GENERAL MEETING. 49 
character, when once apprehended, have proved more acceptable 
to the imagination than has the conception of central force, 
and under appulsion hypotheses (with the aid of that other readily 
accepted property, repulsion, and certain highly artificial hypo- 
thetical media), it has been made to do duty in providing so-called 
explandtions of gravity, under its form of vis viva. 
It has always seemed to me that the mode of approach adopted 
by Boscovich was the most philosophical and rigorous of any. He 
viewed matter for the purposes of mathematical treatment and for 
investigation of its essentials, as divested of accidental and fugitive 
properties; and as the analytical calculus had not then become so 
developed as to wholly fascinate the attention of geometers with ab-, 
stract and ideal relations, he proceeded from prime physical data. 
He thus identified matter by those apparently general and charac- 
teristic properties recognized by Newton as the basis of mechanical 
philosophy in conjunction with the laws of motion. These proper- 
ties are, as before said, gravity, inertia, and repulsion; or, as char- 
acterized by function, attraction, conservation, distribution. In 
this view matter consists of certain loci of central forces, mutually 
attractive by the first property according to a variable law in the 
duplicate inverse ratio of distance without limit, but restricted in 
manifestation as to the second property to the infinitesimal locus, 
thereby excluding unitary dimension. Contemplating matter un- 
der this aspect alone, a dilemma arose. For gravity waxing by 
the law of inverse squares of the distance up to the focus or origin 
involves the consideration of infinite force and apparently of infi- 
nite velocity in the limit,in the supposable case of rectilinear ap- 
and quantity, i. e., of resistance to change of state except in conformity 
with motion impressed, the property is called vis imsita, which may be vis 
insita activa (momentum), or vis insita passiva (vis inertie of mass.) In 
its aspect of acquirement of a new state of motion by interaction with other 
forces or masses, Newton called the new state thus superposed vis impressa ; 
which, when the operation of acquirement has ceased, becomes again vis 
insita. In its aspect of persistence of mass towards uniform direction of 
motion under the constant deflective stress of vector central force, it is 
called vis centrifuga. And in its active form, conditioned by motion ac- 
quired, its capacity for furnishing motion from its store, either for impressing 
motion upon other mass, with consequent loss, or for supplying the poten- 
tial fund under the drain of adverse central force, is called vis viva (energy.) 
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