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THE JOURNAL OF GEOLOGY.

pleochroic muscovite, that characterizes the conglomerate-gneiss horizon and give to it its greenish color, the result of alteration of a potassium feldspar during dynamic movement. Its other constituents seem to be identical with the neighboring gneisses, but on so slim a basis it is not deemed safe to refer the clastics to any particular gneiss area in the Mount Holly series. The feldspar clastics appear to have been derived from the pegmatite veins that are very abundant in the lower rocks to the east.

The Bear Mountain locality in some respects is more important in its bearing on the question of non-conformity than the one above described; no one area furnishes the data for all the conclusions to be drawn from the horizon. Attention was first called to the abundance of small clastic pebbles of feldspar occurring there, by Edward Hitchcock in 1861,[1] and in 1891, by Mr. Wolff.[2] As remarked by Mr. Pumpelly,[3] there seems to be "no other source than the débris of the deeply decayed Mantle" on which the conglomerate was lain down, and as such they point to a land surface close at hand where sub-aëreal decay had weakened the cohesion of the rocks, permitting a positive movement of the sea to build the more superficial mantle containing the feldspar grains, and a lower semi-disintegrated zone of gneiss and loosened blocks of gneiss into a conglomerate. The phenomenon of false bedding is well shown here, and was figured by Hitchcock[4]; transitions from coarse sediments, when the pebbles of quartz attain a diameter of nearly a foot, to fine material, point to the ordinary conditions obtaining along our coast. So, too, the outlines of the clastics are those that are characteristically produced by wave action, unless deformation has taken place, which is usually the case at this locality. All these facts are subordinate in their value compared to the conclusion to be drawn from the conglomerate-gneiss horizon as a whole, extending as it does across the State of Vermont, and presenting in one

  1. ↑ Opus. cit. p. 34.
  2. ↑ Metamorphism of Clastic Feldspar in Conglomerate Schist.Bull. Comp. Zoöl., Vol. XVI., pp. 173 to 183.
  3. ↑ Opus. cit., p. 211.
  4. ↑ Opus. cit., p. 32.
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