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THE DISTRIBUTION OF ANCIENT VOLCANIC ROCKS.
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structure, etc., in great perfection, although all trace of the original glass has long since disappeared. The rocks collected by Professor Bayley on the north side of Vinal Haven and on the opposite shore west of North Haven are, according to his field observations, all surface flows or tuffs. Of the nine specimens kindly submitted to me for examination by Professor Bayley, one is a medium grained microgranite and all the others

Fig. 1.Devitrified glass-breccia from north side of Vinal Haven, Penobscot Bay, Me. Magnified six times.

are devitrified glassy rocks, which were once either obsidians, glass breccias, or tuffs. No. 94 is a banded flow-felsite, a devitrified glass with narrow chains of spherulites. No. 100 is a devitrified obsidian containing delicate flow-lines produced by trichites, some zircon crystals, and spherulitic bands in which epidote has been secondarily produced. No. 126 is a pale gray felsite containing large round nodules which may be spherulites. Under the microscope it shows a pronounced perlitic structure. These rocks contain spherulitic structures which are not devitrification products but original, if we may judge from their absolute identity with similar structures in the glassy rocks from Obsidian Cliff. The other five specimens are fine grained vol-

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