102 



KNOWLEDGE. 



March, 1911. 



and scattered by small particles in the air — or according to 

 Lord Rayleigh, by the molecules of the air itself — than the red 

 rays with greater wave-length : and the light which reaches the 

 eclipsed moon has passed through a depth of air about twice 

 as great as that through which the light from a setting sun has 

 passed. 



The very great differences in the brightness of the eclipsed 

 moon on different occasions is very curious, and though clouds 

 over large surfaces on the earth might well cause considerable 

 differences in the light, it seems hardly sufficient to account 

 for it entirely. I H r 



.A.RTli'ICI.\L MOCK SL'XS. 

 To the Editors of " Knowledge." 



Sirs. — .-^t the end of November I had a view of four mock 

 suns, and glimpses of five others, all, however, produced by a 

 chance arrangement of windows. 1 was seated in a train 

 tra\elling west along the north shore of the Lake of Geneva : 

 it was between 2. JO and 3 p.m.. and the low sun shone straight 

 into the carriage. 



There were three panes of glass between me and the outer 

 air — viz.: (a) the glass window of the carriage; (61 the glass 

 window of the corridor, distant about two-and-a-half feet 

 from dr) : and. between these (cl the window of the carriage 

 door, which, being open and folded back, was about an inch 

 distant from [a). On either side of the sun, and distant about 

 five degrees, there appeared fainter, but still very bright, sun- 

 images. Beyond each of these again, at the same distance, 

 were faint sun-images. When the carriage was slightly tilted 

 on a curve, fainter images were seen above each of these five 

 suns, ten suns in all. The phenomenon was not visible from 

 the corridor, and was pretty clearly caused by a reflection 

 between the near panes ((7) and (c). How far is this analogous 



to the mock suns of Polar explorers ■ , ,, .. r-r- t-i>i- 



^ AGNLS FK\. 



THK ETERNAL RETURN. 



To flic Editors of " Knovvlkdgh." 



Sirs. — In reply to your correspondent. Mr. H. D. Barclay. 

 re the theory of Nietzche. I would suggest that much depends 

 upon the meaning attached to the words "identical individual." 

 ( )ur identity consists of the consciousness of the continuation 

 of our psychic reality, notwithstanding repeated entire material 

 changes and replacings of our bodily organism. The inde- 

 structibility of the material constituting the organism is a 

 possible conception, as also its adaptability to new combina- 

 tions : but to assume that a re-combination of the precisely 

 same elements will constitute the same being, is to assume 

 that the identical psychical entity is not only dependent 

 upon, but is ahsolutelv produced by, that particular 

 combination. 



This is to grant eternity to matter, but to make the actual 

 existence of mental phenomena subject to creation and 

 destruction. .Again, many misleading words .are used in 

 reference to force. To speak of the " sum total of force " is 

 to give it "reality," to constitute it a tangible entity, having 

 dimensions and duration, a power real and potent to move 

 inert matter. But we know of no such force. "Matter and its 

 activities" is the limit of physical science, force is the name 

 of those activities. To give it occupation in space is to create 

 it matter; "to pervade infinite space" is to exclude the 

 possibility of other existence. 



Mr. Barclay, I venture to think, is right in affirming that 

 absolute vacant space seems unthinkable, though this may be 

 so "in the absolute." Vacant space is not only thinkable, but 

 an essential concomitant to material existence. 



May we have better elucidations of this most interesting 



subject from more cap.able pens ? 



FRED OILMAN. 



.S()L.\R I)I,STrRr..ANCES DlIRIi\(i J.XNUARY, 1911. 

 By FRANK C. DENNETT. 



Thk great tailing ott in the number of outbreaks upon the 

 solar surface was very marked during January. With the 

 exception of the five days, the 4th, 5th, 17th, 21st and the 

 22nd. the sun has been examined every day. Upon the 19th, 

 20th, 25th, 27th and the 2Sth no trace of disturbance, bright 

 or dark, could be found. On ten other dates faculae alone 

 were to be seen. The longitude of the Central Meridian at 

 noon on January the 1st was 294" 30'. 



No. 1. — \ spot first seen near the east limb on January the 

 3rd. There appeared to be two umbrae on the 7th, the larger 

 being again cut across by a bright bridge ; two pores were 

 situated just behind it. One pore still there on the 8th, and 

 the umbra bridged. On the 10th the bridged umbra seemed 

 of a violet hue, and the filamented penumbra appeared to 

 brighten inwards. The bright fringe, especially on equatorial 

 side, still seen, as well as the bridging, on the 13th and the 

 14th, when the spot was evidently dwindling. On the 15th. 

 when last seen, still bridged, the umbra seemed to be edged 

 with brightness, but a penumbral wing stretched south-east. 

 The greatest diameter of the spot was 15,000 miles. As it 



neared the western limb it became surrounded by faculae. 



.\ group of faculae. A, like a companion outbreak to No. 1, 

 seen on the 14th. 



B and C. faculic ridges seen on the 14th-15th round the 

 eastern limb, the latter seen again the 2 5th-26th, when 

 approaching the western limb. 



D. a small bright taenia near the western limb on the 25th. 



Near the eastern limb on the 25th a bright ridge, E, recorded. 



A small faculic knot in a disturbed area, F, seen on the 31st. 



This great falling oft' in the number of outbreaks seems to 

 indicate that we are approaching the time of solar minimum. 

 As one cycle ends the spots are as a whole nearer to the 

 equator. The new cycle is usually indicated by the outbreak 

 of spots far away from the equator, so that it is necessary to 

 watch the outer boundaries of the spot-zones. It seems 

 probable that the signs of returning activity may be noted in 

 the northern zone. 



The chart is constructed from the combined observations of 

 Messrs. J. McHarg, A. A. Buss, E. E. Peacock, W. Strachan, 

 and F. C. Dennett. 



DAY OF lANUARY. 



10 20 50 40 50 60 



90 100 110 \}0 150 140 150 160 irO ISO 190 :00 ?I0 2J0 230 J40 250 260 270 280 2=10 .300 310 320 iW W> -"SO 360 



