Page:Geology and Mineralogy considered with reference to Natural Theology, 1837, volume 1.djvu/105

 Rh freshwater from a bursting lake, or unusual land flood, is often fatal to large numbers of the inhabitants of the waters thus respectively interchanged.

The greater number of fossil fishes present no appearance of having perished by mechanical violence; they seem rather to have been destroyed by some noxious qualities imparted to the waters in which they moved; either by sudden change of temperature or an admixture of carbonic acid, or sulphuretted hydrogen gas, or of bituminous or earthy mutter in the form of mud.

The circumstances under which the fossil fishes are found at Monte Bolea seem to indicate that they perished suddenly on arriving at a part of the then existing seas, which was rendered noxious by the volcanic agency, of which the adjacent basaltic rocks afford abundant evidence. The skeletons of these fish lie parallel to the lamimæ of the strata of the calcareous slate; they are always entire, and so closely packed on one another, that many individuals are often contained in a single block. The thousands of specimens which are dispersed over the cabinets of Europe, have nearly all been taken from one quarry. All these fishes must have died suddenly on this fatal spot, and have been speedily buried in the calcareous sediment then in the course of deposition. From the fact that certain individuals have even preserved traces of colour upon their skin, we are certain that they were entombed before decomposition of their soft parts had taken place.