1166, 107. 168] NORTHERN LIGN1T1C- -CLAYSTONES. Ill 



quently meet, within the mass, irregular veins and lenticular sheets of a very 

 hard, gray or brown siliceous rock (at times almost a pure hornstone, at others 

 consisting in part of clay), whose drusy, nodular surface plainly shows its origin. 



166. Stratified clay stones (6 to 18 inches in thickness) are of common 

 occurrence at or near the top of the Lignitic strata of Tippah and Pontotoc, at 

 no great distance from the border of the cretaceous formation. These clay- 

 stones sometimes differ from the clay itself in little else than their greater 

 hardness, but usually they are somewhat sandy, and contain numerous black 

 grains — in some instances, grains of greensand. Through these claystones, 

 evciy degree of lithological transition from the pure, almost white clay, to the 

 fossiliferous sandstone of N. Tippah (U 168) may be traced, and careful exami- 

 nation will sometimes detect in them unequivocal remnants ot marine fossils. 

 Such is the case with the (glauconitic) claystone overlying the lignitic clays at 

 Mr. Brougher's place, S. 7, T. 5, R. 2 E., Tippah county, and at an outcrop a 

 mile W. of Pontotoc. At the latter place a Turbinolia ! and part of the nucleus 

 of a Natica ? was found, with other impressions too indistinct to be recognized ; 

 at the former, the exterior cast of a small, deeply ribbed Venericardia ? or Area ? 



I have not met with any of these claystones on the territory of the Northern 

 Lignitic S. of the outcrop mentioned, near the town of Pontotoc. Thence S. 

 to the Succarnoche River, I have seen only the whitish "Flatwoods Clay ; n 

 where the latter is massy or nodular, it rarely contains unequivocal signs of 

 vegetable fossils. Westward of the Flatwoods proper, however, the clays are 

 commonly laminated, less uniform in their character, and interstratified more or 

 less with sand. Such usually are the clays associated with the lignite beds, 

 and containing impressions of leaves ; nevertheless, the genuine "Flat woods- 

 Clay" character frequently re-appears, locally, over the whole region. 



167. The greatest deversity of material generally obtains in connection with 

 the Lignite beds. They are usually overlaid, and sometimes underlaid also, by 

 yellow sands, or sandy clays, or numerous alternating layers of these materials, 

 often strongly lignitic themselves, and correspondingly dark colored. On the 

 other hand, pure, refractory, blue or green clay, of a massy cleavage, and void 

 of sand, is sometimes found associated with the lignite beds, and especially as 

 forming the subjacent stratum. 



A special description of the lignite beds will be found under the head of the 

 Useful Materials of this group (1T252, ff.). Within the light colored, laminated 

 clays of this formation, are not unusually found rounded masses, from the size 

 of a mans head to that of several bushels, of a black substance so much resem- 

 bling stone-coal, as to render it undistinguishable, at times, even to a practised 

 eye. It is a kind of bitumen, similar to that found sometimes in the Rotten 

 Limestone ; in the fire it is semi-fused like Cannel coal, swells and burns with 

 a brilliant, smoky flame, producing a light, spongy coke, which burns with 

 difficuity, leaving but very little, white ash. A more eligible material for the 

 manufacture of illuminating gas could scarcely be procured , but thus far, no 

 continuous deposit of this substance has been discovered. Among the locali- 

 ties where it has been found, I may mention : Mr. Brougher's place, S. 7, T. 5, 

 R. 2 E., Tippah county ; Dr. John Thompson's, S. 8, T. 12, R. 2 E., Calhoun 

 county; Mr. Madison Carr's, S. 6, T. 11, R. 5 W., Yallabusha county ; between 

 Sun Creek and Trim Cane Creek, in Mr. Dillon's neighborhood, Ocktibbeha 

 county. 



168. Localities of the Northern Lignitic Group. — Near Mr. David Reeve's, 

 S. 36, T. 1, R. 3 E., N. Tippah county, we obtain, along the bed of a branch, the 

 followinc: section : 



