A description of
this is given in Appendix A.
[3] Galton, Francis, _Inquiries into Human Faculty_, 1907 edition, pp.
153-173. This volume of Galton's, which was first published in 1883, has
been reissued in Everyman's Library, and should be read by all
eugenists.
[4] What is said here refers to positive correlations, which are the
only kind involved in this problem. Correlations may also be negative,
lying between 0 and -1; for instance, if we measured the correlation
between a man's lack of appetite and the time that had elapsed since his
last meal, we would have to express it by a negative fraction, the minus
sign showing that the greater his satiety, the less would be the time
since his repast. The best introduction to correlations is Elderton's
_Primer of Statistics_ (London, 1912).
[5] Dr. Thorndike's careful measurements showed that it is impossible to
draw a hard and fast line between identical twins and ordinary twins.
There is no question as to the existence of the two kinds, but the
ordinary twins may happen to be so nearly alike as to resemble identical
twins. Accordingly, mere appearance is not a safe criterion of the
identity of twins. His researches were published in the _Archives of
Philosophy, Psychology and Scientific Methods_, No.
Pages:
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716