Statistical theories of matter, radiation and electricity

The atomic or “kinetic” theory of gases, with its interpretations of such qualities as temperature, pressure, viscosity and conductivity, has ranked for more than half a century as a very important part of theoretical physics. A corresponding theory for radiation and for negative electricity is much to be desired, since it is known that in many ways each of these entities behaves as though it were atomic. There are, however, differences among the three, and only within the last five years have these been formulated suitably. This article is devoted to the resulting statistical theories.