298 
ASTRONOMY: H. SHAPLEY 
Proc. N. a. 
for the comparability of the spectral phenomena in globular clusters with 
those of the solar neighborhood. 
Color frequency-curves for intervals of one magnitude are shown in 
figures 1 and 2, based on the data of table I. The striking progression 
of maximum frequency toward the blue, with decreasing magnitude, 
again emphasizes the law of average color for giant stars in clusters, viz., 
the brighter the giant star the greater its color index. The progression of 
average color with luminosity is also clearly shown by the means in the 
last two columns of table I, which are plotted in figure 3, the six stars 
brighter than — 4.0 being omitted. 
A double maximum appears in the color curve for stars between magni- 
tudes 0.0 and — 1.0. It is not the result of the combination of observa- 
TABLE II 
Data for Luminosity Curves 
(Tabulated quantities are numbers of stars) 
COLOR INDEX 
ABSOLUTE 
CO 
00 
0 
q 
0 
ALL 
PHOTOVISUAL 
d 
1 
q 
d 
d 
d 
d 
+ 
d 
+ 
+ 
+ 
-1- 
-1- 
+ 
<N 
-f- 
COLORS 
MAGNITUDE 
0 
0 
+ 
0 
0 
0 
0 
.1-1 
0 
0 
+j 
0 
0 
0 
IN 
0 
(N 
CD 
00 
q 
CO 
d 
d 
0 
d 
d 
d 
d 
1 
I 
d 
+ 
+ 
+ 
+ 
+ 
+ 
+ 
+ 
+ 
-5.0 to -4.5 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
-4.5 to -4.0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
-4.0 to -3 .5 
0 
0 
0 
1 
0 
1 
0 
0 
0 
0 
0 
0 
2 
-3.5 to -3.0 
0 
0 
0 
0 
0 
1 
3 
3 
6 
5 
3 
2 
23 
-3.0 to -2.5 
0 
0 
0 
1 
1 
10 
8 
13 
11 
5 
1 
1 
51 
-2.5to -2.0 
0 
0 
1 
2 
7 
8 
17 
16 
6 
1 
2 
0 
60 
-2.0to -1.5 
0 
0 
1 
4 
20 
9 
25 
17 
3 
1 
0 
0 
80 
-1.5 to -1.0 
0 
4 
0 
10 
22 
56 
32 
11 
2 
0 
0 
1 
138 
-1.0 to -0.5 
0 
1 
15 
30 
13 
54 
71 
17 
1 
1 
0 
0 
203 
-0.5 to 0.0 
2 
54 
71 
47 
49 
103 
54 
8 
1 
0 
0 
0 
389 
All magnitudes 
2 
59 
88 
95 
112 
242 
210 
85 
30 
13 
6 
4 
946 
tions from clusters at different stages of development, because it is shown 
separately for Messier 3 and 13. It may be due to unequal evolutionary 
values for the different intervals of color — to a relatively speedier develop- 
ment, that is, throughout the interval of color index -|-0.2 to +0.6, for 
stars of a certain mass. 
Table II, similar in form to table I, contains data for the luminosity 
curves (fig. 4), showing the distribution in color and absolute magnitude 
of 946 stars from Messier 3, 11, and 13. These curves, for intervals of 
0.4 mag. in color index, indicate that our material gives the complete 
distribution of luminosity for the red giants, but that for the blue stars 
the maximum frequency falls below zero absolute magnitude. 
