granite of the neighbouring 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 a 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-inclosing Nodules were probably formed.—Chemical Effect of Animal Matter in discharging the Colour from Red Sandstone.-Origin of the prevailing Tint to which the System owes its Name. -Successive Modes in which a Metal may exist. The Restorations of the Geologist void of Colour.-Very different Appearance of the Ichthyolites of Cromarty and Moray. THE period of death passed, and over the innumerable dead there settled a soft muddy sediment, that hid them up from the light, bestowing upon them such burial as a November snow-storm bestows on the sere and blighted vegetation of the previous summer and autumn. For an unknown space of time, represented in the formation by a deposit about fifty feet in thickness, the waters of the depopulated area seem to have remained devoid of animal life. A few scales and plates then begin to appear. The fish that had existed outside the chasm seem to have gradually gained upon it, as their numbers increased, just as the European settlers of America have been gaining on the backwoods, and making themselves homes amid the burial mounds of a race extinct for centuries. For a lengthened period, however, these finny settlers must have been comparatively few,-mere squatters in the waste. In the beds of stratified clay in which their remains first occur, over what we may term the densely-crowded platform of violent death, the explorer may labour for hours together without finding a single scale. It is worthy of remark, however, that this upper bed abounds quite as much in the peculiar vegetable impressions of the formation as the lower platform itself. An abundance equally great occurs in some localities only a few inches over the line of the exterminating catastrophe. Thickets of exactly the same algæ amid which the fish of the formation had sheltered when living, grew luxuriantly over their graves when dead. The agencies of destruction which annihilated the animal life of so extended an area, spared its vegetation; just as the identical forests that had waved over the semi-civilized aborigines of North America continued to wave over the more savage red men, their successors, long after the original race had been exterminated. The inference deducible from the fact, though sufficiently simple, seems in a geological point of view a not unimportant one. The flora of a system may long survive its fauna; so that that may be but one formation, regarded with reference to plants, which may be two or more formations, regarded with reference to animals. No instance of any such phenomenon occurs in the later geological periods. The changes in animal and vegetable life appear to have run parallel to each other from the times of the tertiary formations down to those of the coal; but in the earlier deposits the case must have been different. The animal organisms of the newer Silurian strata form essentially different groupes from those of the Lower Old Red Sandstone, and both differ from those of the Cornstone divisions; and yet the greater portion of their vegetable remains seem the same. The stem-like impressions of the fucoid bed of the Upper Ludlow Rocks cannot be distinguished from those of the ichthyolite beds of Cromarty and Ross, nor these again from the impressions of the Arbroath pavement or the Den of Balruddery. Nor is there much difficulty in conceiving how the vegetation of a formation should come to survive its animals. What is fraught with health to the existences of the vegetable kingdom is in many instances a deadly poison to those of the animal. The grasses and water-lilies of the neighbourhood of Naples flourish luxuriantly amid the carbonic acid gas which rests so densely over the pools and runnels out of which they spring, that the bird stoops to drink, and falls dead into the water. The lime that destroys the reptiles, fish, and insects, of a thickly-inhabited lake or stream, injures not a single flag or bulrush among the millions that line its edges. The two kingdoms exist under laws of life and death so essentially dissimilar, that it has become one of the common-places of poetry to indicate the blight and decline of the tribes of the one by the unwonted luxuriancy of the productions of the other. Otway tells us, in describing the horrors of the plague which almost depopulated London, that the "destroying angel stretched his arm" over the city, - Till in th' untrodden streets unwholesome grass A melancholie poisonous green." The work of deposition went on : a bed of pale yellow saliferous sandstone settled, tier over tier, on a bed of stratified clay, and was itself overlaid by another bed of stratified clay in turn. And this upper bed had also its organisms. The remains of its sea-weed still spread out thick and dark amid the foldings of the strata, and occasionally its clusters of detached scales. But the circumstances were less favourable to the preservation of entire ichthyolites than those under which the organisms of the lower platform were wrapped up in their stony coverings. The matrix, which is more micaceous than the other, seems to have been less conservative, and the waters were probably less still. Data is wanting, in the obscurity of the remains, to decide whether a change of species took place in consequence of the catastrophe of the lower platform. Nothing, however, is more probable. The process went on. Age succeeded age, and one stratum covered up another. Generations lived, died, and were entombed in the ever-growing depositions. Succeeding generations pursued their instincts by myriads, happy in existence, over the surface which covered the broken and perishing remains of their predecessors, and then died and were entombed in turn, leaving a higher platform and a similar destiny to the generations that succeeded. Whole races became extinct,-through what process of destruction who can tell? Other races |