January, 1913. 



KNOWLEDGE. 



^9 



Mars is a morning Star, but practically invisible. 



Jupiter is still badly placed, having been in conjunction 

 with the Sun on December 18th. It is, however, just coming 

 into view as a morning star. Polar semi-diameter, 15i". 



Table 4. 



Configurations of Jupiter's satellites at 6 h m for an inverting 

 telescope. 



Satellite phenomena visible at Greenwich, l d 6 h 24™ II. Sh. 

 I. ; 3 d 5 h 48 m I. Tr. I. ; 7 h 19 m I. Sh. E. ; 10 d 6 h 56 m I. Sh. I ; 



I. Ec. D. ; 

 I. Tr. E.; 



I. Sh. E.; 5 h 43" 

 24" 5 h 58 m 27 s III. Ec. D. 

 II. Tr. I.; 6 h 14 m I.Tr. I.; 6 h 19" 



D.; 18 d 6 h 3 m 34 s 



II. Tr. E. ; 6 h 13 m 



26 d 5 h ll m I. Sh. I.; 5 1 



II. Sh. E. ; 27 d 5 h 45 m I. Oc. K. 



All the above are in the morning hours. 



Attention is called to the simultaneous transits of I. and II. 

 on the 19th and again on the 26th. 



Saturn is an evening Star, 6° South of the Pleiades. Polar 

 semi-diameter 8|". The major axis of the ring is 43", the 

 minor axis 17i". The ring is now approaching its maximum 

 opening and projects beyond the poles of the planet. 



East elongations of Tethys (every fourth given). February 

 2 d 6 h -4 m, 9 d 7 h -7 e, 17 d 9 h -0 m, 24 d 10 h -2 e. Dione (every 

 third given). February 5'' 7 h -8 m, 13 d h '9 e, 21 J 6 h -0 e. 

 March l d ll h - 2e. 



Rhea (every second given). February l d 2 h - 8 e, 10 3 -7e, 

 19 d 4 h -7c, 28 d 5 h -7e. 



For Titan and Iapetus, E. W. mean East and West 

 elongations, I. S. Inferior and Superior Conjunction, Inferior 

 being to the North, Superior to the South. Titan, 3 d 4 h -8e I., 

 7 d h -9 e W., 11" h -0 e S., 15 d 3 h -4 e E., 19 d 4 h -0 e I., 

 23 d h -4 e W., 26 d ll h -6 m S. Iapetus 19 d 8 h -9 e I. 



Uranus is invisible, having been in conjunction with the 

 Sun on January 24th. 



Neptune was in opposition on January 14th. Its motion 

 may be traced on the map of small stars which was given in 

 "Knowledge" for December, 1911, page 476. 



Meteor Showers (from Mr. Denning's List) : — 



Double Stars and Clusters. — The tables of these given 

 last year are again available, and readers are referred to the 

 corresponding month of last year. 



Variable Stars. — Tables of these will be given each 

 month ; the range of R.A. will be made four hours, of which 

 two hours will overlap with the following one. Thus the 

 present list includes R.A. 6 h to 10 h , next month 8 h to 12 h , and 

 so on. In the case of Algol variables, the time of one 

 minimum is given where possible, and the period. Algol, 

 owing to its brightness, will be given for wider limits. 



Table 5. 



Of long period variables Ceti (Mira) will reach a maximum at the end of April, when it will be invisible in the sunshine, but 



it may be seen brightening early in the year. 



REVIEWS. 



ASTRONOMY. 



The Sun. — By Charles G. Abbot, of the Smithsonian 

 Institution. 448 pages. Numerous illustrations. 8-in.X5-in. 



(D. Appleton & Co. Price 7/6 net.) 



The publication of this treatise is indicative of a most 



healthy change that is coming over astronomy. All through 

 it exhibits an able attempt to explain phenomena, to correlate 

 and to classify observations. A dynamical deduction that 

 furnishes a clear explanation even if not the final word on (he 

 subject is of value. It is said that truth more easily arises 

 from error than from confusion. Attempting to observe with- 



