No. 276.] 
145 
which crack and crumble to pieces when exposed to the weather; this 
tendency renders it unsafe for masonry of importance. It is employed 
to great extent in the construction of field walls; a large portion of the 
county is enclosed by walls of this stone. 
GRAYWACKE. 
This rock has the widest distribution of any in the county. It occu- 
pies all the town of Deerpark, laying northwest of the Basher's kill. 
In this region, it assumes all the various forms usually called by this 
name, including the wacke slate. In some of the ridges of mountains, 
it is in thick massive layers, dark coloured and compact. In others, it 
is in layers of but a few inches in thickness, light gray colour, very hard 
and sonorous, when a blow of the hammer is applied. In others, still, 
it is soft; colour, dark and dull, with a strong tendency to decomposi- 
tion; and finally it passes into wacke slate, which is sometimes the 
colour of the rock, and at others nearly brick red. Between the 
Neversink and Mongaup rivers, the redwacke runs nearly across the 
town. The direction of the mountain ridges in this section of the 
county, coincide very nearly with most others to the east, that is, north- 
east and southwest nearly. There are, however, some variations. Some 
of the strata lay quite flat, approaching a horizontal position; others are 
much more inclined. The general angle of dip may be included be- 
tween 15° and 25° to the northwest and north. The Delaware river 
occasionally runs a short distance between these ridges, but generally 
crosses them obliquely. At low water, the hardest layers of the rock 
may be seen in many places forming a reef across the stream. From a 
little below the mouth of the Mongaup, the Delaware takes the direc- 
tion of the strata for near three miles before it linds an exit to the south 
and east. In this distance, the mountain attains an elevation of 800 
or 1,000 feet; in some places, it is almost perpendicular. Here nearly 
all varieties of this rock may be seen, except the red. Most of these 
three miles, the Delaware and Hudson canal is built in the river, the 
mountain forming one bank, and a wall of stone from fifteen to twenty- 
five feet high, on which is the tow-path, forming the other bank. The 
strata of graywacke extend from the Delaware river into Sullivan coun- 
ty. In this stratum, west of the Shawangunk mountain, I have not 
been able to detect a single fossil in place, although faint arborescent 
appearances are discoverable on the surfaces of some layers. The Shaw- 
angunk mountain extends in a single unbroken ridge from the New^- 
Jersey line to Sullivan county. Near or at the summit of this ridge, 
the graywacke appears again, but here its position, at first nearly ver- 
[Assem. No. 275.] 19 
