172 G. H. KNIBBS. 



The mean result from I. was (K3015, from II., (K3022, that 

 is to say the mean distance of the stars of the first three magni- 

 tudes is slightly less than the mean distance of those of the next 

 three or four magnitudes ! Proctor argues that large proper 

 motion is an argument for proximity; that since there is no 

 apparent agreement with proper motions and brightness, we are 

 forced to accept the former, rather than the latter, as the best 

 available evidence. 



(65) Flammarion, 1872. — Flammarion treats upon the motion 

 of our translation through space in the third volume of his studies 

 published in 1872. 1 



(66) Villarceau, 1872. — In a note to the French Academy of 

 Sciences in 1872, Villarceau discusses theoretically the velocity 

 of light and the aberration constant in relation to the absolute 

 movement of the solar system in space. 2 The paper is obviously 

 important from the theoretical point of view, in respect of the 

 accurate determination of star places, from which the proper 

 motions are ascertained. 



(67) Doppler, Fizeau, Huggins, Zollner, 187 3, etc. — The progress 

 of science about 1873 opened up an entirely new possibility of 

 investigating the sun's motion in space. In 1841, Doppler of 

 Prague had pointed out that the system of waves in the lumini- 

 ferous medium emanating from a luminous point, must be affected 

 by its motion to or from an observer, 3 the consequence of which 

 he erroneously (Bolzano previously referred to erring with him) 

 thought would be a perceptible change of colour. The genius of 

 Fraunhofer 4 had opened up a way of detecting the shift of the 

 spectrum, since the lines crossing it, measured by him with such 

 amazing diligence, really do shift with motion of the light-source, 



1 Translation du systeme solaire dans Fespace et relation du soleil avec 

 les etoiles les plus proches. — Etudes et lectures, t. in., p. 59, 1872. 



a Sur la constante de l'aberration et la vitesse de la lumiere, con- 

 siderees dans leurs rapports avec le mouvement absolu de translation du 

 systeme solaire. — Comptes rendus, t. lxxxv., pp. 854 - 860. 



3 Abhandl. d. kon. bohm. Ges, d. Wiss., Bd. n., p. 467- 



4 Bibl. Univ. vi., 1817, pp. 21-26. 



