XXVlll 
TABLE OF CONTENTS. 
Page. 
Geological position. 317 
Range of outcrop and extent. 317 
Composition of this division .. 317 
1 . Ithaca and Chemung group.•. 317 
2. Hamilton group. 317 
3. Marcellus shales. 317 
Other groups absent in the First District. 317 
Upturned in some places. Thickness. 317 
Extent in other States. 318 
Joints. Flagstones. 318 
Localities where the strata and fossils can be examined. 318 
Tully limestone, possibly in Schoharie county. 319 
Septaria of the Marcellus shales. 323 
Excavations for coal in the Marcellus shales... 323 
Fossil remains found by Mr. Gebhard. 323 
Catskill and Erie divisions form the Catskill mountain region. 323 
3. Helderberg division . 324 
(a) . General characters and composition. 324 
Range and extent. 324 
Conformahility and unconformability with underlying rocks. 324 
References to figures to illustrate the above facts. 324 
Thickness of strata, and their accessibility for examination. 324 
Divisions of the formation, and thinning out of some. 324 
Divisions into members or groups and S 3 monims. 324 
Section at Schoharie by Mr. Gebhard. 324 
Subdivisions, and explanations of Scutella and Delthyris limestones. 325 
Economical applications. 325 
Building stones and marbles.•. 325 
Lime and hydraulic cement. 328 
(b) . Derangements of the rocks of the Helderberg division ...... 330 
Derangements at various localities. 330 
Section opposite Wilbur. 331 
Anticlinal axis, faults, double faults, and disruption. 331 
Enigmatical dip near Carpenter’s point. 332 
Effects of the Shawangunk axis along the Mamakating valley. 332 
Directions of lines of disturbance and fracture. 333 
Of dip. 333 
Of the oblique dip explained. 333 
Double elevatory movements, echelon movements. 334 
Streams and veins along lines of fracture. 334 
Periods of elevation. 33 ^ 
Overturned strata. 33 g 
