HISTORY OF GEOLOGICAL SURVEY. 



33 



party measured the length of the profile of the "Old Man of the Moun- 

 tains," finding it to be thirty-six feet from chin to top of the head, — the 

 face itself being twelve hundred feet above the lake beneath. Soon after 

 the disbanding of the first, a new party was formed, consisting of A. A. 

 Abbott, W. Flint, and W. Upham, with the aid of E. C. Atwood for a 

 short period. This second party remained, some of them, two months 

 longer, exploring the country as far south as Sandwich. 



Description of the Map. 



With the report there appeared a geological map embodying the results of all our ex- 

 plorations. The colors upon the map indicated the geographical relations of ten groups. 

 In the absence of precise knowledge, spaces were left uncolored in certain districts. 

 The topographical basis is the map of C. H, V. Cavis, prepared for Eastman's White 

 Mountain Guide, upon the scale of five miles to the inch, it being the most convenient 

 one accessible to us. On account of the difficulties in the way of exploring among the 

 mountains, which have already been described, this delineation can only be regarded 

 as a reconnoissance, especially as the true position of the rocks did not suggest itself 

 till late in the spring of 1872, when the field notes were being compared with specimens. 

 The areas will be briefly mentioned, and the most important conclusions dwelt upon 

 at length. 



1. Porphyritic Gneiss. This is an ordinary gneiss, carrying numerous crystals of 

 orthoclase or potash-feldspar, from a quarter of one to two inches long. The longer 

 axes may be parallel to the strike, or arranged helter-skelter. It passes into granite 

 with the same porphyritic peculiarity of structure. Its most northern area lies along 

 the Ammonoosuc river in Bethlehem, Littleton, and Whitefield. Next, commencing 

 west of Haystack mountain, at some unknown point, is another range, which passes 

 southerly on the west flank of Profile mountain, and makes up the great mass of Kins- 

 man or Blue mountain; thence passes southerly to Woodstock and Campton. It 

 crops out on the west side of Moosilauke— how extensively has never been determined. 

 A spur from this appears at the Lake of the Clouds on Mt. Lafayette, and passes 

 southerly towards the Basin. It may occupy part of the uncolored area west of the 

 Lafayette range. Upon the other side of the Pemigewasset country, this formation 

 shows itself in the valley of Sawyer's river, on the south side of Mt. Carrigain. It is 

 there covered by compact feldspar. It reappears in Waterville, on Cascade brook, 

 Snow's mountain, Bald Knob, and upon other high mountains in Sandwich, whence it 

 passes out of the limits of the map. We suppose this to be the oldest formation 

 among the mountains. Geologists speak of a rock of this character as common in the 

 Laurentian, in various parts of North America and Europe. 



2. Bethlehem Gneiss. The whole of Bethlehem is underlaid by a gneiss abounding 

 in a talcoid mineral, perhaps pinite. The orthoclase is abundant, usually pink or flesh 



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