294 THE POPULAR SCIENCE MONTHLY, 



present positions as far as they were moved forward in our second 

 diagram. The result is a figure having no resemblance to either of 

 the others. It is a sort of cross, with Beta at the point of intersec- 

 tion, Alpha marking the extremity of the left arm, and Gamma that 

 of the right ; Beta the top, Epsilon, Zeta, and Eta, the stem. Eta 

 was, properly speaking, not yet in association with the other six. 

 For the rest, on analyzing the movement of these stars, we see that 

 five of them, Beta, Gamma, Delta, Epsilon, and Zeta, are associated 

 together by a common tie. They are a group of friends : they move 

 on with one accord, and, as will be seen, maintain the same relative 

 position to one another. Alpha and Eta are only intruders, and, 

 though they happen just at present to be with the group, they really 

 have nothing to do with it. Look at Fig. 2 : Alpha, which is ever 



Fig. 3. 



Ursa Major 100,000 Years ago. 



moving toward the right, will, in time, quit the group for good. On 

 the other hand, Fig. 3 shows Eta coming in on the left ; previously 

 that star had no relation at all to the five. 



The remarks just made with regard to the secular transformation 

 of Ursa Major might be applied to all the other constellations. We 

 have selected that one, because it is the best known of all, and one of 

 the most characteristic. To sum up : we find that a knowledge of the 

 proper movements of the stars completely transforms our common 

 notions about the fixity of the heavens. The stars move in all direc- 

 tions through the endless realms of space, and as the aspect of the 

 heavens changes, so does the constitution of the universe also change 

 from age to age, undergoing innumerable metamorphoses. — Revue 

 Scientifique* 



