III.—On a Pebbly Quartz-Schist from the Val d'Anniviers (Pennine Alps)

IN 1893 I described in this Magazine a group of quartz-schists which may be traced for many miles along the Alps—a group belonging to the series which appear to be the newest among the crystalline schists of that chain. I may refer to this paper for a description of their mode of occurrence, distribution, and structure, both macroscopic and microscopic, merely stating that, while considering them to have had a clastic origin—in other words, to be metamorphosed sandstones—I pointed out that they presented some material differences from ordinary quartzites, and that “original fragments [could not] be distinguished with certainty in any of them,” though “here and there a clastic structure,” of which I gave instances, “may be suspected.”