The Inter-Generation Period. 
503 
located. Neglecting, then, the first three generations presented, 
the mean of the remaining periods is 33.3. 
E F 
X 
11 
1586 
24 
90 
VI 
9 
1602 
28 
94 
IX 
21 
1610 
36 
101 
V 
14 
1630 
31 
103 
VIII 
40 
1646 
30 
98 
IV 
13 
1661 
35 
95 
VII 
33 
1676 
35 
100 
III 
7 
1696 
37 
VI 
27 
1711 
33 
93 
II 
3 
1733 
23 
V 
16 
1744 
32 
98 
I 
2 
1756 
IV 
8 
1776 
28 
100 
II 
11 
1790 
34 
III 
4 
1804 
38 
III 
64 
1822 
32 
II 
2 
1842 
34 
IV 
113 
1855 
33 
99 
I 
2 
1876 
V 
167 
1880 
25 
90 
164 
403 
Mean 
period. 
. 32.2 
Mean 
period. 
. 30.9 
Omitting generations VIII, Omitting first and last gen- 
IX and X......33.3 orations. 32.1 
The graphic representation of this family may be examined 
from a somewhat different point of view. Opposite the place 
of the earliest ancestor of each name is given the mean period 
computed on the line from that ancestor to the common descend¬ 
ants in which all the lines unite. These fifty-seven periods lie 
between the extremes 27.3 and 36.7, and they give a mean value 
of 33, if the line from each ancestor is allowed the same weight, 
a course which perhaps is hardly correct, since some of these 
lines include many more generations than others. But it is 
largely true that these long lines have become known not merely 
by favoring accident, but because a tendency to early marriages 
brought more generations within the time and conditions limit¬ 
ing the research, which gives these families an undue influence 
in the determination. It may, therefore, be just to allow these 
two considerations to balance. But, if each line be given a 
weight proportional to the number of generations included, the 
corrected mean becomes 31.5. 
Table F presents five generations of the ancestors and four 
generations of the descendants of the couple represented by gen¬ 
eration I, and gives a mean inter-generation period of 30.9. But 
