INTRODUCTION. 1 1 



du Syst. du Monde, p. 384 ; Kosmos, Bd. iii. S. 22, and 32 

 Anm. 39 ; Eugl. p. 21, and vii., Note 39). 



As in the visible world it is especially on the oceanic 

 horizon, that optical illusions often hold out to the expec- 

 tation of the discoverer the promise of new lands, which for 

 a time remains unrealised, so has it been on the bounds of 

 the ideal horizon, in the remotest regions of the intellectual 

 world, that to the earnest inquirer many promising hopes 

 have arisen and have again faded away. Great discoveries 

 in recent times are indeed suited to heighten expectation on 

 this subject; such are contact-electricity, rotation-mag- 

 netism, which can be excited by substances either in a fluid 

 or a solid state, the attempt to regard all affinity as a con- 

 sequence of the electric relations of atoms to a predominating 

 polar force, the theory of isomorphous substances applied 

 to the formation of crystals, many phsenomena of the electric 

 state of the living muscular fibre, and the knowledge gained 

 of the influence of the height of the Sun (the temperature- 

 raising solar rays) on the greater or less magnetic suscepti- 

 bility of a constituent of our atmosphere, oxygen. When 

 we see new light dawning from a previously unknown group 

 of phenomena in the material world, we may the more 

 hopefully think ourselves on the verge of new discoveries, 

 if the relations of the new facts to those with which we 

 were previously acquainted, appear obscure or even con- 

 tradictory. 



I have by preference adduced examples in which dynamic 

 actions of motive forces of attraction appear to open the 

 path by which we may hope to approach nearer to the solu- 

 tion of the problems of the original, invariable (and therefore 

 termed elementary) heterogeneity of substances (as oxygen, 



