sh., transit of the shadow.

I.

II.

Jupiter's Satellites for July.

Phases of the Eclipses of the Satellites tor an Inverting Telescope.

APPARENT Orbits of the Seven Inner Satellites of Saturn, AT OPPOSITION IN 1900, AS SEEN IN AN INVERTING Telescope.