BODIES SMALLER THAN" AToMS. 237 



oral is electrical in its origin is a fascinating one, although if has not 

 at present been reconciled with the results of experience. 



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

 a very valuable means for investigating the details of molecular 

 .structure, a structure so tine that even waves of light are on far too 

 large a scab 1 to be suitable for its investigation, as a single wave 

 length extends over a large number of molecules. This anticipation 

 has been fully realized by Lenard's experiments on the obstruction 

 offered to the passage of these corpuscles through different substances. 

 Lenard found that this obstruction depended only 14x111 the density 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 were 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. 

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

 elements were aggregations of a large number of equal particles of 

 equal mass; the mass of an atom being proportional to the number 

 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 wa} r . 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 

 be the same if the number of particles in unit volume were the same, 

 whatever the nature of the atoms might be into which these particles 

 are aggregated. The number of particles in unit volume is, how r ever, 

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

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

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

 cisely Lenard's result, which is thus a strong confirmation of the view 

 that the atoms of the elementaiy substances are made up of simpler 

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

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

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

 compounds of hydrogen. 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 T of the nature of the 

 elements on spectroscopic grounds, but the view has neA T er been more 

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



"The smallest particles of matter may cohere b} T the strongest 

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

 these may cohere and compose bigger particles whose virtue is still 



