194 GRANITES AND GRANITIC VEIN-STONES. [XL 



fied gneisses ( 6) which I have elsewhere provisionally desig- 

 nated the Terranovan series * [since called Montalban], 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 south- 

 ward along the Blue Ridge as far as Georgia, and northeast- 

 ward beyond the limits of Maine. It is in this State that I 

 have particularly studied the granitic vein-stones 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 southeast at angles of 

 from 15 to 40. Yery similar beds are found in the adjoin- 

 ing town of Topsham, and in both places they include numer- 

 ous endogenous granitic veins. The course of these veins is 

 generally northwest, 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 oifer 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 some cases, 

 colorless vitreous quartz greatly predominates, and encloses 

 crystals of milk-white orthoclase, often modified, and from one 

 to several inches in diameter. At other, times pure vitreous 

 quartz forms one or both walls, or the centre of the vein, or 

 else is arranged in bands parallel with the sides of the vein, 

 and sometimes a foot or more in thickness, alternating with 

 similar bands consisting wholly or in great part of orthoclase, 



* American Journal of Science for July, 1870, page 83, and Can. Naturalist, 

 V. 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, with Macfarlane and Credner, I refer the crystalline schists, 

 with associated serpentines and diorites, of the Green Mountains. [See further 

 in this connection Paper XIII. and its Appendix; also the third part of Paper 

 XVI. and the Introduction to III.] 



