228 
ASTRONOMY: ADAMS AND STROMBERG 
The agreement of the maximum frequency as well as that of the maximum 
motion with Stream I is quite remarkable, when we take into account the 
small number of stars available (88), the more so as X is only 13°; the influence 
of Stream II also, although not so strong, can be plainly seen. 
More material for different parts of the sky will of course be necessary before 
we can conclude with any certainty that stars as faint as the 14th and 15th 
magnitudes show the stream-motion. 
^ van Maaneri, Adriaan, Mt. Wilson Contr., No. 167, 1919. 
2 van Maanen, Adriaan, Astr. J., Albany, N. F., 27, 1912 (139-146). 
3 Buisson, H., Ch. Fabry, and H. Bourget, Astrophys. J., Chicago, III, 40, 1914 (241- 
258). 
^ Eddington, A. S., Steller Movements^ London, 1914, page 100. 
ON THE USE OF THE SPECTROSCOPIC METHOD FOR 
DETERMINING THE PARALLAXES OF THE 
BRIGHTER STARS 
By W. S. Adams and G. Stromberg 
Mount Wilson Observatory, Carnegie Institution of Washington 
Read before the Academy, April 28, 1919 
When the method of deriving the luminosities and the parallaxes of stars 
by means of the intensities of certain lines in their spectra was developed by 
Adams and Kohlschiitter a few years ago the applicability of the method to 
the stars of highest luminosity and smallest parallax was necessarily somewhat 
uncertain. This was due to the fact that the method depends upon the cali- 
bration of a scale of line-intensities by means of stars of known parallax and 
magnitude, and that at this time the observational material for stars of small 
parallax was necessarily scanty and subject to relatively large percentage er- 
rors. All that could be done was to select a few stars with the best parallaxes, 
so far as could be estimated, and base upon them a set of provisional reduc- 
tion-curves for the spectroscopic determinations. As a result the values for 
the absolute magnitudes derived in this way while sufficiently accurate to in- 
dicate clearly that the parallaxes of certain stars were very small were not of 
such a quality as to show in all cases the slight differences between individual 
stars of small parallax. 
The situation has improved greatly in recent years. On the one hand the 
parallaxes of a large number of stars have be^n measured with high accuracy 
by various observers with the aid of photographic methods. On the other 
hand the amount of spectroscopic material for the stars of various magnitudes 
and proper motions has accumulated to such an extent that use can be made of 
the extremely valuable method of determining mean parallaxes for groups of 
stars from the parallactic motion. Accordingly it has now become possible 
