GREAT MEN OF MODERN HISTORY. 



137 



1766, and that Dr. Erasmus was the fourth son of Robert, who 

 was the second son of William, who was the eldest son of William, 

 Sr., born in 1620. This gives in years between Erasmus and 

 the first William, which, divided by three, gives an average of 

 thirty-seven years in the ancestry of Dr. Erasmus. But eldest, 

 second and fourth sons are not born from the same age of parents. 

 Having recourse to my tables and dividing this in years propor- 



ERASNIU5 %OBRT 



FIG. 8 DIAGRAM OF THE DARWINS, SHOWING BIRTH-RANKS FOR THREE 



GENERATIONS. 



tionally, I found the probable periods to be thirty-one, thirty-five 

 and forty-five years respectively. This would place Erasmus 

 Darwin in class A, and may be considered a fairly accurate esti- 

 mate. Robert Waring being forty-three, places Charles Darwin 

 in class B ; Erasmus being thirty-five, places Robert in class D ; and 

 we have just estimated Erasmus in class A. Taking these ages 

 and drawing a diagram (Fig. 8) for them, we have a curve that 

 represents the birth-ranks for three generations. If we should 

 draw a curve representing the mental greatness of these three 

 men, it would be practically the same line. The only fault to be 



