22 THE JOURNAL OF GEOLOGY. 



served.^ His descriptions are, however, very suggestive, espe- 

 cially in light of the truly volcanic rocks which have been 

 recently discovered in the older strata of Maine. C. H. Hitch- 

 cock, 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. ^ 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 south- 

 east of Kennebago lake, in western Maine, as composed of com- 

 pact 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: i) detrital accumulations which have fallen through 

 the air; 2) true lava flows; 3) dykes. They seem to belong to 

 various horizons of Silurian age.'* A similar series of interstrati- 

 fied 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. s 



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- 



^ First Report on the Geology of the State of Maine, 1837, p. 12 and pp. 36-42. 



^Geological Report, 1861, p. 190, and p. 432 ; also ib., 1863. p. 330. 



sProc. Am. Assn. Adv. Sci., Vol. 26, p. 286, 1-877. 



"•Am. Jour, of Science (3d ser.), Vol. 32, pp. 40-43, 1886. 



5 Eighth Ann. Report U. S. Geol. Survey, pp. 1037, 1043, 1054. 1889. 



