GEOLOGY OF THE WHITE MOUNTAIN DISTRICT. 24 1 



porj^hyry containing perfectly formed crystals of quartz and orthoclasc, 

 mentioned upon Mt. Pequawket, is much more finely developed upon Mt, 

 Willard ; and the band has been mentioned heretofore (p. 177) as belong- 

 ing to the Albany granite. 



[Note to Page 100. Since the printing of the statement concerning the section 

 from Mt. Lafayette to Bald hill, additional observations at the Wing road have con- 

 firmed our supposition that the porphyritic gneiss underlies the Bethlehem group. The 

 particular details of structure appear in the illustration, PI. VI, Fig. 7.] 



[Note to Page 119. A reexamination of the ledges enables us to modify certain 

 statements upon page 119. Above the fifth mile-board, for a quarter of a mile, the dips 

 are mostly low and undulating, like those at the end of the fifth mile. The high dips 

 mentioned here have an existence, they being the occasional plunging downwards of 

 one side of the curves. I could not satisfy myself that the dip of 5o°-6o° N. 73° W., 

 at No. 44, pertained to a ledge. And it is erroneous to state that the ledge in the sharp 

 angle of the road overlooking the Great Gulf is one hundred and fifty feet long. The 

 sedgy plat near No. 47 is now known as the "cow pasture." Instead of saying "ten 

 rods north of mile-post No. 7," it would be more correct to put it "ten rods before 

 coming to mile-post No. 7." There is a ledge at the first great easterly bend, corre- 

 sponding essentially with No. 48. Below the barn the first ledge dips 50° S. 82° W. 

 I have not preserved the observation respecting a dip at No. 50. 



We remark that the steep side of all the curves is on the east, or down the mountain. 

 One of the zigzags at the fifth mile-board is now called "Willis's Seat." Since the 

 drawing of the plan, the sixth and seventh mile-boards have been moved down the 

 mountain, so that, as measured on the plan, the distance between five and six is less 

 than a mile. I have retained the old positions for them. No. VI is now placed more 

 than half-way towards No. 45 of the space between 6 of the plan and 45 ; and, conse- 

 quently, VII has been shifted to stand at No. 48. In the neighborhood of Willis's 

 Seat the large andalusite crystals have been altered into quartz and Damourite. 



For comparison, I have drawn upon the section through Mt. Washington (PI. VII) 

 the dips along a nearly parallel line, down Tuckerman's ravine to the Pinkham Notch 

 road. The anticlinal and synclinal axes correspond well with each other. The lower 

 end of the section at the Notch represents the eastern boundary of the Montalban .sys- 

 tem, which appears on the carriage-road at the Half-way house ; though I have some- 

 times thought the rocks about Willis's Seat belonged to the newer group. The greatest 

 amount of crushing is manifested in the area of the slates between Nos. 12 and 36. 

 The structure of the latter seems to be a complicated and crushed inverted synclinal.] 



[Note to Page 182. There are a few points concerning the representation of the 

 boulder showing curvatures in the strata requiring mention. It is figured in Plate X, 

 Figs. 22, 23, and 24. Fig. 22 is the one spoken of as on the left, and Fig. 23 as the 

 one on the right. Fig. 24 is an additional view of what may be termed the bottom, 



