CLASSIFICATION OF THE NEW HAMPSIHRE FORMATIONS. 665 



Swift Water, and hornblende series for its lower division, the Lyman 

 argillitic schists for the second, and a thin band of conglomerate (aurifer- 

 ous) for its third or upper division. To establish this classification there 

 is no need of resort to inversion, as the strata dip naturally in the basin 

 form. The groups named are covered by several later series, — the clay 

 slate, the Coos schists, and the Helderberg area. The first two are 

 monoclinal, and the Helderberg rocks often stand on edge, owing to the 

 enormous pressure that has been exerted upon them. The slates illus- 

 trate finely the change from the basin to the inverted form. In Bath 

 the synclinal shape is perfectly distinct. In passing north the angle of 

 inclination increases. Hills of the Lyman and Lisbon rocks have pushed 

 through the slate very much as a nail punches through the same material 

 in the form of tiling. Patches of the upper rock in Lyman remain as 

 fragments of the original basin, but eventually near the Littleton line 

 all the dips are westerly, and of course inverted. They are in separate 

 parallel bands, divided by the greenstone. 



There is another set of rocks, consisting of quartzites and mica schists, 

 called the Coos group, that seems to underlie the Calciferous group, inter- 

 vening between the limestone and clay slate. They all belong to essen- 

 tially the same period, and their precise relations to each other are not 

 of great consequence in the present discussion. The latest group of 

 strata have a well-defined horizon in consequence of the discovery of 

 Lower Helderberg fossils in them. They are found resting upon the clay 

 slates and greenstones, while fragments of the Coos group aid in the 

 building up of a supposed Helderberg conglomerate. For these and 

 other reasons set forth in the sketch of the Bernardston deposits (p. 

 452) it is thought the Helderberg series is distinct from and newer than 

 the Coos or Calciferous group ; but if the Helderberg rocks carry with 

 them any of our formations, it would be those named, and no others. 



The next important question concerns the relations between the green- 

 stones and the gneisses. This answer can be given quickly, assuming 

 the correctness of the structure of the greenstones and calcareous groups, 

 as already set forth. Gneiss dips westerly beneath the Ammonoosuc 

 rocks, and easterly from the Green Mountain region, thus making a syn- 

 clinal. There is no great difference between these gneisses, and they are 

 referred to our Lake division in the descriptions. Some of the Bethlehem 

 VOL. II. 84 



