68 DIVISIBILITY OP MATTER ATOMIC THEORY. 



measure of minuteness the sole measure we have ; 

 fo the instances already given, and the many that 

 might be added, marvellous though they are, do not 

 make it certain that we have reached what is ultimate 

 in the atomic scale. If we come to ether, as a mate- 

 rial medium, occupying universal space, we are forced 

 for the fulfilment of its offices, from actual pheno- 

 mena, to assume a degree of divisibility of matter 

 which no statement can convey to our conception. 



The exquisite mobility of atoms is another condition, 

 equally necessary and collateral, indeed, to that just 

 stated. It is a condition expressed not solely through 

 motions and changes obvious to sense, or such as occur 

 in fluid or gaseous states of matter, but with equal cer- 

 tainty through the changes produced in the densest 

 bodies by the various action of light, heat and 

 electricity, &c. atomic motions real in themselves, 

 however produced. When we speak of telegraphic 

 communication, next to instantaneous, between Lon- 

 don and Edinburgh or across the Atlantic, we denote 

 the assured fact that every single atom of the inter- 

 vening metallic wire has undergone for the moment 

 some specific change, whatever it be, in this wonderful 

 transmission of force. A figure solid a crystal, for 

 example may be wholly altered in its internal or 

 atomic structure, without any appreciable change of 

 outward form. The proof of such intestine motions of 

 atoms is as perfect as if the eye could discern them. 

 The microscope discloses many marvellous facts in this 

 direction of research, but there is a microcosm of 

 movement and change which lies far beyond its reach. 



