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Show FEAGMENTAL V0LC.OJT0 EOCKSâ€"CONGLOMEEATES. 77 pletely the notion that these fragments have been hurled into their present positions by the explosive energy at the vents. Scoriaceous or slaggy fragments, "volcanic bombs," and the many forms which lava takes when the blast from the crater carries up portions of the liquid and scatters them round the surrounding cone, are not found in the conglomeratesâ€"at least I have never observed them. I will except from this statement, however, one locality in the southern part of the Sevier Plateau, where a profound gorge (named Sanford Canon) gives a brief exposure of what seems to have been an ancient trachytic vent subsequently buried by massive outflows, and which is composed chiefly of cinders. This can hardly be called a conglomerate, however. The fragments of the true conglomerates are apparently pieces of massive lava, just such as are riven by the frost and other agencies of secular decav from cold rocks in situ. Very many of them show more or less weathering or corrosion of their surfaces, and very many do not indicate a trace of such action beyond a slight discoloration. That these fragments have been broken from massive rocks is too patent to admit of question. The only explanation of .the origin of the conglomerates which does not involve us in absurdity is that they are derived from the waste of massive volcanic rocks under the normal processes of degradation manifested in all mountainous regions. While active vents usually throw out fragmental matter in great quantities, and while some of the fragments may have been thus derived, yet I conceive that this process has contributed but an insignificant portion of the entirety of the conglomerates. In the chapter on the Sevier Valley and its alluvial conglomerates, I shall describe the process, now in visible operation, by which beds of a similar nature are accumulating at the present day upon a scale of magnitude not inferior to that which produced the colossal formations now seen in the palisades of the plateaus. Throughout the valleys which intervene between the ranges of plateaus fragmental beds are accumulating in vast masses High up in the tabular ranges the frosts, rains, and torrents are gradually breaking up, not only the anciently-outpoured masses of lava, but also the older conglomerates, and are bearing down through the great ravines and gorges the debris torn from the rocks, and are scattering them over the valley plains in the form of very depressed |