Using the sources of heat before mentioned, and employing diathermanous lenses, or silvered minors, to render the rays from those sources parallel, the absorption of radiant heat was determined, first for the liquid layer, and then for its equivalent vaporous layer. As before, a representative experiment or two will suffice for illustration. When the substance was sulphuric ether, and the source of radiant heat an incandescent platinum spiral, the absorption by the column of vapor was found to be 66.7 per cent. of the total beam. The absorption of the equivalent liquid layer was next determined, and found to be 67.2 per cent. Liquid and vapor, therefore, differed from each only 0.5 per cent.; in other words, they were practically identical in their action. The radiation from the lime light has a greater power of penetration through transparent substances than that from the spiral. In the emission from both of these sources we have a mixture of obscure and luminous rays; but the ratio of the latter to the former, in the lime light is greater than in the spiral; and, as the very meaning of transparency is perviousness to the luminous rays, the emission in which these rays are predominant must pass most freely through transparent substances. Increased transmission implies diminished absorption; and accordingly, the respective absorption of ether vapor and liquid ether, when the lime light was used, instead of being 66.7 and 67.2 per cent., were found to be Vapor....................33.3 per cent. Liquid...................33.3 " no difference whatever being observed between the two states of aggregation. The same was found true of hydride of amyl. This constancy and continuity of the action exerted on the waves of heat when the state of aggregation is changed, I have called "the thermal continuity of liquids and vapors." It is, I think, the strongest illustration hitherto adduced of the conservation of molecular action.