OF STRATA. 



of a slaty texture. Millstone grit and Greij rubble, when the ,^ J^' 

 grains are in part coarse and more or less conglomerated, tion. 

 either white or grey ; often very hard. 



Localities. The slate embraces the Carbondale and Lehigh pennsylva- 

 coal of Pennsylvania, extends along the east base of AUe- "i^ coal, 

 gany and Catskill Mts. from Georgia to Lake Ontario, un- 

 derlays Utica and Rome. In the valleys of M'Comb's Mt. 

 it is the genuine limestone shale of Farey, where it contains ^Limestone 

 remains of the trilobite or cancer, or both. Millstone grit Millstone 

 overlays the slate from Lake Ontario to Little Falls on the 

 Mohawk, and mostly caps the Catskill and Allegany Mts. 

 along their eastern ridges, from Albany county to Georgia ; 

 and the grei/ rubble accompanies, underlays, or embraces it 

 throughout most of its whole extent. All the divisions are 

 often red and sandy. 



Remark. A distinct stratum called old red sandstone^ and No red 

 another called millstone grit, have been given by most geolo- a distinct 

 gists. But the latest European geologists very properly re- 

 ject them. Because the red sandstone is found passing into 

 all the three graywackes, and the millstone grit is found pass- 

 ing into all the three grey rubbles ; not as strata meeting at 

 their surface, but as continuous rocks. I shall, however, 

 describe the red saliferous rock, as separate from the second 

 graywacke ; though I may hereafter follow those who may 

 unite it with second greywacko. 



13. Saliferous Rock, consists of red, or bluish-grey, 

 sand or clay-marle, or both. The grains of sand are mostly 

 somewhat rounded, and all the varieties of this rock in some 

 localities, form the floor of salt mines and salt springs. Subdi- 

 visions. Marl-slate, when the rock is soft slaty, and contains springs 

 minute grains of carbonate of lime. Sandy, when it is in. solid 

 blocks or layers, consisting of red or bluish-grey quartzose 

 sand. Varieties. Greij-band, the uppermost layers of bluish- 

 grey sandrock. CongloineratCj (breccia) consisting chiefly 



