HELDERBERG DIVISION. 
333 
That near Redbridge, dips at an angle of fifty to seventy degrees to the west-northwest, 
and is traversed by veins of calcspar. The direction of the veins is S._60° E. The lime¬ 
stone belongs to the Water-lime series, though some of it makes good lime. This is the case 
with many of the strata in the Water limestone series, in almost all the localities where the 
strata are exposed. Two miles farther down the valley to the north-northeast, the rock ap¬ 
pears again on the land of Mr. Wurts. The upper beds of the Water limestone series here 
emerge from the quaternary deposits, on the east side of the Sandberg creek. Some of them 
would make fine marbles, and the rock has been burnt for lime. Like that at Redbridge, 
the rock is traversed by veins of calcspar, the direction of which is S. 60° E. 
Near Napernock, the same strata are visible in the meadows opposite to where the Esopus 
creek enters the Mamakating valley and unites with the Sandberg creek. 
Near Wawarsing, on the west side of the valley, the same strata were seen ; and in all these 
cases, they dip rapidly to the west, and plunge below the rocks of the Erie division. 
In the vicinity of Rochester, Ulster county, the limestones of the Water-lime group are 
visible in many places, and here the Pentamerus limestone is seen in some localities above the 
Water-lime group, and characterized by its peculiar fossils. 
Fossils were rarely seen in the limestones of the Helderberg division south of Rochester, 
except in those of the mountain east of Carpenter’s point, between that place and the Sha- 
wangunk mountain, and at this place they were extremely abundant. The specimens of tri- 
lobites were so numerous, and particularly the Asaphus, that Dr. Horton and myself gave the 
hill the name of Trilohite mountain. 
Fossils abound in the limestone strata overlying the Water-lime group south of Rochester, 
between the Stony kill and the Rondout kill. On Mr. Schoonmaker’s land between those 
streams, the water limestone is well exposed. Some of the strata will make marbles and fine 
building stone. Lime and cement could also be made in this vicinity from the beds of the 
Helderberg division. 
The lines of disturbance and upheave in this vicinity correspond with the general directions 
recognized in the First district of New-York. The main line here is N. 20° E. and S. 20° 
W., and the dip is N. 20° W. about 10°. 
It will be observed here that the direction of the dip is not perpendicular to the direction 
of the main axis of elevation. This is a very common fact, and observed in a great number 
of localities in the regions of the First district of New-York, where the strata have been 
broken up since their original formation. 
The strata are traversed by two great systems of fracture, one longitudinal, and approaching 
more or less to the direction of the strike ; the other transverse. Their usual directions are 
S. 20° W. and N. 20° E. for the first, and S. 60° E. and N. 60° W. for the second. 
When the elevatory movement has been along the transverse fractures, the dip is sometimes 
to the north-northeast, but most frequently to the south-southwest; and when the upheave 
has been along the longitudinal fractures, the dip is to the west-northwest or to the east-south¬ 
east. The upheaves have generally occurred along both these lines of fracture, giving echelon 
movements to the masses of strata, so that their dip is commonly oblique to the direction of 
