11(1 i EOLOGICAL REPOTtT. ' L64, 165 



(Paris 36) 



Lower Vicksburg? stage 34 to'35 



.1 ackson stage 31 to 34 



Claiborne stage 26 to 30 (< onrad) 



Siliceous Claiborne (lower) 25 to 2G 



The latter numbers (viz : 25 to 26) arc also those of the fossil occurring in 



the estuary deposit of Tippah: affording an additional presumption in favor of 



the lower eocene age of the bed in question. 

 Leaving open the question of the age of these Lignitic strata, until settled. 



perhaps, by a comparison of the iloras, I shall comprehend under the head of 



the "Northern Lignitic", as a whole, all the beds found on the territory X. of 



the line of the marine Tertiary, and W. of the Cretaceous. 



I. THE NORTHERN LIGNITIC GROUP. 



164. The territory occupied by this group — marked on the map 

 by the lighter shade of brown — is generally billy, with the excep- 

 tion of the level belt immediately bordering on the cretaceous for- 

 mation — the 'Tost Oak Flatwoods," which will be more specially 

 described in the Agricultural Report. In these, the material of 

 the Lignitic formation itself (generally in a disintegrated condi- 

 tion), forms the surface : on the rest of the territory, the Orange 

 Sand generally overlies the latter thickly, having been, as usual, 

 deposited on a deeply denuded surface, whose hills and valleys 

 cause great irregularity in the occurrence of outcrops, as well as 

 uncertainty, in many cases, as to the very existence of the lignitic 

 formation, unless accidentally demonstrated by deep borings. 

 Nevertheless, there are extensive regions in which these strata 

 appear at and above the level of the drainage, forming the base of 

 the hills, and the beds of the streams ; and being, very generally, 

 the water-shedding stratum. 



165. In the Flatwoods, and the hills immediately adjoining them to the 

 westward, the materia', of the formation is usually a hard, gray or whitish clay, 

 sometimes laminated, but more usually of a massy cleavage, with a tendency to 

 conchoidal or nodular forms, which are conspicuous in most of the outcrops 

 found on whitened hillsides in the Flatwoods. This clay shows but little ten- 

 dency to disintegrate by the atmospheric agencies alone ; it does not "slake" 

 readily, so long as it retains its original structure, and hence, it is very generally 

 worn into genuine pebbles by the streams. When however, it has once been 

 broken up and worked into a plastic mass by mechanical means (as for in- 

 stance by denudation and re-deposition, or in roads), it resumes this condition 

 with extraordinary facility. Such is the nature of the surface material of the 

 Flatwoods, obviously derived from the (originally hard and intractable) clays of 

 the underlying strata, which it covers to a depth of from two to ten feet, form- 

 ing, to a great extent, both the soil and subsoil. These surface clays possess a 

 cleavage strictly massy, the cleavage planes being generally of a reddish tint ; 

 a rain falling on this mass, instantly converts it into the toughest mud. This 

 toughness is rarely impaired through the presence of sand ; the uncombined 

 siliceous matter contained in the mass is usually in a state of fine division, and 

 is to a great extent perhaps derived from subsequent infiltration with siliceous 

 solutions, which evidently have been active within the mass after its deposition. 

 For not only do we often find the clay itself indurated into a claystone of con- 

 siderable hardness, through the intervention of a siliceous cement, but we fre- 



