A. O. POWYS 
239 
Although the last column shows the usual aggregations at the decennial 
years of age, it was not found practicable to graduate or adjust the numbers 
in consequence of the number of oft'spring also being involved. This will not 
however vitiate the comparison between the mothers of the different sized families, 
as the error is common to all. The average duration of life was determined by 
means of the single years and a half-year added to each result to allow for the 
life lived in the year of death on the assumption of the equal distribution of 
deaths throughout that year. The statistics relating to families of more than 
seventeen children were not used, being altogether too small to furnish reliable 
results. The average duration of life beyond age 45 of the mothers of various 
sized families who had survived their forty-sixth year, and of those beyond 60 
and 75 by survivors of those ages, is given in Table VI. 
TABLE VI. 
Mean Duration of Life of Mothers. 
After 45 years of age 
After 60 years of age 
After 75 years of age 
Number of 
children 
in Family 
Number of 
Average Life 
Number of 
Average Life 
Number of 
Average Life 
Deaths 
(years) 
Deaths 
(years) 
Deaths 
(years) 
0 
1110 
22-63 
794 
13-33 
327 
6-90 
1 
533 
22-29 
362 
14-15 
159 
7-63 
2 
581 
23-41 
412 
14-76 
195 
7-64 
8 
644 
22-82 
450 
14-36 
200 
7-46 
h 
702 
23-39 
499 
14-75 
230 
7-73 
5 
813 
23-68 
596 
14-42 
271 
7-51 
6 
855 
23-61 
621 
14-53 
289 
7-33 
7 
976 
22-91 
703 
13-54 
282 
7-18 
8 
963 
23-41 
703 
14-06 
314 
7-38 
9 
847 
23-14 
603 
14-10 
260 
7-57 
10 
786 
22-96 
585 
12-91 
233 
6-95 
11 
568 
22-26 
404 
12-75 
152 
6-15 
12 
422 
22-94 
308 
13-29 
130 
6-19 
13 
226 
22-68 
171 
12-06 
57 
6-22 
U 
129 
23-62 
99 
13-42 
41 
7-16 
15 
57 
21-94 
45 
10-72 
10 
6-20 
16 
39 
23-24 
31 
10-60 
10 
6-20 
17 
12 
18-58 
8 
9-38 
Guided approximately by the statistics, each of these series was broken up 
into two sections — from 0 to 8 children and from 9 to 17 in the first two, and 
from 0 to 8 and 9 to 16 children in the last series. The correlation and the 
regression straight lines were then determined for the six sections with the results 
set forth in Tables VII. and VIII. 
Although the correlation cannot be regarded as high in any of the series 
there are some significant facts in connection with the results — first, the cor- 
relation in each of the series 0 to 8 children is positive, and from 9 children 
upwards it is negative ; that is, that fertility up to about 8 children is apparently 
