THE TETRAKINETIC THEORY 277 
Newton’s third law of the equality of action and reaction is the 
foundation of the modern doctrine of energy, not only in the Newto- 
nian sense but in the most general sense. Newton divined the prin- 
ciple of the conservation of energy in mechanics; Rumford (1798) 
maintained the universality of the laws of energy; Joule (1843) 
established the particular principle of the conservation of energy, 
namely the exact equivalence between the amount of heat produced 
and the amount of mechanical energy destroyed; and Helmholtz, in 
his great memoir Uber die Erhaltung der Kraft, extended this system 
of conservation of energy throughout the whole range of natural 
phenomena. A familiar instance of the so-called transformation of 
energy is where the sudden arrest of a cool but rapidly moving body 
produces heat. This was developed as the first law of thermodynamics. 
At the same time there arose the distinction between potential 
energy, which is stored away in some latent form or manner so that 
it can be drawn upon for work—such energy being exemplified me- 
chanically by the bent spring, chemically by gunpowder, and elec- 
trically by a Leyden jar—and kinetic energy, the active energy of 
motion and of heat. 
While all active mechanical energy or work may be converted 
into an equivalent amount of heat, the opposite process of turning 
heat into work involves more or less loss, dissipation, or degradation 
of energy. This is known as the second law of thermodynamics and is 
the outgrowth of a principle discovered by Sadi Carnot (1824) and 
developed by Kelvin (1852, 1853). The far-reaching conception of 
cyclic processes in energy enunciated in Kelvin’s principle of the 
dissipation ‘of available energy puts a diminishing limit upon the 
amount of heat energy available for mechanical purposes. The avail- 
able kinetic energy of motion and of heat which we can turn into work 
or mechanical effect is possessed by any system of two or more bodies 
in virtue of the relative rates of motion of their parts, velocity being 
essentially relative. 
These two great dynamical principles that the energy of motion 
can be converted into an equivalent amount of heat, and that a certain 
amount of heat can be converted into a more limited amount of power 
were discovered through observations on the motions of larger masses 
of matter, but they are believed to apply equally to such motions as 
are involved in the smallest electrically charged atoms (ions) of the 
chemical elements and the particles flying off in radiant energy as 
phosphorescence. Such movements of infinitesimal particles underlie 
