1870.] On certain Drifting Motions of the Stars. 



169 



mind should treat its ideas, and at every step in the progress of a pro- 

 blem the machine indicates the proper condition of a mind exempt from 

 mistake. 



It is believed that this logical machine may be usefully employed in the 

 logical class-room to exhibit the complete analysis of any argument or 

 logical problem ; and it is superior for this purpose to a more rudimentary 

 contrivance, the logical abacus, constructed by me for the same purpose, 

 and previously described. But by far the chief importance of the machine 

 is in a theoretical point of view as demonstrating, in the simplest and most 

 evident manner, the character and powers of a universal system of logical 

 deduction, of which the first, although obscure solution, was given by 

 Dr. Boole. 



II. " Preliminary Paper on certain Drifting Motions of the Stars." 

 By Richard A. Proctor, B.A., F.R.x\.S. Communicated by 

 Warren De La Rue, V.P.R.S. Received October 26, 1869. 



A careful examination of the proper motions of all the fixed stars in the 

 catalogues published by Messrs. Main and Stone (Memoirs of the Royal 

 Astronomical Society, vols, xxviii. andxxxiii.) has led me to a somewhat in- 

 teresting result. I find that in parts of the heavens the stars exhibit a well- 

 marked tendency to drift in a definite direction. In the catalogues of proper 

 motions, owing to the way in which the stars are arranged, this tendency is 

 masked ; but when the proper motions are indicated in maps, by affixing 

 to each star a small arrow whose length and direction indicate the magni- 

 tude and direction of the star's proper motion, the star-drift (as the phe- 

 nomenon may be termed) becomes very evident. 



It is worthy of notice thatMadler, having been led by certain considera- 

 tions to examine the neighbourhood of the Pleiades for traces of a commu- 

 nity of proper motion, founded on the drift he actually found in Taurus 

 his well-known theory that Alcyone (the lucida of the Pleiades) is the 

 common centre around which the sidereal system is moving. But in 

 reality the community of motion in Taurus is only a single instance, and 

 not the most striking that might be pointed out, of a characteristic which 

 may be recognized in many regions of the heavens. In Gemini and Cancer 

 there is a much more striking drift towards the south-east, the drift in 

 Taurus being towards the south-west. In the constellation Leo there is 

 also a well-marked drift, in this case towards Cancer. 



These particular instances of star-drift are not the less remarkable, that 

 they (the stars) are drifting almost exactly in the direction due to the proper 

 motion which has been assigned to the sun, because the recent researches 

 of the Astronomer Royal have abundantly proved that the apparent proper 

 motions of the stars are not to be recognized as principally due to the sun's 

 motion. Mr. Stone has shown even that we must assign to the stars a 

 larger proper motion, on the average, than that which the sun possesses. 



