Auo. 31, 1883.] 



KNOWLEDGE 



141 



Parliament) moon, though everybody would welcome it i£ 

 it came somehow with no questions asked. 



If anybody doubts your opinion of Macaulay's style, 

 which was always mine, let them try it by the test of 

 reading it aloud, against Froude's, or Hume's old but 

 matchless History, and they will soon find how tiresome 

 it is. I have made his admirers give in by that test. 

 Gibbons is sickening when you have learnt the trick of it, 

 and its want of simplicity. I never saw Mr. Spencer's 

 " Essay on Style " (is it a separate book ^i*). Some of his 

 own is good enough ; but when he wants to be particularly 

 precise and lucid he is often particularly the contrary, and 

 his style, in my opinion, most abominable. Nevertheless, 

 he may pi-each better than he practises, and inculcate 

 better English than philosophy, in spite of Mr. T. Foster. 



Edm. Beckett. 



THE FACE OF THE SKY. 



Feom Aug. 31 to Sept. 14. 



By F.R.A.S. 



THE usual daily watch will be kept upon the sun for spots and 

 facula). The aspect of the night sky is shown in Map IX. of 

 *'The Stars in their Seasons." Mercury attains his greatest 

 eastern elongation (26° 42') from the sun on the 11th, but sets too 

 nearly with the sun now to be visible to the naked eye. Venus is 

 ([uite invisible. Mars rises before 11 h. 30 m. p.m. now ; but, as 

 wo said a fortnight ago, merely presents the appearance of a very 

 largo red star in Gemini. Jupiter does not yet rise until after 

 midnight. Saturn rises before 10 p.m. on the 1st of September, 

 and soon after 9 o'clock by the 14th, so that he will be well above 

 the horizon by midnight. He is situated between 3° and 4° north 

 of Aldebaran, and just to the Bast of it. Uranus and Neptune are 

 both invisible. The moon's age at noon on Aug. 31 is 28'4 days ; 

 and at the same time to-morrow it will evidently be 29'4 days. 

 Her age on Sept. 2, at noon, is 09 day, and quite obviously will be 

 12'9 days by the 14th. Two occultations of stars will take place on 

 the night of the 14th — firstly of c' Capricorni, a 4i magnitude 

 star, which will disappear at the moon's dark limb at 8 h. 44 m. 

 at an angle of 171° trom her vertex, reappearing at her bright 

 limb, at an angle of 208° from her vertex, at 9 h. 5m. p.m. 

 At 8 h. 47 m. p.m. c- Capricorni, a star of the Gth magnitude, 

 will disappear at the dark limb of the moon, at a vertical 

 angle of 91°, to reappear at her bright limb, at 10 h. p.m. 

 at an angle of 300° from her vertex. The moon, after travelling 

 through a portion of Leo, descends into Sextans about 10 p.m. on 

 Aug. 31, and (occupying about 9 hours in crossing the northern 

 part of that constellation) re-enters Leo at between 7 and 8 p.m. 

 on Sept. 1. It is between 9 and 10 o'clock on the night of Sept. 

 2 before she finally quits Leo and enters Virgo. It takes her until 

 9 a.m. on the 6tli to cross this constellation ; from which, at the 

 hour named, she passes into Libra. Her passage through Libra 

 occupies, as nearly as may be, 48 hours, and about 9 a.m. on the 8th 

 she enters the northern part of Scorpio; over this she takes 12 

 hours to travel, and at 9 p.m. crosses into the southern part of 

 Ophiuchus. Skirting, for a very short time, the extreme southern 

 limit of Serpens, she travels into Sagittarius about 5 o'clock in the 

 afternoon of the 10th. Sho does not leave this constellation for 

 Cai)ricornus until 2 a.m. on the 13th. It takes her until between 

 5 and 6 p.m. (or some 15J hours) to go over the northern part of 

 Capricornus, which she then quits for Aquarius. She is still 

 crossing Aquarius on the 14th. 



It is stated that there are 3,985 paper-mills in the world, 

 producing yearly 9.59,000 tons of paper made from all 

 kinds of substances, including rags, straw, and alfa. About 

 one-half the quantity is printed upon; and of those •170,000 

 tons, about 300,000 tons are used by newspapers. The 

 various Governnumts consume in official business about 

 100,000 tons; schools, 90,000 tons; commerce, 1:^0,000 

 tons ; industry, 90,000 tons ; and private correspondence 

 another 90,000 tons. The paper trade employs 19:^,000 

 hands, including women and children. 



• It is in the second volume of his collected easaya. — S. P. 



" Let Knowledge grow from more to more." — Alfeed Tennyson. 



Only a small proportion of Letters received can possihly he in- 

 serted. Correspondents must not he offended, therefore, should their 

 letters not appear. 



All Editorial communications should be addressed to the Editor op 

 Knowledge; all Business communications to the Publishers, at the 

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DELAYS ARISE FOR WHICH THE EDITOR IS NOT RESPONSIBLE. 



All Remittances, Cheques, and Post Office Orders should ie made 

 payable to Messrs. Wymak & Sons. 



The Editor is not responsible for the opinions of correspondents. 



No communications are answered by post, even though stamped 

 and directed enwelope be enclosed. 



PHENOMENA OBSERVED IN RAILWAY TRAVELLING. 



[906] — Wheu travelling in a train and looking out of a window, 

 the nearest objects appear to me, of course, to fly rapidly back- 

 wards, and the more distant to go slower until those on the 

 horizon seem to travel slowly in the same direction as the train. If 

 I have been looking out of the window at the landscape for some 

 time, and the train stops, the landscape appears to slowly unwind 

 itself, as it were, the nearer objects moving slowly forwards, and 

 the remoter just perceptibly backwards. I should like to know 

 whether this is a common experience, or one peculiar to my own 

 somewhat over-sensitive nerves. I should also like to know 

 whether the phenomenon is analogous to that of complementary 

 colours. I explain it to myself by supposing that while the train is 

 in motion the nerves of the lower part of the retina are continually 

 conveying impressions of forward motion (the nearer objects being, 

 of course, reflected upon the lower part of the retina), and those of 

 the upper part conveying impressions of backward motion. Then, 

 when the nerves are no longer excited from the outside they rest 

 themselves by complementary sensations, as in the case of comple- 

 mentary colours. 



Hoping that I have not wasted your valuable time in describing 

 what you are already familiar with, Leonard Browx. 



LUMINOUS RING. 



[907] — I enclose two photographic prints — one of my chemical 

 laboratory, the other of my dining-room — both taken by gaslight. 

 In each of these (and, of course, in the negatives) I observe a per- 

 fectly well-defined circle of light surrounding the gas-flame. 



I showed the pictures to my friend Mr. Grcnsted, who gave what 

 seems to me a very satisfactory explanation of the matter, and one, 

 indeed, which is interesting as affording another instance of the 

 analogy which exists between the human eye and the photographic 

 camera. Chas. Harris. 



With regard to the above, I have for many years seen a prismati- 

 cally-coloured similar ring, with the naked eye, when looking at a 

 candle-flame against a background of shadow. I thought it to be 

 either an emanation from the flame or caused by floating particles 

 in the eye. The first hypothesis is disproved by the fact that one 

 of the prints shows the ring overlapping the frame in which it is 

 reflected. The constitution of a camera lens disproves the second. 

 Is it a diffraction ring caused by reflections from the interior sur- 

 faces of the lens ? Fred. F. Grensted. 



FLIGHT OF A VERTICAL MISSILE. 

 [908] — Conservation of Angular Momnitum. By this principle 

 practical engineers perform such operations as adjusting a balance- 

 weight to the driving-wheel of a locomotive. Stated in this form 

 it carries its own proof witli it, being simply another expression for 

 the law that action and reaction are equal and opposite. Had the 

 principle been generally known by this phrase, it would have guided 

 your correspondent, Jlr. Bray, to a correct solution of the problem. 

 The ball, instead of moving east with the velocity of a point on the 

 earth'.s surface, moves east with a velocity inversely as its distance 

 from the earth's centre. Measuring the arc so described at the mean 

 height evidently doubles his former result. 



