Page:Great Neapolitan Earthquake of 1857.djvu/227

Rh the weather (meteori). One of the most surprising examples of this kind of decay may be observed in the upper part of the valley of Tramonti, in the province of Salerno, where the phenomenon extends over a large tract of ground. In some places, as in the vicinity of Amalfi, the magnesian limestone presents the characteristics of Dolomite, having a granular texture, and dissolving slowly in acids. However, we cannot subscribe to the opinion of those who attribute the presence of magnesia to the action of internal plutonic masses, which have given to the sedimentary limestone rocks the characteristics of Dolomite. There is no ground for refutation of the opinion, that true Dolomite is of neptunian origin, and therefore its presence is insufficient to prove that the change has been occasioned by plutonic rocks. And the reasons which prevent our applying the theory of dolomization to our Apennine mountains are—1st. The absence of plutonic rocks in their vicinity, which might occasion the phenomenon. 2nd. The rare occurrence of true Dolomite, and the fact that it is confusedly mixed with magnesian limestone, which does not possess the distinctive characteristics of Dolomite. And, lastly, the organic forms of well-preserved fossils in those rocks which most manifest dolomitic qualities. The last is one of the best arguments against the maintenance of the Dolomite theory in reference to our magnesian limestones, but of it we do not find many examples. We might conclude that the presence in great quantity of carbonate of magnesia is adverse to the propagation of marine animals, or that it has contributed to the destruction of the shells of the ancient fauna. In the Dolomite of Amalfi, where we found several well-preserved casts of Terrebratulæ and Ammonites, this opinion is still further strengthened; for in all the examples which we examined their shells were entirely destroyed. The preceding considerations, however adverse to the phenomenon of dolomization in the rocks of our Apennines, do not exclude the internal plutonic forces, by which they were disturbed from their primitive position, and raised to their present height; nor the phenomenon of metamorphosis, which is clearly manifested in some particular districts, where limestone is found at a short distance from crystalline rocks of igneous origin. In the district of Castrovillari, perhaps more than anywhere else, frequent examples of VOL. I.