SECT. XXXVI. PROPER MOTIONS OF THE STARS. 405 



ally, and 61 Cygni describes a line in space of 5"'12 in the same 

 time. These motions are probably in curves, but at the distance 

 of the earth they will appear to be rectilineal for ages to come. 

 The motion of little more than five seconds of space, which 61 

 Cygni describes annually, seems to us to be extremely small ; 

 but at the distance of that star an angle of one second corresponds 

 to twenty-four millions of millions of miles ; consequently the 

 annual motion of 61 Cygni is 120 millions of millions of miles, 

 and yet, as M. Arago observes, we call it a fixed star. From the 

 same cause it is evident that the crowding of the stars in the 

 Milky Way may be apparent only, and that the stars may be at 

 vast distances from one another, and no doubt are. 



Were the solar system and the whole of the stars visible to 

 us carried forward in space by a motion common to all, like ships 

 drifting in a current, it would be -impossible for us, moving with 

 the rest, to ascertain its direction. Sir William Herschel per- 

 ceived that a great part of the motions of the stars is only 

 apparent, arising from a real motion of the sun in a contrary 

 direction. Among many discrepancies he found that the stars in 

 the northern hemisphere have a general tendency to move towards 

 a point diametrically opposite to x Herculis, which he attributed 

 to a motion of the solar system in a contrary direction. For it 

 was evident to him, that the stars, from the effects of perspective 

 alone, would seem to diverge in the direction to which the solar 

 system was going, and would converge towards the space it had 

 left, and that there would be a regularity in these apparent 

 motions which would hereafter be detected. Since Sir William 

 Herschel's time the proper motions of the stars have been deter- 

 mined with much greater accuracy, and many have been added 

 to the list by comparing the ancient and modern tables of their 

 places ; his views have been established by four of the greatest 

 astronomers of the age, MM. Lundahles, Argelander, Otto 

 Struve, and Peters, who have clearly proved the motion of the 

 sun from that of the stars in the northern hemisphere, and Mr. 

 Galloway has come to the same conclusion from the motions of 

 the stars in the southern hemisphere (N. 234). The result is, 

 that the sun, accompanied by all his attendant planets, is moving 

 at the rate of 422,424 miles or over a space nearly equal to his 

 own diameter in the course of a day, and that the motion is 



