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 f The object of this book is to answer this question.
My data are the autobiographical replies to a very long series of printed questions addressed severally to the 180 men, whose names were in the list I have described, and they fill two large portfolios. I cannot sufficiently