March. 191. t. 



KNOWLEDGE. 



91 



Configurations of satellites at 4'' 30° a.m. 

 Jupiter's Satellites. 



The following satellite phenomena are visible at 

 Greenwich, all in the morning hours: — T^ 5*" 9" I. Sh. E. ; 

 10<" 4" 44"" 46' II. Ec. D. ; 14" 4'' 44" I. Sh. I. ; IS"" 5" 1"" I. 

 Oc. R.; ig'' 4'' 21°" II. Sh. E. ; 20" 4" 32°" IV. Tr. I.; 

 22" 3" 48°" 52' I. Ec. D. ; 23" 4" 22" I. Tr. E. ; 26" 4" 3" 

 II. Sh. I.; 27" 3" 59" III. Sh. I.; 28" 3" 44" 17" IV. Ec. 

 D., 4" 7" II. Oc. R. ; 30" 4" 3" I. Tr. I. 



The Northward motion of Jupiter will make this year's 

 opposition (which occurs on September 17th) more favourable 

 for European observers than those of the last four years, in 

 which it has been very low down. 



Saturn is between Taurus and Gemini. Is now 

 approaching conjunction with the Sun. Was in quadrature 

 March 17th. Polar semi-diameter 8". Major axis of ring 40", 

 minor 18". Angle P-5°-9. 



Eastern elongations of Tethys (every 4th given) 2" 0'' -8 c, 

 10" 2''-l m, 17" 3''-4 e ; of Dione (every 3rd given) 2" l*- -6 

 m, 10" ei-'S m, 18" Noon; of Rhea (every 2nd given) 

 3" 2" -0 e, 12" S^-O e. 



For Titan and Japetus E., W. stand for East and West 

 elongations, 1. for Inferior (North) conjunction, S. for Superior 

 (South) conjunction. Titan 1" 5'' -7 m W., 5" 5'' -2 m S., 

 9" 7'' -7 m E., 13" 7" 7 m I., 17" 5'' ■ 1 m W. ; Japetus 

 10" 2^ tn E. 



Uranus is a morning star but badly placed. Was in 

 conjunction with Sun on February 1st. 



Neptune is stationary on 8th, diameter 2". 



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



Double Stars and Clusters. — The tables of these, 

 given three years ago, are again available, and readers are 

 referred to the corresponding month of three years ago. 



Variable Stars. — Stars reaching their maxima in or near 

 April, 1915, are included. The lists in recent months may 

 also be consulted. (See Table 17.) 



Comets. — A new comet (1915a) was discovered by Mr. 

 J. C. Mellish, about Feb. 10th, in R.A. 17^ N.Dec. 3°. Daily 

 motion + 1", South 6'. Its place in April cannot yet be 

 predicted. Medcalf's Periodic Comet has been detected by 

 Miss Leavitt. It passed perihelion about 1914, June 5th 

 (period 7 years 8 months), and is now extremely faint. 



Table 17. Long-period Variable Stars. 



Night Minima of Algol 1" , 5" 5''-0m, 8" l"'-8m, 10" 10" -ee, 13" 

 Principal Minima of ^ Lyrae 9" l^c. 22" ll"*;. 



•4e, 28" 3"- 5 m. Period 2" 20'' 48" -9. 

 Period 12" 21" 47" -5. 



REVIEWS. 



AERONAUTICS. 



The Aeroplane. — By C. Grahame-White and Harry 



Harper. 280 pages. 16 plates and other illustrations. 



7-in. X 5-in. 



(T. C. & E. C. Jack. Price 3/6.) 



This book is a good popular account of present-day 

 aerial machines. We say present-day because these 



inventions progress so rapidly that the date of publication 

 is of importance, though no year appears on the title page. 

 The work comprises a general history of the development 

 of the flying machine from earliest times, and, after detailing 

 the early experiments of Lilienthal, Maxim, and the brothers 

 Wright, describes all the more recent machines. There 

 is a short chapter, or rather portion of a chapter, dealing 

 with balloons and airships, and there are incidental brief 



