LIBERATING ENERGIES.
When any body or particle possessing Potential Energy is prevented from aggregating with any other body or particle which attracts it, by the interference of an antagonistic Force, its Energy can only assume the Kinetic Mode through the intervention of some external Energy. Such external Energy is itself necessarily in the Kinetic Mode. It is known as a Liberating Energy.
Put in more concrete language, this principle may be otherwise stated thus. A body can only be disengaged from the attraction of one Force and brought under the direct influence of another, by some movement affecting it. A moment’s consideration will make it clear that this is a corollary from previously stated laws.
As we saw that the stronger Force necessarily outweighs the weaker, and as Forces cannot increase or decrease in intensity, the only manner in which any body or particle can be released from the Force which actually governs it and brought under the influence of another Force, is by some movement which either severs it from the sphere of the existing Forces, or brings it within the sphere of a stronger one. In the latter case, it is immaterial whether the movement brings the body into proximity with other bodies, or brings other bodies into proximity with it.
Molar Liberating Energies are those which release masses from the interference of a Force antagonistic to gravitation. The commonest instance of such a Liberating Energy is seen when we remove some obstacle which by its cohesion prevented the aggregation of gravitating masses. Thus a ball suspended by a thread is released by the separative Energy of a knife or scissors. A clock weight wound up but checked by a catch, is released through the Energy which removes the catch. A stone perched on a ledge is released by the puff of wind or the blow from a hand which causes it to topple over. A head of water confined by a sluice is released by the Energy which raises the sluice. A mass of ice on a mountain top is released by the Energy of heat, which breaks down the cohesion of its particles and allows it to trickle down the sides. Even in those cases where the intervention of the Energy is less apparent, we can see in an ultimate analysis that such Energy is really the moving Power at work. Thus, when the string decays instead of being cut, it might seem at first sight that the cohesion melted away imperceptibly; but a closer consideration will show us that the dropping of water, the action of heat and light, the approach of chemical solvents in minute quantities, and the incidence of other unobserved Energies is really the cause of the decay. So, too, if the water makes a way through the sluice, or cuts a path for itself through the bank, it can only do so by the slow action of incident Energies, which wear away the cohering substance that retains it. And the stone can never topple over from its ledge unless some animal pushes it, or some slow water action wears away its supporting mass. Molar Liberating Energies may also be seen in a few cases where a chemical body undergoes a separation which precipitates the heavier among its constituents.
Molecular Liberating Energies are those which release molecules from the interference of a Force antagonistic to cohesion. Two planed pieces of iron cannot cohere if laid side by side on a table: they are restrained in their places by gravitation. But the energy which apposes them to one another acts in this case as a liberator. In other instances, heat performs the same function, by loosening cohering molecules from their existing arrangement, and bringing them within the sphere of their mutual attractions, as when we weld two pieces of iron by heating them, or by hammering them together. The contained energy of water fulfils a like office in gumming or glueing, and in mixing plastic clay or dough. In these cases, one cohesion has interfered with another, and the Liberating Energy, by causing a partial disengagement, finally permits the complete saturation of both affinities.
Atomic Liberating Energies are those which release atoms from the interference of a Force antagonistic to Chemical Affinity. Occasionally it is the mere Force of gravitation or cohesion which opposes this affinity, and in that case, the Energy employed in bringing the substances together is the liberating agent; as when we expose phosphorus to Chlorine. In other instances, however, the mere apposition of the elements is not sufficient, as when we expose carbon to oxygen; heat is then needed as a liberating agent; and we may conjecture that it acts by setting up such a molecular vibration in the carbon as takes each atom out of its existing stable arrangement with other like atoms, into a compound carbon molecule, and brings it within the sphere of the stronger affinity exerted by oxygen. This case leads on to those where the interference is between rival Chemical Affinities. The Energy which brings together two substances and permits the stronger affinity to overcome the weaker acts as a liberating agent. In this instance, too, heat is sometimes necessary as an additional factor, probably for the same reason as before. In the case of Cl and H light acts as the liberating energy. Other less obvious cases resemble those of a match, where friction performs the same function.
Electrical Liberating Energies are those which release Electrical Units from the interference of a Force antagonistic to Electrical Affinity. The usual vagueness of electrical science prevents any definite treatment of these phenomena; but we may consider the Energy which closes the circuit of a battery, or brings the discharging tongs to a Leyden jar, as essentially analogous to the cases noted above. Their fundamental similarity will be seen if we recollect that any Energy spent in overcoming the cohesion of the glass partition in the Leyden jar, and so causing it to break, would produce exactly the same effect.
Under the head of Liberating Energies it will be convenient to include those other Energies which act so as to permit the escape of suppressed Kinetic Energies. Such will be the Energy which turns the valve of a steam-engine or the stopcock of a vessel containing compressed gases. A more familiar instance is found in the Energy which draws the cork of a champagne bottle. And if we were correct in supposing an analogy between known suppressed Energies and explosive nitrogenous compounds such as gunpowder and nitro-glycerine, then the match or blow which explodes them acts as an analogous liberating agent. Liberating Energies of this description may be conveniently described as Liberators of Suppressed Energies.