166 Dynamic Evolution 



on both sides of the house immediately back 

 of the grandparents. We also find here 

 college education when college education was 

 rare. 



By comparing this list of eminent men with 

 the group- tables just preceding it, it will be 

 seen that all of these men come in the last 

 group, representing less than 25 per cent, of all 

 births, and that thirty-one of them come in 

 that extreme which represents only one per 

 cent, of persons born. An effort to find other 

 men of similar mental caliber to fill up the 

 shorter spaces of time between grandfather 

 and grandson is futile. Such men never 

 existed. We are therefore driven to the con- 

 clusion that time between generations is a 

 factor in the production of mental power. 

 As mental power is energy, and time is a 

 factor in the measurement of energy, there 

 is no difficulty in understanding the relation- 

 ship of the two to each other. As nearly as 

 may be, with the other factors unknown, the 

 mental energy found is proportional to the 

 length of time occupied in concentrating it. 



