412 On the Geological Age of the White Mountains. 
structure of the whole chain and the nature of the forces of ele- 
vation. In the present short paper we propose to submit a con- 
cise abstract of these observations, and the results to which they 
have brought us. 
By inspecting the accompanying little 
map, the reader will notice that the gen- 
eral direction of the Gorge of the Saco, 
neglecting the local windings in its course, 
is nearly from north to south. In one 
place, about half way between Crawford’s 
and the Willey house, the contracted val- 
ley as we trace it south bends abruptly to 
the westward, and in the distance of per- 
haps a furlong sweeps back again into its 
former southerly direction, making a dou- 
ble or sigmoid curve. ‘This feature is es- 
pecially favorable to the exhibition of the 
range and dip of the rocks, which are here exposed endwise in the 
transverse section. In the mountain on the north and west of 
the Gorge, the end of which is full in front of the traveller as he 
ascends the valley from the Willey house, the stratified struc- 
ture of the rocks throughout this gigantic ridge, is plainly to be 
seen in the differently colored perpendicular belts which outerop 
edgewise along its naked and nearly mural face. 
At the Notch (represented in the sketch at a) the rocks on 
both sides of the narrow chasm are traversed by two sets of 
nearly vertical planes or joints, the one running nearly N. E. and 
. W., the other nearly N. W. and §. E. Though in this place 
the irwtineation is but obscurely indicated, we succeeded in 
making out the planes of bedding; and in some cases with such 
satisfactory clearness as to prove the true strike of the beds to 
be N. E. and 8. W., and the dip to be for the most part vertical, 
but with some local arching. Observations made both at this 
locality and elsewhere, induced us to regard the rocks of the — 
Gorge generally as a group of highly metamorphic sandstones and 
slates, traversed by enormous beds and veins of syenitic granite, 
by the heating agency of which they had for the most part been 
rendered semi-crystalline, and in some cases had even been trans- 
formed into apparent gneiss and granite. At certain points in 
these altered strata, the original sedimentary structure is still dis- 
