We also may account for the absence of organic remains in rock-salt to the following cause: the chloride of sodium, when in a state of fusion, might have possessed the property of disintegrating, dissolving, and absorbing within itself, however minute they might be, all particles of organic matter with which it came into contact. Dr. Mantell writes: “It cannot, however, be with certainty determined whether the absence or paucity of fossils in a deposit is owing to the actual reduction of the amount of life in the seas of a given area, or to the mineral character of the strata not having been favourable to the preservation of organic remains.” A very serious difficulty presents itself in the great thickness of many strata of salt; which, if regarded as the solid residuum of sea-water, must have necessarily required a proportionate volume of water, unless the seas of those distant periods contained a larger amount of saline ingredients than they do at the present time: an inference for which there are no reasonable grounds. Wherever there are deposits of the chloride of sodium, they are almost always accompanied with layers and intercalations of gypsum; and the peculiar circumstance of two powerful acids, the sulphuric (in the gypsum, or sulphate of lime), and the muriatic or hydro-chloric (in the chloride of sodium), being so abundantly and uniformly present, seems to point to a common origin; both are productions of volcanic agency, though of the two I think salt frequently owes its origin more to the subterranean activity than the gypsum, because we find there are beds of salt where there is no gypsum, and isolated salt lakes which might have been elevated into mountains had the process, during their production, been of the same force as that used in the formation of rock-salt, owing to an unexplainable interruption and premature desinence. The relation between the formation of gypsum and volcanic action seems to be borne out by the fact that in North America, where the coal measures are not associated with rocks resulting from volcanic agency, there are no gypsum-beds; while on the contrary, there are large deposits of gypsum, where igneous rocks are interpolated beneath the stratum of coal, in Nova Scotia.[44] Sir Charles Lyell, after a careful inquiry into the phenomena exhibited by these strata of gypsum, gives his opinion that the production of these gypsiferous beds in the carboniferous sea was closely connected with volcanic agency, whether in the form of heated vapours or stufas, or of hot mineral springs, or some other effects resulting from submarine igneous irruptions.