The extreme internal mobility betrayed by Carrington's and Spörer's observations led to the inference that the matter composing the sun was mainly or wholly gaseous. This had already been suggested by Father Secchi[435] a year earlier, and by Sir John Herschel in April, 1864;[436] but it first obtained general currency through Faye's more elaborate presentation. A physical basis was afforded for the view by Cagniard de la Tour's experiments in 1822,[437] proving that, under conditions of great heat and pressure, the vaporous state was compatible with a very considerable density. The position was strengthened when Andrews showed, in 1869,[438] that above a fixed limit of temperature, varying for different bodies, true liquefaction is impossible, even though the pressure be so tremendous as to retain the gas within the same space that enclosed the liquid. The opinion that the mass of the sun is gaseous now commands a very general assent; although the gaseity admitted is of such a nature as to afford the consistence rather of honey or pitch than of the aeriform fluids with which we are familiar. On another important point the course of subsequent thought was powerfully influenced by Faye's conclusions in 1865. Arago somewhat hastily inferred from experiments with the polariscope the wholly gaseous nature of the visible disc of the sun. Kirchhoff, on the contrary, believed (erroneously, as we now know) that the brilliant continuous spectrum derived from it proved it to be a white-hot solid or liquid. Herschel and Secchi[439] indicated a cloud-like structure as that which would best harmonise the whole of the evidence at command. The novelty introduced by Faye consisted in regarding the photosphere no longer "as a defined surface, in the mathematical sense, but as a limit to which, in the general fluid mass, ascending currents carry the physical or chemical phenomena of incandescence."[440] Uprushing floods of mixed vapours with strong affinities--say of calcium or sodium and oxygen--at last attain a region cool enough to permit their combination; a fine dust of solid or liquid compound particles (of lime or soda, for example) there collects into the photospheric clouds, and descending by its own weight in torrents of incandescent rain, is dissociated by the fierce heat below, and replaced by ascending and combining currents of similar constitution.