THE SUN'S MOTION IN SPACE. 187 



and when the hypothesis of a place for the centre of inertia is 

 introduced from Class IV., the one determination alone is allow- 

 able, viz. R A = 274 .o 2j D . = + 19 . og 



Referring to a modification of Bischof 's solution, Ristenpart pointed 

 out that the result is changed from 



R.A.=290-°8, D.= +43-5 

 to 290-5 42-8 



practically the same result. The epoch throughout is 1850. 



On the basis of Gylden's hypothesis the velocity is about 

 V. = 25*6 kilometres per second, 

 the simple mean of Horaann's results is 28*8 kilometres. Risten- 

 part considered further the relation of the solar motion to the 

 stellar motus peculiaris. He shewed that the P.M. affords a far 

 better criterion of distance than magnitude does. From his 

 analysis it appeared further that the product of the mean P.M. 

 and distance of any class of stars continually increases with 

 increase of distance from the sun : and that the linear motus 

 peculiaris is a function of the stars position in space. 



The following distance relations are given by Ristenpart : — 

 Magnitudes 1234567 8 9 



Pickering '794 1'258 1-994 3160 5*006 7 929 



BOn mus?erun h ff 1,00 ° 1531 2 ' 343 3 ' 583 5 ' 473 8345 12 ' 690 19 " 231 28 ' 967 

 (93) Porter, 1892 (Oct.)— Employing Schonfeld's method 1 and 

 an adaptation of his formulae, Porter deduced the solar motion 

 from the 1,340 proper motions given in No. 12 of the publications 

 of the Cincinnati Observatory. 2 He divided these according to 

 their magnitude into four groups, and obtained the results shewn 

 hereunder : — 



R.A. 



281-9 

 280-7 

 285-2 

 277-0 



Group. 



P.M. 



No. of 

 3tars. 



I. 



< 0-3 



576 



II. 



0-3-0-6 



533 



III. 



0-6-1-2 



142 



IV. 



1-2- <: 



70 



D. 



Annual 

 Motion E. 



+ 53-7 



0\L6 S 



40-1 



0-30 



340 



0-55 



34-9 



1-66 



1900. 



1 Vierteljahrsschrift Astr. Gesell. Bd. xvn., p. 256. 



2 Astr. Journ., Vol. xn., pp. 91 - 93, 1892. Also The Observatory, Vol. 

 xvi., p. 456, 1892. 



