174 STRATIGRAPHICAL GEOLOGY. 



Were the valley full of rock, as has been supposed to account for the 

 trap dykes, this vein would have a northerly inclination of ten or twelve 

 degrees. In fact, it proves denudation just as well as the dykes. 



A trip up this ragged edge of Webster starts from the Conway granite 

 in the valley. Thence, over an interminably long slope of debris, we come 

 to the base of the large cliff more than a hundred feet high. Upon ex- 

 amination it proves to be composed of several kinds of rock. At the 

 north end of its summit the Montalban schists occur with the strike 

 N. i6^ E. These are traversed by segregated veins of granite twenty or 

 thirty feet v.-ide, analogous to those in the first cuttings in the Notch. 

 Next to this is two hundred feet width of Breccia granite, the line of 

 junction being N. 68° E., at right angles to the edge of the cliff, and 

 the rocks meet with vertical faces towards each other, pointing into the 

 mountain. At the southern edge of this precipice are more of the hard 

 schists, followed by Conway granite, supposed to extend southerly from 

 this point for miles uninterruptedly. Lower down the precipice are 

 towers or quadrangular pinnacles of the hard schists, precisely like the 

 Pulpit in the Notch. The Conway granite is supposed to extend also 

 from the road to the base of the cliff. The top has about the same ele- 

 vation as Mt. Willard. The course to the north edge of the Conway 

 granite on Willard is N. 57° W. Supposing these rocks to conform to 

 their course on the railroad, we should suppose the south part of the 

 schists corresponds to the Breccia adjoining the Conway granite. 



Passing up the ragged edge seen in the heliotype, we find the Conway 

 granite again, directly over this cliff, as far to the upper precipice as 

 indicated upon p. 123. At the middle one the rock is very characteris- 

 tic, with prominent joints running N. 6^^° E., vertical. A small flume 

 ten feet wide has been excavated out of them, carrying a thin, light- 

 colored trap dyke. Other joints dip 50° N. 38° E., agreeing with the 

 position of Montalban schists half a mile to the north. The edges of 

 the schists are traversed at their lower edges (the upper cliff) by very 

 large granite veins, — some of them corresponding in lithological features 

 with the coarser varieties traversing the Notch cuts, and twenty or thirty 

 feet wide. Others possess a very fine grain, and are somewhat like the 

 finer Breccia cement, lacking the porphyritic aspect. All the rocks are 

 terribly decayed through weathering. The schists are much like those 



