AMM =—s- On the Gleological Age of the White Mountaans. 
thick-bedded white semi-crystalline altered sandstone, which is 
intersected by injections of feldspathic granite, and is itself in 
many parts concreted into a near approximation to a binary granite 
composed of distinctly developed quartz and white feldspar, with 
a few sparsely scattered specks of mica. In its weathered surfaces 
this rock wears a close resemblance to some fine grained quartzo- 
feldspathic granites, but upon inspecting a fresh fracture with a 
magnifier, we instantly perceive many rounded grains of quartzose 
sand: we perceive moreover much, of the feldspar to be only 
imperfectly formed, as if congealed when in transitu, though the 
mica has more nearly reached the standard condition which it 
has in ite. In some of the coarser varieties of this white 
rock, small distinctly rounded pebbles of quartz are to be seen, 
giving unequivocal evidence, even to the naked eye, of its bemg 
an altered sandstone. .Upon inspecting many varieties of this 
rock, we felt no hesitation in deciding it to have been a coarse 
sili ous white sandstone, now almost granitized by 
extensive metamorphic action. ‘he slope of the steep moun- 
tain side is in many places strewed even to its base, with long 
trains of the angular blocks of this seeming granite fallen from 
the high crowning cliffs above. Seen in places near the summit 
of the mountain, the rock presents two or more systems of. ex- 
tensive and very regular joints or planes of cleavage, by which 
the whole mass is cut into cubical and trapezoidal blocks. This 
jointed condition, itself so significant of an extensive internal 
structural change, is a principal cause of the magnitude of the 
piles of fragments which clothe the slopes of the mountain. . It 
is beheld even more conspicuously in the shattered crests which 
bound the valley above and below the Willey house, where an 
almost continuous thick sheet of coarse angular debris conceals 
the stratification except in the craggy precipices near the sum- 
mits. 'Those sublimely terrific and desolating slides which have 
occurred here at different times, are therefore primarily attributa- 
ble to this jointed structure. This has permitted the elements 
to dislodge the fragments and heap an unusually abundant and 
heavy talus high upon the slopes of the steep hills, where its 
unstable equilibrium, weakened by saturation from copious rains, 
has caused great bodies of the rubbish to give way and rush 
down with destructive impetuosity into and across the bed of the 
narrow valley beneath. 
