THE FECUNDITY AND FERTILITY OF WOMEN. 



483 



Neglecting the difference of the quinquenniads in the two tables, and taking 

 11 instead of 12, for the sake of direct comparison, as the value of F at 15-19 in 

 the first, we have — 



Calculated 



11 



8-16 



5-5 



34 



1-9 



0-55 



Observed 



1085 



8-24 



50 



4-0 



... 





These numbers agree as well as could possibly be expected. 



5. If we project the numbers above given for / 17 .../ 47 , and try to represent 

 the values of/ for all ages by the ordinates of a curve, whose abscissae denote the 

 corresponding ages, we have the continuous curve of the following diagram : — 



15 



20 



25 



40 



45 



50 



30 35 



Fecundttt at Different Ages. 

 The continuous curve is founded on Edinburgh and Glasgow Tables. The dotted curve on Tables of Sterility. 



The straight line from the formula h (50 — t). 



The straight line, which almost coincides with the continuous curve — at least 

 from the age of 17 to that of 40— and whose departure from it above that age 

 must depend to some extent on the defects of the table pointed out in § 3, inter- 

 sects the axis at 50. We may obviously assume it as very nearly representing 

 the tables. And we can therefore express the value of/ t by a number proportional 

 to 50-*. Thus— 



/ t =*(50-«) 



(where k is a number, whose value we can easily find), is a simple formula very 

 closely representing the tabulated results. 



