GEOLOGY OF THE WHITE MOUNTAIN DISTRICT. 23 1 



as the Eozoic, — probably the same with the strata disturbed in the White 

 Mountains, — or the Montalban group. Hence it is not proper to say that 

 the Green Mountain rocks are of Sikirian age, as is claimed by some 

 authors. 



I will add a few words descriptive of the Vermont locality, that those 

 who are interested may examine the region for themselves. Fig. 21 

 exhibits the relations of the granite there to the surrounding groups, 

 as portrayed upon a map of the Cuttingsville region, in the towns of 

 Shrewsbury and Wallingford. The Chocorua area is oval in shape, and 

 about a mile and a quarter long. Its western border is a rather coarse 

 sienite. The eastern part is a somewhat fine-grained variety of feldspar, 

 with a bare sprinkling of hornblende in it, but no quartz. The whole 

 constitutes a large hill, with a higher mountain of gneiss to the south, in- 

 the edge of Wallingford. Mill river flows by the eastern base of the hill, 

 parallel with the railroad. The dips of the gneiss, at a few points around 

 Cuttingsville, are given. On the east is a vein of magnetic iron pyrites, 

 which has been stripped for a quarter of a mile on the western slope of 

 the hill back of the depot. Its course is N. 65° E., and it seems to con- 

 stitute an anticlinal ridge. Limestone and hornblende schist accompany 

 the ore, all of these bands pointing directly for the granite hill, which has 

 interrupted their continuity. Where the railroad crosses Mill river, two 

 miles south from Cuttingsville, the dip is 35° N. 80° W.; on passing up 

 the hill west of this, hornblendic gneiss dips S. 5° W. Midway between 

 the railroad and J. Pelsue's house, at the end of a road, there is a large 

 exposure of the Potsdam quartzite, with some calcareous layers. North 

 of Pelsue's the gneiss dips 80° N. 2$° W., and resembles the Laurentian 

 gneiss of Whitehall, N. Y. The highest and principal part of this hill is 

 composed of similar material. The gneiss and hornblende adjacent to 

 the gneiss dips northerly, and farther north it dips westerly, so that its 

 strike is irregular in direction. The jointed planes of the sienite dip 

 northerly. Some of these seams are lined with manganese peroxyd. 

 The sienite hill may be three hundred and the other five hundred feet 

 above the valley of Mill river. 



We conclude, from these statements, that this felsite mass is truly 

 eruptive ; that it issued from a rent transverse to the course of the strata, 

 but parallel with the main range of the Green Mountains. Its age must 



