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Show 6 THE BOPIES OF SPACE. the experiment has been tried, no se~sible parallax could be detected· from which the same Inference was to be rnade in th~ir case. But a sensible parrallax of about one second has been ascertained in the case of the double star, a a, of the constellation of the Centaur,* and one ?f the third of that amount for the double star, 61 Cygni; which gave reason to presume that the ~is.tance of. the former might be about twenty thousand millions of miles, and the latter of much greater amount. If we suppose that similar intervals exist between all the stars V{e shall readily see that the space occupied by even the con1paratively small nutnber visible to the naked eye must be vast beyond all powers of conception. The number visible to the eye is about three thousand; but when a telescope of small power is directed to the heavens, a great number more com~ into vie'"·' and the number is ever increased in proportion to the Increased power of the instrument. In pne pl~ce, ~~ere they are more thickly sewn than elsewhere, Sir Wilham Herschel reckoned that fifty thousand passed over a field of view two degrees in breadth in a single hour. It was first surmised by the ancient philosopher, Democritus, that the faintly white zone which spans the sky under the.name of the Milky Way, might be only a dense collection of stars too remote to be distinguished. This conjecture has been verified by the instruments of modern astronomers, and some speculations of a most remarkable kind have been formed in connexion with it. By the joint labors of the two Herschels, the sky has been " gauged" in all directions by the telescope, so as to ascertain the conditions of different parts with respect to the frequency of the stars. The result has been a conviction that, as the planets are parts of the solar systems, so are solar s~stems parts of what may be called astral systems-that Is, s:vstems composed of a multitude of stars, bearing a c.ertain relation to each other. The astral system to which we belong, is conceived to be of an oblong, flattish form, with a space wholly or comparatively vacant, in the «?entre while the extremity to one direction, parts into tw?. The stars are most thickly sown in the outer parts of th1s vast ring, and these constitute the Milky Way. Our sun is- believed to be placed in the southern portion of the • By Mr. Henderson, Professor of Astronomy in "he Edinbur#{b U iliversity, and Liet:teuant Meadows. • '!"HEIR ARRANGEMENTS AND FORl\fATIO:tt. r1ng, near its inner edge, so that we are prescr!ted with many more stars, and see the Milky Way much more clearly in tb at direction, than to\vards the north in which line our eye has to traverse the vacant ce~tral space. Nor is this all.. Sii: "\Villiam I-Ierschel, ~o curly as 1783, detected a motwn In our solar system wjth respect to the stars, and announced that ]twas tendinv towards the 3tar A, in the constellation Hercules. Thf has be~n ge*nera~ly verified by recent and mor exact calcuJatwns, whiCh fix on a point in Hercules, near the star 143 of the 17th ~uur, according to Piozzi's catalogue, as that towar~s which our. sun is proceeding. It i. th ·refore, .rec~d1ng from the Inner edge of the ring. .1\Iotions of thi.s kmd, th_rough such vast regions of pace, mu t be long In producing any changes sensible to the inhabitants of our planet, and it is not easy to grasp their general charac~er; but grounds have nevertheles been found for supposing that not only our sun, but the othe~ sun of the . system, purs~e a wavy course round the ring from. we t lf! east, crossing and recrossing the middle of the annular c~rcle .. " Some st~rs w~ll depart more, others less, from either Side of ~he cu:cumference of equilibrium, according to th~ _pla~es Jn which the~ are ~ituated, and according to the ~uection and t~e velocity ·wtth which they are put in motion. Our. sun Is probably one of tho e which d art fu!tt1h.est hfrom.It, and descend furthest into the empty p~'lce WI un t· e r 1 ng. "t A ccord I· ng t o th · . ~ ' 1 view, a time may ctome when we shall be much more in the thick of the s ars of our astral system than we are now anrl have ot ~~u:se much more brilliant nocturnal skies; but it may addcodnntlesls adges before the eyes which are to see this e resp en ence shall exist. besT'dh e evidence .o f th e ex.1 ·s t ence of other astral systems I. es ou,r own Is much more decided than might be e ~ ~=~~~db.~:~~~e~e consid~r that. the nearest of them mu t The eld~/ Her<;l at a . mig~ty I~terval beyond our own. the ~,;d· . 1 ~chel, duecting his wonderful tube to,vards • " ~l o our S'-·~tem Wl1 • t . rarely u d · · J1" ' ei e s ai s are plan ted mo t ' . . raising t le powers of the instrument to the • Made b .l\1 at Abo. y Argelander, late director of the Obser""rttory t ProiL~or Mossotti o th C . . of which the Sun for~s ~ e tonshtutton of the Sidereal Sy t M Philosophical Magazine Febprar .-Londtm, Edinburgh, and Du~li~ ' uary, 1843. |