262 
MR. J. LARMOR ON" A DYNAMICAL THEORY OF 
terms organized energy and 'unorganized energy with the same meaning, the reference 
being now to the material medium as a continuous organic whole, transmitting applied 
forces by stress, not as a numerical aggregate of separate molecules. But it is to be 
observed that the distinction which is thus intended to be made is not the same as 
the thermodynamic division \\\io free and hound energy, employed by vox Helmholtz, 
which is itself precisely equivalent to the earlier division into available and dissipated 
energy, formulated by Lord Kelvin and Eankixe. The energy which in its actual 
condition is as regards direct mechanical effect unorganized, may become in part 
organized by aid of a physical transformation involving sifting processes of molecular 
fineness, which are necessarily non-mechanical and have no place in the dynamics of 
finite bodies. Thus the unorganized energy of two masses of different gases, at the 
same temperature and pressure, may be in part converted into organized energy and 
so into mechanical work by allowing them to transpire into each other across a porous 
partition, tlie diameters of whose pores approach molecular dimensions ; and the trans¬ 
formation in this case shows itself in a resulting fixll of temperature, when the work 
has been done. In the same way mechanical work may be derived from the 
unorganized energy of liquids by utilizing osmotic pressure; and the stores of energy 
of chemical combination of electrolytic substances, which as it exists in them is 
unorganized, can be largely utilized by making use of the sifting agency of electric 
force on their dual constituents. All these unorganized energies are therefore in part 
thermodynamically available, and others not now available may become so by means 
of yet undiscovered processes. But the unavailable or bound energy of thermo¬ 
dynamics is tlie residuum which we cannot render mechanical by any sifting process 
in bulk, or by anything short of the application of constraint to the individual 
molecules. This residuum may not be absolutely irreducible, but as the knowledge 
of phvsical transformations increases, some parts of it may be raised into the domain 
of available energy: on the other hand the recognition of temperature coefficients in 
reversible processes will show that some energies previously considered as wholly 
available are really in part unavailable. Each such discovery in fact involves an 
amendment or improvement in the corresponding thermodynamic relations ; a process 
which has happened, for example, with respect to Lord Kelvin’s law of electromotive 
force of a voltaic cell. 
aO. Once the idea of temperature is acquired, the whole science of Thermodynamics 
is implicitly involved in the principle of dissipation, that the unavailable part of the 
energy of an isolated material system always tends to increase, never of its own accord 
to diminish. The inference follows directly from this principle, by the reasoning first 
employed by Sadi Carnot, that if the system pass from a state A to a state B such 
that it can retrace its jiath back to A, the unavailable part of the energy is not 
changed: thus there is a whole “ complexus of states, with perfect conti¬ 
nuity of transformation among them, so that any one state is freely convertible 
whether the process has been actually discovered or not—with any other for which 
