350 



* KNOWLEDGE ♦ 



[Dec. 7, 1883. 



Chess as a scientific game, though some correspondents 

 who apparently know little of the game and nothing of its 

 real charms, objurgate us for allowing what they call a 

 mere chance game to be dealt with in these columns. We 

 invite those who so view Whist to study the game which 

 adorns our Whist column this week, and to consider 

 whether an average problem in Mathematics would more 

 efiectively test the powers of combination than the problem 

 which was presented to all four players at the close of this 

 remarkable game. Whist is of course, like Chess, to be 

 regarded really as a mental relaxation only, not as a 

 suitable subject for profound time-consuming study ; but 

 that it should be so excellent as a recreation yet so actively 

 exercising the mind (as cricket, football, and like good 

 recreations tend to strengthen the body) justifies its recog- 

 nition here as worthy of a place alongside that prince of 

 scientific home-games, Chess. Yet Whist, unlike Chess, 

 will not appear weekly. 



" Our Mathematical Column " we no longer promise to 

 continue seriatim, though it will by no means disappear. 

 Should it reappear as a weekly feature, it will probably be 

 limited to illustrative problems of interest to students as 

 akin to those which appear in examination papers. 



We cannot promise at present such increase in the 

 quantity of matter oflered to our readers as can only be 

 safely and steadily provided for when our circulation has 

 attained to a number already definitely decided upon. 

 Some readers have pointed to publications kindred to 

 Knowledge in certain respects, which offer more matter to 

 their readers. We can only reply that if we filled these 

 columns with correspondence, borrowed matter, and matter 

 oflered for nothing (and for the appearance of which in 

 type the authors would even be willing to pay), we 

 ■could safely purvey half as much matter again as weekly 

 appears in our pages. But as matters actually are, 

 the case is otherwise. Among the objects in view when 

 Knowledge was started, the appearance weekly of a 

 certain amount of original matter was not held to be the 

 least important. The Editor may also remind readers that 

 the time devoted to Knowledge by him is not spare time, 

 but time specially withdrawn from other work. It is most 

 pleasant to him, and worth some sacrifice of time and labour, 

 to be brought directly into communication with great num- 

 bers of those who have kindred tastes and follow kindred 

 studies. He trusts the pleasure is mutual. But for this 

 as for everything that is worth anything, he has to pay a 

 price ; and what he can afford rather than what he would 

 wish to pay has to be considered. 



Readers have however shown so kindly and considerate 

 an interest in Knowledge and its progress, that the work 

 cannot but become constantly lighter and more pleasurable. 

 Each who adds one to the number of our readers does his 

 share towards doubling our constituency ; and with each 

 such increase comes " the promise and potency " of increased 

 etiicienoy and value in Knowledge itself. 



The Editor desires to state that during the last four 

 weeks he has been prevented from attending to literary 

 work as he could wish, by the return of head pains similar 

 to those which followed the railway accident of July 21st 

 last. These seem now yielding to treatment 



THE FACE OF THE SKY. 



From Dec. 7 to Dec. 21. 

 By F.E.A.S. 



FINE individual spots and groups of spots continue to appear 

 upon the Sun's face, which should be examined on every clear 

 day. The aspect of the night sky will be found delineated on 

 Map XII. of ** Stars in their Seasons." Mercury is for all prac- 

 tical pm-poses invisible, his great south declination involving 

 him in the horizontal mist of the winter sky — an observation which 

 applies equally to Venus. Mars does not south until morning, but 

 may be very fairly well seen after ten or eleven p.m. The angular 

 diameter of his disc increases to 13"-1 by the 2l8t ; but he is, of 

 course, under these circumstances, a relatively small object, and 

 requires a powerful telescope to scrutinise him with anything like 

 a satisfactory result. A small one, however, will suffice to 

 show that his disc is still gibbous — i.e., less than a circle. 

 Mars is in the barren part of the sky, to the west of Leo 

 ("The Stars in their Seasons," Map III.). Jupiter is by far 

 the most brilliant object now in the night sky, and is very well 

 placed for the observer, although he still souths after midnight. He 

 is situated to the south-west of the "Praesepe" in Cancer (same 

 map). The phenomena of his Satellites visible before 1 a.m. during 

 the period covered by our notes are as follows : — To-night (7th) 

 Satellite III. will re-appear from occultation at llh. 58m. p.m., and 

 the shadow of Satellite I. come on tn Jupiter's face at 12h. 6m. On 

 the 8th an eclipse of the First Satellite will happen at 9h. 18m. 26s. 

 p.m., the Sams Satellite reappearing from occultation (of course, 

 after passing behind the body of the planet) at 12h. 32m. On- the 

 9th the shadow of Satellite I. will quit Jupiter's disc at 8h. 54m., 

 followed by the Satellite casting it at 9h. 50m. p.m. On the 10th 

 the ingress of the shadow of Satellite II. will happen at 8h. 25m., 

 Satellite II. itself coming on to the planet's face at lOh. 15m. At 

 llh. 19m. the shadow will pass off the opposite limb, Satellite II., 

 though, not doing so until between 1 and 2 a.m. on the 11th. There 

 will be an eclipse of Satellite III. on the 14th, at 8h. 36m. 24s. p.m., 

 and one of Satellite I. on the 15th at llh. 11m. 50s. On the 

 night of the 16th four sequent phenomena will reward the student. 

 At 8h. 28m. the shadow of SatelUte I. will enter on to Jupiter's 

 face, followed by the Satellite itself at 9h, 16m. The shadow will 

 leave the| planet' at lOh. 48m., as will the Satellite at llh. 36m. 

 On the 17th Satellite I. will reappear from occultation at 8h. 44m. ; 

 the ingress of the shadow of Satellite II. will happen at 11 o'clock, and 

 that satellite will begin its own transit 3.3 minutes after midnight. 

 On the 19th II. will reappear from occultation at lOh. 25m. On 

 the 20th the comparatively rare phenomenon of a transit of 

 Satellite IV. will occur, and should be carefully watched to deter- 

 mine whether the Satellite is invisible while superposed on Jupiter, 

 whether it looks brighter than his belts, ic, or whether it looks 

 dark, like its own shadow. Curious observations of transits 

 of the two outer Satellites are extant, and no opportunity 

 should ever be lost of watching them across Jupiter's disc. 

 Satellite IV. will leave the planet's face at llh. 5m. p.m., on the 

 20th. On the 21st, SatelUte III. will be eclipsed at 12h. 34m. 48s. 

 p.m. Finally, on the night of the 23rd, the ingress of the shadow 

 of Satellite I. begins at lOh. 22m., the Satellite follows its shadow 

 at llh. Im., and the shadow passes off 42 minutes after midnight. 

 Saturn travelling away from i Tauri in a westerly direction (" The 

 Stars in their Seasons," Map I.) continues to be almost as favour- 

 ably placed as he can be for the observer. There is no sensible 

 change in the opening of his ring-system. Our drawing and de- 

 scription in p. 319 will instnict the student exactly what to look for 

 in this wonderful and interesting system. Uranus is not yet fairly 

 visible ; but any one who cares to regard a seeming-dullish Sth mag. 

 star, may fish for Neptune some 3° or 4° south of S Arietis (Map I. 

 of " The Stars in their Seasons.") Pons' Cotr.et of 1812, to which 

 we have previously referred on pp. 292 and 319, travels during our 

 specified period from the north-eastern part of Lyra across Cygnus, 

 passing over a portion of the Milky Way between the 11th and 21st. 

 The moon's age at noon, to-day, is 7'7 days ; and, quite obviously, 

 on the 21st, it will be 21'7 days ; so that, up to about the 18th, she 

 will be very well situated for the observer. During the interval 

 covered by these notes, four occultations of stars will happen at 

 convenient hours. The fii-st will be that of the Gth mag. star, 

 B.A.C. 1272, which will disappear at the moon's dark limb at 

 6h. 10m. p.m. on December 12, at an angle from her vertex of 9°; 

 and will reappear at her bright limb, '37 minutes later, at an angle 

 of 296' from her vertex. On the afternoon of the 13th, m Tauri, a 

 star of the 5^ mag. will disappear at the dark limb, at a vertical 

 angle of 96° ; to reappear at the moon's bright limb at 5h. 23m. 

 p.m., at an angle of 200* from her vertex. At 7h. 20m. p.m. on 

 the 15th, X Geminorum, a Si mag. star, -will disappear at the moon's 

 bright limb at an angle from her vertex of 37°, reappearing at her 



