26 ASTRONOMY: H. SHAPLEY 
Nearly forty plates, made with the 60-inch reflector, have been used 
in the present work. In addition to the above-mentioned catalog of 
stars in and near the cluster, photographic and photovisual magni- 
tudes of more than 300 stars in four other neighboring fields have been 
determined by comparisons with the cluster and checked by direct 
comparisons with the Polar Standards. Special care was taken to avoid 
Percentage Frequency of Colors in Galactic Cloud Fields 
COLOR CLASS 
60 
65 
aO 
fl.5 
/o 
/5 
go 
g5 
m 
kS 
mO 
mS 
Field I 
0 
2 
6 
12 
18 
12 
12 
16 
12 
4 
2 
4 
Field II 
1 
3 
7 
17 
13 
8 
8 
8 
12 
12 
5 
6* 
Field III 
0 
2 
17 
29 
10 
10 
10 
8 
4 
8 
4 
0 
Field IV 
0 
0 
2 
27 
24 
22 
10 
0 
8 
4 
4 
0 
All fields 
0.3 
2 
8 
20 
15 
11 
9 
8 
10 
8 
4 
4t 
* 2.5% have color indices greater than -|-2.00. 
1 1.3% have color indices greater than +2.00. 
ha f k g m 
16 
12 
8 
0 
FIG. 1. FREQUENCY OF COLORS IN GALACTIC CLOUDS. ABSCISSAE ARE COLOR CLASSES; 
ORDINATES ARE PERCENTAGES. 
the use of questionable photographs or of doubtful star images, and 
systematic errors of any importance are probably completely absent 
from the results. The average probable error of a color index varies 
in the different fields from a tenth to a twentieth of a magnitude. 
The interval of photovisual magnitude investigated is from 11.0 to 
15.5. The relative frequency of color class is given in the accompany- 
ing table for each field separately and for the four together. Figure 1 
