PREFACE 



THIS work is a record of the achievements in 

 scientific discovery and invention of one of 

 the greatest minds of the nineteenth century. 

 Helmholtz was one whose private life was 

 known only to a few, and he would have 

 instinctively recoiled from biographical revela- 

 tions of a purely personal character. At the 

 same time, I have endeavoured to give the 

 reader some idea of the man calm, placid, 

 reserved, thoughtful whose love of truth, 

 yearning spirit of inquiry, and great intel- 

 lectual powers give him a place in the front 

 ranks of the interpreters of Nature. A life 

 full of intellectual activity, creative, ever pro- 

 ductive, could not contain much in the way 

 of trivial incident. I have also tried, by 

 following a historical method, to trace the 

 history of any branch of inquiry up to the 



