SOLAR AND STELLAR PROPER MOTIONS. 
163 
have an appreciable parallax, and most of these are of large 
magnitude. Hence it was inferred that the larger stars were 
nearer the solar system, and that the apparent brightness 
was a guide to their relative distances. It was also assumed 
that if the apparent motion of the stars was caused wholly, 
or partially, by the motion of the sun, the nearer or larger 
stars would be affected by the greatest proper motion. 
In 1827, the elder Struve 31 devised an ingenious scheme of 
relative stellar magnitudes and distances, in which the stars 
then called the first magnitude, were taken as the unit of 
magnitude, and the mean distance of these stars from the 
solar system, was assumed as the unit of distance. This 
scheme included not only the relative magnitudes and dis¬ 
tances, but the relative brightness of the stars, together with 
the number of stars of each magnitude which would be 
equal in brilliancy to the adopted standard. 
This system, or some modification of it, has been employed 
in nearly every study of the direction and velocity of. the 
solar motion undertaken since these supposed relations were 
published. It is apparent that this system was founded bn 
the assumption that all the stars are of the same real mag¬ 
nitude and brilliancy, and that all changes in those charac¬ 
teristics are due to the varying distances from the solar sys¬ 
tem. If these assumptions be true, then all stars of the same 
magnitude ought to have the same parallax. Sirius, appar¬ 
ently the largest stellar body known, and theoretically the 
nearest to the solar system, has an annual parallax of less 
than 0".4, while the 7th magnitude star, Lalande 21185, has 
an annual parallax of 0".5. According to the generally 
accepted theory the fainter star should be more than eleven 
times as far from the sun as Sirius is, while the observations 
for parallax show that it is nearer than Sirius by the ratio of 
five to four. Many comparisons showing similar discrep¬ 
ancies between theory and fact could be easily shown. 
If all stars of the same magnitude were at equal distances 
21 Struve, F. G-. W. Catalogus Novus Stellarum Duplicium et Multi- 
plicium. Dorpat, 1827 ; XXXV. 
