THE CONSTITUTION OF MATTER. 55 i 



atoms in molecules is the ten-millionth part of ^ of an inch. Gaudin 

 follows Thomson in the attempt to give some sensible notion of the 

 truly amazing minuteness of a dimension like this. He calculates, 

 upon this estimate, the number of chemical atoms contained in about 

 the size of a pin's- head, and he finds that the number requires for its 

 expression the figure 8 'folio wed by twenty-one ciphers. So that, if we 

 attempted to count the number of metallic atoms contained in a large 

 pin's-head, separating each second ten millions of them, we should 

 need to continue the operation for more than 250,000 years 1 



There are, then, atoms in matter, and atomism is a fact, whenever 

 we rest in the affirmation of the existence of atoms. But these are not 

 the real principles, the simple and irreducible elements of the world. 

 After decomposing sensible matter into atoms, we must subject the 

 latter to an analysis of the same kind. Let us, then, consider any two 

 heterogeneous atoms whatever, an atom of iron and an atom of hydro- 

 gen, for instance, and examine in what respect they can really, essen- 

 tially, differ from each other. What is it which at bottom truly dis- 

 tinguishes these two atoms, as atoms? It is not any peculiarity of 

 form, solidity, fluidity, hardness, sonorousness, brightness, because 

 these properties evidently depend on the mutual arrangement and dis- 

 position of atoms, that is, becaule they are not relative to the individ- 

 uality 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 prop- 

 erties 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 qualitative difference, but 

 simply a quantitative one. Consequently, any two heterogeneous 

 atoms whatever, compared together, as atoms, have scarcely any of 

 the differential attributes peculiar to the groups which they make up 

 by aggregation, and represent no more than two distinct functions, 

 two different values of one and the same initial matter, of one and the 

 same primitive quality or energy. This simple demonstration estab- 

 lishes the unity of substance, not as a more or less plausible physical 

 hypothesis, but as a metaphysical certainty, alike underivable and 

 necessary. If we add now, reserving the demonstration for a later 

 period, that dimension, corporeal extension 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. 



