280 
that this ‘‘ volatile alkali’ was classed with 
them before the era of our elements and 
the analogy lead toa vain search for an 
“alkalizing principle’? and later to an 
equally futile pursuit of the metal am- 
monium. 
A further clue to this nature is afforded 
in the remarkable changes of properties 
which can be brought about in some ele- 
ments by ordinary means, and one might 
mention the equally remarkable veiling of 
properties induced by the combining of two 
or more atoms. Thus copper exists in a 
cuprous and a cupric condition, and the 
change from one to the other can be readily 
brought about. And this is true of many 
other elements. 
This has doubtless been a tedious enum- 
eration to you of well-known facts and 
arguments, but it has been necessary, for I 
wish to lead you to the summing-up of 
these arguments and to induce you to 
draw boldly the necessary deductions. It 
is high time for chemists to formulate their 
opinions in this matter. It would seem as 
if we were shut up to one or two conclus- 
ions. Hither these imagined simple bodies 
are after all compounds, built up of two or 
more common constituents, or they are but 
varying forms of one and the same kind of 
matter subjected to different influences and 
conditions. The supposition that they are 
distinct and unrelated simple bodies is, of 
course, a third alternative, but to my mind 
this is no longer tenable. 
The second hypothesis is the one put 
forth by Graham. It was his cherished 
vision of the gaseous particles about which 
he thought so deeply, and in many was so 
truly. Thorpe has written of this as fol- 
lows (loe. cit. 222): 
“ He conceives that the various kinds of 
matter, now recognized as different ele- 
mentary substances, may possess one and 
the same ultimate or atomic molecule ex- 
isting in different conditions of movement. 
SCIENCE. 
[N. 8. Vou. X. No. 244. 
Graham traces the harmony of this hypothe- 
sis of the essential unity of matter with the 
equal action of gravity upon all bodies. He 
recognizes that the numerous and varying 
properties of the solid and liquid, no less 
than the few grand and simple features of 
the gas, may all be dependent upon atomic 
and molecular mobility. Let us imagine, he 
says, one kind of substance only to exist— 
ponderable matter; and, further, that 
matter is divisible into ultimate atoms, uni- 
form in size and weight. We shall have 
one substance and a common atom. With 
the atom at rest the uniformity of matter. 
would be perfect. But the atom possesses 
always more or less motion, due, it must be 
assumed, to a primordial impulse. This 
motion gives rise to volume. The more 
rapid the movement, the greater the space 
occupied by the atom, somewhat as the 
orbit of a planet widens with the degree of 
projectile velocity. Matter is thus made 
to differ only in being lighter or denser 
matter. The specific motion of an atom 
being inalienable, light matter is no longer 
convertible into heavy matter. In short, 
matter of different density forms different 
substances — different inconvertible ele- 
ments, as they have been considered.” 
The hypothesis that the elements are 
built up of two or more common constitu- 
ents has a larger number of supporters and 
would seem more plausible. Some have 
supposed one such primal element by the 
condensation or polymerization of which 
the others were formed. Thus we have 
the hydrogen theory of Prout, modified to 
the one-half atom by Dumas, and finally 
by Zangerle to the one-thousandth hydro- 
genatom. The suggestion of Crookes as to 
the genesis of the elements from the hypo- 
thetical protyle, under the influence of 
electricity, may also be mentioned here. 
Others have adopted the supposition of 
two elements, Reynolds making one of 
these an element with a negative atomic 
