218 G. H. KNIBBS. 



differences in declination and right ascension for the period 1800 

 - 1900 approximately. In the computations no especial care was 

 taken to ensure accuracy to the nearest tenth of a degreee, since 

 the real uncertainty runs into degrees. The basis of Table III. 

 is, a denoting right ascension, 8 declination, in which N = +, S = - , 

 and t is the period in years, 



Aa/A* = 0-°0128 + 0-°00557 sin a tan 8 



A8/At = 0-°00557 cos a. 

 In each case the nearest star to any determination of the solar- 

 apex has been given : in most cases its coordinates have been taken 

 from the Auwers-Bradley catalogue, and reduced from the epoch 

 of that catalogue 1810 to 1900 for precession merely, the small 

 correction for proper motion being neglected. 



These resulting positions for the epoch 1 900, for the solar-apex 

 and for the nearest stars, have in each case been plotted in the 

 illustrative figures. In the projection employed the celestial equator 

 and the 240° circle of right ascension have been uniformly divided. 

 The radii of the circles of declination are determined on the 

 polyconic system. The arcs of right ascension are circular, the 

 centres lying on the equator and so determined that the intercepted 

 arcs on the parallel of 60° declination shall be one half of those at 

 the equator. For mere diagrammatic purposes the distortion is 

 not serious. 



Conclusion. 



(132) In the Ephemeris of the Observatory of Rio de Janeiro 

 for 1900 it is stated that the approximate coordinates for the solar 

 motion are 1 



R.A. = 280°, D.= +40° 

 the point being in the constellation Hercules. It will be manifest 

 however, from the results tabulated in II. and shewn in the illus- 



1 O Sol, centro de attraccao dos planetas, nao e fixo no espaco. As 

 observacoes estellares provao que elle se desloca, arrastandando comsigo 

 o systema planetar e dirigendo-se para um ponto denominado Apex, situado 

 na constellacao de Hercules, e cujas coordendas approximadas sao : — 

 K.A. = 280°, D. = 40°.— Annuario de 1900, p. 104. 



