GEOLOGY OF THE MERRIMACK DISTRICT. 475 



west, — (i) gneiss ; (2) quartz bands, with well defined walls (the rock is 

 very much jointed, and resembles a dyke) ; (3) we have a chloritic rock ; 

 (4) we have the intrusive quartz repeated. In the Surry cut we have 

 hornblende schist, which terminates abruptly at the line of a fault, and 

 there is a slight change in the inclination of the strata. The inclination 

 of the fault is about 70° easterly. At the line of the fault we have a band 

 of quartz twenty or thirty feet wide. The inclination of the strata of the 

 hornblende schist is very nearly the same as that of the gneiss ; so we 

 have simply a downthrow of the rocks at the east end of the cut. It is 

 the best defined of any fault that we have found, and it is shown in Fig. 

 80. Here, as in this quartz elsewhere, there are some fragments of gneiss 

 included in it. Gneiss begins abruptly against the quartz, and going 

 west the inclination of strata is aj^parently quite variable, — generally, 

 however, about 15° v/esterly, but more inclined as we go west. There 

 are several quartz veins penetrating the gneiss, and in one of these pyr- 

 rhotite was found. On Gray's hill, a little west of south from the Surry 

 cut, the protogene gneiss is found on the summit and westward, and it 

 is probably continuous from the railroad. It is here cut by the intrusive 

 quartz veins ; — the strata seem to be nearly horizontal, and resting on it 

 are hornblende and chloritic schists. The protogene gneiss occupies the 

 entire western part of Keene, except where it is covered by other rocks. 

 It is also found on the western slope of the hills east of the central part 

 of the city of Keene, just west of the road along Beech hill. Hence it 

 is altogether probable that this rock underlies the drift across the valley 

 of the Ashuelot from West mountain to Beech hill. 



Besides the rocks on Gray's hill there are outcrops a mile south-east 

 of the Wilson farm, half way from school-house No. 12 (of the county 

 map, now No. 7) to the railroad crossing, near D. B. Stearns's, at G. Per- 

 ry's, and on the hills both north and south along the Chesterfield road 

 from Keene west of the railroad. On West mountain there are extensive 

 outcrops ; but the reddish protogene rock disappears in the north part of 

 Swanzey, but the rock southward does not differ very much from some 

 varieties of the protogene northward. From the eastern slope of West 

 mountain, in the broad valley of the Ashuelot, we find only drift until we 

 ascend the hills on the east side of the valley, where there is a decom- 

 posing gneiss, probably the common variety of this section in the Beth- 



