CHAPTER III. 



GEOLOGY OF THE WHITE MOUNTAIN DISTRICT. 



IWIHE outlines of the White Mountain district have been defined in 

 J^ Volume I, page 184. It includes the principal mountainous region 

 between the Connecticut river and the Maine line, embracing the larg- 

 est areas of the Labrador granites. A reference to the description of 

 the topographical features, as above cited, but more particularly to the 

 map opposite page 171, will serve to fix in the mind the exact limits of 

 the district now under consideration. The leading formations developed 

 here are the following, in the supposed order of their age: i, Porphyritic 

 gneiss; 2, Bethlehem gneiss; 3, Berlin or Lake gneiss; 4, Montalban 

 group; 5, Franconia breccia; 6, Labrador system or Pemigewasset series 

 of granites, Ossipytes, compact feldspars, etc.; 7, Sienite; 8, Andalusite 

 slates ; 9, Pequawket or Mt. Mote granite. The facts relating to surface 

 geology and the utilization of valuable ores and building materials belong 

 to subsequent chapters. 



I. Porphyritic Gneiss or Granite. 



This rock is always readily recognizable in this district by the pres- 

 ence of large crystals of orthoclase or potash-feldspar scattered through 

 a base of much finer materials. These larger crystals are usually about 

 three quarters of an inch in length, rarely two inches. There is much 

 diversity in respect to their arrangement. Sometimes the crystals are 

 placed in the rock with their longer axes parallel to each other, and this 



