coos AND ESSEX DISTRICT. 53 



Huronian rocks consist of light gray siliceous schists and clay slates; 

 but the band of argillaceous sandstone of Dalton mountain is probably 

 a much newer rock. 



Other IIukoxian Rocks. 



There is a band of rocks extending from the Magalloway river through 

 the Academy grant, and occupying a large area in the Dartmouth College 

 grant, which consists chiefly of light gray schists. It is frequently, how- 

 ever, of a dark gray color, and sometimes it passes into shades of olive 

 green, and it resembles the hydro-mica schists of Vermont. Its limit on 

 the state line north is not known, but south it extends about a mile below 

 the north-east corner of the College grant. Near the south line of the 

 Academy grant, and west of the Little Dead Diamond, it forms high hills 

 and ridges, often jutting out in high overhanging cliffs. The Little Dead 

 Diamond, in places, has worn deep channels in this rock. One of these, 

 not far from the north line of the College grant, is from twenty to thirty 

 feet deep, and extends nearly four hundred feet along the stream. Here 

 the rock contains an abundance of small crystals of magnetite. It ex- 

 tends south in the College grant nearly to the mouth of Linnell brook. 

 Its south-western limit has not been determined. Everywhere the strata 

 are nearly vertical, but they are generally inclined to the west. Succeed- 

 ing this rock on the south-east is a mica schist containing garnets. On 

 Linnell brook the garnets are of a deep red color, often translucent and 

 very abundant. On the Swift Diamond the rock is more gneissic, and 

 contains staurolite. The crystals are half an inch thick, and from one 

 and a half to two inches in length. On the high hills, near the Magallo- 

 way and north of the Swift Diamond, the mica schist, with garnets and 

 staurolite, is interstratified with hornblende schist, and the strata stand 

 nearly vertical. On Mt. Dustin the schist contains staurolite. The crys- 

 tals are small, being from one to two lines thick, and three fourths of an 

 inch in length. Eastward, extending perhaps a mile east of the College 

 grant, we find mica schist, and southward it is found west of Wentworth 

 pond. Between Aker's pond and the Androscoggin the outcrops of mica 

 schist are very numerous. Between the road to Upton and Umbagog 

 lake, particularly towards the south end of the ridge, the schist is very 

 much contorted. West of Bragg's bay, and south of Clear stream, the 



