276 
definition to build upon, a rational system 
of chemistry became, for the first time, a 
possibility. 
Thus the elements were recognized as 
simple bodies because there were no sim- 
pler. They were not complex or com- 
pound. The distinction was clearly drawn 
between bodies simple and bodies com- 
pound, and the name simple body has been 
frequently used as a synonym for element 
through a large part of this century. Nat- 
urally the question of simplicity was first 
settled by an appeal to that great arbiter of 
chemical questions, the balance. And, quite 
as naturally, many blunders were made and 
the list of bodies erroneously supposed to 
be simple was very large. All whose weight 
could not be reduced were considered ele- 
mentary. When, however, from such a 
body, something of lesser weight could be 
produced, its supposed simplicity was, of 
course, disproved. 
This test for the elemental character has 
been clung to persistently, and is perhaps 
still taught, although it was long ago recog- 
nized that many of the elements existed in 
different forms, a phenomenon to which 
Berzelius gave the name allotropism. One 
only of these could be simplest, and the 
others could be reduced to this one and 
rendered specifically lighter. -With the dis- 
covery of this relation it should have been 
quite apparent that the old definition 
would no longer hold good. But many 
years passed before chemists were made to 
feel that a new definition was necessary, 
and adapted one to the newer knowledge. 
The iusight into what Lucretius would 
eall ‘the nature of things’ was becoming 
clearer ; the mental grasp upon these elu- 
sive atoms about which the old Epicurean 
reasoned so shrewdly was becoming firmer. 
Through what one must regard as the veil 
interposed by the earlier idea of the element, 
the chemist began to grope after the con- 
stituent particle or atom. It must be borne 
SCIENCE. 
[N. S. Vou. X. No. 244. 
in mind that the definition of the element 
was largely formulated before the resuscita- 
tion of the atomic theory by Dalton, and the 
mental picture of the one has perhaps re- 
tarded the clearing up of the ideas concern- 
ing the other. From the atomic point of 
view the element was next defined as one in 
which the molecules or divisible parts were 
made up of similar indivisible particles. 
This afforded an easy explanation of allo- 
tropism as a change in the number of atoms 
in a molecule. As Remsen says: ‘“ An ele- 
ment is a substance made up of atoms of 
the same kind; a compound is asubstance 
made up of elements of unlike kind.”’ 
Laying aside, then, all vaguely formu- 
lated ideas of essences, or principles, or 
simple bodies, or elemental forms, we 
found our present building upon the con- 
ception of the ultimate particle, be this 
molecule or atom. 
As to this. atom some clear conception is 
needed, and here we come to the crux of the 
modern theories. The chemist regards this 
atom as a particle of matter and is unwill- 
ing to accept the theory of Boscovich that 
it is infinitely small, and hence a mathe- 
matical point, nor can he admit that it is 
merely a resisting point, and hence that all 
matter is but a system of forces. And yet 
it seems as though some authorities would 
lead up to such a conclusion. 
While we need not consider these atoms 
as mere centers of forces, we are compelled 
to study them by the operation of forces 
upon them. What are called their proper- 
ties have been studied and recorded with 
great care. These properties are evinced 
in the action of the forces upon matter, and 
the exhibition of force without matter can- 
not be admitted. This study of the prop- 
erties has been the especial occupation of 
the century now closing, and so the ele- 
mental atom has come to be regarded as a 
collection of properties. As Patterson- 
Muir puts it (Alchemical Essence and the 
