METHODS 15 



very different in their dimensions. And this simple obser- 

 vation already shows that life is not localized in one point 

 of a series of natural phenomena, but occupies a considerable 

 place in the general activities of the world. When we see 

 a rainbow forming in the spray of a fountain, we find that 

 the movement of liquid drops does not displace the 

 luminous apparition ; the second phenomenon is therefore 

 absolutely independent of the first, whose rapidity belongs 

 to the same order of magnitude as sound movements. 

 Life, which is sensitive to movements in both these two 

 parallel series, offers us in like manner two sorts of distinct 

 activities corresponding roughly with the rainbow light and 

 the spray of the fountain. 



Second Example : Chemistry, Colloids, Nebulae. 



Our first example was taken from oscillatory movements ; 

 the second concerns structures, mechanisms, which are 

 comparable, at least provisionally, to buildings constructed 

 by men and owing their particular properties to the manner 

 in which they are constructed. 



Now that the atomic theory has conquered the world, 

 we can define chemistry as " the science of molecular edifices 

 built up with atoms, and the study of the conditions in 

 which such edifices destroy and construct each other." 

 Chemical phenomena, accordingly, are of the order of mag- 

 nitude of atoms, or, at least, of the distances which separate 

 atoms in the molecules or molecules from each other. 



For some years the attention of scholars has been par- 

 ticularly drawn to special bodies called colloids, which are 

 neither frankly solid nor frankly liquid ; their name comes 

 to them from a comparison between such bodies and a 

 watery solution of glue. Theory, at first, and microscopic 

 observation in diffracted light afterwards, have shown 

 that these colloids result from the existence of particles 



