THE 



LONDON, EDINBURGH and DUBLIN 



PHILOSOPHICAL MAGAZINE 



AND 



JOURNAL OF SCIENCE. 



SUPPLEMENT to VOL. XL FOURTH SERIES. 



LXIV. On the Interaction of Natural Forces''^. jByH.HELMttoLTZ, 

 Professor of Physiology in the University of Konigsberg^. 



THE following article is a translation of a popular lecture, 

 but it will, I doubt not, be studied with interest by many 

 of the readers of this Journal. I once had thoughts of presenting 

 the lecture in a condensed form, omitting allusions, which though 

 proper and necessary in a spoken discourse, might not appear 

 so in a strictly scientific article. On reflection, however, I think 

 it better to let the accomplished author state, in his own fashion, 

 the important question which he has contributed so much to 

 expand and elucidate. — J. T. 



A new conquest of very general interest has been recently 

 made by natural philosophy. In the following pages I will 

 endeavour to give a notion of the nature of this conquest. It 

 has reference to a new and universal natural law, which rules 

 the action of natural forces in their mutual relations towards 

 each other, and is as influential on our theoretic views of natural 

 processes as it is important in their technical applications. 



Among the practical arts which owe their progress to the 

 development of the natural sciences, from the conclusion of 

 the middle ages downwards, practical mechanics, aided by the 

 mathematical science which bears the same name, was one of 

 the most prominent. The character of the art was, at the time 

 referred to, naturally very different from its present one. Sur- 

 prised and stimulated by its own success, it thought no problem 

 beyond its power, and immediately attacked some of the most 

 difficult and complicated. Thus it was attempted to build auto- 

 maton figures which should perform the functions of men and 

 animals. The wonder of the last century was Vaucanson's duck, 

 which fed and digested its food ; the flute player of the same 



* A Popular Scientific Discourse, delivered the 7th of February, 1854. 

 t Now of the University of Bonn. 



Phil. Mag. S. 4. No. 75. Huppl. Vol. 11. 3 K 



