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ALGONKIAN ROCKS IN VERMONT.
399

below the Olenellus quartzite into two periods is thought to occur.

Geology.

Outline of the views previously held regarding the structure and age of the Green Mountains.—As far back as 1845, Adams in his first Annual Report on the Geology of Vermont[1] referred to the "Primary" system the rocks of the main range of the Green Mountains as far as the state boundary, and eastward. Among the rocks mentioned under this head which occur in the area studied by me are Green Mountain Gneiss, Mica Slate and Talcose Slate. In this report these horizons are placed below the Stockbridge limestone and the associated quartzite of the Taconic, but their relative age is confessedly unknown. In his second annual report,[2] however, he leaves the problem as to whether these are "Taconic," "Primary," or "Metamorphic," an open question, but still inclines towards a belief in their primary origin. This belief is inferred from his statement that the evidence goes to show that the limestone and quartzite of Plymouth valley on the east side of the range is equivalent to the Stockbridge limestone and quarzite on the west side, making the core of the Green Mountains the older. Adams in no place makes the statement that the belt of primary rocks represents the axis of the range, and it is doubted if he had any clear conception of the relations of the rocks on the east and west sides of the Green Mountain divide. In 1847, however, Edward Hitchcock gave two sections in his text book of Geology[3] of the Green Mountain anticline partially and completely folded as we see it to-day. The anticline is represented as overturned slightly to the west, with a flat crest and a rude fan-shaped cross-section; the text[4] mentions that the strata grow newer as one goes westerly, although apparently the series is descending. Such a conclusion reached at that time is the happy result of a coincidence of schistosity and stratification at

  1. ↑ p. 62.
  2. ↑ Second Annual Report on the Geology of Vermont.Adams, 1846, p. 168.
  3. ↑ Elementary Geology, Edward Hitchcock, 1847, figs. 27 and 28, p. 37.
  4. ↑ Opus. cit., p. 36.
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