It is necessary, in the first place, to refer briefly to the
phenomena attending the transfer of energy within and into
inanimate material systems. It is not assumed here that these
phenomena are restricted in their sphere of action to inanimate
nature. It is, in fact, very certain that they are not; but while
they confer on dead nature its own dynamic tendencies, it will
appear that their effects are by various means evaded in living
nature. We, therefore, treat of them as characteristic of
inanimate actions. We accept as fundamental to all the
considerations which follow the truth of the principle of the
Conservation of Energy.[1]
[1] "The principle of the Conservation of Energy has acquired so
much scientific weight during the last twenty years that no
physiologist would feel any confidence in an experiment which
showed a considerable difference between the work done by the
animal and the balance of the account of Energy received and
spent."--Clerk Maxwell, _Nature_, vol. xix., p. 142. See also
Helmholtz _On the Conservation of Force._
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Whatever speculations may be made as to the course of events very
distant from us in space, it appears certain that dissipation of
energy is at present actively progressing throughout our sphere
of observation in inanimate nature. It follows, in fact, from the
second law of thermodynamics, that whenever work is derived from
heat, a certain quantity of heat falls in potential without doing
work or, in short, is dissipated. On the other hand, work may be
entirely converted into heat. The result is the heat-tendency of
the universe. Heat, being an undirected form of energy, seeks, as
it were, its own level, so that the result of this heat-tendency
is continual approach to uniformity of potential.
The heat-tendency of the universe is also revealed in the
far-reaching "law of maximum work," which defines that chemical
change, accomplished without the intervention of external energy,
tends to the production of the body, or system of bodies, which
disengage the greatest quantity of heat.[1] And, again, vast
numbers of actions going on throughout nature are attended by
dissipatory thermal effects, as those arising from the motions of
proximate molecules (friction, viscosity), and from the fall of
electrical potential.
Thus, on all sides, the energy which was once most probably
existent in the form of gravitational potential, is being
dissipated into unavailable forms. We must
[1] Berthelot, _Essai de Mécanique Chimique._
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recognize dissipation as an inevitable attendant on inanimate
transfer of energy.
But when we come to consider inanimate actions in relation to
time, or time-rate of change, we find a new feature in the
phenomena attending transfer of energy; a feature which is really
involved in general statements as to the laws of physical
interactions.[1] It is seen, that the attitude of inanimate
material systems is very generally, if not in all cases,
retardative of change--opposing it by effects generated by the
primary action, which may be called "secondary" for convenience.
Further, it will be seen that these secondary effects are those
concerned in bringing about the inevitable dissipation.
As example, let us endeavour to transfer gravitational potential
energy contained in a mass raised above the surface of the Earth
into an elastic body, which we can put into compression by
resting the weight upon it. In this way work is done against
elastic force and stored as elastic potential energy. We may deal
with a metal spring, or with a mass of gas contained in a
cylinder fitted with a piston upon which the weight may be
placed. In either case we find the effect of compression is to
raise the temperature of the substance, thus causing its
[1] Helmholtz, _Ice and Glaciers._ Atkinson's collection of his
Popular Lectures. First Series, p.120. Quoted by Tate, _Heat_,
p. 311.
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expansion or increased resistance to the descent of the weight.
And this resistance continues, with diminishing intensity, till
all the heat generated is dissipated into the surrounding medium.
The secondary effect thus delays the final transfer of energy.
Again, if we suppose the gas in the cylinder replaced by a vapour
in a state of saturation, the effect of increased pressure, as of
a weight placed upon the piston, is to reduce the vapour to a
liquid, thereby bringing about a great diminution of volume and
proportional loss of gravitational potential by the weight. But
this change will by no means be brought about instantaneously.
When a little of the vapour is condensed, this portion parts with
latent heat of vaporisation, increasing the tension of the
remainder, or raising its point of saturation, so that before the
weight descends any further, this heat has to escape from the
cylinder.
Many more such cases might be cited. The heating of india-rubber
when expanded, its cooling when compressed, is a remarkable one;
for at first sight it appears as if this must render it
exceptional to the general law, most substances exhibiting the
opposite thermal effects when stressed. However, here, too, the
action of the stress is opposed by the secondary effects
developed in the substance; for it is found that this substance
contracts when heated, expands when cooled. Again, ice being a
substance which contracts in melting, the effect of pressure is
to facilitate melting, lowering its freezing point. But
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so soon as a little melting occurs, the resulting liquid calls on
the residual ice for an amount of heat equivalent to the latent
heat of liquefaction, and so by cooling the whole, retards the
change.
Such particular cases illustrate a principle controlling the
interaction of matter and energy which seems universal in
application save when evaded, as we shall see, by the ingenuity
of life. This principle is not only revealed in the researches of
the laboratory; it is manifest in the history of worlds and solar
systems. Thus, consider the effects arising from the aggregation
of matter in space under the influence of the mutual attraction
of the particles. The tendency here is loss of gravitational
potential. The final approach is however retarded by the
temperature, or vis viva of the parts attending collision and
compression. From this cause the great suns of space radiate for
ages before the final loss of potential is attained.
Clerk Maxwell[1] observes on the general principle that less
force is required to produce a change in a body when the change
is unopposed by constraints than when it is subjected to such.
From this if we assume the external forces acting upon a system
not to rise above a certain potential (which is the order of
nature), the constraints of secondary actions may, under certain
circumstances, lead to final rejection of some of the energy, or,
in any
[1] _Theory of Heat_, p. 131.
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case, to retardation of change in the system--dissipation of
energy being the result.[1]
As such constraints seem inherently present in the properties of
matter, we may summarise as follows:
_The transfer of energy into any inanimate material system is
attended by effects retardative to the transfer and conducive to
dissipation._
Was this the only possible dynamic order ruling in material
systems it is quite certain the myriads of ants and pines never
could have been, except all generated by creative act at vast
primary expenditure of energy. Growth and reproduction would have
been impossible in systems which retarded change at every step
and never proceeded in any direction but in that of dissipation.
Once created, indeed, it is conceivable that, as heat engines,
they might have dragged out an existence of alternate life and
death; life in the hours of sunshine, death in hours of darkness:
no final death, however, their lot, till their parts were simply
worn out by long use, never made good by repair. But the
sustained and increasing activity of organized nature is a fact;
therefore some other order of events must be possible.
[1] The law of Least Action, which has been applied, not alone in
optics, but in many mechanical systems, appears physically based
upon the restraint and retardation opposing the transfer of
energy in material systems.
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