318 
POPULAR SCIENCE REVIEW. 
in the N. and 40 in the S. hemisphere, Galle has deduced a value for the 
solar parallax of 8"*873. 
Jupiter. — Flammarion has made an extensive series of observations on the 
satellites. He thinks that his results show a difference in their intrinsic 
nature. IV is less luminous, though larger, than I and II, and very vari- 
able, from 6 to 10 mag., probably not from permanent spots, but atmo- 
spheric changes. Ill seems invariable, at 5*9 mag. I and II are about 6-8 
and 7 mags., both slightly variable and very white. I can be seen by day, 
when IV is invisible. Daylight alters the relative lustre, the size of the 
larger discs gaining by night. I has sometimes appeared smaller than II. 
Reduced to equal surfaces, the light would stand I, II, III, IV ; sometimes 
II brighter than I. Order of variability, IV, I, II, III. There is some 
evidence that the changes in IV may arise in part from its always turning 
the same face to the primaiy ; but its brightness appears complicated with 
•atmospheric disturbance. 
Saturn. — A series of micrometrical measures of the satellites has been made 
with the Greenwich 12f-in. equatorial. 
Uranus. — Mr. Isaac W. Ward, of Belfast, appears to have repeatedly 
succeeded in glimpsing by averted vision the two brighter satellites with an 
object-glass of only 4*28 inches by Wray, the estimated positions being 
subsequently found very fairly accordant with those in Marth’s tables* 
Webb also believes that he has caught sight of Titania with a very fine 
'938 silvered glass u With ” speculum. 
Stars and Nebidce. — Baron Dembowski has been continuing the measures 
of double stars, which have for many years given him a high pre-eminence 
among observers. The following periods of revolution which he has 
adopted for comparison may be found of use : — £ Herculis (Dun6r), 34 *22 
years, rj Coronce (Wijkander), 4138 y. £ Scorpii (Thiele), 49‘05 y. £ Ur see 
Mag. (Hind), 60*68 y. £ Canci'i (0. Struve), 62*4 y. 70 Ophiuchi (Schur), 
94*37 y. 2 3062 (Schur), (112-64 y. £ Bootis (Hind), 1689 y. y Virginis 
(Thiele), 185*01 y. 8 Cygni (Behrmann), 415*1 y. Castor (Thiele), 996 85 y. 
2 634 = 19 Camelopard. Hevel = P IV 269. This pair is called by Smyth 
an elegant object, 5^- and 9 mags, light yellow, pale blue. The components 
are certainly in motion, having been, according to 2, nearly 37" apart in 
1827, but now only about 20". 0. Struve considers it undecided whether 
this approach may be due to opposite proper motions or orbital connection : 
he thinks they may be at a comparatively small distance from us, and may 
show a sensible parallax, for which the pair is very favourably situated. 
Sirius. — Mr. Erck has observed a considerable diminution in the angle of 
position of the' comes. Auwers has computed a period of 49*399 years, but 
the agreement is latterly less satisfactory. 303 double stars have been 
measured with the 85-in. Alvan Clark refractor at Rugby. Algol. — 
Schonfeld has combined 55 observations of minima of his own with 
183 by Schmidt, and 50 by Argelander, all between 1846 and 1875. The 
.resulting period is 2*867288 days, probable error + 7m. The most pro- 
bable duration of the variation, from 2*2 to 3*7 mag., is 9^h., diminishing 
most rapidly lh. 26m. before mm., and increasing most perceptibly at an 
equal brightness lh. 47m. after min. Dr. Schjellerup has published a 
translation of the Arabic u Description of the Fixed Stars,” by Abd-al- 
