146 Geological Nomenclature*.. 



layers of crystalline granite, often twenty or thirty feet in 

 breadth. On the south-east side, at Fort Washington, the 

 slaty granite passes into mica slate. On the north-west side, 

 it meets the granitic hornblende rock, which passes into the 

 gneisseoid variety. This last rock, terminates the Highlands 

 up the river, with the lofty mountain, usually called Butter- 

 hill. A similar succession of rocks follows the mica slate, 

 and terminates the Highlands down the river. 



On following the Highland range about one hundred miles 

 in a north easterly direction, to its junction with the Green 

 Mountains, where it appears on our geological profile under 

 the name of Savoy, we see it pass westerly under the gran- 

 ular quartz, and that under the granular limestone. There 

 is however an intervening range of granular quartz and 

 limestone, between the main primitive range and the Saddle 

 Mountain range ; or rather these rocks seem to be separated 

 to a great distance north and south. As this does not de- 

 range the general order of succession (for alternations are 

 found every where) we here actually see the very arrange- 

 ments of rocks as set down in the Synopsis, with the ex- 

 ception of mica slate. As there is no mica slate on the 

 west side of the primitive range, we look elsewhere for evi- 

 dence of its relative position.* 



On the south-east side of the slaty granite in the High- 

 lands, we find mica slate, before the hornblende rocks com- 

 mence. In Saratoga county, in the McComb range, the 

 slaty granite passes into mica slate. On the east side of the 

 Green Mountain range, the mica slate and hornblende rock 

 alternate several times. Between Worcester and Boston, 

 there is certainly some mica slate ; and the hornblende rock, 

 is the last primitive rock towards Boston. On the whole, 

 leaving out the supposed mica slate, west of the Green 

 Mountain range, we have no good reason for admitting the 

 hornblende rock between the granite and mica slate. 



This statement presents my reasons in short, for the ar- 

 rangement of our primitive rocks. Next we see the granu- 

 lar limestone pass directly under the argillite, which is on the 

 east boundary of Rensselaer county, our next starting point. 



I shall not detain the reader with any apologies for former 



* In the first part of the Canal survey, I was misled on this subject by high 

 authority, but I have now fully investigated the subject. There is no mica slate 

 m Berkshire County, on the west side of the Green Mountain range. 



