ASTRONOMY: KAPTEYN AND ADAMS 
15 
tory.i The Bonn observations by Kiistner came to hand too late for 
any extended use. The classification used is that of the Harvard Col- 
lege Observatory, and the spectra given in Campbell's catalogue are, 
with a very few exceptions, those of the Harvard Revised Photometry 
The Mount Wilson stars have been classified by the method described in 
the paper by Adams and Kohlschiitter.^ Occasionally large differences 
have been found from the estimates of the Harvard observers for the 
same stars. 
The observed radial motions were first reduced to velocities (p) relative 
to the center of gravity of the stellar system by applying the component 
of the sun's motion through space with reversed sign; that is, the cor- 
rection V cos d, where V is the sun's velocity, and 6 the angular distance 
between star and apex. For the apex we adopted the position a (1900) 
= 18h, Om; 5 = + 31°, and for V the value 20.0 km. per second. The 
values of p thus obtained were grouped: (1) according to amount of 
proper motion; (2) according to distance X from the nearest true vertex 
of the two star-streams. The positions of these vertices, according 
to the determinations of Kapteyn, Eddington, and others are: 
Stream I, 18h 12m -12°; Stream H, 6h 12m -|-12° 
The results are summarized in Table I. The letter denotes the 
total proper motion, and W and C refer to the radial velocity determi- 
nations by the Mount Wilson observers and by Campbell, respectively. 
Average values are indicated by dashes over the letters, and figures in 
parentheses denote the number of stars on which each average is based. 
The two columns under X are, as a rule, limited by values of X 60° to 
90° (Pi), and 0° to 49° (P2). A third group between the narrow hmits 
50° to 59° was formed, but is omitted from the table. In a few cases 
where the number of stars was small this middle group was used to in- 
crease the weight of the extreme groups. Six stars of abnormal velocity 
have been excluded out of a total of 1106 stars. These are: 
Lai. 15290 -249.4 A.Oe 20452 -163.0 Boss 130 - 80.7 
Boss 315+ 62.8 Boss 1511 +163.0 A.Oe 14320 +299.4 
An inspection of Table I shows clearly: first, that the average velocity 
of the stars near the vertices is considerably greater than that of the stars 
far away from these points; second, that the average value of p increases 
rapidly with the proper motion. 
The first of these conclusions is indicated most concisely by the values 
of the ratio P2/pi in the last column. It is a necessary consequence of 
the existence of two star streams with opposite motions. Thus, it is 
