September 24,1870.] THE PHARMACEUTICAL JOURNAL AND TRANSACTIONS. 
255 
will surely serve to melt down national animosities, and 
to render impossible the breaking out of disasters so 
fatal to the progress of science and to the welfare of 
humanity as that of which we are now, unfortunately, 
the spectators. 
With regard to the position of chemical science at the 
present moment, it will not take a careful observer long 
to see that, in spite of the numerous important and bril¬ 
liant discoveries of which every year has to boast, we 
are really but very imperfectly acquainted with the funda¬ 
mental laws which regulate chemical actions, and that 
our knowledge of the ultimate constitution of matter upon 
which those laws are based is but of the most elementary 
nature. In proof of this I need only refer to the different 
opinions expressed by our leading chemists, in a discussion 
which lately took place at the Chemical Society on the 
subject of the atomic theory. The President (Dr. William¬ 
son) delivered a very interesting lecture, in which the 
existence of atoms was treated as “the very life of 
chemistry.” Dr. Frankland, on the other hand, states 
that he cannot understand action at a distance between 
matter separated by a vacuous space; and although 
generally granting that the atomic theory explains 
chemical facts, yet he is not to be considered as a blind 
believer in the theory, or as unwilling to renounce it if 
anything better presented itself. Sir B. C. Brodie and Dr. 
Odling both agree that the science of chemistry neither 
requires nor proves the atomic theory; whilst the former 
points out that the true basis of this science is to be 
sought in the investigation of the laws of gaseous com¬ 
bination or the study of the capacity of bodies for heat, 
rather than in committing ourselves to assertions incap¬ 
able of proof by chemical means. Agreeing in the main 
myself with the opinions of the last chemists, and be¬ 
lieving that we must well distinguish between fact and 
theory, I would remind you that Dalton’s discovery of 
the laws of multiple and reciprocal proportions—I use Dr. 
Odling’s word—as well as the differences in the power of 
hydrogen replacement in hydrochloric acid, water, am¬ 
monia, and marsh gas, are facts, whilst the explanation 
upon the assumption of atoms is, as far as chemistry is 
as yet advanced, a theory. If, however, the existence of 
atoms cannot be proved by chemical phenomena, we must 
remember that the assumption of the atomic theory 
explains chemical facts as the undulatory theory gives a 
clear view of the phenomena of light. Thus, for instance, 
one of the most important facts and relations of modern 
chemistry which it appears difficult, if not impossible, to 
explain without the assumption of atoms, is that of 
isomerism. How, otherwise than by a different arrange¬ 
ment of the single constituent particles, are we to account 
for several distinct substances in which the proportions 
of carbon, hydrogen and oxygen are’the same P Why, 
for instance, should forty-eight parts by weight of carbon, 
ten of hydrogen and sixteen of oxygen united together, 
be capable of existing as three different chemical sub¬ 
stances unless we presuppose a different statical arrange¬ 
ment of the parts by which these differences in the de¬ 
portment of the whole are rendered possible ? If, then, 
it be true that chemistry cannot give us positive infor¬ 
mation as to whether matter is infinitely divisible and 
therefore continuous, or consists of atoms and is dis¬ 
continuous, we are in some degree assisted in this inquiry 
by deductions from physical phenomena which have been 
recently pointed out by the genius of Sir William 
Thomson. He argues from four different classes of phy¬ 
sical phenomena, and comes to the conclusion, not only 
that matter is discontinuous, and, therefore, that atoms 
and molecules do exist, but he even attempts to form an 
idea of the size of these molecules, and he states that in 
any ordinary liquid, transparent or seemingly opaque 
solid, the mean distance between the centres of contiguous 
molecules is less than the hundred millionth, and greater 
than the two-thousand millionth of a centimetre. Or, to 
form a conception of this coarse-grainedness, imagine a 
rain-drop or globe of glass as large as a pea, to be magni¬ 
fied up to the size of the earth, each constituent molecule 
being magnified in the same proportion; the magnified 
structure would be coarser-grained than a heap of small 
shot, but probably less coarse-grained than a heap of 
cricket balls. 
There is, however, another class of physical considera¬ 
tions which render the resistance of indivisible particles 
more than likely. I refer to the mechanical theory of 
gases by means of which, thanks to the labours of eminent 
English and German philosophers, all the physical pro¬ 
perties of gases, their equal expansion by heat, the laws 
of diffusion, the laws of alteration of volume imder pres¬ 
sure, can be shown to follow from the simple laws of 
mechanical motion. This theory, however, presupposes 
the existence of molecules, and in this direction again we 
find confirmation of the real existence of Dalton’s atoms. 
Indeed, it has been proved that the average velocity with 
which the particles of oxygen, nitrogen, or common air 
are continually projected forward, amounts, at the ordinary 
atmospheric pressure, to 50,000 centimetres per second, 
whilst the average number of impacts of each of these 
molecules is 5000 millions per second. The mention of 
the molecular motions of gases will recall to the minds of 
all present the great loss which English science has this 
year sustained in the death of the discoverer of the laws 
of gaseous diffusion. Throughout his life Graham’s aim 
was the advancement of our knowledge in the special sub¬ 
ject of the molecular properties of gases. With this intent 
he unceasingly laboured up to the moment of his death, 
in spite of failing health and pressure of official business, 
unfolding for posterity some of the most difficult as well 
as the most interesting secrets of nature in this branch 
of our science. “ What do you think,” he writes to Hof¬ 
mann, “ of metallic hydrogen, a white magnetic metal ?” 
And yet now, through his labours, the fact of the con¬ 
densation of hydrogen in the solid state by metallic palla¬ 
dium, and to a less extent by other metals, has become 
familiar to all of us. Then, again, I would remind you 
of Graham’s recent discovery of the occlusion of hydrogen 
gas in certain specimens of meteoric iron, whilst earth- 
manufactured iron contains not hydrogen but absorbed 
carbonic oxide gas, proving that the meteorite had pro¬ 
bably been thrown out from an atmosphere of incandescent 
hydrogen existing imder very considerable pressure, and 
therefore confirming in a remarkable degree the conclu¬ 
sions to which spectrum analysis had previously led us. 
The position in the ranks of British science left by 
Graham’s death will not be easily filled up; he accom¬ 
plished to a certain extent for dynamical chemistry what 
Dalton did for statical chemistry, and it is upon his ex¬ 
perimental researches in molecular chemistry that Gra¬ 
ham’s permanent fame as one of England’s greatest che¬ 
mists will rest. 
As closely connected with the above subjects, I have 
next to mention a most important research by Dr. An¬ 
drews, of Belfast, which, marking an era in the history 
of gases, shows us how our oldest and most cherished 
notions must give way before the touchstone of experi¬ 
ment. No opinion would appear to have been more 
firmly established than that of the existence of three 
separate states or conditions of matter, viz. the solid, the 
liquid and the gaseous. A body capable of existing in 
two or more of these states was thought to pass suddenly 
from one to the other by absorption or emission of heat, 
or by alterations of the superincumbent pressure. Dr. 
Andrews has shown us how false are our views on this 
fundamental property of matter, for he has proved that 
a large number of, and probably all, easily condensable 
gases or vapours possess a critical point of temperature 
at and above which no increase of pressure can be made 
to effect a change into what we call the liquid state, the 
body remaining as a homogeneous fluid; whilst below 
this critical temperature certain increase of pressure 
always effects a separation into two layers of liquid and 
gaseous matter. Thus, with carbonic acid, the point of 
critical temperature is 30 - 92° C., and with each given 
