84 



KNOWLEDGE 



[Apeil 1, 189C. 



here the bright indefinito patch (part of the annulus) 

 usually visible, oven when the rest of the annulus is com- 

 paratively inconspicuous. 



You will see that this theory seems to account for : — 

 (1) The apparent repulsion of the S. equatorial belt, 

 resulting in the great bay opposite the red spot ; (2) the 

 well-known shoulder following the latter ; (8) the bright 

 annulus surrounding the red spot ; (4) the bright patch 

 (forming part of the annulus) usually visible at the 

 preceding end of the spot ; (5) the broad bright channel 

 always seen separating the spot from the S. equatorial 

 belt. And all this in the simplest way possible. 



It is true that I cannot imagine what kind of a con- 

 stitution the red spot can have to act as such a substantial 

 obstacle, and yet to drift about as it has done. Neverthe- 

 less it seems to me that the foregoing is worth suggesting 

 as a working hypothesis, especially since there appears to 

 be no theory which is not open to serious objections. 



Until lately 1 was a little doubtful whether the white 

 material in the channel north of the spot does move in 

 accordance with the above hypothesis, but according to a 

 letter just received from Herr Brenner, of the Manora 

 Observatory, there appears to be no doubt of this. 



A. Stanley Willums. 



MIRA CETI. 

 To the Editors of Kno\\'ledge. 



Sirs, — Unfortunately the weather seems to have hin- 

 dered the observation of this star for a week in the early 

 part of January, and I only know of a few observations of 

 it made afterwards until the middle of that month. 



On the 9th I compared the brightness of Mira with that 

 of S Ceti, and the former appeared to have the benefit in a 

 slight degree. This would make its magnitude not much 

 above the fourth order, at which it was placed by Mr. 

 David Flanery on January 8th. 



On January 10th I again observed the star, and placed 

 its magnitude at nearly that of y Ceti, there appearing to 

 have been a rise of almost half a magnitude in the 

 twenty-four hours. 



A few dull evenings then intervened until the 15th, 

 when I could find no appreciable difference between Mira 

 and y Ceti, although on the 19th the latter seemed to me 

 to be very slightly the brighter. 



From that date I have made very few observations 

 of Mira under favourable conditions, but at the end 

 of February no remarkable decrease in its magnitude 

 was noticed. 



Exeter. W. E. Besley. 



PEXTACLE PrZZLE. 

 To the Editors of Knowledge. 



Sirs, — I owe an explanation to the readers of my letter 

 (Knowledge for March, p. 63), which perhaps led some to 

 think I had actually solved the problem myself, whereas 

 it was simply tentative. But I fear the problem is 

 insolvable in its complex statement, and perhaps also in 

 the simple statement touching the summations of the five 

 lines only. 



I would suggest that possibly the law may be that such 

 results occur only when the lines of the figure chosen are 

 parallel. 



I find further that this problem goes very much on the 

 same lines as the endeavour to find exact relations between 

 the radius and the periphery of a circle. 



Brighton. I. G. Ouseley. 



[Note. — It has been pointed out by several corre- 

 spondents that the sum of the numbers 1 to 10 being 55, 



which is indivisible by 8, the sum of any five of the 



numbers cannot be double or half the sum of the remaining 



five ; and since in the problem the five external numbers 



are to count double the five internal numbers, the problem 



is insolvable. — Eds.] 



— *-♦-, — 



ZODIACAL LIGHT (?). 

 To the Editors of Knowledge. 



Sirs, — I venture to write you respecting an unusual 

 phenomenon witnessed by myself on the outskirts of this 

 town on the evening of March 4th. Happening to look 

 westwards I saw a solitary bright streak of light (in width 

 apparently about 5°) issuing from behind a dark cloud on 

 the W.N.W. horizon, and stretching almost half-way to 

 the zenith. 



This was at 8.39, and it remained very bright for three 

 minutes (so bright, in fact, that a light cloud passing over 

 it did not entirely hide it from view), when it gradually 

 faded away to a glimmer, and in ten minutes no trace was 

 to be seen. 



Both sides of the streak were well defined, and were 

 parallel to one another throughout the whole length. It 

 attracted the attention of all passers by, who stopped to 

 look at it, and were asking what it could be. Was this 

 the zodiacal light '? If so, it was very bright, and was 

 hardly at all inclined to the horizon. It was certainly not 

 caused by any terrestrial agency. 



Shrewsbury. W. Lyon Browne, Jun. 



" 20" PUZZLE. 



Note. — We are informed that the publication in our 

 columns of possible solutions of this clever puzzle con- 

 stitutes an infringement of the copyright ; we therefore 

 willingly express our regret to Messrs. T. Ordish and Co., 

 99, Fore Street, London, E.C. (Publishers), and also to 

 Messrs. Joseph Wood Horsfield & Co., of Dewsbury, the 

 proprietors of the puzzle, for any infringement of their 

 patent or copyright inadvertently committed in the pages 

 of Knowledge. 



PLINY AND CUVIER. 



By E. Wai.ter Maunder, F.E.A.S. 



THE two lunar photographs which we reproduce in 

 the present number of Knowledge are, like those 

 which we gave in Jr.ne, 1895, from enlargements 

 by Dr. Weinek of a photograph taken by MM. 

 Loewy and Puiseux with the large equatorial coude 

 of the Paris Observatory on March 14th, 1894. Dr. 

 Weinek's photographs were on a scale of four metres to 

 the lunar diameter, a magnification of 28 -36 times linear. 

 The present reproductions are on a scale of 2-9 metres to 

 the lunar diameter. 



The two districts shown are sharply contrasted in charac- 

 ter. The left-hand picture shows the borderland between 

 two of the principal waria or grey plains— the Mare 

 Tranquillitatis and the Mare Serenitatis — and shows a 

 countiy mostly open, and but little diversified or broken 

 up. i'he one on the right hand, on the contrary, is taken 

 from far within the great disturbed region of the Moon 

 which has its centre in Nasireddin, a region strewn with 

 crater-pits and full of overlapping and interlaced forma- 

 tions. 



The object occupying the centre of the first picture is 



