48 GEOLOGICAL REPORT. [180, 81 \ 81 2 



80. The chief materials of the formation have already been 

 mentioned as consisting of limestone (of different degrees of purity), 

 chert or hornstohe, and siliceous sandstone. The several degrees 

 of transition of these rocks into one another are also represented, 

 besides which, we find underlying the sandstone in several localities, 

 a black clay shale charged with iron pyrites — the representative, 

 perhaps, of the hydraulic slate of Eastport. 



81 1 Localities of the Carboniferous Formation. — At Red Sulphur Springs, in 

 T. 1, R. 10 E. (in Tennessee), a spring of strong sulphur water comes up from 

 beneath a ledge of gray, non-fossiliferous, slaty hydraulic limestone of a 

 perfectly uniform, dense, texture; which characterizes the northern portion of the 

 formation. It is here as elsewhere overlaid by a stratified hornstone formation, 

 whose lower portion is very hard and solid, and fossiliferous {Fenestella, Pro- 

 duct us) ; but further up it becomes very brittle and almost void of fossils, and is, 

 interstratified with layers of pebbles imbedded in clay, which have been described 

 before (If31). Very nearly the same condition of things obtains all along Yellow 

 (.'reek, so far as its course lies through the territory of this formation ; on the 

 lower portion of its course, however (from the crossing of the Eed Sulphur 

 Springs and Eastport road, to its mouth), we find on the left bank, the gray 

 slaty limestone overlaid by a variety of aluminous sandstones, which in their 

 highest portion became merely a soft, gray, sandy shale, void of fossils. Judging 

 from some apparent transitions, these sandstones (of which there are some 15 to 

 20 feet) are the equivalents of the hornstone. We see, however, on the right 

 bank (e. g. at Billing's mill) the slaty limestone itself appearing at the same 

 level at which, on the opposite side, we find the sandy rocks. The former here 

 gives rise to bald rocky hilltops, on which little else than the Prickly Pear and 

 Stone-crop can find sufficient nourishment ; and similar hilltops (which are of 

 some importance as furnishing an excellent hydraulic limestone) are said to occur 

 with frequency in the hills bordering on the Tennessee River, in the State of 

 Mississippi. At Eastport, it is seen on the slopes of the ridge towards the river ; 

 in the bed of Big Bear Creek, and in that of a small creek which empties into 

 the latter, close to the town. Here, as elsewhere, it is totally destitute of fossils ; 

 it cleaves readily into lenticular plates, with it a rough surface, and contains not 

 unfrequently, hard, flat, siliceous nodules, of a few inches diameter, in which 

 we generally see a few golden yellow crystals of iron pyrites. Analyses of this 

 rock, as well as of that occuring on hilltops near Billings' Mill, will be found 

 below (U92-93). 



Impure gray limestones, at times deserving rather the name of calcareous 

 chert, crop out frequently in the bed of Yellow Creek, from its mouth upwards. 

 Near Scruggs' bridge, on S. 16, T. 2, E. 10 E., there is an extensive outcrop of 

 rock resembling in every respect, that of Eastport. 



81 2 The siliceous deposits which overlie this rock in the neighborhood of 

 Eastport, have already been, in part, described (IT 31). The large masses of 



