GLACIAL DRIFT. 1 99 



climb the steep and lofty barrier of the south spur? Nevertheless, there are indications 

 of just such a change as this. 



If we place one foot of a i^air of imaginary compasses on the summit of Mt. Monad- 

 nock, and with the other strike a curve from the west spur to the south spur, we shall 

 hardly have made a more complete change of direction from one spur to the other than 

 is indicated by the strite in the short space of a mile and a half. It is difficult to pass 

 over all parts of the valley between these two spurs, the upper portion of it being ex- 

 tremely craggy or uneven. It is better to go down to the open pastures at the base of 

 the mountain. Beginning at the foot of the western spur, and skirting the base of the 

 mountain towards the east, the first thing to excite attention is the immense number of 

 boulders. They exceed in multitude any other deposit about the mountain, but form 

 no part of its talus, which does not fall on this side. They seem to be in some way 

 connected with the change of the drift current, which began at this place, and with the 

 position of the ridge, under the lee side of which they lie. Passing through these boul- 

 ders, which continue for half a mile or more, we come to the first bare ledges. These 

 are marked with stria; N. 20° W. These are soon succeeded by others, 30°, 40°, and 

 50° west of north. They may not all occur in regular order. On some ledges there 

 are two or three sets of stride of different angles. Proceeding a mile and a half, we 

 arrive at the easterly slope of the south spur, near the Mountain house. The road to 

 this house was built north and south on sloping ground ; and for half a mile the fresh 

 surface of the rock was in many places exposed to view. It is everywhere scratched 

 and polished. These scratches vary from 50° to 60°, and 70° west of north. Climb- 

 ing the slope of the ridge, everywhere the exposed prominences of rock are embossed 

 in the same direction. Arriving at the crest of the ridge, it is everywhere serrated 

 and uneven. 



On this height we again overlook the whole country. Here, on the narrow crest of 

 the ridge, the striae are very generally N. 40° or 45° W. In one place an angular 

 trough, perhaps 20 feet long and 6 feet deep, runs across the crest. In this are long, 

 continuous striae due east and west. They appear to be exceptional, and suggest the 

 idea that this shallow trough had been able to control and change the direction of the 

 striating force. Standing on this ridge, and looking towards the east, we see that the 

 mountain on this side is very precipitous, and that probably there are no strice on its 

 broken surface. Higher up the mountain, within a thousand feet of the summit, the 

 stris are 35° and 30° west of north ; lower down, at the extremity of the south spur, 

 the end of the long dam, they vary from 40° to 25° west of north. What kind of striae 

 should we expect to find under the lee of this four-mile breakwater? Another expedi- 

 tion and another day were required to answer this question. The country east of the 

 four-mile ridge is mostly wooded and difficult to traverse. The rock is mostly covered 

 by drift. Beginning at the south end, and travelling north, no striae were found until 

 two thirds of the distance had been passed over. Curiosity was at last gratified by 

 finding large, flat surfaces of naked rock, scored all over with long parallel lines much 

 better preserved than those on less wooded and more exposed parts of the mountain. 



