GEOLOGY OF THE WHITE MOUNTAIN DISTRICT. 1 87 



and the mica slate seen on the summit of the mountain, is but a superficial crust or 

 superimposed layer. [Page 160.] 



In Volume I, page lo, I have reproduced Dr. Jackson's ideal view of 

 the stratigraphical structure of the White and Green Mountains, in their 

 relations to the formations of the adjacent states, with his figure. A few 

 critical remarks will be found there, expressive of what is correct and 

 what is erroneous in these views, according to the latest interpretation. 



E. Hitchcock's victvs. In 1841 my father ascended Mt. Washington 

 from the old Notch house, and, in a paper upon Glacio-aqiicoiis action in 

 North America, makes the following statements respecting the rocks:* 



The principal part of the White Mountains, I will not say all, appears to me to 

 consist of steep parallel ridges of granite and mica slate, running about north-north- 

 east and south-southwest, with occasional spurs. The Notch is a passage through the 

 highest of these ridges. * * * This ridge [Clinton to Washington] is composed 

 essentially of a peculiar kind of mica slate, occasionally containing feldspar, and some- 

 times traversed by veins of granite. It also abounds, as does the same rock at Monad- 

 nock, with a mineral which has been called fibrolite, but which demands further 

 examination. It often constitutes a large proportion of the rock. All the peaks, except 

 Clinton, which I ascended, (Jefferson and Adams I did not ascend,) are made up of 

 broken fragments of this slate, which have been entirely removed from their original 

 position by frost, and form sometimes a coating of loose angular blocks several feet 

 thick. This is particularly the case upon the summit of Washington, and downward 

 about one thousand feet. But in all the valleys between these peaks, more or less of 

 the rock in place appears. 



Views of H. D. and W. B. Rogers. Of all the papers published upon 

 the geology of the White Mountains previous to 1869, that by the Pro- 

 fessors Rogers in 1846! is the most valuable, and therefore it is copied 

 here entirely, save a few paragraphs relating to some supposed fossils, 

 which they themselves subsequently discovered to be simply singular 

 mineral aggregations. % 



The White Mountains, the most elevated of the mountain masses of the Atlantic 

 side of North America, have been hitherto regarded as consisting exclusively of the 

 granitic and gneissoid rocks under their several modifications, and as having originated 

 in the so-called primary periods of geological time. This common notion of their 



* Trans. Assoc. Ainer. Geologists and Naturalists, pp. 183, 184. 

 t Amer. Jour. Sci., II, Vol. I, p. 411. 

 t /d.,U, Vol Y, p. ii5. 



