GEOLOGY OF THE WHITE MOUNTAIN DISTRICT. 20^ 



Mt. Washington. The highly incHncd PIcldcrberg strata at Littleton 

 and Owl's Head, P. O., certainly bear witness to the exertion of a pow- 

 erful elevating agency. 



LABRADOR SYSTEM. 



There seem now to be seven areas of labradorite rocks among the 

 White Mountains. Some that have hitherto been supposed to consist of 

 this mineral prove to be another variety of feldspar. The genuine areas 

 are the following: i, upon Norway brook, and 2, upon Sabba Day brook, 

 the opposite sides of Tripyramid mountain in Waterville; 3, on Mt. 

 Washington river; 4, Loon Pond mountain, near Pollard's in Lincoln; 

 5, south end of the Lafayette range; 6, Bean's Purchase; 7, Mill moun- 

 tain, Stark. I will describe each of these areas in turn, so far as known. 



The older geologists regarded all the crystalline rocks as those first 

 formed, or "primary." The granites were considered as remains of the 

 original crust, cooled down from the condition of intense fusion ; and the 

 gneiss, mica schists, etc., resulted from the action of eroding agencies, 

 tearing off fragments of the granites and depositing them in the lower 

 areas. These unstratified and stratified rocks have also been styled 

 Azoic, from the supposed absence of life in these early periods. Only 

 lithological names had been applied to the different Azoic rocks till 

 1855,* when Sir William E. Logan and T. Sterry Hunt proposed that 

 the Azoic formations in Canada beneath the Potsdam sandstone should 

 receive local appellations ; and they accordingly separated them into two 

 groups, calling the older Laiwcntian and the newer Huronian. These 

 terms expressly excluded the crystalline rocks of New England, which, by 

 many authors, had already been considered to be of Paleozoic age. So 

 early as 1845 Logan had perceived that the gneiss of Canada, afterwards 

 termed Laurentian, could be divided into two groups, dei^endent upon 

 the presence or absence of beds of limestone, and in 1857! suggested 

 that such a division would probably be found desirable. The suggestion 

 was not carried out, since the studies of Dr. Hunt, from 1852 onwards, 

 upon the feldspars, led him to question the appropriateness of this classi- 

 fication of the Laurentian, because the lime-feldspars seemed of greater 

 importance in the distinguishing of new groups. In the report upon the 



* Esquissc Geoiogii^ue dii Canada, f Proc. Aincr. Asso. Adv. Set., Vol. XI, Part II, p. 47. 

 VOL. II. 27 



