470 



KNOWLEDGE. 



December, 1911. 



With the above data the longitude of the centre of Mars 

 can easily be calculated for any moment. It may be noted 

 that the zero meridian passes through the bay of the Sinus 

 Sabaeus. The following well-known markings are visible at 

 9 p.m. on the dates mentioned below : — Am^orae Sinus on the 

 6th. Sinus Sabaeus on the 12th. Syrtis Major on the 19th and the 

 Mare Cinnueriuin on the 2Sth. Most of the markings require 

 at least a telescope of six inches aperture and good seeing to 

 discern any detail, though dusky patches can be made out on 

 the planet's disc with telescopes of smaller aperture. The 

 Moon appears near Mars on the morning of the 5th. 

 conjunction taking place at 3.55 a.m., Mars being 0" 50' to the 

 South. 



Jupiter: — 



The Moon will appear near the planet on the evening of the 

 31st, Saturn being 4° to the South. 



Jupiter is a morning st.ar, rising at 6.50 a.m. on the 1st and 

 at 5.22 a.m. on the 31st; owing to his apparent proximity to 

 the Sun, the planet is not observable till the end of the month, 

 and for the same reason his satellites are inobser\ able. The 

 planet appears in Scorpio and is in conjunction with ji Scorpii 

 on the 20th. the planet being about 16' tn the South of the 

 star. 



S.-^TURN : — 



Saturn is a very conspicuous object in the evening sky look- 

 ing S.E. ; he appears about 10° to S.W. of the Pleiades and 

 Mars. He appears due south at 10.15 p.m. on the 1st, 

 9.12 p.m. on the 16th. and 8.11 p.m. on the 31st, that is, about 

 four minutes earlier each day. 



(Jn the meridian he appears about 52 ' above the horizon as 

 the brightest star in that portion of the heavens, excepting 

 Mars, but he may readily be distinguished from Mars by his 

 lustreless appearance. 



The planet may be seen in detail in quite small telescopes ; 

 even telescopes of only 2-in. aperture are sufficient to observe 

 details on the disc as well as the Cassini division in the ring, 

 using a magnification of 100, whilst the ring itself may be seen 

 with a magnifying power of 50. The dark or crape ring 

 requires at least a 4-in. telescope, but it is seen to better 

 advantage in larger telescopes. The diameter of the ball is 

 18". whilst the diameters of the outer major and minor axes of 

 the ring are 45" and 16" respectively. The Southern surface 

 of the ring is presented to us at an angle of 21° to our line of 

 vision ; thus the ring appears well open. 



l.'ranus is approaching conjunction with the Sun. which 

 takes place 20th January, and hence is practically unobserv- 

 able, as he sets about 6.30 p.m. near the middle of the month. 



Neptune rises at 7 p.m. on the 1st, and at 5 p.m. on the 

 31st, whilst on these dates he is due south at 3 a.m. and 1 a.m. 



He is becoming more favourably placed for obser\ation in 

 the evenings, as he is in opposition on Jaimary 13th. 



The planet is situated in Gemini, where he is describing a 

 short retrograde path about 7° due south of Pollux and about 

 5° E. by S. of S Geminorum. but in small telescopes without 

 setting circles it is difficult to identify from the numerous 

 small stars in the same field of view. He may, however, be 

 detected by his motion, if observations are made on several 

 successive nights. 



Meteors. — The principal shower of meteors during the 

 month is the Geminids. December 10th to 12th ; the radiant is 

 near Castor, in R.A. VIl'' 12", Dec. +55°. The meteors are 

 short and quick, and difticult to record accurately. 



Minima of .Algol may be observed on the 14th at 11 p.m., 

 the 17th at S p.m., and the 20th at 4.30 p.m. The period is 

 2'' 20'' 49™. from which other minima be calculated. 



Telescopic Objects: — 

 Double Stars. — 1 Pegasi 21'' 17-5 

 4-5, 8-6; separation 36"- 2. 



N 



N. 



N. 



N. 19° 20'. mags. 

 55° 11', mags. 4-0, 8-0; 

 2° 17', mags. 3-7, 4-7; 

 29' 50', mags. 5, 6-4; 



separa- 



separa- 



ir .Andromeda O"" 31-5'^ 

 tion 36" -3. 



a Piscium l*" 56- 

 tion 3" -6. 



I Trianguli 2'' 6- 

 tion 5" ■ 5. 



Clusters.— (W VI. 55, 34.) 

 to the naked eye and situated about midway between 7 Persei 

 and 5 Cassiopeia. These magnificent clusters are described 

 by Smyth as " affording together one of tlie most brilliant 

 telescopic objects in the heavens." 



(M 34.1 A mass of small stars about the Sth magnitude; 

 not very compact. The cluster is just perceptible to the naked 

 eve about 5° North-West of .Algol. 



separa- 



The Perseus clusters visible 



NOTICES. 



ROYAL INSTITUTION.— A General Monthly Aleeting 

 of the Members of the Royal Institution was held on 

 November 6th, the Duke of Northumberland, K.G., President, 

 in the Chair. The Chairman reported the decease of 

 the Right Hon. Earl Cathcart. D.L.. J. P.. a Manager. 

 Professor G. L. Van der Mensbrugghe, Professor W. V. 

 Spring and Professor L. J. Troost, Honorary Members 

 of the Royal Institution, and resolutions of condolence with 

 the families were passed. The Highty-sixtli Christmas Course 

 of Juvenile Lectures, foimded at the Royal Institution in 1826. 

 by Michael Faradav, will be delivered this vear bv Dr. P. 

 Chalmers Mitchell,' D.Sc, LL.D., F.R.S., Secretary of the 

 Zoological Society, his subject being " The Childhood of 



.Animals." The Lectures will be delivered on the following 

 dates, at 3 o'clock : Thursday, December 28th ; I')eceniber 

 30th, 191 1 : January 2nd. 4th, 6th, and 9th. 1912. 



INTERNATIONAL CONGRESS OF ENTOMOLOGY. 

 CORRECTED D.ATE. — The Second International Congress 

 of Entomology will be held at Oxford, from August 5th to 

 10th, 1912, and not as previously announced. The President 

 of the Congress is Professor E. B. Poulton. D.Sc, F.R.S. 

 .Ml coinnnmications and entiuiries should be addressed to the 

 General Secretary of the Executive Committee. Dr. Malcolm 

 Burr, c,o F2ntomological Society of London, 11, Chandos 

 Street, Cavendish Stjuare, London, W. 



