GEOLOGY OF THE WHITE MOUNTAIN DISTRICT. 1 37 



it is coarser, and, so far as examined, seems to be a true granite. This 

 variety prevails in tlie western part of tlie territory mentioned above, and 

 may also be seen along the Ammonoosuc as far as Twin river. The other 

 variety occurs extensively from Jefferson brook past Ammonoosuc station 

 along the base of Monroe, Franklin, and Pleasant. It consists of a gran- 

 itic aggregate much like the other variety, having two kinds of mica and 

 especially long, slender feldspar crystals scattered throughout. In pass- 

 ing along the turnpike above Twin river one sees numerous boulders of 

 this variety, in which the long, slender feldspar crystals are conspicuously 

 brought to view through weathering. This rock does not extend above 

 the junction of Franklin with Pleasant brook, with seams dipping io° N. 

 47° E. Below it are great masses of feldspathic mica schists, and abun- 

 dant evidence of its intrusion through strata. It is thought the schists 

 do not extend very much below Franklin brook. Between the lowest 

 schists and Twin river the outcrops are altogether of this variety of 

 granite. Near the "White Springs" on the turnpike there are seams 

 with a high westerly dip, and the rock is quite ferruginous. 



On the west side of Mt. Webster, between the Notch and "Pleasant 

 River bridge" over the Saco, there is developed a granitic aggregate of 

 quartz and feldspar, the former predominating. Its eruptive character is 

 inferred from the presence in it at various localities, particularly on the 

 Silver stream, of large fragments of micaceous quartzite, and to its oc- 

 currence as a dyke at Bemis's saw-mill at the mouth of Nancy's brook. 

 The occurrence of this granite is a marked feature in the geology of 

 the Notch. 



The enormous brecciated traps on the Mt. Washington carriage-road 

 and at the Crystal cascade, the light-colored dykes in Tuckerman's ravine, 

 Mt. Webster, the valley of Mt. Washington river, and elsewhere cannot 

 be treated of satisfactorily at present. At a saw-mill rather more than a 

 mile above the mouth of Rocky Branch in Bartlett, are large trappean 

 dykes containing fragments of three kinds of granite. They may be 

 related to the Mts. Pequawket and Mote porphyries. 



The Fkanconia Breccia. 



The most notable locality of this rock is just above the celebrated 

 Basin in Lincoln. Innumerable pieces of porphyritic granite, dark gneiss, 



VOL. IL 18 



