36 



ASTRONOMICAL PHENOMENA AND PROGRESS. 



OBSERVATIONS OF MINOR PLANETS FOR THE 

 DETERMINATION OF THE SOLAR PARALLAX. 

 A method of determining the solar parallax 

 from observations of the interior asteroids 

 when in opposition was proposed by Dr. 

 Galle some years since. A series of observa- 

 tions to be employed for this purpose was 

 recently arranged by Dr. Gill, the Astronomer 

 Royal for the Cape of Good Hope. The minor 

 planets Sappho and Victoria were favorably 

 situated for such observations at their oppo- 

 sitions in 1882. In the northern hemisphere 

 the necessary observations were made at Clin- 

 ton, N. Y., Dublin, Strasburg, Berlin, Both- 

 kamp, Leipsic, Upsala, and Moscow ; and in 

 the southern hemisphere at Melbourne, Rio 

 de Janeiro, the Cape of Good Hope, and Natal. 

 The number of stations south of the equator is 

 less than in the north, but from the clearer 

 skies of the southern hemisphere an equal 

 number of available observations was looked 

 for as probable. The value of the sun's hori- 

 zontal parallax resulting from the observations 

 will doubtless be made known at an early 

 day. 



Dr. Gill, it will be remembered, had pre- 

 viously deduced a value of the solar parallax 

 from helioineter observations of Mars in oppo- 

 sition. 



OBSERVATIONS OF PROFESSOR HOUGH. The 

 annual report of Professor G. W. Hough, Di- 

 rector of the Dearborn Observatory, at Chi- 

 cago, was issued in June, 1882. The planet 

 Jupiter has been an object of special study dur- 

 ing the past year, as it had been, in fact, since 

 1879. Recent observations, it is claimed, en- 

 able us to decide definitely in regard to the 

 motion of certain points on the disk, though 

 the physical condition of the planet is still 

 somewhat uncertain. The most important 

 conclusions reached by Dr. Hough are: that 

 the changes taking place on the planet are 

 very slow in their operations ; that the ob- 

 served phenomena on the disk are probably 

 periodical, as has been found to be the case on 

 the sun's surface ; that some of the marks or 

 objects noticed are much more permanent in 

 their positions than others; that at least the 

 superficial parts of the planet are in a liquid or 

 plastic condition; that the great red spot is 

 not fixed as a solid portion of the planet's 

 crust, but, on the contrary, is slowly retro- 

 grading ; that the mean period of rotation be- 

 tween September '25, 1879, and March 29, 

 1882, was 9 h - 55 m - 35 -9'- ; that the apparent rota- 

 tion period has increased about four seconds 

 since the opposition of 1879, indicating a total 

 drift of the red spot in longitude of 40,000 

 miles; and that this interesting object may be 

 regarded as "an immense floating island 29,- 

 .600 miles in length, by 8,300 miles in breadth, 

 which has maintained its shape and size, with- 

 out material change, during more than three 

 years." 



Several small elliptical white spots have 

 been also carefully watched. Two in particu- 



lar, a little south of the great red spot, were 

 systematically observed from November 21, 

 1881, to February 23, 1882. The following 

 spot of this pair was apparently at rest rela- 

 tively to the red spot from November 22d to 

 December 6th. About the latter date it com- 

 menced drifting in the direction of rotation ; 

 the total drift in seventy-nine days amounting 

 to 41. During the last sixty days the average 

 motion relatively to the planet's surface was 

 fifteen miles per hour. 



The two white spots did not retain the same 

 relative positions in longitude with respect to 

 each other. The observations also indicate 

 that the whole surface of Jupiter outside the 

 equatorial belt rotates with nearly the same 

 angular velocity. Also that these spots are 

 not fixed, but may have a slow direct or retro- 

 grade motion. Professor Hough remarks that 

 the observations of these spots may have an 

 important bearing on the theory of the plan- 

 et's physical condition, as well as en that of 

 the rotation of its different parts. 



There are also two principal white spots in 

 the great equatorial belt, differing in longitude 

 about 15, and in latitude about V. The rota- 

 tion period for these spots has been found to 

 be 9 h - 50 m - 9-8 B - or 5 m - 28' less than that of the 

 great red spot. In other words, the equatorial 

 spots drift in the direction of Jupiter's rotation 

 at the rate of 260 miles per hour ; making a 

 complete revolution on the planet's surface in 

 about forty-five days. Professor Hough adds 

 that " from observations on other small white 

 spots, as well as on dark markings near the 

 equator, it is probable that the matter in the 

 equatorial regions constantly drifts in the di- 

 rection of the planet's rotation ; and it seems 

 probable that the rate of this drift depends on 

 the latitude." From all the observations we 

 may infer that no exact period can be assigned 

 as that of Jupiter's rotation, and that, in fact, 

 the period varies with the latitude. 



Mr. S. W. Burnham, who had been absent 

 some months at the Washburn Observatory, 

 Wisconsin, has returned to Chicago, and re- 

 sumed his observations on double stars with 

 the great refractor of the Dearborn Observa- 

 tory. He is preparing for publication a cata- 

 logue of 151 double stars, discovered by him- 

 self during the past three years, and also a 

 collection of all his star observations during 

 the same period. 



Professor Hough's report has an engraving 

 of the Chicago University, showing the tower 

 of the Dearborn Observatory, one of the 18^- 

 inch equatorial, and twelve colored drawings 

 showing the appearance of Jupiter's disk at 

 different times, giving the forms, positions, 

 and colors of the belts and spots. A compari- 

 son of these drawings shows very clearly the 

 relative drift of the spots on the planet's sur- 

 face. 



COMETS. The first comet of 1882 was dis- 

 covered by Mr. Charles S. Wells, at the Dudley 

 Observatory, Albany, N. Y., on the night of 



