as characteristic of a different formation.] But the ravages of no such disease, however extensive, could well account for some of the phenomena of this platform of death. It is rarely that disease falls equally on many different tribes at once, and never does it fall with instantaneous, suddenness; whereas in the ruin of this platform from ten to twelve distinct genera seem to have been equally involved; and so suddenly did it perform its work, that its victims were fixed in their first attitude of terror and surprise. I have observed, too, that groups of adjoining nodules are charged frequently with fragments of the same variety of ichthyolite; and the circumstance seems fraught with evidence regarding both the original habits of the creatures, and the instantaneous suddenness of the destruction by which they were overtaken. They seem, like many of our existing fish, to have been gregarious, and to have perished together ere their crowds had time to break up and disperse. Fish, have been found floating dead in shoals beside submarine volcanoes--killed either by the heated water, or by mephitic gases. There are, however, no marks of volcanic activity in connection with the ichthyolite beds--no marks, at least, which belong to nearly the same age with the fossils. The disturbing granite of the neighboring eminences was not upheaved until after the times of the Oolite. But the volcano, if such was the destroying agent, might have been distant; nay, from some of the points in an area of such immense extent, it must have been distant. The beds abound, as has been said, in lime; and the thought has often struck me that calcined lime, cast out as ashes from some distant crater, and carried by the winds, might have been the cause of the widely-spread destruction to which their organisms testify. I have seen the fish of a small trouting stream, over which a bridge was in the course of building, destroyed in a single hour, for a full mile below the erection, by the few troughfuls of lime that fell into the water when the centring was removed. CHAPTER XIII. Successors of the exterminated Tribes.--The Gap slowly filled.--Proof that the Vegetation of a Formation may long survive its Animal Tribes. Probable Cause.--Immensely extended Period during which Fishes were the Master-existences of our Planet.--Extreme Folly of an Infidel Objection illustrated by the Fact.--Singular Analogy between the History of Fishes as Individuals and as a Class.--Chemistry of the Lower Formation.--Principles on which the Fish-enclosing Nodules were probably formed.--Chemical Effect of Animal Matter in discharging the Color from Red Sandstone.--Origin of the prevailing tint to which the System owes its Name.--Successive Modes in which a Metal may exist.--The Pest orations of the Geologist void of Color.--Very different Appearance of the Ichthyolites of Cromarty and Moray.