2 7 o THE POPULAR SCIENCE MONTHLY 



Make the mighty ocean 

 And the wondrous land, 



and we doubtless speculate as to whether the sand grain and the water 

 drop are not likewise divisible into smaller portions, and whether these 

 smaller portions differ in quality from the larger. And so in the 

 youth of science we find some philosophers maintaining the infinite 

 divisibility of matter, and on the other hand the school founded by 

 Leukippos and Demokritos, to whom we owe the conception and the 

 word atom, the indivisible (or at least never divided) particle which 

 forms the ultimate structure of matter. In these atoms, their cease- 

 less motion and their various groupings, is to be found the interpreta- 

 tion of the manifold phenomena of nature. 



Both of these schools of thought have contributed to modern science. 

 From the former we obtain the conception of a continuous medium 

 which has developed into the theory of the all-pervading ether. From 

 this school too we received the doctrine of the limited number of ele- 

 mentary substances from which all things are formed; a number which 

 has grown from the four of Empedokles — earth, air, fire, water — 

 through many vicissitudes into the eighty or so of the present day. 

 But to the opposing school we owe a far greater debt, a debt which we 

 can not lightly repudiate with Clifford by saying " The atomic theory 

 of Demokritos was — no more than a guess — which was more near the 

 right thing than the others." The atomic theory is much more than 

 a guess. Incorporated into the system of Epikuros, and expounded in 

 the marvelous poem of the Eoman Lucretius, it forms a well-reasoned 

 and well-balanced system of thought which it is true lacked in definite- 

 ness but was not without marked success in furnishing a framework 

 on which to erect an image of nature. So successful was it that after 

 two millenniums it has suffered little modification. As an illustration 

 let us compare the atom of Lucretius with that of Newton. 



These are the words of the Eoman poet : 



The atoms are of solid singleness, and, compact of smallest parts are closely- 

 coherent — not compounded from a combination of these parts but strong in 

 their everlasting singleness; from these Nature allows nothing to be broken off 

 or diminished; . . . very different are they in their forms; varied by mani- 

 fold shapes. 2 



While the description by Newton is as follows : 



It seems probable that God in the beginning form'd Matter in solid, massy, 

 hard, impenetrable, moveable Particles, of such Sizes and Figures, and with 

 such other Properties ... as most conduced to the End for which he form'd 

 them; and that these primitive Particles being Solids, are incomparably harder 

 than any porous Bodies compounded of them; even so very hard, as never to 

 wear or break in pieces. 3 



A comparison of these passages shows how the two conceptions are 



2 1., 609, and II., 333. 



