TRANSLATOR'S PREFACE. 



IN bringing this Translation of Helmholtz's Popular 

 Scientific Lectures before the public, I have to thank Mr. 

 A. J. Ellis for having placed at the disposal of the 

 Publishers the translation of the third Lecture ; and also 

 Dr. Francis, the Editor of the ' Philosophical Magazine,' 

 for giving ine permission to use the translation of the fifth 

 Lecture, which originally appeared in that Journal. 



In addition to the Editorial charge of the book, my 

 own task has been limited to the translation of two of the 

 Lectures. I should have hesitated to undertake the work, 

 had I not from the outset been able to rely upon the aid 

 of several gentlemen whose names are appended to the 

 Contents. One advantage gained from this division of 

 labour is, that the publication of the work has been 

 accelerated; but a far more important benefit has been 

 secured to it, in the co-operation of translators who have 

 brought to the execution of their task special knowledge 

 of their respective subjects. 



E. ATKINSON. 



