396 THE CANADIAN NATURALIST. [Dec. 



teristic in concretionary veins not granitic in composition, is pro- 

 bably not less marked in granitic veinstones, and often appears in 

 these in a remarkable manner, showing that they have been form- 

 ed by successive depositions of mineral matter, and generally in 

 open fissures. This structure, and various peculiarities to be ob- 

 served in granitic veinstones, will be best illustrated by descrip- 

 tions of various localities, most of w^hich I have personally examin- 

 ed. It is proposed to notice first, the veins of the gneiss and mica- 

 schist series of New England, and secondly those of the Lauren- 

 tian rocks of New York and Canada. In the latter class will be 

 noticed the more or less calcareous veinstones into which the 

 Laurentian granitic veins are found to graduate. 



§ 16. It is in the series of micaceous schists with interstratified 

 gneisses (§ 6) which I have elsewhere provisionally designated 

 the Terranovan series,^ that I have seen concretionary granitic 

 veins in the greatest abundance and on the grandest scale. This 

 stratified system, which is well seen in the White Mountains, 

 appears to extend southward to Long Island Sound and north- 

 eastward beyond the limits of Maine. It is in this state that I 

 have particularly studied the granitic veinstones of this system, 

 whose history may be illustrated by a few examples from notes 

 taken on the spot. In Brunswick the strata near the town are 

 fine-grained, friable, dark colored, micaceous and hornblendic, 

 passing into mica-schist on the one hand, and into well-marked 

 gneiss on the other, and dipping to the S. E. at angles of from 

 15^ to 40'^. Very similar beds are found in the adjoining towns 

 of Topsham, and in both places they include numerous endogenous 

 granitic veins. The course of these is generally N. W., or at right 

 angles to the strike, though occasionally for short distances with 

 the strike, and intercalated between the beds ; the veins vary in 

 breadth from a few inches to sixty feet, and even more. They 

 generally consist in great part of orthoclase and quartz, with some 

 mica and tourmaline, and offer in the associations and grouping 

 of these minerals many peculiarities, which are met with not only 

 in different veins but in different parts of the same vein. In 



* Anier. Journal of Science for July, 1 870, page 83, and Can. Xaturalist, 

 Y. p. 198. — The rocks of this White Mountain series are in the present 

 state of our knowledge supposed to be newer than the Huronian system 

 noticed in § 5, to which, withMacfarlane and Credner, I refer the crystal- 

 line schists with associated serpentines and diorites of the Green 

 Mountains. 



