ASTRONOMICAL PROGRESS AND DISCOVERY. 



53 



Double and Binary Stars. J. E. Gore gives in 

 the ''Monthly Notices of the Royal Astronom- 

 ical Society" for Decemher, 1887, formulae for 

 the rectangular co-ordinates of the double star 

 2 1847, and gives the proper motion of the star 

 as 0-1053" per annum in the direction of posi- 

 tion angle 114'1. The following table gives: 



The 36-inch equatorial of Lick Observatory 

 shows, "at a little less than one fifth of the 

 width of the ring from its outer edge, a fine 

 but distinct dark line, a mere spider's thread, 

 which could be traced along the ring nearly to 

 a point opposite the limb of the planet, this 

 line marked the beginning of a dark shade, 



The Sun. The minimum period for sun-spot 

 occurrence was prolonged during the first four 

 months of 1887. There was a sudden slight 

 increase in the number of spots in the begin- 

 ning of May, 1887. In the present eleven-year 

 period two minima have occurred : one, from 

 Sept. 22 to Dec. 8, 1886, and the other from 

 January to May, 1887. Including both of these 

 periods in the same minimum, by neglecting 

 the interruptions at the close of 18*86, then the 

 whole minimum period includes 222 days, and 

 the date of the minimum may be given ap- 

 proximately as Jan. 10, 1887. This does not 

 refer to the absolute minimum for this eleven- 

 year period. On Oct. 28, 1887, some faculse, 

 attached to a group of faint spots, are reported 

 to have become on a sudden intensely bright, 

 and faded again as quickly. No other change 

 of importance occurred in the spots themselves, 

 or in their neighborhood. Within three min- 

 utes both faculae and spots had entirely dis- 

 appeared. The magnetic instruments indicated 

 no disturbance. There were many days in 

 1887 when the sun was without spots, but very 

 rarely were faculaa entirely absent. 



Saturn. Many skillful observers, among 

 whom may be mentioned M. Trouvelot, Dr. Ter- 

 by, and Mr. Elger, consider that the rings of Sat- 

 urn are not stable, but are subject to continual 

 changes. Dark masses have been observed on 

 ring 0, indentations have been seen on its 

 inner edge, and other noticeable appearances 

 recorded. Some astronomers have been in- 

 clined to consider that these appearances have 

 no real existence, but that they are due to bad 

 seeing, distorting eye-pieces, etc. Prof. Hall, 

 in using the great Washington glass, was, we 

 think, unable to see some of the markings 

 drawn on the rings by Trouvelot in his well- 

 known picture of Saturn, as seen with a 26- 

 inch instrument. Mr. Keeler, of Lick Observa- 

 tory, in the February number of the " Sidereal 

 Messenger," in speaking of the distortion of 

 Saturn's shadow, drawn by Trouvelot, says he 

 had often noticed the distortion " when observ- 

 ing with the 12-inch equatorial, with a low 

 power on a poor night; but it always dis- 

 appeared on employing a sufficiently high 

 power, or with improvement in the definition." 



which extended inward, diminishing in intensi- 

 ty, nearly to the great black division. At its 

 inner edge the ring was of nearly the same 

 brightness as outside the fine division. No other 

 markings were visible." 



In the supplements to the "Pulkowa Ob- 

 servations," Prof. H. Struve discusses his own 

 observations made with the 15-inch refractor 

 in 1884-'86 on lapetus, Titan, Rhea, and Dione, 

 with a view to correcting the elements of these 

 satellites and also of determining the mass and 

 ellipticity of Saturn. Herr Struve's value of 

 the mass of Saturn agrees closely with Bessel's, 

 being 1 -f- 3,498; the sun being unity. 



G. W. Hill, in the " Astronomical Journal." 

 of July 12, 1888, discusses the motion of Hy- 

 perion and the mass of Titan. He points out 

 the errors in the calculations of several com- 

 puters, and gives as his value of the mass of 

 Titan 1 -=- 4,714, the mass of the planet being 

 unity. 



Mars. Prof. Schiaparelli's observations on 

 Mars, made during the opposition of 1881-'82, 

 have been published. His new map agrees in 

 general with that drawn in 1879. There are 

 some noticeable differences, however, these 

 being in a region seen by a number of observ- 

 ers to undergo changes. The main interest of 

 this memoir centers in the full account of the 

 " remarkable duplication of many of the 

 canals." Thirty duplications are recorded be- 

 tween December, 1881. and February, 1882. 

 The author thinks the phenomenon is periodic, 

 and he concludes that duplication is connected 

 with a period corresponding to the tropical 

 year of Mars, and depending on the martial 

 seasons. The tendency to duplication is pointed 

 out as showing itself in other regions of Mars. 

 Other observers have noted this tendency. 

 Schiaparelli thinks it impossible to deny the 

 reality of the duplications, however difficult of 

 explanation they may be. E. W. Maunder, in 

 the September number of " The Observatory," 

 in discussing Schiaparelli's observations, re- 

 marks that " it seems impossible to accept this 

 as a description of a real objective change tak- 

 ing place upon the actual surface of the planet, 

 though as a record of a subjective appear- 

 ance it must be unhesitatingly received. Prof. 



