coos AND ESSEX DISTRICT. 43 



clined to the south-cast 55°. The bed is 30 feet wide, and will furnish a 

 weak lime, since it contains only about two thirds of its weight of pure 

 carbonate of lime. If burnt very carefully, it slacks with difficulty into a 

 granular mass, but if the heat is raised to whiteness, it melts into a slag 

 or glass, owing to the formation of silicate of lime."* The extensive 

 deposit of marl in Lime pond will be noticed under alluvial deposits. 



Along the Connecticut, south of Sims stream, there is a small area of 

 this group of rock. It begins in a point one fourth of a mile south of the 

 stream. The outcrop of the rocks can be seen from the road, and where 

 it begins the strata seem to have been pushed to the west, as the strike 

 will readily be seen to run in a different direction from what it does a few 

 rods south. The area increases in width as we go southward, until it is 

 about two miles wide; then it becomes narrower, and, in the south part of 

 the town, it is not far from one mile. The rocks are micaceous and argil- 

 laceous schists and siliceous limestone. Near Mrs. Ross's the limestone 

 is noticeable from the road, on account of its dark color, as, in weathering, 

 the lime is removed, and only the siliceous portion of the rock is left. 



In the north-east part of Pittsburg, in the area between the Connecti- 

 cut and the Magalloway, there is a band of the Coos group. These rocks 

 form the water-shed between the head waters of these streams ; and it is 

 a very noticeable fact, that these Coos rocks here form a synclinal axis, 

 and both on the east and west we have Huronian rocks, which here con- 

 sist of greenish siliceous schists with epidotic nodules. 



In Vermont, opposite Columbia, the Coos group is developed. It ex- 

 tends southward, and probably terminates near the south line of Bloom- 

 field. Northward, it outcrops in Canaan, and extends west to Little 

 Averill pond, where it is interrupted by an intrusive granite, but it 

 appears again in Holland, whence it extends southward through Ver- 

 mont. An interesting area of this group is found in the south-east part 

 of East Haven, and it outcrops again in the vicinity of the church in 

 Granby. In both these localities it forms beds in the older rocks. 



Where Specimens were Collected, and the Dip of the Strata. 



At the north end of Lake Megantic, in Quebec province, the strata, 

 both of the Coos and Huronian groups, stand nearly vertical. The rocks 



* Jackson's final Report, p. io6. 



