1 8 THE RELATIVE STRENGTH OF 



Employment of the mothers then Is associated 

 to a small extent with lighter weight and shorter 

 stature of their sons, but I am not sure that even 

 the small association we find is necessarily a true 

 measure of cause and effect. There are secondary 

 obscuring effects of heredity. The weaker and 

 more delicate mothers may not seek external em- 

 ployment, and naturally they would have weaker 

 children. This lowers the association. Further- 

 more, inferior physique in the fathers may be a 

 reason for the necessity of the mothers work. 

 This would raise the association. We know from the 

 C.O.S. report that the mother's work is associated 

 with a lower rate of wage of the father — the average 

 wage of the husband of an unemployed woman is 

 26s. 2d. and of an employed woman is 22s. iid. It 

 seems reasonable to suppose that a man of inferior 

 physique may have to take a lower wage, and thus 

 it is his wife who will be obliged to work. Now if 

 the husbands of these working women are physically 

 weaker than other husbands we should expect their 

 sons to be shorter and lighter than other persons' 

 sons, whether the mother worked or not. We want 

 to know the height and weight of the husbands of 

 employed and unemployed mothers before we can 

 be sure what proportion of the correlation we see 

 between the mother's employment and son's height 

 and weight is due actually to the mother's work and 

 what is really due to the less weight and height 

 of the fathers. I quite realize that we may find low 

 wages do not depend on the physique of a workman 

 at all, but, if they do, then some of the apparent 



