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MR. J. J. WATERSTON ON THE PHYSICS OF MEDIA COMPOSED OF 
Appendix I. 
Extract from the Proceedings of the Royal Society (vol. 5, p. 604—March 5, 1846). 
On the Physics of Media that are composed of free and perfectly elastic Molecules in 
a state of Motion. By J. J. Wateeson (sic), Esq. Communicated by Captain 
Beaufort, R.N., F.R.S. 
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 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. 
In an Appendix, the author enters into a full explanation of a table of gases and 
vapours, drawn up with reference to the subjects discussed in his paper. 
