PRESIDENT’S ADDRESS—SECTION A. 19 
3. The Conception Convenient, rather than Necessary.— 
According to the late Professor Clifford, this conception is some- 
thing more than hypothesis ; he even went so far as to say, in con- 
cluding his “ fiddle-string” illustration of the contrast between 
molar and molecular vibration, that “ the modern theory of the 
constitution of matter is put upon a basis which is wholly inde- 
pendent of hypothesis. The theory is simply an organised state- 
ment of the facts.” Despite this dictum, one is tempted to 
think that the conception is justified by its convenience, rather 
by an absolute necessity ; it is always possible, and by no means 
always undesirable, to regard the phenomena of Nature from the 
purely empirical standpoint, and it is assuredly quite legitimate 
to esteem either the verbal or mathematical expression of the 
laws or uniformities subsisting among those phznomena, even 
though these laws be deduced from the most elementary 
hypotheses, and justified by the most complex experiments, as 
purely formal. There is, however, some advantage to the stu- 
dent of physics, as such, in treating physical conceptions as 
though they exactly coincided with the realities intended to be 
represented by them. To the great majority the hypotheses of 
physical science are, and ever will be, verities of verities; and 
in the imagination of these the atom will always, as with 
Democritus, possess a reality that is unique. And so long as 
such materialistic conceptions are not obtruded into that higher 
region with which mental philosophy is concerned, it is well that 
the terms and thought of our Natural Philosophy should be cast 
in a purely materialistic mould, and with that philosopher we 
may say, concerning of course the material world only, “in truth 
nothing exists but atoms and void.” (a). 
4. Scope of Subject as Treated—F¥rom the purely physical 
point of view, therefore, I propose to review historically the 
origin and progress of this theory of the constitution of matter, 
to touch, perforce incidentally, upon the part it has played in the 
explanation of some few of the facts of physical science, and 
finally to submit for your consideration some observations upon 
the philosophy of atomism, that is, upon what I conceive to be 
the real nature of materialistic explanations, and upon the limi- 
tations of the atomic conception itself. 
5. The Origin of Atomism Remarkable.—The theory that the 
ultimate constituents of all material substances are extremely 
minute and insecable particles, i¢., drow, seems never to 
have arisen into prominence in the western world before the 
time of Anaxagoras (4), although it has been alleged that atoms 
were spoken of by Mosphus of Phrygia before the siege of 
(a) ren 6€ drowa Kali Kevov. Mullach. Frag. Philos. Greee. I. 357. 
(>) [500?— 428 B.C.] For the doctrines of Anaxagoras see Mullach. Frag. Philos. 
Gree. I. 243—257. 
B2 
