471 
ORIGINAL AND EXTRACTED ARTICLES. 
THE CONSTITUTION OE MATTER. 
BY WILLIAM A. TILDEN, B.SC. LOND., F.C.S., 
DEMONSTRATOR OF PRACTICAL CHEMISTRY TO THE PHARMACEUTICAL SOCIETY. 
[Continued from, page 415.) 
It is urged by Dr. Williamson, in bis recent lecture just quoted, tbat the 
objections to the atomic theory hitherto put forward have never assumed the 
character of open and systematic attack. This is indeed true, but it cannot 
be forgotten that these doubts and objections have arisen from men occupy¬ 
ing the highest rank, not only among metaphysicians, but among chemists 
and physicists. That chemists generally have uttered little complaint may 
be ascribed to a very natural disinclination to find fault with a theory which, 
in one form or other, has done to their science so much good service. Even 
those who do not place faith in the atomic theory as a truth, are not unwilling 
to retain it for the sake of the facilities the application of it affords for the 
expression and colligation of facts. # 
Putting aside for the present abstract speculations as to the possibility ot 
the existence of finite particles, we shall do best to confine ourselves to con¬ 
siderations which most nearly interest the chemist and physicist. I venture 
to offer the following examples from the category of phenomena w hich cannot 
at present be considered capable of explanation by an appeal to the doctrine 
of atoms. The instances I have selected are taken from the great number 
which might be adduced ; but, in stating them, I do so in no spirit mimical 
to the ordinarily received doctrine, but merely to show that our knowledge of 
the rationale of such phenomena is at present only imperfect. However firm 
our allegiance to the doctrine of atoms, it can do no harm to view it from 
the stand-point of an opponent. 
1. The great mainstay of the belief in atoms possessing definite weight is the 
fact that the best known compounds present an invariable composition, 
which is not altered by increased or diminished pressure, temperature, and 
the like ; and that the proportions of the constituents in any two oxides, 
chlorides, sulphides, etc., of the same metal are in a simple ratio to one an- 
I consider it yet remains to be more satisfactorily shown that this definite 
character belonging to ordinary chemical combinations passes through to the 
more complicated instances of which so many are known ; such, foi instance, 
amongst others, as the following. „ . 
There are certain substances, like carbon, silicon, boron, and some ot the 
metals, which it is well known it is next to impossible to obtain in a state of 
absolute chemical purity. Carbon, for example, has never, so far as I know, 
been obtained from any form of charcoal thoroughly purified from minute 
quantities of hydrogen, oxygen, or nitrogen. . 
If we take a piece of pure white sugar, and heat it m an open platinum 
capsule, it melts, catches fire, and, when the combustion is extinguished, 
there remains a shining brittle mass, which may be heated rec.-hot m the an 
for hours ; chlorine gas may be passed over it; it may be boiled m various 
solvent liquids, and dried over again at a red-heat; and, do what we may, 
the charcoal which remains holds a certain, but not fixed, quantity oi hydro¬ 
gen most tenaciously. Now, in the original carbonaceous compound, the 
elements are considered to be in a state of chemical combination ; if so,, n 
must be admitted that the hydrogen which is retained by the charcoal is also 
