PREFACE 



THE life of a professional man of science seldom offers 

 such variety of incident and interest as to justify more 

 than a brief record. In most cases a summary of his 

 work and an estimate of its value in the onward march 

 of knowledge form for such a man the most fitting 

 memorial. Now and then, however, a leader has ap 

 peared, who, by the fascination of his personality, or 

 by the extent and importance of his individual achieve 

 ments, has exercised so marked an influence on his 

 contemporary fellow-workers, or on the general ad 

 vancement of science, that the desire naturally arises 

 to know something more of him and of his surround 

 ings, than the mere list of his labours. One would 

 fain learn how he came to be drawn into the ranks of 

 the soldiers of science, and by what process of training 

 or what stages of evolution he rose to be a captain in 

 those ranks. The story of his discoveries may some 

 times have had a vivid personal interest, and those 

 who can best appreciate the value of these discoveries 

 would gladly know how they were made. 



The subject of the present memoir stood in the 



