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siderable quantities from this source. This earth or petre-dirt, as 

 it is called, is obviously a sediment deposited from the waters, for- 

 merly or at the present time found within the caves, and has some- 

 times a texture of such impalpable fineness as to indicate that the 

 deposition took place while the liquid was in a very quiet state. Be- 

 sides the saltpetre or nitrate of potash, it also contains a large 

 amount of nitrate of lime, which, by the usual process of mingling 

 the washings of common ashes with those of the petre-dirt, is by a 

 direct chemical action converted into saltpetre. Immense heaps of 

 the earth from which the salt was formerly obtained, may be seen in 

 some of the wide chambers of the Singing and otner caves, which 

 there is reason to believe in process of time, will become as rich in 

 this substance as before. 



In the same caves Gypsum is also found mingled with the petre- 

 dirt, and sometimes enclosing large lumps of it in a thick crystal- 

 line envelope. In the Organ Cave so much of it is found both in 

 this condition and replacing the shells originally existing in the 

 slaty limestone, as to make it worthy of inquiry, whether it might 

 be turned to profitable use. 



Returning to the profile at the point marking the intersection of 

 Howard's creek with the line of observation, we remark the com- 

 mencement of a series of sandstones and slates differing from 

 those of the Alleghany, and presenting that want of accordance in 

 the dip which may probably mark the beginning of the great western 

 series. The rocks of the former kind here exhibit what is called a 

 diagonal lamination, a structure very general among the sandstones 

 of the west, and one from which the geologist derives important 

 hints as to the natural circumstances existing when these strata 

 were deposited. 



On the eastern side of the Greenbrier, is an outlying hill com- 

 posed of horizontal beds of limestone, resting upon red and green 

 friable slate. At several points south of this, in a direction towards 

 the Salt Sulphur springs and Uniontown, this limestone is discover- 

 ed, and in proceeding some distance towards these points, the hills 

 as well as valleys present scarcely any other rock but a limestone, 

 which, judging by its fossils and other characters, may be re- 

 garded as probably the same as that here represented. Beyond this 

 point, we meet with west-dipping strata of reddish shale, with a thin 

 band of limestone on the descent of the hill, approaching Lewisburg. 



