GEOLOGY OF THE WHITE MOUNTAIN DISTRICT. 257 



What should have caused the force to spend itself in this northerly or 

 southerly direction is not so easily apprehended. On the north of the 

 mountains, the Bethlehem and Lake groups run nearly east and west. 

 Is it possible that this area served as a buttress against which the south- 

 easterly masses of rock (in the Lake district) were crowded, and, being 

 immovable, reacted upon the pliable upper schists, bending them to con- 

 form to its own shape ? Perhaps an inspection of the maps may suggest 

 other and better explanations. The age of this last elevation will be 

 referred to again, as it belongs to the Paleozoic period. 



Another limited area of Montalban rocks in Pemigewasset has been 

 discovered since w^-iting pages 1 31-137, and it is shown upon the map 

 (PI. XII). It is situated along the west side of Hancock Branch, between 

 Black mountain and the Greeley Pond notch. Nothing is known of the 

 position of the strata there, nor are the proper limits of its distribution 

 ascertained. It is mentioned upon page 109, in connection with the 

 Bethlehem group. 



Franconia Breccia. Much of what needs to be said about this forma- 

 tion has just been stated. In brief, there are two areas of it in this dis- 

 trict, — in Franconia and Lincoln, where it is overlaid and divided into 

 two parts by the Conway granite, — and in the White Mountain notch. 

 The ledges consist of angular pieces of porphyritic gneiss and Mont- 

 alban schists, cemented by a fine-grained granite. In the Notch the 

 fragments do not seem to have been transported at all. The ledges 

 have been shivered, and the pieces cemented again so near each other 

 that one can see the same line of fracture in those that are adjacent. 

 The breccia was thought at first to be a local formation (p. 141). Now, 

 in consequence of the discovery of similar rocks in the Notch, and the 

 ejection at the same time of granite veins all along the sides of Mts. 

 Webster and Crawford, the disturbance seems to have extended over 

 more than a local district. Specimens from other parts of the state are 

 like this granitic cement, and future research may suggest the occur- 

 rence of the breccia in the other topographical districts. 



3. Labrador System. The modifications of the first five groups are 



of less importance than those Vv^hich follow. The evidence is plain that 



the Labrador system does not include, besides the triclinic feldspars, the 



porphyries and all the Pemigewasset granites. Hence the statements 



VOL. XL 33 



