50 



ASTRONOMICAL PHENOMENA AND PROGRESS. 



The path of totality of the eclipse of the 

 eun on Sept. 8, as is not infrequently the case, 

 was confined almost wholly to the ocean, the 

 only exception being the southern end of the 

 northern and the northern end of the southern 

 of the two islands of New Zealand, where to- 

 tality lasted nearly two minutes. The last cen- 

 tral eclipse visible in these islands occurred on 

 Dec. 29, 1796, and was annular. The next cen- 

 tral eclipse in New Zealand will occur on Jan. 

 3, 1927, and will be annular. During the to- 

 tality of the solar eclipse of Sept. 8 of this 

 year, the planet Jupiter was within the sun's 

 corona, being but 46' from the sun's limb. In 

 the total solar eclipse of 1870, Saturn had a 

 similar place, being within the corona, yet, 

 strangely enough, appears not to have been 

 seen by any observer. It seems quite logical, 

 therefore, to infer that, if Saturn could thus 

 escape detection, the non-discovery of anintra- 

 mercurial planet during the total eclipse at 

 Caroline Island need excite no surprise. 



Jnpiter. The " great red spot " that appeared 

 so unexpectedly and, it is probable, somewhat 

 suddenly in 1878 upon this planet has been 

 made the subject of telescopic study by every 

 astronomer of the world. Many hypotheses 

 possibly all valueless have been advanced to 

 account for its formation, its color, its drifting 

 both in longitude and latitude, its immense size, 

 and long-continued duration. It is still visible, 

 though so much fainter than during the first 

 two years of its existence as to lead several 

 astronomers erroneously to announce its disap- 

 pearance. At the present writing it is slowly 

 increasing in brilliance, and its entire outline 

 can now be traced, though it is exceedingly 

 faint, and its color very pale. The extraordi- 

 nary fact is mentioned by several observers 

 notably Mr. Denning, of England, and Prof. 

 Young, of Princeton, N. J. of the appearance 

 of a white cloud upon the red spot and con- 

 centric with it, which, being a little smaller, 

 leaves an elliptical annulus of a pinkish hue, 

 about 2" in width, surrounding it. This interior 

 obliteration, now perfect, has been a very grad- 

 ual process, first remarked about a year ago, 

 but, until March, April, and May last, not suf- 

 ficiently intensified to attract general notice. 

 At the latest observations of Jupiter, previous 

 to his too near approach to the sun to render 

 further examinations possible, it was thought 

 that the central portion of the spot was slowly 

 filling with matter of a brick-color, but so pale 

 as almost to elude detection. This spot will be 

 watched with increasing interest by astrono- 

 mers, to ascertain, if possible, if its changes 

 are marked by periodicity. The average size 

 of this spot, which Prof. Hough calls a floating 

 island, is 29,600 miles in length by 8,300 in 

 breadth. Its disjunction with the planet is 

 proved by its drifting in longitude, which dur- 

 ing the first year amounted to 10,000 miles, 

 and in the second year to 30,000 miles. 



For several years, especially during the past 

 two or three years, there have appeared with 



considerable frequency small, round, white 

 spots, with outlines of limb as sharply defined 

 as those of a satellite in transit. The cause of 

 these apparitions lies enshrouded in even deeper 

 mystery than that of those peculiar and inter- 

 esting markings called his belts, which are never 

 wholly absent, or of the great red spot. In an 

 article on Jupiter's spots by Prof. Young, in 

 the " Sidereal Messenger " for May, 1885, he 

 says : " On March 25 nine brilliant white spots, 

 each as large and several of them as round and 

 as well defined as the disks of satellites, were 

 seen. These bright spots were seen again on 

 April 1, having preserved their configuration 

 sensibly unchanged during the week." 



The dark transits of Jupiter's satellites con- 

 tinue to engage the attention of astronomers, 

 but as yet no solution has been reached. No 

 theory of causation, meeting with general ac- 

 ceptance, has been advanced. Many dark 

 transits of his satellites, especially of satel- 

 lites III and IV, have been observed during 

 the year. 



The physical conditions of Jupiter appear, 

 in at least one respect, to be somewhat analo- 

 gous to those existing on the sun, for, as the 

 sun's rotation period as determined by spots 

 near the equator, gives a different value from 

 that obtained from those nearer the solar poles, 

 so also the rotation period of Jupiter, as ascer- 

 tained by the rotation of spots near and more 

 distant from his equator, differs, and renders the 

 true determination of this value though to 

 only a limited extent a matter of uncertainty. 

 The difference in either case is accounted for 

 by the fact that the spots have a proper mo- 

 tion that is to say, that they appear disjoined 

 to the bodies themselves and free to move, and 

 seem to drift both in latitude and longitude, 

 particularly in the latter co-ordinate. 



To the assiduous labors of Prof. Hough, of 

 the Dearborn Observatory, Chicago, who for 

 several years has made the planet Jupiter a 

 special study, we are indebted for the most ac- 

 curate value of his rotatory period. The re- 

 ceived value for the past hundred years has 

 been: 



E. = 9h- 55m. 80-- 



By great red spot, 1877 " = 9- 65"- 84'2- 



By great red spot, 1884-'85 " = 9 h - 55- 40'4- 



Mean rotation from Sept. 25, 1879, to 



June 29, 1885, = 2,104 days = 5,086 



rotations " = 9 h - 55 m - S7'4- 



Hough's probable value of this element, 



as deduced from the equatorial white 



spots, is " = 9n. 50">- 09-8-- 



Comets. Prof. W. Tempel, of Florence, Italy, 

 while searching for Encke's comet, on the even- 

 ing of Dec. 13, 1884, ran upon a nebulous ob- 

 ject of exceeding faintness, which proved to be 

 the expected comet. Its apparent position was 

 in K. A. 22 h - 44 m - 25-63% Dec. + 3 44' 26-3". 

 This was its twenty-ninth return to perihelion 

 since its discovery on Jan. IT, 1786, by Me- 

 chain. Its period is the shortest of all the pe- 

 riodic^ comets, being 3-3 years. As heretofore, 

 it exhibited only a short tail (a characteristic 

 of all the known periodic?, except Halley's). 



