No. 50.] 
255 
distance up the mountain on its western side. It may also be seen in 
several places between this locality and the New-Jersey line. 
On the road between the Shawangunk lead mine, and the smelting 
house, the red rock is seen as a crumbling slaty sandstone of a choco- 
late colour. 
At the High falls of the Roundout, in Marbletown, Ulster county, 
the red rock is a shale and fine slaty grit, spotted with green, and in- 
terlaminated with thin bands of limestone. It is there covered by the 
water-lime series of the Helderberg limestone group. 
South of Rochester, Ulster county, near the locality of pyritous grit 
mentioned above, is a red shale passing into a red clay* by exposure 
to the weather. It covers the white rock in patches in this vicinity. 
The grit rock is here waved in gentle swells, along axes of elevation 
which are subordinate to the two main axes of the Shawangunk moun- 
tains.! It is thought probable that beds of iron ore may be found in 
connection with this rock, which is highly ferruginous and frequently 
pyritiferous. Iron ore abounds in some parts of Pennsylvania and 
New-York in a similar geological position. 
* The clay beds and loams of maay parts of the valley of the Rondout, and of this 
part in particular; are reddish, as is supposed from the intermixture of the materials 
derived from the " red rock." 
t The fact of two great systems of fracture in our rocks, which approach to regu- 
larity of direction within comparatively narrow limits, and that the southerly ends of 
masses of strata are almost constantly elevated along the traverse lines of fault, while 
the proper axes of elevation follow the other or longitudinal lines of fracture, has 
already been adverted to. The results of these combined elevations, are echelon 
movements of the strata to a greater or less extent. The successive ridges sink gra- 
dually to the northeast, until they disappear, while they are frequently succeeded by 
other ridges, which are not in the exact lines of prolongation of the former, but 
obliquely lateral to them. These in turn sink, and so on. If the faults are numerous, 
a serrated or broken outline is given to the ridges. The Shawangunk mountains are 
less broken than any others with which I am acquainted, and which have been up- 
heaved along an axis of elevation ; but several breaks may be observed in them. These 
mountains continue with but slight breaks, from the New-Jersey line near Carpenter's- 
Point, to opposite Ellenville and Wawarsing, in Ulster county, where this ridge is 
crossed, by great breaks and faults. The ridge then sinks and rapidly disappears be- 
neath the valley, while several subordinate parallel axes of elevation spring up on the 
east at about the same height, run northeastward between the Stony kill. Mule kill, 
Sanders kill, &c, sink down gradually towards the mouths of those streams, and finally 
disappear below the valley in Rochester and Marbletown, or show their continuation 
only by low broken ridges of upheaved limestone. These axes of elevation are termi- 
nated, apparently, on the south, by the high cliffs along the transverse lines of fault. 
