554 STRATIGRAPHICAL GEOLOGY. 



south are imperfect gneisses with interbedded granites, dipping 30° north- 

 westerly. Near the quartz a more careful measurement indicated a dip 

 of 50° N. 30° W. Traces of similar rocks are to be found all the way to 

 Sawyer's pond, the materials being very crystalline close to the water. 

 At M, Collins's, east of the pond, the layers are micaceous, dipping 50° 

 N. 30° W, Not a great distance beyond are layers of granite, entirely 

 devoid of any marks of stratification, arranged between seams of mica 

 schist. Wherever the schists are bent, the granite layer is also curved in 

 conformity with them. These granite beds are from one to six inches 

 thick. With them are occasional bunches of crystalline feldspar, eighteen 

 inches thick. Rude crystals of quartz occur in some of the feldspar 

 bunches. Before reaching the old Rowe's station on the C. & P. Railroad, 

 a ledge of granite appears. This is the height of land, and, consequently, 

 the eastern boundary of our district. 



Near the south line of Hooksett, next to Manchester, feldspathic schists, 

 with narrow granite seams, dip N. 30° to 50° W. Similar rocks occur 

 occasionally all over the north part of Manchester. At the Trotting 

 Park is a ledge of similar character, planed down thoroughly by ice. A 

 little south of the Reform School is a field of granite which has been quar- 

 ried. This points to the similar material on the west side of the Amos- 

 keag bridge. Opposite to it, near the river, are ledges of micaceous gneiss. 



There is a great amount of glacial drift in Manchester, serving to con- 

 ceal ledges, yet many exposures of rock may be seen. There is an inter- 

 esting bunch of granite less than a mile north-east from the Amoskeag 

 reservoir, quarried by the Amoskeag Company and by Bodwell. One 

 would judge from the appearances that this granite occupied an elliptic 

 space in the midst of coarse mica schists. It might be said to be a 

 gigantic egg-shaped concretion, containing the good materials segregated 

 from the surrounding uncouth rock. Such an impression is not gained 

 for the first time from the inspection of these quarries. I have thought 

 of the same illustration at Fitzwilliam and Concord. Early in the work- 

 ing of the Bodwell quarry I noticed that a species of cap rock extended 

 over the granite. This required to be blasted away before good stone was 

 found. But the presence of a cap rock was not universal. On the south- 

 east side of the Amoskeag quarry coarse mica schist dips 75° N. 20° W., 

 and also more north-westerly. The granite runs against the edges of the 



