248 Jordan on the Floatage of 



diminishing the temperature of the steam, and the due propor- 

 tion of heat, the particles of water approach to within distances 

 at which they attract each other, the attractions of the heat by 

 the diminished accumulation of its particles being also dimi- 

 nished, the particles of water run together, the mass loses its 

 transparency, but the particles of water lose not their power of 

 floatage, until by the further diminution of heat, and consequent 

 union of particles of water into larger and larger masses, they 

 form drops, and are precipitated, or by further diffusion of heat, 

 and of the particles of water in atmospheric air, they are again 

 attracted by the air, and again dissolved in it, even at lower 

 temperatures than that of steam. When coals are exposed to 

 the action of fire, vapours are thrown off more gross and black 

 at first, subsequently, of colours less and less dark. 



The exhibition from Meux's brew-house a few years ago, of 

 the vapour of water from a steam-pipe, and at the same time 

 of that of coal from a chimney close to the other, formed objects 

 of curious and amusing observation. The beautiful white va- 

 pour from the steam-pipe, as contra-distinguished from that of 

 the chimney, and the consideration that one was composed 

 entirely of water, and that the other contained none or scarcely 

 any, led to reflections on the general formation of vapours, and 

 state of those of the metropolis, and the general principles upon 

 which the floatage of small bodies in the atmosphere depends, 

 which lead also to the explanation of many curious phsenomena. 



All idea of the repulsions of the particles of bodies by each 

 other, and of light by bodies at any distances, as advanced by 

 philosophers, has long been superseded by the better opinion 

 and proof that what was supposed to be by the repulsion of one 

 body, was effected by the attraction of another, and in the 

 Newtonian observations, has been distinctly shown by repeating 

 and varying his experiments on the inflections of light. One 

 grand exception, however, exists in the case of heat, the par- 

 ticles of which repel each other, although attracted by, and 

 attracting, the particles of all other bodies. The preceding 

 observations confirm the doctrine in all cases of vapour from 

 steam, of vapour from water in the atmosphere, and of dry 



