530 PRESIDENTS ADDRESS—SECTION A. 
arise from stresses which accompany distribution of strain. Col- 
lisions between strain-figures will not set them vibrating so that 
an atom would, as required by the dynamical theory of heat, 
have a finite number of degrees of freedom. The size and nature 
of possible strain-figures, therefore of possible atoms, would be 
limited by conditions of equilibrium, thus giving rise, perhaps, 
to a discrete series. The theory does not, any more than Lord 
Kelvin’s, explain why the mass of a material body equals the 
mass of its atoms. The supposition of limitations implies struc- 
ture in the ether. The limit in the number of atoms may, it is 
thought, be determined by the “ coarse-grainedness” [and other 
qualities ?] of the medium (d). Larmor’s doctrine is essentially 
similar to Burton’s. His electrons, or the ultimate constituents 
of the atoms, form rotating systems, and are singular points in 
the zthereal plenum. 
This concludes the history of fundamental conceptions of 
atomism, approached from the standpoint of general physics. 
AG 
ATOMISM IN CHEMISTRY. 
24. General.—No sketch of the atomistic conception, however, 
would be adequate which omitted all reference to the illustrious 
part it has played in the evolution of chemistry, for it is there 
that its practical value is best seen. The power it has conferred 
upon our effort to operate upon the more simple forms of 
matter, and to produce forms many of which apparently do not 
occur in the ordinary course of Nature, is a signal example of 
the potentiality of abstract conceptions, even though they are 
admittedly defective. 
25. Boyle.—This history of chemistry, a history of brilliant 
achievements, may almost be said to commence with Boyle, to 
whom reference has previously been made (sec. 12). Enunciat- 
ing the views that only the undecomposable constituents of 
bodies are to be regarded as elements in the chemical sense, that 
any adequate theory must be founded on extensive observations 
and experiments, that the corpuscular view of the constitution of 
matter throws light upon the formation and decomposition of 
bodies, Boyle brought about the demise of the then prevailing 
theory of the threefold constitution of matter, and paved the 
way for a truer science. 
26. The Genesis of the Chemical Atomic Period.—The quan- 
titative work of chemists quickly revealed the fact that in 
chemical combination the proportions are definite. About 1790 
(d) [I.¢., p. 872. ] 
