DISTANCES OF THE STARS. 425 



from us — at the horizon of the heavens, so to speak — and our base- 

 line of 184,000,000 miles is as nothing in comparison with this remote- 

 ness. But if it is displaced, then we know that it annually describes 

 a small ellipse, corresponding to the annual revolution of the earth. 

 Every one has remarked, while traveling by rail, how the trees and 

 other objects near at hand move in a direction contrary to our own, 

 their speed being greater in proportion to their nearness ; whereas 

 distant objects on the horizon remain fixed. This same effect is pro- 

 duced in space, in consequence of our annual motion round the sun. 

 But though we move incomparably swifter than an express-train, our 

 rate being 1,632,000 miles per day, and 68,000 per hour, the stars are 

 so distant that they scarcely budge. Our 184,000,000 miles of dis- 

 placement are almost nothing as concerns even the nearest of them. 

 The inhabitants of Jupiter, Saturn, Uranus, or Neptune, with their 

 orbits five, nine, nineteen, and thirty times as large as ours, could de- 

 termine the distance of a far greater number of stars than we. 



This mode of measuring the distance of the stars by the perspec- 

 tive effect produced by the earth's annual displacement w^as antici- 

 pated by the astronomers of the eighteenth century, and in particular 

 by Bradley, who, while attempting to measure the distances of the 

 stars by comparing together observations made at an interval of six 

 months, discovered — something else. Instead of finding the distance 

 of the stars on which his observations were directed, he discovered a 

 very important optical phenomenon, viz., the aberration of liykt^ the 

 effect produced by the motion of light and the motion of the earth 

 combined. Similarly, William Herschel, wiiile seeking the parallaxes 

 of the stars by comparing bright stars with their nearest neighbors, 

 discovered the systems of double- stars. So, to*o, Fraunhofer, while 

 seeking the limits of the colors in the solar spectrum, discovered the 

 absorption rays, the study of w^hich has given rise to spectrum Analy- 

 sis. The history of the sciences shows that frequently discoveries 

 have been made in the course of investigations which had but little 

 to do with them directly. Columbus discovered the New World while 

 aiming to reach the eastern coast of Asia by sailing to the west. He 

 would never have discovered it, would never have sought for it, had 

 he known the true distance between Portugal and Kamtchatka. 



It was not till 1840 that the distance of any of the 'stars was as- 

 certained. This discovery is, therefore, of recent date, and we are 

 only now beginning to form an approximate idea of the real distances 

 which separate us from the stars. The parallax of the star 61 in the 

 Swan, which was the first to be determined, w^as ascertained by Bes- 

 sel, and was the result of observations made at Konigsberg from 

 1837 to 1840. In 1812, Arago and Mathieu had made observations 

 on this star, but without reaching any certain results. The parallax 

 of Alpha in the Lyre was found by Struve, in the course of observa- 

 tions made at Dorpat betw^een 1835 and 1838 ; but it was not pub- 



