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served.^[1] His descriptions are, however, very suggestive, especially in light of the truly volcanic rocks which have been recently discovered in the older strata of Maine. C. H. Hitchcock, in his Maine reports, regards the acid volcanic rocks near Machiasport as altered slates, and mentions extensive areas of similar rocks on Moosehead, Portage, Long, and Chamberlain lakes, as well as along the Aroostook and Penobscot rivers, in the interior of the state.^[2] Goodale gives four patches of analogous "siliceous slates" in York county, and five in Oxford county, and J. H. Huntington describes the summit of the diorite southeast of Kennebago lake, in western Maine, as composed of compact felsite, which he regards as an eruptive rock.^[3] The first definite descriptions of ancient volcanic rocks in Maine was given by Professor Shaler, who examined the regions about Eastport and Mount Desert. Near Eastport, and especially on McMaster's island, three types of volcanic material are largely developed: 1) detrital accumulations which have fallen through the air; 2) true lava flows; 3) dykes. They seem to belong to various horizons of Silurian age.^[4] A similar series of interstratified volcanic breccias, lava flows and ash beds are described as forming a large part of Mt. Desert island south of Southwest Harbor, and the Cranberry Isles.^[5]

The writer has had the opportunity to personally examine the volcanic rocks of the Mt. Desert region, and he is indebted to Professor W. S. Bayley of Waterville, Me., for specimens and slides of the beautiful lavas of Vinal Haven, and to Mr. E. B. Mathews for notes and specimens of similar rocks from Mt. Kineo on Moosehead Lake.

Along the shores of Cranberry Island occur hard jaspery felsites, often porphyritic, and exhibiting such characteristic features of glassy rocks as spherulites, single and in bands, flow-