is: 



ON THE 



INTEKACTION OF NATUEAL FOECES. 



A Lecture delivered February 7, 1854, at Konigsberg, in Prussia. 



A NEW conquest of very general interest has been recently made 

 by natural philosophy. In the following pages I will endeavour 

 to give an idea 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 mathe- 

 matical 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. Surprised 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 automaton figures 

 which should perform the functions of men and animals. The 

 marvel 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 elder, and 

 the pianoforte-player of the younger, Droz ; which latter, when 

 performing, followed its hands with its eyes, and at the con- 



