The Birmingham age-herald., 1905-12-03
Drennen & Company

judged from Homer's Hymn to Castor and Pollux:"
 "when wintery tempests OCT the savage
 sea
 Are raging. and the sailors tremblingly
 Call on the twins of love With prayer
 and VOW,
 Gathered in fear upon the lofty prov,
 Even then they suddenly appear,
 Fair omen of the voyage; from toll and
 dread
 The sailors rest rejoicing in the sight
 And plough the quiet sea in safe delight
 The star to the north, at A, Fig. l. Is
 called Castor, and the one to the south is Pollux.
 The stars marked c, D. E and F, are
 beautiful doubles, all of them except the
 one at E being visible even in quite small telescope. But the most interest," ing of all the doubles in this constella- ton Is the bright star Castor itself. This has long been known to be beautlfui double star, the components feVolvlhg slowly about one another In a period or about 900 years Quite recently. however, is was discovered by the spectroscope that these components which make up Castor are themselves double, though Tar too close together to be ever seen wis., uallv. the whole forming of the appar- ently single star magnificent quadrupie system of suns. The distance apart or the two suns which we see when we turn the telescope on Castor Is more than loo times as great as the distance from the earth to the sun. That is, these two I suns are more than thousand Hlliiioh
 miles apart, and yet they are so m i fnitely far away that to the naked eye they are indistinguishable and appear as one single star.
 How astronomers measure the distances of the stars. IL. Fig shows the great telescope or the yerkes Observatory of the university or Chicago, the largest effective telescope Ill the world. The end through which the oo- server looks is, of couse, at A. When the taIosoona Id nointed to the sky this end
 nav he 30 or 40 feet above the floor, put hv small motor the entire floor Is lifted nm with the observer on it, until he IS as mar the end of the great tube as may be desired. .u
 The observer then finds that the small CT end of the telescope looks as snowm ! in Fig. 8. Applying his eye to the shlan hold at B he would see, 1T the .eieseops .,l,. were pointed at a high star not only this
 S.,.ss. star itself. but a number of very
 faint stars. also which are far too rant to ha seen with the naked eye. besiue l these. he will notice two me stra'en. lines the whole looking, perhaps' aS shown in Fig 5. ,,.., ,,a.r
 Tshs two fine lines are two little spider l threads which are lit up at night oy 'ho i,,tle lamp at L. Fig 4. One Of these ines can he moved back and forth over the eoId of view by turning the very hhe .orev of which the end Is at 5, TIE. s' | inc number of turns of the screw, "non .l arc made in moving the tnreau run star to star being shown by the sraou- ated head at H. .,4 tba dis- In Fig. 5, 1t is supposed ,nA. !. I tance from the star U 10 ,no ..,,ont Sa,rg measured. The whole instruneii.
 pei.,s ad ,,ntil the wires are perpendic- ! .s ..,.u to tsa line joining c and A ana the ..o, of turns of the screw necessary ~ ,,,ove one of the threads from to ~ ,s then found. In this way IL IS eVi- s.rt that the exact position or In reier- | as to all the little faint stars III the | vicinity can be measured" | yt ,nav he that If theue measures are ,ont,nued from month to month II VIII | Ss sound that c does not stay always III .as same position In reference 10 the l sn..,. stars If the various measured posi- | .snas og q are drawn on a map tf1g. o) IL o, he found that in moving aoout m i,,t,e elliptical path, starting al M l ,n,ne N three months later, ana then ,n tweive months coming back to M | ,,r We then know that c Is really not
 nootion at all: 1t is only displaced haonward and forward on the sky be- cause we ourselves are moving arouho | tha sun in a great circle, lS6 miiiloh miies In diameter In exactly the same way messenger on train may see the nearby l frees and houses apparently rusn past . distant range of hills or mountains, d.