SECTION IV. 



MOTION OF THE SUN AND FIXED STARS. 



To common observation, the fixed stars retain sensibly 

 the same relative position from age to age ; but the ex- 

 act observations of modern astronomy have detected a 

 relative motion in a large number of them. A small star 

 in the leg of the Great Bear (called 1830 Groombridge) 

 has an annual motion of seven seconds of arc as compared 

 with neighboring stars ; and, there are more than thirty 

 stars known, whose annual proper motion exceeds one 

 second. It might have been expected, a priori, that mo- 

 tion of some kind must exist among such a multitude of 

 objects all subject to mutual attraction; and it appears 

 highly probable, not to say certain, that the sun must 

 participate in this movement. The effect of a motion 

 of the sun, with reference to the stars, would be an ap- 

 parent divergence or separation of those stars toward 

 which we were moving, and an apparent convergence or 

 closing up of the stars in the region which we were leav- 

 ing. We might therefore expect to detect such a motion, 

 if it really exists, by comparing the proper motions of all 

 the stars in the firmament. In accordance with this idea, 

 Sir William Herschel, in 1783, by a comparison of the 



