Kemp — Gp;ology of Essex County. 



581 



The western border of Chesterfield is a very wild, rough and mountainous 

 district, and needs more detailed study to make the delineations of the for- 

 mations of other than a general character. 



Series I. On entering Chesterfield from Jay, the area of rich quartzose, 

 feldspathic gneiss that is extensively developed in the northwestern part of 

 the latter town, runs across the border. I went up over Bald mountain, and 

 collected specimens 11 and 12. In thin section they exhibit quartz and 

 microperthitic feldspar, with the dark silicates in No. 12 only represented by 

 decomposition products. The quartz is especially rich and is rolled out in 

 lenticular masses. 



On the north side of Bald mountain, is the wild gulch called the " Gulf," 

 and south, still further, and on the east side of Black mountain, is another 

 ravine scarcely inferior. Plumbago prospects are reported in the " Gulf," 

 from which I saw samples that would suggest the probable presence of 

 crystalline limestones as well ; but from pressure of time and the necessity of 

 traversing the southern side of the county to get the broader geologic 

 features of that section recorded, I was unable to fully explore the region. 



The gneiss extends south from Chesterfield into Lewis township, and at 

 No. 42 (of the Jay map) appears in the high, rough ridge of Bluff mountain, 

 and at No. 43 in the outlying spur of Jay mountain on the south. Both of 

 these specimens, in thin section, show much quartz, with which, in No. 42, is 

 strongly microperthitic untwinned feldspar, and a few shreds of nearly 

 opaque hornblende. In No. 43, quartz is in excess. With it occurs much 

 augite, some scapolite, and almost no plagioclase. Regarding the other series 

 of rocks, no new facts have been noted. 



Jay. 



Jay is a very irregularly shaped township, as the map indicates. Its 

 greatest length is about thirteen miles from north to south, and except in the 

 narrow extension into the wild mountainous country in the southeast, it 

 averages about six miles from east to west. The greater part of it lies in a 

 valley along the east branch of the Ausable river. The valley is open and 

 broad on the north, where the surrounding hills are two to three miles apart, 

 but < >n the south they close in decidedly and, at the line with Keene, the valley 

 is narrow. The altitude of the river varies from 550 feet A. T., at Ausable 

 Forks to about 700 at the Keene line. Except along the main stream of the 

 Ausable river on the northeast, the border line with Chesterfield is a very 



