ASTRONOMICAL PHENOMENA AND PROGRESS. 



that the inner edge of Cassini's division, which 

 is situated at the distance thus indicated, is 

 especially distinctly marked. The outer edge 

 is very indistinct, the influence of Rhea and 

 Titan being much feebler, on account of their 

 great distance. 



" One tifth the period of Dione corresponds 

 to about the distance of Encke's division. One 

 eighth of Rhea's period and one halt' of Titan's 

 approximate roughly to the same distance. The 

 division is faint and ill-defined. One third the 

 period of Tethys, the simplest relation now re- 

 maining, indicates the outer boundary of the 

 ring system, and one seventh that of Rhea, and 

 one twenty-sixth that of Titan, correspond to 

 distances of nearly the same amount. 



" The only simple relation omitted is that of 

 one fifth the period of Tethys, and this closely 

 corresponds to integral parts of the periods of 

 the three next outer planets. There should, 

 therefore, be another division at about 14'7". 

 Dr. Meyer does not seem aware of the fact; 

 but several observers of Saturn have noticed 

 that ring B begins to shade off a little nearer 

 Saturn than the center of the ring, which would 

 correspond to a distance of about 14'T" or 

 14 - 8". Prof. Holden speaks of the point where 

 this shading off begins as 'a definite point.' 

 The correspondence between calculation and 

 observation as to the divisions of Saturn's rings 

 would, therefore, seem to be complete." 



At a meeting of the Philosophical Society of 

 Washington, Oct. 13, 1883, William B. Taylor 

 recalled attention to M. Struve's conclusion, 

 announced in 1851, that the rings of Saturn 

 are increasing in breadth, while the interval 

 between the inner brigh't ring and the planet 

 is gradually decreasing. This conclusion, ac- 

 cording to Mr. Taylor, is confirmed by later 

 observations ; although the change is probably 

 less rapid than was inferred by Struve, from a 

 comparison of the measures up to 1850. This 

 process of convergence, it was shown, is a 

 necessary consequence of the modern discov- 

 ery that the rings consist of dense streams of 

 indefinitely small satellites. All parts of the 

 ring are subject to perturbations by the exte- 

 rior members of the Saturnian system. The 

 bodies composing the ring can not, therefore, 

 revolve in circular orbits. Hence the friction 

 or collision of the different parts must fre- 

 quently occur, resulting in a " degradation of 

 motion," a convergence of orbits, and a short- 

 ening of the periods. In this theory of their 

 constitution Mr. Taylor foresees the ultimate 

 precipitation of the rings upon the surface of 

 the planet. 



Uranus. The question whether Uranus has 

 any measurable ellipticity seems to have been 

 definitely settled by the recent observations of 

 Profs. Safarik, of Prague; Schiaparelli, of Mi- 

 lan ; and Young, of Princeton. The polar com- 

 pression, according to these astronomers, is 

 about T V. This is greater than that of Jupi- 

 ter, and nearly equal to that of Saturn a fact 

 indicative of a rapid rotation. Prof. Young 



has also observed certain spots or markings on 

 the surface of the planet, similar to those on 

 Jupiter and Saturn, by the continued exami- 

 nation of which the rotation period may pos- 

 sibly be determined. 



Comets. On the evening of February 23, 1883, 

 a comet was discovered by W. R. Brooks, of Red 

 House Observatory, Phelps, N. Y. The same 

 body was independently detected only a few 

 minutes later on the same evening by Dr. Swift, 

 of the Warner Observatory, Rochester. About 

 the first of March the comet was described as 

 nearly round, and with a very condensed nu- 

 cleus. According to some observers, it had a 

 granular appearance, somewhat resembling a 

 resolvable nebula. It had a faint tail, about 18' 

 in length. From observations made at Cam- 

 bridge, Mass., on February 24th, March 5th, 

 and March 17th, and one at Albany, N. Y., on 

 March 5th, Messrs. Chandler and Wendell, of 

 Cambridge, computed the following elements : 



Perihelion passage = 1888, Feb. 18 '9357, G. M. T. 



Longitude of perihelion 29" 00' 00" 



Longitude of ascending node 278 7 41 



Inclination 78 4 40 



Perihelion distance 0-7599 



On the night of September 1st, W. R. Brooks 

 observed a small object, which he at once sus- 

 pected to be a comet. Cloudy weather pre- 

 vented satisfactory observations till the night 

 of the 3d, when his suspicions were fully con- 

 firmed. The comet was circular, more than a 

 minute in diameter, had a well-defined 'star- 

 like nucleus, and was without a tail. From 

 about two weeks' observations at the Dudley 

 Observatory, Albany, N. Y., Prof. Lewis Boss 

 found the elements of the comet's orbit so 

 nearly coincident with those of the comet dis- 

 covered by Pons on the 20th of July, 1812, as 

 to leave no doubt of their identity. This fact 

 was announced on the evening of September 

 19th. The sameness of the two bodies, how- 

 ever, had been independently shown one day 

 earlier by the Rev. George M. Searle, of New 

 York. Mr. Searle's conclusion reached by a 

 method different from that employed by Prof. 

 Boss was at once forwarded to Harvard Col- 

 lege, where it was received on the morning of 

 September 20th. Marked changes of structure 

 in approaching the un were observed within 

 three weeks from the date of its discovery. In- 

 dications of a nucleus were seen at Harvard on 

 the night of September 21st. The next night its 

 appearance was greatly changed ; the bright- 

 ness being nearly equal to that of an eighth- 

 magnitude star. On the night of the 23d it 

 had lost its stellar .aspect, had become blurred, 

 had a rather distinct nucleus, and was begin- 

 ning to develop traces of a tail. The perihelion 

 passage will occur about 1884, January 25th. 



Attention has been called to the fact that 

 the elements of this comet strikingly resemble 

 those of De Vico's comet of 1846, with the ex- 

 ception that the ascending node of the one co- 

 incides with the descending node of the other. 

 This close coincidence of orbits has been thought 

 to indicate a common origin. 



