Geological Survey of the State of Neio York. 79 



" The lower Ludlow rock has its equivalent in a grit above the 

 Oriskany sandstone." 



The full account of this extended series will prove of great value 

 in investigating the formations of our northwestern States. In 

 general, the reports of their surveys present but little that is avail- 

 able to a scientific classification. The lithological character of 

 the rocks may be obvious, and easily interpreted ; but it is clearly 

 impossible to decide upon their geological relations or equivalent 

 character, especially when comparing formations of distant coun- 

 tries, without a particular knowledge of their organic remains. 

 The conditions that govern the development and existence of or- 

 ganic beings, are so complicated, and, if we may so say, of an order 

 so much higher, that their coincidence in different localities is far 

 more remarkable than that of those producing similar rocks ; and 

 of course the evidence based upon the resemblance or dissimi- 

 larity of the fossils, should be more weighty than that derived 

 from these qualities of a rock. 



Mr. Mather's survey of the first district, has developed " the 

 Catskill mou7itain series, consisting of coarse and fine grits, gray- 

 ish, greenish, and various shades of red and brown, which lie 

 thick bedded with water lines of deposition, strongly marked 

 where a cross fracture exhibits the structure ; conglomerates, of 

 various degrees of coarseness, grayish, greenish, and red ; slaty 

 sandstones, with slates and shales of various colors, red, green, 

 spotted, gray and black. Testacea are the principal fossils of 

 the lower, and plants of the upper portion of the series, with 

 seams and layers of pure anthracite ;" and probably all of them 

 are below the old red sandstone ; and they have below them the 

 Helderberg limestone group, No. 7, of Mr. Conrad's synopsis, in 

 his second report, which " embraces a series of limestones, with 

 subordinate beds of shales, slates, and silicious grits. It skirts 

 the group of rocks last described, in a parallel zone, and under- 

 lies them, it is supposed, through their whole extent." 



" The Shawangunk grit, next below, varies from a conglome- 

 rate to a fine grained grit rock : it is almost entirely silicious, and 

 generally white or light gray, in color, with one bed at the upper 

 part that is red. The mountain on which this rock abounds, has 

 taken its name from the predominant color of the rock — the word 

 Shawangunk (Shongum) meaning, it is said, in the language of 

 the aborigines of the country, white rocks. This rock, which is 

 largely developed in Pennsylvania and New Jersey, is much less 



