19S 



KNOWLEDGE 



[October 2. 1898. 



frequently measured of any star, is about 7 to 7i light 

 years off. But let us take our nearest neighbour and try 

 to see something of the isolation of our solar system in 

 space. Let us try to conceive of a sphere of which the 

 sun is centre with a radius of 4-35 light years, so placing 

 our nearest stellar neighbour on its circumference — trans- 

 lated into the more familiar unit its diameter is over fifty 

 billion miles and its cubic contents nearly three hundred 

 and fifty cubic light years, or seventy thousand sextillions 

 (7 with 40 ciphers) of cubic miles, for a cubic light year 

 is rather more than two hundred sextillions cubic miles. 

 Here is isolation indeed ! The sun, with all its vastness, 

 does not fill one two hundred thousand trilliontb (2 with 

 23 ciphers) part of the sphere that has our nearest stellar 

 neighbour on its surface ; the gigantic volume of the sun 

 in such a space is like an isolated shot containing but 

 one half of a cubic inch immersed in the whole water of 

 the sea,* while a Uttle speck less than the two millionth 

 of a cubic inch suspended in the three hundred and 

 seventy-three trillion gallons of the sea would represent 

 the earth suspended in the sphere, the radius of which 

 reaches only to the nearest star. 



Did we set the Pole star at the limits of our space 

 sphere, the volume of the sphere would be three thousand 

 times as great ; and the sun must be thought of as 

 occupying the six thousandth part of an inch in the four 

 hundred milUon cubic miles of sea. 



Were Vega, at a distance of ninety-six light years, on 

 the boimdary of our sphere, the space that reaches to our 

 nearest neighbour must be increased ten thousand times in 

 volume, and the earth becomes a difficult microscopic 

 object in the vast abyss of sea. These are all stars whose 

 distance has been measured with more or less accuracy, 

 but there are other objects more remote that have defied 

 all attempts to measure them — in literal fact, they are 

 iiiinuanuralilij remote distances. 



Whether we are to reckon the number of their light 

 years by centuries only, by thousands or by millions, it is 

 premature to guess. One thing at least is clear ; the 

 figures given here to show the position of the earth in 

 space are wholly paltry and inadequate compared with the 

 (as yet) unknown reality. Much has been learnt and the 

 way prepared for yet greater advances. Man has de- 

 throned himself from the chief position in the universe ; 

 has seen his world cease to be the centre round which all 

 else revolves ; has recognized his abode as the tiniest 

 imaginable speck In space ; man — 



" Who sounds wiUi a tiny plummet, who scans with a purblind eye, 

 The deptlis of that fathomless ocean, the wastes of that limitless sky " 



— yet has a longing to penetrate still farther through the 

 star depths to win yet other secrets from the mysteries of 

 space. 



Though thus enlarging his horizon, he sees the earth 

 sink into insignificance more and more, yet relatively to 

 himself it becomes more important ; it is part of a larger 

 whole, and it must supply him with the key to unlock the 

 secrets of the universe elsewhere. It is the starting-point 

 for the survey that has revealed so much, that will reveal 

 still more, but ever as the boundary of the known extends, 

 it is encompassed by an unknown that is extended too. 

 However vast in space or time the knowable becomes, the 

 unknowable is vaster still ; the man whose horizon is 

 widest, whose knowledge is most profound, knows best and 

 feels most reverently that, however much we learn, there 

 remains a mystery beyond, surrounding all. 



• I have 8bo^^l, in an article published in Lon(jmatCs Mat^uzine 

 for June, 1893, that all the water of the sea, eolleetcd into a sphere, 

 would fill a space about uiue hundred miles in diameter. 



THE FACE OF THE SKY FOR OCTOBER. 



By Herbert Sadler, P.E.A.S. 



AT the time of writing, a very fine group of spots is 

 visible on the Sun. There is an annular eclipse 

 of the Sun on the 9th, but it is invisible at 

 Greenwich, and the path of the annulus lies 

 almost wholly across the Pacific Ocean ; it there- 

 fore needs no further notice. Conveniently observable 

 minima of Algol occur at lOh. 23tn. p.m. on the IGth, and 

 7h. 12m. P.M. on the 19th. 



Mercury is too near the Sun during the month to be 

 visible. Venus is an evening star, but, owing to her great 

 southern declination, is very badly situated for observation. 

 On the 1st she sets at 6h. 41m. p.m., or Ih. 4m. after the 

 Sun, with a southern declination of 18° 5', and an apparent 

 diameter of 14|", about fths of the disc being illuminated. 

 On the 15th she sets at 6h. 27m. p.m., or Ih. 22m. after 

 the Sun, with a southern declination of 22° 47', and an 

 apparent diameter of IG", -ri/oths of the disc being 

 illuminated. On the 31st she sets at 6h. 23m. p.m., or Ih. 

 49m. after the Sun, with a southern declination of 25° 49', 

 and an apparent diameter of 17^", y^b'^'^s o^ ^^^ '^'^'^ 

 being illuminated. During the month she passes from 

 Libra through Scorpio into Ophiuchus, being very near 

 S Scorpii on the evening of the 12th. 



Mars is, for the purposes of the amateur observer, 

 invisible. 



Jupiter is an evening star, and is admirably situated for 

 observation. He rises on the 1st at 7h. 24m. p.m., or 

 111. 44m. after sunset, with a northern declination of 

 19° 20', and an apparent equatorial diameter of 45". On the 

 15th he rises at 6h. 26m. p.m., or Ih. 21m. after sunset, with 

 a northern declination of 19° 8', and an apparent equatorial 

 diameter of 465". On the 31st he rises at 6h. 20m. p.m., or 

 three-quarters of an hour after sunset, with a northern 

 declination of 18° 47', and an apparent equatorial diameter 

 of 48". During the month he describes a short retrograde 

 path in Taurus, to the south-west of the Pleiades. The 

 following phenomena of the satellites occur while the 

 planet is more than 8° above and the Sun 8° below the 

 horizon : — On the 1st a transit egress of the first satellite at 

 3h. 53m. P.M. On the 4tli a transit ingress of the shadow of 

 the second satellite at lOh. 4m. p.m. On the 5th a transit 

 ingress of the first satellite at Oh. 9m. a.m. ; a transit egress 

 of the shadow of the satellite at Oh. 24rQ. a.m. ; and a transit 

 egress of the satellite itself at 2h. 24m. a.m. On the Gth 

 an eclipse disappearance of the third satellite at Ih. 7m. 15s. 

 A.M. ; its reappearance at 2h. 3Gm. 48s. a.m. ; an eclipse 

 disappearance of the first satellite at 3h. 43m. SOs. a.m. ; 

 an occultation disappearance of the third satellite at 

 5b. 20m. A.M. ; an occultation reappearance of the second 

 satellite at 9h. 26m. p.m. On the 7th a transit ingress of 

 the shadow of the first satellite at Ih. 2m. a.m. ; a transit 

 ingress of the satellite itself at 2h. 2m. a.m. ; a transit 

 egress of its shadow at 3h. 14m. a.m., and of the satellite 

 itself at 4h. 13m. a.m. ; an eclipse disappearance of the 

 first satellite at lOh. 12m. 20s. p.m. On the 8th an 

 occultation reappearance of the first satellite at Ih. 20m. 

 p.m. ; a transit ingress of the first satellite at 8h. 28m. p.m. ; 

 a transit egress of its shadow at 9h. 42m. p.m., and a transit 

 egress of the satellite at lOh. 39m. p.m. On the 9th a 

 transit egress of the third satellite at 8h. 30m. p.m. On 

 the 12th a transit ingress of the shadow of the second 

 satellite at Oh. 40in. a.m. ; a transit ingress of the satellite 

 itself at 2h. 30m. a.m. ; a transit egress of its shadow at 

 3h. Om. A.M., and of the satellite at 4h. 45m. a.m. On the 

 13th an eclipse disappearance of the third satellite at 

 5h. 7m. 10s. a.m. ; an eclipse disappearance of the second 



