WITH ANTICLINAL AXES AND FAULTS. 333 



west. At all these points much gaseous matter is evolved along 

 with the water, consisting in great part of nitrogen, with some 

 carbonic acid, a very Utile and in certain cases no oxygen, and 

 at two or three points a slight admixture of sulphureted hyckogen. 

 The position of this valley between two lofty ridges, which 

 uniting at its opposite extremes form a complete enclosm-e around 

 it, and the steep inclination of the strata along the western part of 

 its surface, are just such conditions as might be expected to give 

 rise to a large accumulation of water at great depth, and to furnish 

 a hydrostatic force capable of raising it to the surface. It appears 

 to me, therefore, that in speculating upon the mechanical agencies 

 concerned in the emissions of these thermals, we are not called 

 upon to imagine any other force than that of the simple pressure 

 of aqueous columns, either continuous or interrupted by gases 

 accumulated in the same fissures or cavities within the earth. 

 Nor, in tracing to their origin the temperature, evolved gases, and 

 the chemical ingredients of these waters, do I conceive that any 

 further conditions are required, than the access of the air and 

 meteoric waters to rocky masses at a great depth below the sur- 

 face, and whose temperature, due to that depth, sustains the 

 chemical actions necessary to give the proper impregnation to 

 the springs. 



In glancing the eye along Section I, it will be seen that the 

 flexures of the strata are such as to give the axis-planes an oblique 

 position, dipping towards the southeast ; a structm-e equally dis- 

 tinct also in the other sections, and which is in conformity with a 

 general law, already announced by my brother. Prof. H. D. Rogers 

 and myself, in a joint paper ' On the Structure of the Appalachian 

 Chain,' read to the Association.* In consequence of such a flex- 

 ure, the strata of the Mill Mountain, on the western side, are 

 thrown into an inverted position ; those on the east, in which the 

 Thermal of Panther Gap rises, preserving a moderate dip towards 

 the southeast. This bold spring, accompanied by a good deal of 

 gas, chiefly nitrogen, issues from beds of limestone belonging to 



* To tliis paper, and the accompanying Sections and Diagrams, 1 would refer for a full 

 exposition of this law, and for explanations of the terms normal aitd folded flexures, 

 axis-plane, &c., used in the present article. 



