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 of the broad gneiss range of Worcester county, I would here 

 remark, we find limited beds ofmica 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- 



