October 1, 1900.] 



KNOWLEDGE, 



229 



how solid or rugged its substance may be, it is no great 

 stretch of imagination to suppose that the solar beams, 

 impinging on tlie i-uggcd surface of the moon, will be 

 broken up and dispersed in all directions, as the sea 

 waves arc broken up and scatt-ered in foam when they 

 dash against a rock-bound shore. This theory is not 

 confuted, as may seem at lirst sight, by the appearance 

 of the moon's dark bodj- moving across the luminous 

 area. We take it for granted that the rays of the sun 

 in course of an eclipse are at all times focussed upon a 

 given point of the moon's sphere, that point being in a 

 direct lino between the eye of the observer and the 

 centre of the sun, and that said rays are dispersed 

 within a given area describing a circle. Now, as the 

 central point of the moon's sphere approaches coinci- 

 dence with the central point of the solar orb, the in- 

 creasing diameter of the moon will encroach on the 

 circle of visible dispersion, and seem to pass across the 

 face of the illuminated area. The extent of this 

 luminous circle of dispersed light will vary — to the 

 observer— and might be expected to increase in bril- 

 liance and in area in proportion to the decrease of 

 direct light from the sun, until when complete coin- 

 cidence takes jjlace and darkness lies over the land a 

 more or less concentric ring of light will result, extend- 

 ing far beyond the borders of the moon. 



With reference to the analogy between this phenomenon 

 and the Zodiacal Light it may be obsei-\'ed that before 

 and immediatelv after the sun sinks below the horizon, 

 to a beholder its rays are refracted solely by the earth's 

 atmosphere ; and cloud and sky assume an endless 

 variety of beautiful and evanescent hues ; but as the 

 earth revolves on its axis, the beholder changes his 

 position relative to the direction of the solar rays, 

 which form an ever-widening angle with the observer's 

 line of vision. This being so, is it not just possible 

 that given a certain position for sun, earth, and beholder, 

 the reflected light of earth and atmosphere together 

 are jirojected upwards in the direction of the zenith, 

 and become visible from the observer's standpoint after 

 the darkness is sufficiently dense to show it up ? This 

 earth-shine anyone can see with naked eyes by 

 examining a new moon. A Country Lad. 



Galston, Ayrshire. 



[A friend of oui-s having been shown the anatomy of 

 a caterpillar under a microscope, exclaimed in wonder, 

 " I never knew that a caterpillar had organs ; I always 

 thought it was only skin and squash." There might 

 have been something in " A Country Lad's " suggestion, 

 if either the Corona or the Zodiacal Light were mere 

 shapeless glares of light. A single glance at the actual 

 Corona, or the comparison of a few good photographs, 

 would convince " A Country Lad " that it was no more 

 an amorphous " squash " than a caterpillar is, but that 

 it possessed a real and definite structure ; a structure 

 quite independent of " the i-uggcd surface of the moon." 

 It is a real entity; not a mere diffusion or refraction 

 effect. So the Zodiacal Light, although much less definite, 

 proves by the character of its motion amongst the stars 

 that it too has an actual objective existence. 



[E. Walter Maunder.] 



" THE 100 BEIGHTEST STAES." 



TO THE EDITORS OF KNOWLEDGE. 



SiES, — In the article on the " Hundred Brightest 

 Stars " there are several points I should like to ask 

 about. I will number them. 



L No. 7 is given as '• Rigel (a Ononis) " and No. 11 

 as " a Orionis." If the second "a Orionis " is Betelgeux 

 it is given as " /3 Orionis '' iu my chart. 



2. Sliould not the note en No. 2 road " does not rise " ? 



3. The uote numbered (it! looks as though it belonged 

 to Algol, 68. 



4. In the list there does not seem to ho a sharp line 

 between the magnitudes as given on my little chart. Can 

 you say on what ]ilan or on whose autbcirity these "rough" 

 charts (my own is Philijis' Star Maps) mark the magni- 

 tudes ? L. CUTUBERTSON. 



:?2, Sparsholt iioad, Croiu^h Hill, N., 

 September 12, 1900. 



[1. No. 7, Rigel (a Orionis), is a misprint for /3 Orionis. 

 2. Yes. 



8. 66 is a mistake and should road CiH (Algol). 

 4. The magnitudes shown on po|)ular star m:ips are 

 always more or less unreliable. — J. E. Gore.] 



OCCULTATION OF SATURN ON SEPTEMBER 3. 



TO THE EDITORS OF KNOWLEDGE. 



Sirs, — This phenomenon was witnessed here under the 

 best of atmospheric conditions. I turned a 4-inch 

 Cooke refractor on the moon at Gh. 35m., and with a 

 power of 65 immediately saw Saturn a little east of the 

 dark limb and exceedingly faint. Increasing the power 

 to 235 I calculated the approach of the two bodies, and 

 then the gradual encroachment of the moon's dark 

 periphery upon the W. ansa, the ball, and finally the E 

 ansa. The effect was very picturesque and novel during 

 the 110 seconds over which the disappearance extended. 

 This interval applies to the time elapsing from the first 

 observed flattening of the ring to complete occultation. 



At reappearance the moon was much brighter 

 in the darker sky, and the relative brilliancy of Saturn 

 and the limb of our satellite afl'orded a notable dif- 

 ference. When the outer section of the ring emerged 

 it was only just perceptible, being nearly obliterated 

 by the intensity of the light from objects on the lunar 

 margin. The reappearance of the planet occupied a 

 shorter period than the disappearance, as it emerged at 

 a different angle i-elativcly to the major axis of the rings. 

 When quite free the comparison of tint between the 

 planet and moon was very interesting, the feeble leaden 

 line of Saturn being in striking contrast with the vivid 

 lustre of our satellite. 



As the ball of Saturn was emerging from occultation 

 I looked for a dusky band fringing that part of the 

 moon's edge projected on the planet, but no such 

 appearance could bo discerned. A feature of this kind 

 seems to have been occasionally noticed on Jupiter 

 during occultation of that planet. 



The times of first and last contact of the outer edge 

 of Saturn's ring with the moon were very I'oughly 

 noted by my watch, as 7h. 12Jm. and 8h. 10m. About 

 15 minutes after the I'eappearancc Saturn became dis- 

 tinctly visible to the naked eye near the S.W. limb of 

 the moon. W. F. Denning. 



Bishopston, Bristol, 



1900, September 6th. 



JUPITER. 



TO THE EDITORS OF KNOWLEDGE. 



Sirs, — I regret that in my drawings of Jupiter, pub- 

 lished in the September number of Knowledge, the 

 planet was shown with a circulai' instead of an oblate 



