According to equivalent (1) growth of entropy is a passage from more to less available energy. The comment already made on [p. 42] indicates sufficiently that this increase in unavailability is due to the growth of the ungovernable features of molecular motions as number of complexions increases.
Equivalent (2) states growth of entropy to be a passage from a concentrated to a distributed condition of energy. In this scattered state the energy is certainly less controllable and for the same reason as that given concerning equivalent (1).
Equivalent (3) is based on the idea of irreversibility, and we saw on [p. 36] that the growth in the number of complexions is the measure as well as the criterion of irreversibility. This growth is therefore a sufficient and necessary feature of this equivalent.
The equivalents grouped under (4) are all based on the theory of probabilities. We have seen on pp. [36], [62], and elsewhere, that the probability
of a state is the logarithm of the number of complexions of the state. This number is therefore a necessary feature of this set of equivalents and hence constitutes its physical significance.
The set of equivalents grouped under (5) are all closely related, their dependence being more or less indicated by the order in which they are there stated. The outcome of the series is that growth of entropy corresponds to an increase in the number of complexions.
The mathematical concept stated under (6) covers more than molecular configurations; it covers configurations whose elements are those of energy as well, and has been successfully applied by PLANCK in problems dealing with the energy of radiation. Every such configuration has a number of complexions.
SECTION E
PHYSICAL SIGNIFICANCE OF THE MORE SPECIFIC STATEMENTS OF THE SECOND LAW GIVEN ON PAGES [44]-[47]
In making here the contemplated comparisons and interpretations we must keep in mind the three helpful propositions given on [p. 44].