Min&i^alogy and Geology of the White Mountains. Ill 



No. 7 was not visited for want of time ; but as I am informed, 

 is similar to those last described. 



Porphyritic Granite. 



Proceeding E. from Plymouth, two and a half miles, we find 

 houldei^s of this rock ; soon the underlying rock, a decomposing 

 pyritous mica slate crops out, and at three miles, porphyritic gran- 

 ite appears in situ, and continues several miles, and along the 

 north shore of Little Squam lake. This rock seems to con- 

 sist of crystals of white feldspar, some of which are three to four 

 inches long and two inches wide, and held together by quartz and 

 mica, in about the same proportion to the feldspar as the cement 

 of a breccia to the fragments. 



Co?nmon granite is found in sitti at the top of the hill, after 

 crossing the outlet of the lake ; but the boulders of the porphy- 

 ritic granite are seen, diminishing in number, quite to Centre 

 Harbor ; distant ten miles from where they were first observed. 



Trap Dikes on Red Hill. 



Red hill or mountain, near Centre Harbor, Lake Winnipise- 

 ogee, is usually ascended by visitors to enjoy the beautiful scenery 

 of the numerous lakes, with their hundreds of islands, and also 

 of several mountain ranges not very far distant from this peak. 

 The mountain consists of reddish sienitic granite, and its sides 

 are covered with fragments partly decomposed. Near the path 

 leading to the top of the mountain are two dikes. 



No. 1 is a few rods north of the second house ; seven feet wide ; 

 course E. by N. ; dip 15° to 20° N. ; granite altered at junction, 

 appearing burned and baked ; on the lower side the dike is expo- 

 sed by the removal of the granite, and appears as an inclined wall 

 a few feet high. The color and weight of the trap led some time 

 ago to the supposition, that it was an iron ore, and several tons 

 were quarried under this impression, which, upon better inforaia- 

 tion, were never removed. 



No. 2 is one eighth to one quarter of a mile E. of No. 1. Course 

 N. by E. ; average width twenty-five feet ; dark brown ; slight 

 lustre, owing to brown mica diffused through the mass ; pyritous, 

 and fires with steel. Near this, but separated eighteen inches 

 from the dike, is a mass of trap several feet in dimensions, and 

 pasted into granite. 



