y, changing its form and relative position an enormous number of
times per second in undirected ways. No two such molecules move in the
same way at the same time, and as all the molecules cohere together,
their motions in different directions balance each other, so that the
body as a whole does not change its position, not because there is no
moving agency in itself, but because the individual movements are
scattering, and not in a common direction. An army may remain in one
place for a long time. To one at a distance it is quiescent, inert. To
one in the camp there is abundant sign of activity, but the movements
are individual movements, some in one direction and some in another, and
often changing. The same army on the march has the same energy, the same
rate of individual movement; but all have a common direction, it moves
as a whole body into new territory. So with the molecules of matter. In
large masses they appear to be inert, and to do nothing, and to be
capable of doing nothing. That is only due to the fact that their energy
is undirected, not that they can do nothing. The inference that if
quiescent bodies do not act in particular ways they are inert, and
cannot act in any kind of a way, is a wrong inference. An illustration
may perhaps make this point plainer. A lump of coal will be still as
long as anything if it be undisturbed. Indeed, it has thus lain in a
coal-bed for millions of years probably, but if coal be placed where it
can combine with oxygen, it forthwith does so, and during the process
yields a large amount of energy in the shape of heat. One pound of coal
in this way gives out 14,000 heat units, which is the equivalent of
11,000,000 foot-pounds of work, and if it could be all utilized would
furnish a horse-power for five and a half hours. Can any inert body
weighing a pound furnish a horse-power for half a day? And can a body
give out what it has not got? Are gunpowder and nitro-glycerine inert?
Are bread and butter and foods in general inert because they will not
push and pull as a man or a horse may? All have energy, which is
available in certain ways and not in others, and whatever possesses
energy available in any way is not an ideally inert body. Lastly, how
many inert bodies together will it take to make an active body? If the
question be absurd, then all the phenomena witnessed in bodies, large or
small, are due to the fact that the atoms are not inert, but are
immensely energetic, and thei