HELDERBERG DIVISON. 
351 
of Canterbury, on the road to Salisbury mills. Its apparent position is between the slate and 
grit rock, or millstone grit of Prof. Eaton.* Its dip is to the southeast, at a high inclination. 
Mixed in between the layers of this rock is the hematite, or limonite ore, on the land of Mr. 
Thomas Townsend. Where the ore exists, the limestone is all more or less decomposed, 
some parts of the rock and its fossils retaining their form, but have become white or yellow, 
and soft; other parts, even the nodules of hornstone, are so far changed that they have fallen 
to fine powder, mixed up with the ore in the same condition. This limestone makes but in¬ 
different lime. The distinctive fossil of this rock is the encrinite, although it contains many 
others.”t 
The Strophomena rugosa and S. radiata are very common fossils at the above locality, and 
the rock is considered as belonging to the Catskill shaly limestone, which has here been up¬ 
turned on its edges like the adjoining slates, grits, and other rocks. This locality is the only 
one where the rocks of the Helderberg division have been recognized southeast of the Helder- 
berg mountains, west of the Hudson river. 
Near Hudson in Columbia county, are two outliers of the rocks of the Helderberg division, 
called Becraft’s mountain and Mount Bob.J They are composed of limestones, lying uncon- 
* Shawangunk grit of the Reports of the First District. t Dr. Horton’s Report on the Survey of Orange county, N. Y. 
t At the foot of Becraft’s mountain, the slate dips at a high angle to the east, very near to the junction of the nearly 
horizontal strata of the Helderberg division, but the actual junction was not seen. At one mile and a half from Hudson, 
on the south road along the base of Becraft’s mountain, the slate is visible on the east side of the road-way, dipping 30 
to 40° eastwardly. The strata is S. 30° W., and the dip to S. 60° E. Within two rods of the slate in place is a mass of 
limestone, which at first view would be supposed to be in place; but its dip is south 60°, and its strike is east. These 
circumstances, together with the appearance of the mound in which it is imbedded, give reason to believe it to be a mass 
out of place, that has slidden from the cliff of limestone, that rises with a nearly vertical escarpment sixty or seventy feet 
above the slope of debris at its foot, within a few rods on the east. 
Within a mile farther on the road south from Hudson, many localities almost show the junction of these rocks that 
seem to be unconformabU; and at the fork of the roads, the junetion can be traced to be within a space of six feet. The 
slate is here highly inclined, and the limestone nearly horizontal. 
The eastern side of Becrafl’s mountain is also bounded by a mural escarpment, and there the strata dip slightly to the 
westicard, while on the west side they dip a little to the east. On the north end of the mountain, a cross section is observa¬ 
ble, showing the same thing, the strata dipping east and west towards the central axis of the mountain. This accounts 
for the copious fountain which finds an outlet at the bottom of the inverted arch, which collects the water that drains 
through the fissures, and forms a reservoir. This overflows at the lowest point, at the spring that supplies the city of 
Hudson with water. 
About a quarter of a mile south of Mr. M'Clellan’s on the east side of the mountain, the Umestone and slate are seen 
almost in contact. The slaty divisions of the slate dip at a high angle to the east, while the overlying limestone dips 
about one foot in six to the west. About one-fourth to one-third of a mile farther south, the rock begins to dip in a south¬ 
wardly direction from 5 to 10°; and still farther south is a ridge where the Umestone is overturned, lying nearly vertical, 
and dipping about 80° to the east, as represented on Plate 24, fig. 5. The same upturned Umestone may be seen two or 
three miles farther south in Livingston, and both contain the same Umestones and fossils as the corresponding strata of 
Becraft’s mountain. ' 
Mount Bob, so called, is a hill about one hundred feet high, in the northwest part of Claverack, Columbia county. 
The western side is very steep, and a slope of debris of the blue compact lunestone conceals a part of the rock of the same 
kind, which rises about twenty feet ui a mural escarpment, and dips to the east as is represented on Plate 38, fig. 1, where 
(a) is the blue Umestone, and (b) and (c) strata of grey fossiliferous limestone like that of Becraft’s mountain. The slate 
underUes, apparently unconformable. 
