GENERAL MEETING. 65 
In conclusion, I know nothing of force except as a manifestation 
of matter, and nothing of matter except through its manifesta- 
tions. It is substance that interacts with substance, so far as we 
know, always reciprocally, and force is but the convenient transla- 
tion of the terminology invented by Newton to designate these 
several species or modes of action, in the word vis, with its appro- 
priate adjective. He was arraigned by the Cartesians (and virtu- 
ally is by their modern representatives) as the reintroducer of oc- 
cult qualities into philosophy, but his statement was “hypotheses 
non fingo,’ and to a similar charge brought against him by Leib- 
nitz he pertinently replied that it was a misuse of words to call 
those things occult qualities whose causes are occult though the 
qualities themselves be manifest. 
I have adopted gravity as the type of central inherent force— 
vis centripeta—but I would not thereby be understood as excluding 
from the category of material forces any and all other modes of 
tensile or constraining force which may be hereafter made out as 
specific, by the elucidation of such phenomena as affinity, cohesion, 
tenacity, elasticity, ductility, viscosity, capillarity, polarity, mag- 
netism, etc., now so little understood, any more than I would ex- 
clude any form or mode of energy which may be observed, from 
the category of material phenomena. The Newtonian doctrine of 
force would not be impaired by such discovery, and its strength 
lies in the fact that it as readily includes static phenomena—that 
despair of the kinetist, who has no imaginable hypothesis by which 
to range them under a form of motion—as it does kinematical phe- 
nomena. Statical force (Newton’s vis mortua) cannot be ignored 
in a theory of force. The straw that breaks the camel’s back— 
the very lightning that crashes through the sky—are familiar ex- 
amples of its power made manifest. Its reality may be exemplified 
by suspending two heavy balls of equal weight at equal heights— 
one by an elastic cord, and the other by a tense string. The dif- 
ference of effort required to displace the two vertically upwards, 
which can be measured, makes sensible the difference between the 
two forms of balanced statical forces. In the one case the antago- 
nizing force is suddenly withdrawn, and in the other gradually. 
Wherever strain exists—and it is everywhere—there force. is as 
certainly present as when it becomes manifested in a stress relieved 
by motion and measurable in terms of energy. 
