120 GEOLOGY OF THE SECOND DISTRICT. 



They arc quite even-bedded, witli few or no contortions produced by disturbances subsequent 

 to consolidation ; but the sandy shales arc uniformly composed of undulating lamina, pro- 

 duced probably by unequal accumulations of detrital matter. The entire mass has a slight 

 dip to the southwest, though to the eye it appears nearly horizontal. The sandstone layers 

 are from four to eight inches thick ; and the materials of which they are composed, are always 

 fine, and never a conglomerate or breccia, so far as they are disclosed in the gorges of Lor- 

 rain or Pinckney. They become a brown or yellowish brown, by exposure to the weather, 

 but are not acted upon very rapidly. The argillaceous shales are disposed to disintegrate ; 

 and wliere they form thick beds, are changed by the weather, both disintegrating and decom- 

 posing, so that the natural walls arc falling and breaking down by the pressure of the super- 

 incumbent rock. This process is greatly aided by the presence of sulphuret of iron in many 

 places ; so that in a thickness of twenty feet, the shale becomes a black powdery mass for a 

 depth of several feel, the whole of which has the styptic taste of sulphate of aluminc and sul- 

 phate of iron ; those salts being formed first by the decomposition of the sulphuret of iron, and 

 secondly the action of the free sulphuric acid on the alumine of the rock, and the iron, one 

 of the elements of the pyrites. 



The upper parts of the Lorrain shales are highly fossiliferous, but this condition gradually 

 diminishes, so that in the central portion of the rock, only a few fossils are to be found ; but 

 they are not entirely absent, and what is important to state, is, that some which are abundant 

 in the upper part, are sparingly found in the lower also. Thus, the Pterinea carinata is found 

 at Lorrain within six feet of the mass or rock denominated Utica slate, where it contains its 

 characteristic fossil, the Triarthus beckii. This being the fact, it seems to indicate the pro- 

 priety of preserving entire the whole mass under one name ; and not, as has been proposed, 

 separate the upper from the lower, and make thereby two rocks instead of one. It is cer- 

 tainly no uncommon thing for a rock to be non-fossiliferous in the lower part, and highly fos- 

 siliferous in the upper ; and so far from the fact proving the propriety of making a separation 

 in these cases, it rather goes to show that a separation ought not to be made, especially where 

 the lithological characters are uniform throughout the rock. 



Towards the upper part, the Lorrain shales contain a single layer eight inches thick, which 

 is close-grained and nearly compact, and also quite extensive, being present in the cliffs in 

 Rodman and Pinckney as well as at Lorrain, places which are separated ten or twelve miles 

 from each other. It has a very close resemblance to the carbonate of iron of the coal forma- 

 tion ; and at one place the whole layer has that curious structure denominated cone within 

 cone. No fossils are found in this layer, though they are abundant beneath and above it. 



Another stratum worthy of particular notice, is calcareous, but so meagre and poor, that 

 it is no where sufficiently charged with lime as to be worth burning ; but it is made up almost 

 entirely of fossils, cemented by argillaceous and sihceous matter. It is rarely more than 

 twelve inches thick ; yet it is remarkably persistent, and is found to occupy one position in 

 all the gorges of Lorrain, Rodman and Pinckney. It also forms a prominent stratum at Pu- 

 laski, and at the several localities where this rock is disclosed in the neighborhood of Rome. 



The Lorrain shales, then, as they exist in Jefferson county, consist of thin, even-bedded 



