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THE JOURNAL OF GEOLOGY.

considered after a general description of the rocks comprising the second or lower division of the Algonkian terranes has been given.

The Lower or Mount Holly Series of the Algonkian.

In the amphitheatre already described, the rocks of this series occur well-developed in the towns of Mount Holly and Shrewsbury and extend south probably to near the Massachusetts line. They are perhaps no more characteristically developed in Mount Holly than elsewhere to the south, or possibly to the north, but they are best known to me there of anywhere in the State. It seems best, therefore, to designate the rocks of this central area, or core of the Green Mountains, the Mount Holly series.

In nearly every way the core rocks are contrasted with the Mendon series; these differences will be emphasized below when the question of the relations of the two series will be discussed. A description of the different consecutive members of the series cannot be given, as the rocks are too variable in character, and dynamic action has involved them in such complications. No approach has been made in the determination of the order of their occurrences, and it is doubtful if such a sequence will be made for years to come, unless more discriminating criteria are forthcoming. Many unlike members there are, but they are characterized by no presistence of horizon, or if they are, metamorphism has obliterated all distinguishing features. The area appears as a multitude of patches of different kinds of rocks, whose relations with one another seem impossible of solution. Unlike the Mendon series, there is no pronounced northerly lamination agreeing in the main with the genuine strike of the stratification. The structure here is in part due to zones of unlike mineralogical composition; most of the igneous rocks have been well laminated and the gneisses and schists have their characteristic arrangement of constituent minerals.

A detailed description of all the varieties of rock occurring will not be attempted here; some of the more noteworthy areas will be

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