FUNCTION OF CRITICISM IN ADVANCEMENT OF SCIENCE. 363 
one comprehensive general law, whose principle once fully 
comprehended makes it possible to critically analyze a multi¬ 
tude of subordinate statements regarding the details of 
thought and theory which are found in current scientific 
literature. 
The above law has been stated as an equality dE~ J. dM, 
but this is applicable only to the cyclically reversible phe¬ 
nomena. Now there is the second great class of phenomena, 
called the irreversible, which are not cyclic; that is to say, if 
a certain state exists in a body at an initial moment, and if after 
goingthrough transformations it can be brought back to the 
same state again, it is reversible; but if it cannot return to that 
state, it is irreversible. Now there are many forms of energy- 
transfer which are irreversible; that is where the energy is 
wasted, so far as the efficient value of it is concerned, as where 
heat is lost by dissipation, electric and magnetic energy by 
radiation. Hence there is the law of dissipation of energy 
as well as the law of conservation, and the dissipation of 
higher power energy seems to be the dominant practical fact 
in the world around us. 
Let us glance backward once more to a previous statement 
regarding the onward march of mechanics as the means of 
solving the physical problems of the universe. At first, 
under the influence of astronomy and mechanics of large 
masses, there was every prospect of its success; but when these 
principles were applied to molecular or atomic masses, and 
to physical laws of greater complexity, the difficulties of the 
mathematicians and physicists began, and they have con¬ 
tinued to be insuperable to this day. The essence of the 
mechanical theory is d’Alembert’s law of work, that force 
operating through a distance is the measure of such work, 
dA = X . ds. Lagrange’s equation of work is derived by 
essentially ignoring spacial coordinates and substituting the 
parameters (intensities) which determine the condition of a 
substance while coupling it with the other quantity (capacity) 
which denotes the direction of the change. In doing this 
two steps are involved: (1) the potential energy of the me- 
