Geology, ^c. of the Connecticut. 13 



Granitic veins are very numerous in many parts of the 

 map, especially in the region of the South Hampton granite. 

 In width they vary from a mere line to 30, and perhaps 

 even 40 feet. But I have not observed any that exceed 

 this breadth. They traverse mica slate, hornblende slate, 

 limestone of a peculiar character, sienite, gneiss and gran- 

 ite. Those which traverse the latter rock differ from it only 

 in being of a finer, or a coarser grain. Yet they are as re- 

 ally veins as those zones of granite traversing other rocks. 

 Examples of these are frequent — as near the South Hamp- 

 ton lead mine. 



In these veins all the ingredients of granite are usually 

 present, but in variable proportion. I have seen some that 

 were nearly or quite graphic granite : But usually the mica 

 is in superabundance, especially in the narrower ones, and 

 often it is of a delicate straw or light green colour, as in Go- 

 shen and Conway. The felspar is sometimes of an ele- 

 gant flesh colour, especially in those veins occurring in the 

 gneiss northeast of New-Haven, in Chatham, Haddam, ^c. 

 These veins frequently divide and subdivide like the top of 

 a tree, some of the branches being smaller and some larger. 

 These branches rarely go off from the main stock at right 

 angles, but generally oblique. At one place you will see a 

 vein retaining its width for several feet, or even rods, with 

 mathematical exactness — at another, its width will gradually 

 increase or decrease; and I have seen, in some instances, a 

 sudden reduction of two or three inches, by which a shoul- 

 der was produced. The course of many of these veins is 

 serpentine, resembling that of a river on a map — yet often 

 they scarcely deviate at all from the right line. Some- 

 times they make large curves to the right or left. They 

 usually descend into the rock obliquely to the horizon. 

 They frequently intersect, but I have never noticed any dis- 

 placement of the strata, or mass of the rock, except in the 

 sienite. Some of the veins traversing sienite, (between 

 Belchertown and Ludlow for example,) are so numerous 

 and their intersections so many, that they form what the 

 Germans call a stock works, except that they are not metal- 

 ic. By these cross veins the surface of the rock is some- 

 times divided into triangles, rhombs, or rhomboids j and 

 sometimes it is tesselated. 



