■ H. Helmholtz on the Interaction of Natural Forces. 189 



Art. Xy. — On the Interaction of Nc 



t 



Koni 



A NEW conquest of very general interest has been recently 

 made by natural philosophy. In the following pages I will en- 

 deavor to give a notion of the nature of this conquest *rt 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 pro- 

 cesses as it is important in their technical applications. 



Among the practical arts which o\ye their progress to the de- 

 velopment of the natural sciences, from the conclusion of the 

 middle ages downwards, practical mechanics, aided by the math- 

 ematical science which bears the same name, was one of the 

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

 ferred 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 au- 

 tomaton 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 

 artist, which moved all its fingers correctly ; the writing boy of 

 the older, and the pianoforte player of the younger Droz ; which 

 latter, when performing, followed its hands with its eyes, and at 

 the conclusion of the piece bowed courteously to the audience. 

 That men like those mentioned, whose talent might bear com- 

 parison with the most inventive heads of the present age, should 

 spend so much time in the construction of these figures which 

 we at present regard as the merest trifles, would be incompre- 

 hensible, if they had not hoped in solemn earnest to solve a great 

 problem. The writing boy of the elder Droz was publicly ex- 

 nibiled in Germany some years aeo- Its wheel work is so com- 

 plicated that no ordinary head would be sufficient to decipher 

 its manner of action. When, however, we are informed that 



* A popular scientific discourse, delivered the 7th of February, 1854. Cited from 

 ■PhiL Mag., Fourth Series, volume 11, page 489. where it is accompanied by the fol- 

 lowing note by the translator, John Tyndall, rii.D,, F.R.S.— " The following article 

 is a translation of a popular lecture, but it will, I doubt not, be studied with inter- 

 est by many of the readers of this Journal I once had thoughts of presenting the 

 lecture in a condensed form, omitting allusions, wliich though proper and necessary 

 in a ppoken discourse, niiijht not appear so in a strictly scientific article. On reflec- 

 tion, however 1 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." 



f Now of the Universitr of Bona 



