SEPTEMBER 1, 1899.] 
weight, whatever that may mean. Low 
and others have fixed upon carbon and 
hydrogen as the two elements. 
There are many practical difficulties in 
the way of these suppositions ; the lack of 
uniformity in the differences between the 
atomic weights, the sudden change of elec- 
tro-chemical character, and the impossi- 
bility, so far, of discovering any law under- 
lying the gradation in the properties of the 
elements with the increase of atomic 
weights, are some of the difficulties. In 
comparing these two hypotheses that of 
Graham seems to me very improbable. I 
have thought of valence as dependent upon 
the character of the motion of the atom, 
but cannot well conceive of a similar de- 
pendence of atomic weight and all the other 
properties. There remains, then, the hy- 
pothesis of primal elements by the combina- 
tion of which our elements have been 
formed. These molecules are probably dis- 
tinguished from the ordinary molecules by 
the actual contact and absolute union of 
the component atoms without the inter- 
vention of ether. 
Since these elemental molecules cannot 
as yet be divided, we may retain the name 
atom for them, but the idea of simplicity 
and homogeneity no longer belongs to them. 
The definition of an element as a body 
made up of similar atoms is equally lacking 
in fidelity to latest thought and belief, but 
chemists would scarcely consent to change 
it, and, indeed, it may well be retained, pro- 
vided the modified meaning is given to the 
word atom. But, after al], an element is 
best defined by means of its properties. It 
is by close study of these that we decide 
upon its elemental nature, and through 
them it is tested. Complete reliance can 
no longer be placed upon the balance and 
the supposed atomic weight. 
All elements are acted upon by gravity 
and chemical force and other physical 
forces, but within the last few years certain 
SCIENCE. 281 
gaseous elements have been discovered 
which are not influenced by chemical force 
or affinity. According to some (Piccini, 
Zeits. An. Chem., XIX, 295) this neces- 
sitates a division of the elements into two 
classes. Manifestly, since it is chiefly 
by the action of chemical force that we 
study the elements, the absence of such 
action cuts us off from our chief means of 
finding out anything about them, and it is 
equally clear that bodies so diverse cannot 
well be classified together. If all attempts 
at bringing about the chemical union of 
these gaseous elements with other bodies 
fail, I believe that we should insist upon the 
existence of two classes of elements and 
keep them distinct in all comparisons. 
Of course, we are quite at a loss to say 
just what chemical force is, but it is be- 
lieved to be determined by the electrical 
condition of the atom. Thus we have the 
elements which show the action of chemical 
affinity varying from strongly electro-posi- 
tive to strongly negative. This electrical 
charge of the atom seems to be a primitive, 
inherent property, and so beyond our con- 
trol or power to change. At least no 
change of the kind has ever been recog- 
nized and recorded. Sodium remains posi- 
tive and chlorine negative in spite of all 
that may be done to them. We can, by 
uniting the two temporarily, cloak and neu- 
tralize their opposite natures, but the orig- 
inal condition returns on their release. 
Is it not fair to assume that argon, he- 
lium and their companion gases, having no 
affinity, are without electrical charge— 
atoms from which the electrical charge has 
been withdrawn; the deadest forms of in- 
animate matter? Were they thus without 
electro-chemical properties and affinity 
from the beginning, or did they start out as 
ordinary atoms (if I may so call them), 
and somehow, somewhere lose these prop- 
erties, and with them the power of entering 
into union of any kind, even of forming 
