GEOLOGY OF THE WHITE MOUNTAIN DISTRICT. 1 01 



It is not necessary to particularize the few localities to the north-east 

 where this formation appears, save that it has not been traced beyond 

 the east line of Franconia. One of our maps will show the exact loca- 

 tion of every specimen mentioned in the catalogue ; and reference to 

 these sources of information will render unnecessary much detail in the 

 text. An interesting locality lies above Walker's Staircase in the edge of 

 Lincoln, which is supposed to be the direct continuation of the easterly- 

 dipping ledges just described. Coming down from the south end of the 

 Lafayette range towards the Staircase, I found, about a mile back from 

 the road, nearly horizontal masses of a hornblende rock, underlaid by 

 porphyritic gneiss, running N. 2° W., and having nearly vertical strata. 

 The hornblende rock formed a succession of steps, over which the brook 

 fell in a picturesque way, while the porphyritic gneiss did not rise above 

 the base of the cascade. I cannot locate this spot exactly, since I failed 

 to find it in 1873 in the ascent above the Staircase frequented by the 

 summer visitors. About the same distance back from the carriage-road, 

 however, I have noted the occurrence of the porphyritic rock having the 

 same inclination. At the "Lappara falls," also, just above Apron falls, 

 considerably higher than the Staircase, Mr. Huntington found a gneiss 

 resembling the porphyritic rock, save in the absence of large crystals of 

 feldspar, while at the latter locality the gneiss is Montalban in appear- 

 ance. The other rocks here are of the Conway granite series. 



A specimen of loose Bethlehem gneiss from near Mt. Pemigewasset, 

 just back of the Flume house in Lincoln, led to a reexamination of that 

 eminence in 1873, and the conclusion was reached that the lower part of 

 the mountain consisted of porphyritic gneiss, dipping gently north-west- 

 erly, capped by the Conway granite, the two resembling each other 

 very closely. It is ajDparently a part of the more eastern range on the 

 west flank of Lafayette. 



Further researches in Franconia and Lincoln are desirable in order to 

 determine satisfactorily the limits of the porphyritic gneiss. There is no 

 part of the White Mountains where the travelling is more difficult than 

 here, — hence a considerable time will be required to make satisfactory 

 examinations. Areas requiring a visit arc the district referred to this 

 group, extending from Walker's Staircase into the east part of Franconia, 

 and as far on the north flank of Mts. Haystack and Twin as discoveries 

 will warrant. 



