HERMANN VON HELMHOLTZ 



physiological acoustics. They must be read, referred 

 to, consulted over and over again, before one can 

 appreciate the wealth of material to be found in 

 these volumes. They are not merely historical 

 accounts of all that has been done up to the date 

 of their appearance in that particular department 

 of science, but, at the same time, the bibliography 

 is of the most complete description, showing the 

 unwearied literary activity of the author. A notice 

 is given, often critical, of the works of writers from 

 the earliest down to the most recent times. In 

 these notices there is a generous estimate of the 

 labours of those who have gone before. There is 

 an absence of polemical writing ; if the author does 

 not agree with the results obtained in a particular 

 research, this is frankly stated, and the experimental 

 error, or the illogical result, is pointed out and calmly 

 brushed aside. But great as are the merits of these 

 books, even from this point of view, their charm is 

 their freshness. The reader feels that the author has 

 gone over every bit of the ground himself, and there 

 is scarcely a page that is not enlivened by the results 

 of personal research. Everywhere one feels the grasp 

 of a master, whether in the exposition of the subject 

 in hand or in its mathematical treatment ; and it is 

 characteristic of Helmholtz that, with a kind of 

 literary modesty, a profound mathematical discussion 

 of a difficult question is often relegated to an appendix 

 at the end of the chapter, whilst it really may con- 

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