xiv INTRODUCTION. 



or fail to see tlw probable influence of their writings on the 

 science of the coming time. For many years, therefore, it was 

 my habit to place every physical paper published by these 

 eminent men within the reach of purely English readers. 



The ti-anslation of the lecture on the ' Wechselwirkung der 

 Naturkrafte,' printed in the following series, had this origin. 

 It appears here with the latest emendations of the author 

 ntroduced by Dr. Atkinson. 



The evident aim of these Lectures is to give to those 'whose 

 education has been mainly literary,' an intelligent interest 

 in the researches of science. Even among such persons the 

 reputation of Helmholtz is so great as to render it almost super- 

 fluous for me to say that the intellectual nutriment here offered 

 is of the very first quality. 



Soon after the publication of the ' Tonempfindungen ' by 

 Helmholtz, I endeavoured to interest the Messrs. Longman in the 

 work, urging that the publication of a translation of it would 

 be an honour to their house. They went carefully into the 

 question of expense, took sage counsel regarding the probable 

 sale, and came reluctantly to the conclusion that it would not 

 be remunerative. ' I then recommended the translation of these 

 ' Populare Yortrage,' and to this the eminent publishers imme- 

 diately agreed. 



Hence the present volume, brought out under the editorship 

 of Dr. Atkinson, of the Staff College, Sandhurst. The names 

 of the translators are, I think, a guarantee that their work will 

 be worthy of their original. 



JOHN TYNDALL. 



ROYAL INSTITUTION: 

 March 1873. 



1 Since the date of the foregoing letter from Professor Tyndall, Messrs. 

 Longman & Co. have made arrangements for the translation of Helmholtz's 

 Tonempfindungen, by Mr. Alexander J. Ellis, F.R.S. &c. 



