MOTIONS OF THE STARS. 543 



more delicate means of dealing with the matter. The rainbow-tinted 

 streak forming a star's spectrum is crossed by known dark lines ; and 

 these serve as veritable mile-marks for the spectroscopist. If one of 

 these lines in the spectrum of any star is seen to be shifted toward the 

 red end, the observer knows that the star is receding, and that swiftly ; 

 if the shift is toward the violet end, he knows that the star is swiftly 

 approaching 



Now, Dr. Huggins had been able nearly four years ago to apply 

 this method to the case of the bright star Sirius, though his instru- 

 mental means were not then sufficient to render him quite certain as to 

 the result. Still he was able to announce with some degree of con- 

 fidence that Sirius is receding at a rate exceeding 20 miles per second. 

 In order that he might extend the method to other stars, the Royal 

 Society placed at his disposal a fine telescope, 15 inches in aperture, and 

 specially adapted to gather as much light as possible with that aperture. 

 Suitable spectroscopic appliances were also provided for the delicate 

 work Dr. Huggins was to undertake. It was but last winter that the 

 instrument was ready for work ; but already Dr. Huggins has obtained 

 the most wonderful news from the stars with its aid. He finds that 

 many of the stars are travelling far more swiftly than had been sup- 

 posed. Arcturus, for example, is travelling toward us at the rate of 

 some 50 miles per second, and, as his thwart-motion is fully as great 

 (for this star's distance has been estimated), the actual velocity with 

 which he is speeding through space cannot be less than 70 miles per 

 second. Other stars are moving with corresponding velocities. 



But, amid the motions thus detected, Dr. Huggins has traced the 

 signs of law. First he can trace a tendency among the stars in one part 

 of the heavens to approach the earth, while the stars in the opposite 

 part of the heavens are receding from us ; and the stars which are ap- 

 proaching lie on that side of the heavens toward which Herschel long 

 since taught us that the sun is travelling. But there are stars not 

 obeying this simple law; and among these Dr. Huggins recognizes 

 instances of that community of motion to which a modern student of 

 the stars has given the name of star-drift. It happens, indeed, that one 

 of the most remarkable of these instances relates to five well-known 

 stars, which had been particularly pointed to as forming a drifting set. It 

 had been asserted more than two years ago that certain five stars of the 

 Plough or Charles's Wain the stars known to astronomers as Beta, 

 Gamma, Delta, Epsilon, and Zeta, of the Great Bear are drifting bod- 

 ily through space. The announcement seemed to many very daring, 

 yet its author (trusting in the mathematical analysis of the evidence) 

 expressed unquestioning confidence ; he asserted, moreover, that when- 

 ever Dr. Huggins applied the new method of research, he would find 

 that those five stars are either all approaching or all receding, and at the 

 same rate, from the earth. The result has justified his confidence as well 

 in his theory as in Dr. Huggins's mastery of the new method. Those 



