4 THE RELATIVE STRENGTH OF 



further investigation we might ascertain that such 

 mothers are, on the average older and have older 

 children, from whom time has weeded the weaklings, 

 and that the problem cannot be solved by the simple 

 question of the physique of the children of employed 

 and unemployed mothers, without regard to the age 

 distribution of the children. 



Once more it is conceivable that we might find 

 that the deathrate of innkeepers much in excess of 

 the deathrate of the clergy, and overlook the fact 

 that the average age at starting the occupation of 

 innkeeper is far higher than that of entering the 

 church, because ultimately to keep an inn is the am- 

 bition of men, who begin life in a variety of other 

 callings. As a last illustration we may take the pro- 

 blem of the effect of the drinking of the father on the 

 health and ability of the offspring. We might find 

 that the father who drinks had abler and physically 

 better developed sons than the non-drinker. Yet 

 on closer investigation it might appear (I) that on 

 the average the drinker was the abler workman, 

 and thus the apparently greater ability of the off- 

 spring was really an hereditary matter, (ii) that the 

 abler workman got higher wages, and thus, not- 

 withstanding the drink, the food at home, especially 

 perhaps In the earlier days of the family life, had 

 been ampler and of better quality. There is hardly 

 a single problem of parental occupation and habit, 

 of home environment and school influence which is 

 not of the greatest complexity, and full of pitfalls for 

 even the most cautious statistician. And if this be 

 true, what must be said for the philanthropist and 



