86 STANDARD OF COMPARISON. 



THE MEANING OF BIRTH-RANK. 



This table shows that ten per cent of the children were born 

 when their fathers were less than 24 years and 6 months old, that 

 ten per cent were born after the fathers were 24 years and 6 months 

 old and before they had reached the age of 27 years and i month, 

 and that the other sections of ten per cent each came between the 

 ages specified, the last ten per cent being children of fathers over 

 44 years and 6 months of age. For mothers, ten per cent were born 

 before the mothers were 22 years old, and ten per cent after they 

 were 39 years and 10 months of age. The extreme ages of fathers 

 range from 19 years to 65 years, and for mothers the range is from 

 1 6 years to 45 years. I have designated these classes by letters so 

 that the earliest born ten per cent is represented by a and the latest 

 ten per cent by A. The next per cent in order from either end 

 of the scale is represented by b or B as the case may be, and so on, 

 corresponding sections being represented by corresponding small 

 and capital letters. A person born when his father was 33 years 

 old will be spoken of as being born in class E. I shall also speak 

 of such a person as having the "birth-rank E" or the "birth-rank 

 33," the two terms being used interchangeably. John Smith [42] 

 will means that John Smith was born when his father was 42 years 

 x>ld and consequently that John Smith's birth rank is 42. 



SUBDIVISIONS OF SCALE. 



Prom the nature of our investigation it will be evident that the 

 two extremes of our scale are the most important, the intermediate 

 portions being more or less indifferent or neutral. I have therefore 

 subdivided the classes a and A as follows : 



