8 NATURE AND LIFE. 



they are not relative to the individuality of each atom, 

 but to that of the whole which they form by being grouped 

 together. Neither is it any caloric property, or optic, or 

 electric, or magnetic one, because these properties result 

 from the movements of the ether, within the more or less 

 complex aggregate of the respective atoms of these two 

 substances. Now, if these atoms, taken separately, differ 

 from each other in virtue of none of the properties just 

 enumerated, they can only be dissimilar as regards two 

 attributes, dimension and weight ; but difference in weight 

 results from difference in dimension, and is not a quali- 

 tative difference, but simply a quantitative one. 1 Con- 

 sequently, any two heterogeneous atoms whatever, com- 

 pared together, as atoms, have scarcely any of the differ- 

 ential attributes peculiar to the groups which they make 

 up by aggregation, and represent no more than two dis- 

 tinct functions, two different values of one and the same 

 initial matter, of one and the same primitive quality or 

 energy. This simple demonstration establishes the unity 

 of substance, not as a more or less plausible physical 

 hypothesis, but as a metaphysical certainty, alike underiv- 

 able and necessary. If we add now, reserving the demon- 

 stration for a later period, that dimension, corporeal ex- 

 tension itself, as Leibnitz said and as Magy has lately 

 proved, is only a resultant of force, it will become evident 

 that matter, in the last analysis, is reduced to force. 



Tyndall, in his biography of Faraday, tells us that one 

 of the favorite experiments of this physicist gives a true 

 image of what he was : " He loved to show how water, in 

 crystallizing, eliminates all foreign substances, however 

 intimately mingled they may be with it. Separated from 

 all these impurities, the crystal becomes clear and limpid." 



1 We purposely take no notice of chemical forces, which can only be 

 regarded as attractions, and must therefore be explained by forces acting 

 outside of the atom itself. 



