292 



Scientific Geology. 



directions. The instances which I shall refer to, all occur in the 

 Franklin County range, and mostly in Guilford, Vt. 



In some instances we find veins of quartz in the slate, as repre- 

 resented below. Here it is obvious, both from the curvatures in the 

 undulating ridges of the slate, and from the wedge-form shape of the 

 veins, that a force must have acted laterally on the edges of the lam- 

 inae, while they were in a partially plastic state : and that an infil- 

 tration of quartz must have taken place subsequently. It is not per- 

 haps difficult to conceive how such a lateral action might have tak- 

 en place, when the strata were originally elevated. The specimen 

 from which the drawing was taken, (No. 411,) was found near the 

 north line of Guilford, on the stage road. 



In the principal quarry of slate, on the stage road to Brattle- 

 borough from Greenfield, are seen occasionally cross seams, perpen- 

 dicular to the horizon, and to the laminae of the slate, which are 

 nearly vertical, and run north and south. Not unfrequently, how- 

 ever, the slate at these cross seams, when its edges are viewed from 

 above, is bent as in the following figures, which exactly represent 

 the specimens. (No. 417 and 418.) 



