478 



Scientific Geology. 



(6) Granite and Mica Slate ; Norwich. 



The section below was taken at the same place as the two preceding 

 sketches. It shows an irregular vein or mass of granite protruding 

 through layers of mica slate. The granite mass is only two or.three 

 feet wide, and the mica slate four feet. It is obvious that the upper 

 portion of the slate has here been forced upwards by the granite, so 

 as to stand nearly perpendicular : the general dip being about 45° 

 west.* 



(7) Granite Vein in Mica Slate ; Norwich. 



In the northwest part of Norwich I sketched No. 8. Two beds or 

 veins of granite are here shown: the central one, or that between the 

 strips of mica slate, from 6 to 10 feet wide, and the outer one, which 

 is but partly exhibited, 4 or 5 rods wide. One object 1 have in view, 

 is to show the curvature of the mica slate, where the central mass of 



* This sketch is badly engraved. The dip of the layers of slate ought to de 

 crease nearly one half, where it is farthest from the granite. 



