OF STRATA. 



43 



mlways contains iron pyrites at greater or less intervals, which 



gives it the name of pyritiferous slate and grit. It is always 



above the upper cherty limerock. Subdivisions. Graywacke 



slate, (or pyritous slate) when of a slaty texture. Millstone 4, Quart- 



grit, and grey rubble, when the grains are all or part coarse, JP^^ forma- 



and more conglomerate than those of the other graywackes, 



either white or grey, often very hard. 



Localities, The slaty, on the south shore of Lake Erie, on 

 both shores of Seneca and Cayuga lakes. It embraces the Embraces 

 bituminous coal of Tioga, and the bituminous shale and thin Tioga coal, 

 layers of the same coal near the heads of Cayuga lake, Lake 

 Erie, &c. Millstone grit and grey rubble, accompany each putble and 

 other (the grit generally overlaying the rubble, though they S'''^- 

 alternate sometimes) along the whole extent of the western 

 ridges of the Catskill and Allegany Mts. the grit generally Caps the 

 capping the ridges, and defending them from the action of the ^|g^°^"^ 

 disintegrating agents. Both divisions are often red and sandy. 

 Nodules of a kind of wacke are often found in the slaty kinds, 

 which contain bitumen in a waxy state. 



19. Oolitic Rocks, are aggregates, which contain more 4 Calca- 



or less of carbonate of lime of an earthv texture, either com- forma- 



tion. 



pact and white (chalk) or in minute concentric spheres, (oolite) 

 or combined with fine grains of quartz, (silicious.) The sub- 

 divisions, silicious limestone, oolite and chalk, are character- 

 ised in the preceding definition. 



Localities. Silicious limestone is found in place, in fields, silicious 

 or in large boulders, every where on the western ridges of the lini^stone. 

 Allegany. They are generally dark- brown or black, and the 

 limestone part is disintegrated at the surface ; leaving the 

 quartz only, which seems to be blackened by the disintegra- 

 tion of the pyrites. Oolite has been found in the town of 

 . Franklin, Bergen county, N. Jersey, by Dr. Horton — also in 



Ohio state. The chalk has not hitherto been found in Ameri- 



, ^ . , - . . - No chalk 



ca ; but it abounds in various parts of Europe, associated found in A- 

 with the silicious limestone and oolite. monca. 



'to" 



of 



Oolite. 



