BODIES SMALLER THAN ATOMS. 237 



oral i.s olectrioal in its origin i.s a fascinating one, although it has not 

 at present been reconciled with the results of experience. 



The smallness of these particles marks them out as likely to afford 

 a verA' valuable means for investigating the details of molecular 

 structure, a structure so fine that even waves of light arc on far too 

 large a scale to be suitable for its investigation, as a single wave 

 length extends over a large numlier of molecules. This anticipation 

 has been full}' realized bj' Lcnard's experiments on the ol)struction 

 offered to the passage of these corpuscles through different substances. 

 Lenard found that this ol^struction depended onl}" upon the densit}" of 

 the substance and not upon its chemical composition or physical state. 

 He found that, if he took plates of different substances of equal areas 

 and of such thicknesses that the masses of all the plates Avere the same, 

 then, no matter what the plates were made of, whether of insulators 

 or conductors, whether of gases, liquids, or solids, the resistance they 

 offered to the passage of the corpuscles through them was the same. 

 Kow, this is exactly what would happen if the atom of the chemical 

 elements were aggregations of a large number of ecpial particles of 

 equal mass; the mass of an atom being proportional to the num))er 

 of these particles contained in it and the atom being a collection of 

 such particles through the interstices between which the corpuscle 

 might find its ViHy. Thus, a collision between a corpuscle and an atom 

 would not be so much a collision between the corpuscle and the atom 

 as a whole, as between a corpuscle and the individual particles of 

 which the atom consists; and the number of collisions the corpuscle 

 would make, and therefore the resistance it would experience, would 

 l)e the same if the number of particles in unit volume were the same, 

 whatever the nsi^ure of the atoms might l)e into which these particles 

 are aggregated. The number of particles in luiit volume is, however, 

 fixed by the density of the substance, and thus on this view the density 

 and the density alone should fix the resistance offered hy the sub- 

 stance to the motion of a corpuscle through it; this, however, is pre- 

 cisel}^ Lenard's result, which is thus a strong confirmation of the view 

 that the atoms of the elementar}^ substances are made up of simpler 

 parts, all of«whicli are alike. This and similar views of the constitu- 

 tion of matter have often been advocated; thus, in one form of it, 

 known as Front's hypothesis, all the elements were supposed to be 

 compounds of hA^drogen. We know, however, that the mass of the 

 primordial atom must be much less than that of hydrogen. Sir Nor- 

 man Lockyer has advocated the composite view of the nature of the 

 elements on spectroscopic grounds, but the view^ has never been more 

 boldly stated than it was long ago by Newton, who savs: 



"The smallest particles of matter may cohere by the strongest 

 attraction and compose bigger particles of weaker virtue, and many of 

 these may cohere and compose bigger particles whose virtue is still 



