212 G. H. KNIBBS. 



In these, the former of each pair is from proper motion in declin- 

 ation alone, the latter from the proper motions in declination and 

 right ascension. These results have not been plotted on the 

 illustrative figures, viz. 1 and 1 (a). 



(126) Newcomb, 1899 (Dec.) — Newcomb replied that the 

 definition is tedious, but the point referred to by Backhouse and 

 its definition is well understood. 1 



126a.) Kapteyn, 1900 (Jan.) — The second paper is by Kapteyn, 

 discussing critically the solutions by Airy, Argelander, and Kobold, 

 and shewing the equations of each type of solution or modification 

 thereof. 2 Kapteyn clearly expounds the hypotheses on which 

 these proceed, and shews how far the solutions are in agreement 

 therewith. His conclusion is that what must perhaps more than 

 anything else, hinder us from accepting the methods so far used 

 for the derivation of the solar motion is, that quantities treated 

 as small are in reality not so. 



(127) Yowell, 1900 (March)— Yowell 3 taking 86 fundamental 

 stars from the Berliner Jahrbuch, whose proper motions were 

 greater than 0'"2 and less than 0-"5 per annum, found that 



R.A. =284'°1, D.= + 34-°l 

 He stated that if, employing Kobold's method, he had adopted as 

 a first approximation, the values 270° and 0°, he would have 

 obtained a very small correction, less than 0'°1 each way, and 

 similarly if he had adopted 284° and 34°. He concluded that 

 Kobold's method gives simply small corrections to any assumed 

 position for the apex, and leaves its real position indeterminate. 



(128) Kobold, 1900 (April)— Replying to Yowell's assertion 

 that Kobold's method of indirect solution will furnish only small 

 corrections whatever the assumed place of the solar motion, he, 



l IUd., V . 443. 



2 The determination of the apex of the solar motion. — Translated Proc. 

 Roy. A.cad. Amsterdam, Vol. n., pp. 353 - 374. 



3 Note on a new method of determining the solar-apex. — Astr. Journ., 

 Vol. xx„ No. 479, p. 187. 



