PREFACE TO THE FIRST EDITION 



MY father's life was one of so many interests, and 

 his work was at all times so diversified, that to 

 follow each thread separately, as if he had been 

 engaged on that alone for a time, would be to give 

 a false impression of his activity and the peculiar 

 character of his labours. All through his active 

 career he was equally busy with research into nature, 

 with studies in philosophy, with teaching and admin- 

 istrative work. The real measure of his energy can 

 only be found when all these are considered together. 

 Without this there can be no conception of the 

 limitations imposed upon him in his chosen life's 

 work. The mere amount of his research is greatly 

 magnified by the smallness of the time allowed for it. 

 But great as was the impression left by these 

 researches in purely scientific circles, it is not by 

 them alone that he made his impression upon the 

 mass of his contemporaries. They were chiefly 

 moved by something over and above his wide know- 

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