350 



[April 1, 



Mr. Fontaine points out that the little salt and gypsum 

 bearing valley of Saltville cannot be " eroded along an anti- 

 clinal of Lower Silurian limestones," because the south- 

 east wall hills only are of that age, while the north-west wall 

 hills are of Umbral (Mauch Chunk, Subcarboniferoas) age. 

 He was the first to find in the limestones on that side of the 

 valley an abundance of Umbral fossils, in the highly fossil- 

 iferous shale beds intercallated between the massive lime- 

 stones. The species are the same found in the Umbral near 

 Lewisburg, West Virginia. The Magnesian (Lower Silu- 

 rian) limestone strata, bounding the valley on the south- 

 east, show no trace of fossils. 



Holsten 

 fiver. 



l/mdrdlU. 



Saltville 

 Valley . 



The physical aspects of the two formations also differ. 

 Beds of shale and limestone alternate in the hills N. W. of the 

 valleys ; and some of the limestone is cherty, and some of 

 the shales are red. But the S. E. hills contain only solid 

 limestone strata. Those on the N^. "W. side have a more 

 rounded topography. 



It is, however, quite true that the stratification is in oppo- 

 site S. E. and N. W. directions; gentle to the S. E. and much 

 steeper to the N. W. The structure is therefore anticlinal. 

 But there must be a considerable fault along the axis of the 

 anticlinal, and this fault must run along the south-east edge 

 of the little valley. 



The explanation is then simple. The Umbral limestone 

 ridge is a synclinal ; and the red shale formation comes up 

 on both sides of it, — with north-west dips in the little 

 valley, — and with south-east dips in the valley of the Hol- 

 sten river, at the foot of the mountain, as shown above. 



