rs, child laborers, pauper lunatics,
the more overcrowding and tuberculosis, the higher the birth rate--a
high degree of positive correlation. Little doubt here as to which
elements of the city are making the greater contributions to the next
generation. There may be some doubt, however, so let us consider two
possible qualifications of these results. First, is not the death rate
also higher among these least desirable classes? Yes, it is. Is it not
enough higher to compensate for the difference in the birth rates, so
that after all the least desirable classes are not more than replacing
themselves? No, it is not. After calculating the effect of the
differential death rate among these different social groups it still
remains true that the _net_ fertility of the undesirables is greater
than the _net_ fertility of the desirables: the worst classes are in
reality more than replacing themselves numerically in such
communities; the most valuable classes are not even replacing
themselves. Second, is not this the same condition that has always
existed in these districts? Why any cause for supposing that this is
going to bring new results to this society? Has not such a condition
always been present and always been compensated for somehow?
Fortunately, Heron is able to compare with these data of 1901 similar
data for 1851, and is able to show that every one of these relations
has changed in sign since that date--in fifty years. The significance
of this change in sign is probably clear. It means here that in London
sixty years ago there was a high degree of regularity in the relation
such that the more professional men and well-to-do families the
community contained, the higher the birth rate; that ten years ago
this had all become changed so that the more of these desirable
families found in a district the lower is the birth rate. It means
that sixty years ago the relation was such that the more undesirables
numbered in a district, the lower its birth rate; ten years ago the
more undesirables, the higher the birth rate, and the coefficients of
1901 are unusually high, indicating great closeness and regularity in
this relation. Heron is further able to show that as regards number of
servants employed, professional men, general laborers, and
pawnbrokers in a district, the intensity of the relationship has
_doubled_, besides changing in sign, in the period observed. It is not
necessary to review the history of this change nor to di