10 ENGLISH MEN OF SCIENCE. [CHAP. 



eluded 300 of the same ages, without descending 

 in the scale of scientific position ; also it appears 

 that the ages of half of the number on my 

 list lie between 50 and 65, and that about 

 three-quarters of these may be considered, for 

 census comparisons, as English. I combine 

 these numbers, and compare them with that 

 of the male population of England and Wales, 

 between the same limits of age, and find the 

 required ratio to be about one in 10,000. What 

 then are the conditions of nature, and the 

 various circumstances and conditions of life, 

 which I include under the general name of 

 nurture, which have selected that one and left 

 the remainder ? The object of this book is to 

 answer this question. 



DATA. 



My data are the autobiographical replies 

 to a very long series of printed questions ad- 

 dressed severally to the 180 men whose names 

 were in the list I have described, and they 

 fill two large portfolios. I cannot sufficiently 



