STAR-GROUPING, STAR-DRIFT, AND STAR-MIST. 143 



It is necessary to premise, however, that before the ex- 

 periment was tried, there were reasons for feeling very 

 doubtful whether it would succeed. A system of stars 

 might really be drifting athwart the heavens, and yet the 

 drift might be rendered unrecognizable through the intermix- 

 ture of more distant or nearer systems having motions of 

 another sort and seen accidentally in the same general 

 direction. 



This was found to be the case, indeed, in several 

 instances. Thus the stars in the constellation Ursa Major, 

 and neighbouring stars in Draco, exhibit two well-marked 

 directions of drift. The stars /?, y, 8, e, and of the Great 

 Bear, besides two companions of the last-named star, are 

 travelling in one direction, with equal velocity, and clearly 

 form one system. The remaining stars in the neighbourhood 

 are travelling in a direction almost exactly the reverse. But 

 even this relation, thus recognized in a region of diverse 

 motions, is full of interest. Baron Madler, the well-known 

 German astronomer, recognizing the community of motion 

 between Ursae and its companions, calculated the cyclic 

 revolution of the system to be certainly not less than 7000 

 years. But when the complete system of stars showing this 

 motion is considered, we get a cyclic period so enormous, 

 that not only the life of man, but the life of the human race, 

 the existence of our earth, nay, even the existence of the 

 solar system, must be regarded as a mere day in comparison 

 with that tremendous cycle. 



Then there are other instances of star-drift where, though 

 two directions of motion are not intermixed, the drifting 

 nature of the motion is not at once recognized, because 

 of the various distances at which the associated stars lie 

 from the eye. 



A case of this kind is to be met with in the stars 

 forming the constellation Taurus. It was here that Madler 

 recognized a community of motion among the stars, but he 

 did not interpret this as I do. He had formed the idea 

 that the whole of the sidereal system must be in motion 



