Dec. 21, 1883.] 



• KNOWLEDGE ♦ 



379 



of its sensations much more loudly and effectively 

 tlian the watch can pvoclaiin the sight of an ice- 

 berg when much nearer at hand. The movement 

 of the index could set a fog-horn lustily announcing the 

 approach of danger ; could illuminate the ship, if need be, 

 by setting at work the forces necessary for instantaneous 

 electric lighting ; could signal the engineers to stop and 

 reverse the engines, or even stop and reverse the engines 

 •automatically. Whether so much would be necessary — 

 whether those among lost Atlantic steamships which have 

 been destroyed, as many have been, by striking upon ice- 

 bergs, could only have been saved by such rapid automatic 

 measures as these, may or may not be the case ; but that 

 the u.se of the infinitely keen perception which the sense 

 organs of science possess for heat and cold would be a 

 feasible way of obtaining much earlier and much more 

 effective notice of danger from icebergs than the best watch 

 can give, no one who knows the powers of science in this 

 direction can douht.—Thnes . 



(Siiitonal (gossip. 



I REGRET to say that two members of the Faculty, to wit 

 my family doctor and a doctor specially skilled in matters 

 relating to railway accidents and their effects, regard with 

 disapproval the efforts T have made during the last few 

 months to disregard Nature's warnings. The fact is, the 

 London and South-We.stern Railway Company have 

 endeavoured so earnestly to persuade me that I am none 

 the wor,se for the shock they kindly gave me last July that 

 I have tried to persuade myself I might not be so much 

 the worse for it as I seemed to feel. Anyway, I am now 

 relegated to two months, at least, of absolute rejjose from 

 mental work. Fortunately, there is enough collected 

 material, so far as my share in Knowledge is concerned, 

 for longer than that ; and I believe readers will find no 

 other effect but the omission of " Short Answers " and 

 " Editorial Gossip " — perhaps (if some correspondents are 

 to be believed) an improvement rather than otherwise. I 

 ^hall ask those who stand by Knowledge to continue their 

 support till I am fairly on my feet again. That they have 

 done so, indeed, during the last few months, when I have 

 been as good an on my back (or as bad ?), says much for their 

 good will. 



Some physical results of the Java disturbance help us to 

 understand how small the world is. Take a bowl of water, 

 agitate the fluid in the centre, and the undulations you 

 excite propagate themselves in smooth-swelling concentric 

 rings till they lap against the sides of the bowl. There 

 tlicy break, and slop up in mimic tidal waves. This is an 

 exact illustration — magna coinponere, parvin — of the oscil- 

 lations of the sea reported from both hemispheres this week. 

 The tidal irregularities, as might be expected, were most 

 violent on the north-western seaboard of jV\istralia, which 

 lies right opposite the scene of the Java disturltances. On 

 that coast the sea retreated and advanced a hundred yards. 

 A day or two later oscillations appeared (m the Atlantic 

 .seaboard of America. The particular undulation which, on 

 the fifth day out, .slopped up on the East coast of New 

 Zealand, must have come by way of the Cape of Good I lojie 

 and Cape Horn, and had nearly completed the circuit of the 

 globe. Australia lies as a breakwater between us and Java 

 by the direct route. It gives one a new conception of the 

 littleness of what Henry Ward Beecher calls " this fipenny- 

 lia'penny world " when a man can stand on the Ocean lieach 

 at Dimedin and watch the ripples from a splash made in the 

 Straits of Sunda. — Otago Times. 



THE FACE OF THE SKY. 



Feom December 20, 1883, to jANUARy 4, 1884. 

 By F.E.A.S. 



WHENEVER the winter sky is sufficiently clear, the Sun should 

 be examined for spots. The mist near the horizon will now 

 often enable this to be done with a very light coloured eye-shade 

 on the telescope. Map XII. of " The Stars in their Seasons" ex- 

 hibits the present appearance of the night sky. Mercury is still, 

 for all practical purposes, invisible, as is Venus also. The position 

 of Mars improves nightly, as he rises soon after eight on December 

 20, and about seven o'clock in the evening by January 4. By the 

 latter date his diameter will have increased to 15". He is still 

 perceptibly gibbons, i.e., as we have previously explained, not round. 

 He continues in the western part of Leo (" The Stars in their 

 Seasons," Map. III.). Jupiter, the gem of the night sky, rises about 

 6h. 22m. this evening, appearing above the horizon, of course, 

 earlier and earlier every night ; until by the 4th pros, he rises at 

 5h. 24m. p.m. His diameter increases during this interval from 

 41"-7 to 42"-6. He continues in Cancer, at some little distance to 

 the west of the Pra?sepe (same Map). The phenomena of his 

 Satellites visible before 1 a.m. during the next fourteen days are 

 tolerably numerous. And first, to-night, the young observer 

 should carefully watch as much of the Transit of Satellite IV. 

 across Jupiter's face as he can. The Satellite will leave Jupiter's 

 disc at llh. 5m. p.m. We have referred on page 350 to the 

 curious phenomena often witnessed in connection with the 

 Transits of the outer Satellites, and less frequently seen when 

 the inner ones cross Jupiter's face. On the 21st, Satellite III. 

 will disappear in eclipse at 31m. 48s. after midnight. The shadow 

 of Satellite I. will enter on to the planet's limb on the 23rd, at 

 lOh. 22m. p.m., followed by the Satellite which casts it at llh. Im. 

 p.m. The shadow will pa'ss off at 12h. 42m. p.m., the Satellite 

 not until between 1 and 2 o'clock the next morning. The next 

 night (the 24th), the same Satellite, I., will disappear in eclipse 

 at 7h. 33m. 44g., pass behind the body of the planet, and reappeai- 

 from occultation at lOh. 20m. p.m. On the 25th Satellite I. passes 

 off the limb of the planet at 7h. 47m. p.m. ; as does Satellite 111. 

 at 8h. 35m. Satellite II. disappears in eclipse at 8h. 39m. 2ts. p.m. 

 on the 26th, to reappear from occultation 43 minutes after mid- 

 night. On the 28th, Satellite IV. will suffer eclipse at 

 9h. 40m. 21s. p.m. Sixteen minutes after midnight on the 30th 

 the ingress of the shadow of Satellite I. will begin, the Satellite 

 following it half an hour later. On the 31st, the same Satellite 

 will disappear in eclipse at 9h. 27m. 25s. p.m., reappearing 

 from occultation at 12h. 13m. The night of January 1, if fine, 

 will be a prolific one for the student. The ingress of the shadow of 

 Satellite I. will occur at 6h. 45m., followed by that of Satellite 1. 

 itself at 7h. 12m. p.m. The transit of Satellite III. will begin at 

 8h. 20m. ; the shadow of the 1st Satellite leaves Jupiter's face at 

 Oh. 4m., as will the Satellite casting it at 9h. 32m. Then the 

 shadow of Satellite III. will quit the limb of the planet at lOh. 4m., 

 Satellite III. itself passing off at llh. 55m. On Jan. 2 Satellite I. 

 will reappear from occultation at 6h. 39m. p.m., and Satellite II. 

 be eclipsed at llh. 15m. 283. Lastly, on Jan. 4 the egress of the 

 shadow of Satellite II. will happen at 8h. 19m., as will that of the 

 Satellite from which it proceeds, at 9h. 6m. p.m. Satnrn is still 

 visible during the whole of the ordinary observer's night. He 

 rises this afternoon (the 20th) about 2h. 23m., and is on 

 the meridian at lOh. 16-9m. p.m. By Jan. 4 he will 

 south at 9h. 140m. in the evening, rising about Ih. 27m. 

 in the afternoon. All the leading details of his physical 

 structure are now admirably visible with sufficient optical power. 

 Uranus will scarcely come within the ken of the great mass of 

 amateur observers before February next. The direction we gave 

 a fortnight ago (p. 350) will enable any one to find Neptune 

 who cares to do so. Pons's Comet is now brightening >vith 

 tolerable rapidity, and may be seen with the naked eye. If we 

 draw an imaginary line between y and 35 Cygni, the Comet to-night 

 will be very nearly on this line, about three-quarters of the distance 

 between the larger star and the small one. It will be close to 

 K Cygni on the 27th. By Jan. 4 it will have travelled dovm 

 into Pegasus. The Moon's age at noon to-day is 207 days ; 

 and, evidently, at the same hour on Dec. 29, 297 days. Then 

 she will be one day old on the 30th at noon ; and, of course, six 

 days old at noon on Jan. 4. Sho will not rise to-night until a 

 quarter to twelve o'clock ; and, as she does so later and later every 

 day, the nights up to the end of the year will be practically moon- 

 less. No occultations of stars occur during our specified period. 

 The Moon is travelling across the south-eastern part of Leo to-day, 

 and enters Virgo at midnight. It takes her until 11 a.m. on the 

 24th to cross this large constellation, and at that hour she passes 

 into Libra. Her passage tlurough Libra occupies 48 hours, and at 



