FUNCTION OF CRITICISM IN ADVANCEMENT OF SCIENCE. 359 
Z 
There follows from this, $ = dQ = 0dS. 
*d 
The expression, dS—^Q, is called the entropy law, 
and was put in its final form by Planck. It shows that the 
entropy must increase for a given expenditure of heat oper¬ 
ating at a fixed temperature, or if the entropy is held con¬ 
stant, the temperature must be lower. Hence the entropy 
of the world tends towards a maximum, or the temperature 
of the world is running down towards a minimum. Since 
this formula applies only to Carnot’s reversible processes, we 
find that for all irreversible processes the expression is 
dQ < OdS, and hence the complete expression of the second 
law of thermodynamics is dQ<0dS. For the first law we 
have dE< QdS -f- cL4, where dE is the change in the intrinsic 
energy, 0dS that in heat energy, and dA that from all other 
sources, the sign of equality holding for the reversible pro¬ 
cesses and the sign of inequality for the irreversible pro¬ 
cesses. 
I may well apologize for going so far into technical expres¬ 
sions, but the importance of the conclusion in view is such 
that I beg your indulgence for a very few moments longer. 
When the principles suggested by the second law of thermo¬ 
dynamics are applied to the other processes of nature, it is 
found that nearly every region of phenomena falls under 
the same general form, and that taken together they make 
up one great principle, of which dQ — &.dS. is the type. The 
following table is compiled from Helm’s Energetik, 1898, and 
embraces heat, kinetic and potential mechanical energy, 
central and cyclic work, surface and volume energy, ter¬ 
restrial and universal gravitation, frictional and chemical 
energy, electric and magnetic energy, electric and magnetic 
polarization: 
