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THE JOURNAL OF GEOLOGY.

be removed like the coats of an onion." He also speaks of them as "coarsely brecciated" and "vesicular." A point of some interest is Fletcher's conclusion that "both felsite and syenitic strata are intimately associated as part of the same group of crystalline rocks, differing, not so much in composition as in the degree of crystallization they have been subjected to" (sic).[1] In greatly eroded regions we should expect to find surface volcanic rocks associated with their coarser abyssal equivalents.

In Nova Scotia proper the best known area of ancient volcanic rocks is in the northeastern corner of the province, near Arisaig, in Antigonish county. These were considered by Sir William Dawson in 1850 as "metamorphic."[2] In 1864, Dr. Honeyman described them as vesicular traps, amygdaloids and porphyries, associated with tufa and tufaceous conglomerate.[3] In his first report on eastern Nova Scotia, Fletcher describes variegated, vesicular and amygdaloidal "felsites" and "fragmentary felsites," like those of Coxheath and Louisburg, associated with "syenite" (hornblende granite) and diorite.[4] These rocks are regarded as pre-Cambrian, and are particularly developed at Arichat, Cape Porcupine on the Straits of Canso, and in the Sporting, North and Craignish mountains. In the North Mountains the felsites are said to pass gradually into syenite (l. c. p. 14). The gradual blending of the felsite and overlying George River limestone is attributed to "common metamorphism," rather than "to contemporaneous volcanic origin or subsequent intrusion" (l. c. p. 17). Nevertheless, at Cape Porcupine the felsite is regarded as possibly an igneous rock, since "the apparent lines of bedding are like those of a furnace slag" (l. c. p. 25). In the subsequent report of the extension of his explorations southward and westward in Nova Scotia, Fletcher admits the volcanic origin of the felsitic rocks of Arisaig, Doc-

  1. ↑ Quoted by Gilpin: Quart. Jour. Geol. Soc., Vol. 42, p. 516.
  2. ↑ Quart. Jour. Geol. Soc., Vol. 6, p. 347, 1850.
  3. ↑ Ib., Vol. 20, p. 333, 1864.
  4. ↑ Report of the Geol. Survey of Canada, 1879-80, F.
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