132 



Scientific Intelligence. 



In the eastern portion of the valley of East Tennessee, the correspond- 

 ing rocks swell out to double, or perhaps to more than double the thick- 

 ness they have in the Central Basin. 



Here, too, they may be divided, generally, into two sub-groups, of 

 which the Stones River and Nashville are the western extensions. 



1. The Lower Sub-group — five or six hundred feet thick — is a bed of 

 blue, often knotty or spumous, limestone, containing many fossil shells 

 of species (Maclurea magna, Orthis deflecta, etc.,) identical with those 

 found in the Stones River sub-group. This division is often, in its 

 lower part, interstratified with the gray magnesian limestone. 



2. The upper sub-group is mostly a vast bed of calcareous, and more or 

 less sandy shales. These are developed on a great scale in the Bay's 

 Mountain Ridges. They include, occasionally, thin layers of sand- 

 stone, and are generally highly calcareous, having a sky-blue, rarely a 

 dark-gray color, and weathering to a sandy gray or yellowish-gray, or, 

 when more argillaceous, to a buff surface. The lower portion, es- 

 pecially in Sullivan and Greene, affords fine dark, or even black, argil- 

 laceous shales, which form long and frequently isolated " slate ridges." 

 The topmost portion in Hawkins is often reddish. 



A great band of these calcareous shales extends from the group of 

 mountains mentioned above, down through Jefferson, Sevier, Blount, 

 etc., becoming, however, less important in its southern extension. 



The most characteristic fossils are the linear serrated corals, called 

 Graptolitidce by geologists. They occur (both Oraptolites and Diplo- 

 grapsus) nearly at all points. 



Among the shaly strata of this sub-group, especially in its lower 

 portion, are several extensive interpolated beds, which have their maxi- 

 mum development in different parts of East Tennessee. The most im- 

 portant are the following : 



(a.) The gray marble, which lies at the base of the sub-group. 



(6.) The variegated marble, of which we have spoken. 



(c.) A dark gray, very ferruginous sandy limestone, with a red 

 streak, and weathering into red ferruginous sandy and often porous 

 masses. This bed, sometimes represented by many parallel ranges, 

 commencing in Jefferson and Knox, extends to the Hiwassee, in the 

 southeastern part of McMinn. It is heavily developed in Blount, Mon- 

 roe, and McMinn, forming the red sandy " knobs" of those counties. 



These beds are separated by shales, etc. Hereafter we shall present 

 complete sections of them. 



Passing westward, the shales of the upper sub-group rapidly run into 

 thin-bedded, argillaceous limestones, which, in the narrow valleys of the 

 western portion of the valley of Hast Tennessee, are much like those of 

 the Nashville series. 



(4.) Magnesian Limestone and Shale Group. — 3. Limestone of Knox- 

 ville; 2. Limestones and variegated shales of numerous valleys and 

 ridges in East Tennessee ; 1. Thin-bedded and many-colored sandstones 

 of numerous sharp ridges in East Tennessee : corresponding to the Cal- 

 ciferous sandstone of New York. 



This extensive formation — several thousand feet in thickness — pervades 

 the greater part of the valley of East Tennessee. It is a great series of 



