On the Physics of media that are composed of free and perfectly elastic molecules in a state of motion

Abstract

This memoir contains the enunciation of a new theory of heat, capable of explaining the phenomena of its radiation and polarization, and the elasticity of various bodies, founded on the hypothesis of a medium consisting of a vast multitude of minute particles of matter endowed with perfect elasticity, and enclosed in elastic walls, but moving in all directions within that space, with perfect freedom, and in every possible direction. In the course of these motions, the particles must be supposed to encounter one another in every possible manner, during an interval of time so small as to allow of their being considered infinitesimal in respect to any sensible period ; still, however, preserving the molecular vis viva constant and undiminished. The author then enters into extensive analytical investigations ; first, of the conditions that determine the equilibrium of such a homogeneous medium, as is implied by the hypothesis, and of the laws of its elasticity ; secondly, of the physical relations of media that differ from each other in the specific weight of their molecules ; thirdly, of the phenomena that attend the condensing and dilating of media, and of the mechanical value of their molecular vis viva ; fourthly, of the resistance of media to a moving surface ; fifthly, of the vertical equilibrium of a medium surrounding a planet and constituting its atmosphere ; and lastly, of the velocity with which impulses are transmitted through a medium so constituted.