Topography of the Mica Slate. 



333 



wards the south part of the State, and especially in Connecticut, I 

 have not hesitated thus to mark the whole formation as far north as 

 the rock contains any noticeable quantity of feldspar. I suspect that 

 careful observation might discover that the rock contains feldspar 

 across the whole State, and that the patch of gneiss represented in 

 Whitingham Vt. is a continuation of the range marked on the map as 

 extending only to Savoy. 



Near the central part of this range of mica slate, occurs a range of 

 talcose and chlorite slates, in conformable order, and passing insensi- 

 bly into the mica slate. Hornblende slate and limestone are connect- 

 ed with it still more intimately, as the map will show. 



The mica slate on both sides of Connecticut river in Northfield, is 

 separated from the range just described, by a deposite of argillaceous 

 slate conformably stratified and gradually passing into the mica slate, 

 though the direction of the strata of the clay slate is more towards north- 

 east and southeast than that of the mica slate on the west : On the east, 

 the mica slate becomes decided quartz rock ; and this accompanies the 

 mica slate, though often wanting, as far south at least as Leverett. 



The narrow stratum of mica slate marked on the map in the east- 

 ern part of Hampshire, and Hampden counties, is associated with tal- 

 cose slate on one side, and with gneiss on the other. From having notic- 

 ed occasional patches of mica slate among the gneiss as far north at least 

 sa Enfield, I have been induced to extend the stratum so far, in doubt, 

 however, whether it be continuous over the whole distance. In many 

 other parts ofthebroad gneiss range of Worcester county, I would here 

 remark, we find limited beds of mica slate, apparently interstratified 

 with the gneiss. But to exhibit all such cases on the map would re- 

 quire immense labour, and be of little service. 



In the northwestern part of the gneiss range of Worcester county, 

 will be perceived on the map, a succession of granite, gneiss, and mi- 

 ca slate deposites. I have not in that case attempted to give the ex- 

 act extent of these several rocks in that region : but simply to indi- 

 cate that such a succession of strata exists there ; and that the differ- 

 ent members of it occupy the surface in about the same ratio as the 

 different colours. I apprehend that here is another example of 

 a different composition in the same stratum prolonged. But I 

 throw out this hint merely to excite others to make that thorough 

 examination which I have not been able to do. 



In passing eastward we next come to the Worcester range of mica 

 slate, which has been several times referred to. This rock has hereto- 



