570 DOLBEAR. [VOL. II.. 
has not only not been applied, it has not even-been assumed : 
and all sorts of visionary entities and special forces have been 
summoned to explain their behavior. Phlogiston and Caloric 
for heat, fluids for electricity ; crystallizing force and vital 
force for the phenomena of organization in crystals and living 
things, —a continuation of the philosophies of the pre-New- 
tonian period, which proved to be inappropriate, inadequate, 
and unnecessary when applied to larger masses. The assumed 
explanation was more mysterious, and needed explanation more 
than the phenomenon to be explained by it; for the latter are 
admitted to be mechanical, while the assumed explanations are 
of a super-mechanical sort, for which there is no evidence apart 
from its implied necessity for accounting for the special move- 
ments observed. 
Another Fontenelle might fairly make game of modern philos- 
ophers who offer such inappropriate explanations of the move- 
ments of matter, whether they be large or small, and who refuse, 
in any case, to assume a mechanical cause for any mechanical 
operation. To be sure, Caloric and Phlogiston and electric fluids 
are no longer serviceable in physics, for it is conceded that heat 
7s a mode of motion; and as for electricity, it is also conceded 
that, whatever it may be, it is certainly not a fluid; and many 
are not ashamed to admit being electrical agnostics, and say 
they don’t know what it is. 
It is certainly the business of physical science to explain phys- 
ical phenomena; and there are certain fundamental principles 
sufficiently well attested which may be assumed at the outset of 
every investigation ; namely, the laws of motion, and that these 
laws are always operative and quantitatively never change. 
Hence every change in the position or collocation of a mass of 
matter of any magnitude is referable to the laws of motion 
of matter, is purely mechanical, and is to be explained solely 
upon the assumption of antecedent motion. 
Even the so-called properties of matter are amenable to this 
principle. Physical terminology is, perhaps, to blame for not a 
little of the incoherence, as is the case when the expansibility 
of a gas or its pressure upon the walls of a containing vessel are 
explained as due to molecular repulsion, seeming to endow the 
molecules with an unmechanical property. When a base-ball 
rebounds from the side of a house against which it has been 
