216 G. H. KNIBBS. 



proper motion of the sun from that of the stars, and shews that 

 the evidence of its reality is very cogent. 1 



(129) Defects in Bibliography of subject. — Although no known 

 accessible source of information has been neglected, it has not 

 been possible to make the bibliographical record here attempted 

 — extensive as it is — complete. It is very likely that some dis- 

 cussions of the precessional constant, containing investigations of 

 the solar motion, may have been overlooked, despite the care taken 

 in regard thereto. As an exhaustive determination of this con- 

 stant, demands the eliminination of the motus parallacticus from 

 the proper motion of each star, so that the motus peculiares, affect- 

 ing as they do the value of the constant, may be determined in 

 accordance with the law of probability, particular attention has 

 been paid to all memoirs treating of precession. In some instances 

 I have been unable, however, to obtain copies of the memoir, e.g. 

 Dreyer's, "New determination of the constant of precession.' 2 

 Radau's 3 and Bakhuyzen's 4 articles in the Bulletin Astronomique 

 which also touch on the solar motion, I have likewise failed to 

 obtain. In cases where there was great doubt as to how and when a 

 writer treated of the subject under consideration, I have omitted 

 all reference to him. For example, Villarceau states that Briinnow 

 treats of the theory of aberration, taking account of motion of the 

 solar system. Whether this however was in the earliest edition 

 of his spherical astronomy 5 or not, I cannot ascertain. 



Works treating of the solar motion, of the same type as August 

 Tischner's "Die Richtung der Sonnebewegung," Giralomo Mar- 

 zocchi's "II sole e l'universo,"and William Sandeman's "The Path 

 of the Sun . . . with an exposure of the fallacy of the precession 

 of the equinoxes," I have not troubled to note, for reasons which 

 hardly need explanation. 



1 See also, Nature, Vol. in., p. 487, 1895. 



2 Proc. Eoy. Irish Acad.. 3, 1883, pp. 61V - 623 and Copernicus, 2, 1882, 

 pp. 135-155. 



3 Op. cit. s t. x., p. 407. 4 Ibid., t. xn., p. 97. 



5 Lehrbuck der spharischen Astronomie, Berlin, 1851, 8vo. 



