1870.] T. S. HUNT — ON GRANITIC ROCKS. 399 



cleavage- planes of orthoclase six inches in diameter ; other parts, 

 which are less coarse, abound in mica. Similar banded granite 

 veins abound in the adjoining towns of Xewry and North Bethel, 

 and sometimes present layers of quartz six inches or more in thick- 

 ness, besides large crystals of mica, and more rarely apatite. These 

 veins are often irregular in shape and bulging at intervals, and 

 they sometimes lun partially across the beds, which seem to have 

 been distended and disturbed, a fiict which was also observed in the 

 thin-bedded schists in contact with some of the veins in Brunswick, 

 and is apparently due to the expansive force of crystallization, as 

 noticed in § 27. 



§ 20. The locality already described at Danville offers an 

 iiistructive example of a phenomenon often met with in the region 

 now under consideration, where granitic masses, resisting the 

 actions which have deirraded the soft enclosino; schists, stand out 

 in relief on the surface, and seem to constitute the rock of the 

 country. A careful search will however show that they are 

 simply veins or endogenous masses of very limited dimensions, 

 rising from out of the mica-schists, which are often concealed by 

 the soil. This is well seen about the lower falls of the Presump- 

 scott near Portland, where the mica-schists with some fine-grained 

 gneisses, dipping S. E. at angles of from 30*^ to 40°, enclose large 

 numbers of granitic veins, which, though sometimes but a few 

 inches in breadth, often measure twenty or even fifty feet, and are 

 usually very coarse-grained, with white mica, black tourmaline, 

 and more rarely beryl. They are sometimes transverse to the 

 stratification, but more often parallel, and, rising above the soil, 

 are very conspicuous. 



§21. AVe have already noticed the exotic granites of Bidde- 

 ford, which are intruded among fine-grained bluish or grayish 

 silicious strata. These latter are traversed by numerous veins of 

 endogenous granite, which are very imlike in aspect to the intru- 

 sive rock. One of these veins near Saco Pool, has a diameter of 

 about an inch and a half, and presents on either wall a layer of 

 yellowish crystalline feldspar about one fourth of an inch in thick- 

 ness, which includes long plates of dark brown mica. These 

 penetrate the central portion of the vein, which is a broadly crys- 

 talline bluish orthoclase, enclosing small portions of quartz after 

 the manner of a graphic granite. The yellowish and less coarsely 

 crystalline feldspar with its accompanying mica, had evidently 

 lined the walls of the vein while the centre yet remained open, and 



