GEOLOGY OF THE WHITE MOUNTAIN DISTRICT. 1 95 



the traveller has the White-face range on his right, with apparent gentle dips to the 

 north-west. But on his left he has the Welch mountain range and Mount Osceola, 

 with an unmistakable and universal dip, never over 15°, and much of it under 10°, to 

 the south-east, which can be studied for at least seven miles, north-east and south-east. 

 Turning to the left and ascending Mount Osceola (which Mr. Lesley found by barome- 

 ter to be over 2600 [feet] above the Greeley House, and therefore not much lower than 

 Mount Lafayette), the bridle path mounts over successive outcrop edges of perfectly hor- 

 izontal plates of granite, as evidently and regularly bedded as any of the sandstone 

 masses of the Alleghanies, the bed planes not being at all disguised by the cleavage 

 planes. Between these plates of granite lie plates of unchanged dark blue sandstones ; 

 a rock which at the cascades (two miles from the house in another direction) has been 

 mistaken for greenstone trap. The successive terraces and cliffs of the mountain are 

 evidently the consequences of this horizontal and alternate structure. As in other 

 horizontal mountain plateaus the terraces here are projected between the ravines in the 

 form of noses, with straight crests, and terraced or stepped at their ends. In fact, to 

 a practiced topographical eye, the aspect of the whole White Mountain range is that of 

 synclinal erosion. 



Other considerations reinforce this opinion. The continuation and broadening of 

 the range north-eastward through Maine and Lower Canada, where supersilurian rocks 

 abound, — the termination of the range south-eastward before reaching Massachusetts 

 and Vermont, as the Alleghany synclinal stops at Catskill before crossing the Hud- 

 son, — the presence of horizontal rocks at Worcester and more generally than would be 

 supposed through middle New England, — the fact that the Connecticut Valley runs 

 everywhere under the western escarpment of the White Mountains, separating it from 

 the Silurian range of the Green Mountains, — and the presence of Potsdam and other 

 low formations in eastern Massachusetts — all these facts would find their explanation 

 in a synclinal terminal eroded structure of the White Mountain mass. 



The granite of Mount Osceola and the surrounding heights consists of large crystals 

 of feldspar, smaller crystals of quartz and smaller flakes of mica. Here and there 

 hornblende appears. The rock bears no resemblance to the subsilurian Highland and 

 Blue Ridge range, and Adirondacks. It is friable under the weather, shedding its 

 crystals upon the ground under every overhanging ledge. The boulders are rounded 

 by the weather action apparently more than by movement ; for they have only travelled 

 down the slopes beneath the cliffs from which they have fallen, and where those that 

 remain are sharp-angled. The peculiar gravel and sand of the Mad River Valley is a 

 local drift of similar origin. The metamorphism of these granites is considered by 

 Logan, Hunt, and others, as no longer disputable. They could easily originate in the 

 clayey sandstones of Formations VIII, IX, and X, of the Appalachians. 



Considering the whole White Mountain mass a synclinal plateau, then the summit of 

 Mount Washington, which is such an acknowledged anomaly, becomes regularly the 

 single residual fragment of the highest formation which escaped erosion. Its rock is 

 so different in texture and structure from the rest of the mountains that no other expla- 



