206 
Newtonian physical philosophy, it is next required to show in what 
manner the consequences of its hypotheses may be calculated, and 
how by comparisons of calculated results with facts of observation 
the truth of the hypotheses may be tested. First, it may be 
remarked that the properties of the atoms and of the ether have 
been so defined that they form at once a basis for mathematical 
calculation. In short, under these hypothetical conditions, the 
facts of observation become for the most part only problems to be 
solved according to the principles and rules of Hydrodynamics. 
.Towards effecting such solutions little could be done in Newton’s 
time, because mathematics were not then sufficiently advanced to 
admit of this application. Not long afterwards, the occult quality 
of gravity, as I have already intimated (art. 8), having been 
generally accepted, Newton’s metaphysical views were discarded or 
fell into neglect, and at the present day they are either silently 
put aside, or are even strenuously opposed. Consequentlv for 
pointing out the consequences to which that philosophy conducts 
(which for the purposes of my argument it is necessary to do), I 
am compelled to .advert to researches which I have myself under- 
taken with the view of testing its principles and extending their 
application, none of my scientific contemporaries, for a ^reason 
which I shall shortly have to point out, having occupied the same 
ground. 
25. Previous to stating by means of what calculations the hypo- 
theses of the Newtonian system of Physics are verified, it is 
necessary to obtain a distinct conception of the meaning of 
“ moving force.” Reverting again to the experiment described 
in art. I 5, it will be seen that what is there called a personal effort 
is, in fact, a moving, force in the ordinary sense of this expression. 
It is, however, moving force in a special sense, having reference 
only to the personal efforts required for accelerating different 
masses in the same degree. But clearly another experiment, in 
which the mechanical acceleration of the pilot sphere could be 
changed at each trial, might indicate that different personal efforts 
are required for accelerating the same mass in different decrees 
and might suggest that the effort is in exact proportion to the 
acceleration. Both kinds of experiment are required for exhibit- 
ing the complete meaning of “moving force”; and the meta- 
physical inference to be drawn, according to this philosophy, from 
the two together, is, that moving force is always and everywhere 
in essence personal effort. This, however, is not the inference 
with which we are concerned at present. In consequence of what 
is suggested by these and like experiments, moving force in its 
scientific sense is assumed to consist of two factors, one of which 
expresses that it is exactly proportional to the mass when the 
