182 1 HORNSTONE BRECCIA. 49 



detritus derived from the pebble strata, which here cover the hillsides, render it 

 difficult to observe fully the series of the Carboniferous. The lowest stratum 

 which I have observed overlying the calcareous slate, is the singular deposit of 

 pulverulent silex (11 30) traversed by bands of hornstone in all stages of decay. 

 This deposit, in which I have seen but a few fragments of carboniferous fossils 

 (columns of Peniremites) has been struck in a well at Eastport, and crops out 

 in a valley one mile S. of Eastport. [The occurrence of bluffs of this material, 

 under circumstances similar to those under which it is found in Mississippi, near 

 Gravelly Spring P. 0., Lauderdale county, Alabama (nearly due E. of 

 Eastport), is mentioned by Prof. Tuomey (Second Keport on the Geology of 

 Alabama, p. U)]. The hills enclosing this valley are high and steep ; their upper 

 portion is formed by ferruginous pebble conglomerate or puddingstone, in which 

 fragments of geodes of crystallized quartz are sometimes found ; the lower by the 

 ferruginous hornstone breccia described before (l[30). Underlying it, with 

 a visible thickness of about 8 — 10 feet, appears the white silica deposit. The 

 greater portion of it is pulverulent, and feels gritty (like starch) between the 

 fingers ; it is traversed, however (not always horizontally), by layers of hornstone 

 2 — 6 inches in thickness, which are not solid, but appear as though shattered 

 into fragments ; were the ferruginous cement present, it would form a breccia 

 like that which overlies. In these layers, all grades of transition from solid 

 hornstone into pulverulent, starchy silica, may be traced with ease. 



It seems difficult to account for the condition of these hornstone layers, except 

 by the contraction, in drying, of a gelatinous mass. The adjoining fragments 

 usually fit each other, though not always exactly, and the same is the case in the 

 overlying breccia, which seems to represent the solid hornstone ledges occurring 

 at other points. W. of Eastport, we find this breccia apparently alternating 

 with layers of hornstone, of which, also, it sometimes contains large lenticular 

 masses. Near to the planes of contact of the breccia and the pebble conglome- 

 rate of the Orange Sand (l[30), the ferruginous cement is usually, not brown 

 but brick red. 



On the waters of Little Bear Creek, in the southern portion of T. 3, E. 11 E., 

 we find (e. g. at Mr. Common's gin-house) the hornstone breccia overlyin* 

 directly an impure, sandy limestone, which here contains great numbers of 

 Productus costatus Sow., and a Spirifer (allied to S. bimesialis Hall). 



82. At the point where the M. and C. R. R. crosses Big Bear Creek, limestone 

 more thickly laminated, and purer than the gray slate at Eastport, crops out 

 on the banks. 



S. of the R. R., on SS. 10, 2 and 1, T. 4. R. 11 E., along the old District Road, we 

 find outcrops where a soft calcareous shale, characterized by immense numbers 

 of a Chonetes (allied to C. sarcinulata), but containing also Terebratulce, Produc- 

 tus costatus, stems of Pentremites, Stylopora Prouti, and Zaphrentis spinulifera, 

 overlies a sandy limestone containing abundance of Pentremites conoideus, Hall, 

 Spirifer pseudolineatus, Hall, Terebratula, a very large elongated Productus, 

 Cyathophyllum, and columns of Archimedes. This limestone stratum, which is of 

 inconsiderable thickness (about 10 feet), is underlaid in several localities by sand- 

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