THE INTER-GENERATION PERIOD. 
WITH PLATES X AND XI. 
CHARLES H. CHANDLER. 
The question here considered is whether the popularly re¬ 
ceived idea that the average interval between successive gener¬ 
ations is one-third of a century, has a sufficient foundation in 
fact. The result of an examination of nearly sixteen thousand 
dates of births and the computation of mean dates is presented 
in the accompanying tables and diagrams. 
As all the records involved in this examination have been 
those of New England families, it is evident that it is an en¬ 
tirely pertinent question whether the resulting inferences are 
applicable to other sections of country. Especially may it ap¬ 
pear that in regions where marriages are contracted at an ear¬ 
lier age the interval certainly will be considerably shortened. 
But on the other hand it must be considered that in those 
regions families are larger, and marriages in which the woman 
is very much younger than the man are more frequent, both of 
which conditions tend to lengthen the inter-generation period; 
so that without careful investigation it is by no means safe to 
assume that the generations follow in more rapid succession 
than under what at first seem to be the more deliberate con¬ 
ditions of New England. 
Each of the four tables here given represents the descendants 
of a common ancestor; the first column giving the numbers of 
the generations from that ancestor, the second column the num¬ 
ber of recorded dates of births in each generation, the third the 
mean date of those births, the fourth the interval between each 
generation (after the first) and the one preceding it, and the 
last column the sum of the three preceding intervals. 
