438 Expedition to the 



stratum, if not the old red sandstone should be seen emerg- 

 ing from beneath that secondary along its south-eastern 

 ipargin? We will not however, contend for the name. It is 

 sufficient for our purpose, to state that the sandstone so abun- 

 dant in all the principal ridges accessary to the Alleghany 

 on the east, has the character of a rock belonging to the tran- 

 sition formation of the Wernerians, that is, its strata have a 

 somewhat regular dip and inclination, it contains no beds of 

 bituminous coal, and few remains of animals or plants. Near 

 the summit of the ridge called particularly the Alleghany, 

 the change to more recent secondary begins to appear. With- 

 out the interposition of any other stratum, and without any 

 sudden change of features, the strata of sandstone, become 

 nearly horizontal, assuming gradually all the characters of 

 secondary rocks. About one mile west of the summit of the 

 Alleghany, on the road from Philadelphia to Pittsburgh, 

 the first indications of coal are observed. In the vallies, 

 the metalliferous limestone, and the older sandstones 

 emerge to the light. The same thing happens in the case of 

 Catskill, and other mountains, west of the Hudson, their ba- 

 ses being of transition, and their summits crossed with se- 

 condary.* 



The horizontal sandstones connected with the depositions 

 of coal, occurring along the Ohio, from Pittsburgh to the 

 confluence of Green river, assume various characters, and 

 often support extensive formations of compact limestone. f 



* See Eaton's geological section, at page 280, of the index to the Geolo- 

 gy of the Northern States. 



f The following are descripitionsof the rocks, that alternate with each 

 wther as they occur, in connexion with the coal beds at Pittsburgh, com- 

 mencing with thii uppermost, and proceeding in a regular gradation to the 

 lowest that we have had an opportunity of examining. 



No. 1. A loose grained argillaceous sandstone, composed of minute grains 

 of quartz, and decoinposed feldspar, united by an argillaceous cement. Its 

 colour is yellowish gray, fracture uneven, stratifications imperfect. It 

 contains no organic remains; depth of the bed near four feet. 



No. 2. Bituminous shale; natural colour, brownish black, that of the 

 streak, dark gray. Before the blow pipe it decrepitates, burns with a 

 bright flame, emils a bituminous odour, and soon becomes nearly white. 

 Its structure is slaty: no animal or vegetable remains are contained in it, 

 small veins of clay are dispersed irregularly between the layers. Depth 

 of the bed ten fleet. 



No. 3. A bed of bituminous coal, its colour is brownish black, cross 

 fracture uneven, longitudinal slaty: fragments tabular, right angled, lus- 

 tre resinous, it is semi-hard, sectile, and very brittle. Vertical and hon- 



