614 
The Vehicle of Force. 
[October, 
in local disturbances of the great sum of parallel motions. 
In faCt all the special force phenomena of Nature are con- 
sequences of such local disturbances, and produce but 
temporary variations in the general vigour of attractive 
energy. 
But if, as we have argued, both impact force and directive 
force are results of momentum, it may, at first sight, seem 
as if matter had something to do with them, for at equal 
speeds the vigour of momentum depends upon the quantity 
of matter. And yet, in reality, matter has nothing what- 
ever to do with momentum, which is a property of motion 
alone. In momentum only the vigour of motion is con- 
cerned ; in no sense the quantity of matter. For the motive 
vigour which moves one mass of matter at a certain speed 
will move half that mass at a double speed. And if this 
motive vigour be successively transferred to gradually de- 
creasing masses it will move them more and more rapidly, 
the momentum remaining the same though the quantity of 
matter be infinitely varied. If, finally, the mass of matter 
be diminished to its vanishing point, the speed of motion 
will rise to infinity, the momentum continuing unchanged. 
Momentum, then, is not a property of matter, but of motion ; 
and if impaCt and directive force are both controlled by 
momentum, they are attributes of motion only, and matter 
has no office in Nature save to serve as the vehicle of 
motion, it being the concrete substratum through whose aid 
motion attains manifestation, and becomes capable of 
assuming the most varied and complex arrangements, 
yielding intricate relations of force. 
But there is a secondary result of the law of force which 
is one of the most aCtive influences in Nature, and which 
we must now consider. Directive force, as we have argued, 
tends to draw bodies together or to drive them apart. But 
ordinarily this tendency is resisted and becomes ineffective. 
So far, for instance, as the mutual cosmical motions of par- 
ticles are concerned, every particle may be so placed that 
the attractive energy arising from these motions affeCts it 
equally from opposite directions, and thus becomes neutral- 
ised. Only when some local aggregation of momentum 
causes the attraction in one direction to overbalance that in 
the other, does movement in response to attraction result. 
There is thus a constant tendency in the motions of parti- 
cles to become parallel, in response to their cosmical rela- 
tions, while their local movements are only minor deviations 
from this persistent line of direction. 
But they not only tend to become parallel in direction, 
