90 Notice of the Thermal Springs of North America. 



tion, that an expansion of two per cent, takes place in nitrogen, 

 after phosphorus has been heated and volatihzed in the vessel 

 that contains this gas. 



Now both the above springs he at a distance of about three 

 miles, one from the other, in a valley, the direction of which is 

 nearly north and south, and it may be seen by reference to the 

 section, which Professor William B. Rogers has appended to his 

 Geological Report of the State of Virginia, that they are situated 

 exactly at the anticlinal axis already alluded to.* And on exam- 

 ining the rocks on both sides of these springs, wherever the na- 

 ture of the country allowed of my exploring them, I found every 

 reason to place reliance on the correctness of his representation. 



To the west of the Hot Spring, the more southern of the two 

 thermal waters alluded to, the rocks become more and more in- 

 clined towards the west, as they approach nearer to the spring, 

 until at length in its immediate vicinity, they assume an almost 

 vertical position. 



Immediately surrounding the spring which issues from the bot- 

 tom of the valley are vertical beds of a blue fossilliferous lime- 

 stone, which is called number two, by Professor Rogers, being the 

 lowest but one of the rocks incumbent on those of the Blue 

 Ridge, which are included in his series. 



A very compact sandstone used as a freestone succeeds, then 

 beds of clay slate again, and afterwards an highly ferruginous 

 sandstone. 



Up to this point, the rocks are inclined at so high an angle, 

 that they may be regarded as vertical, and in consequence of being 

 so near the axis of the movement, they are often contorted and 

 much disturbed. Further to the west, however, they are suc- 

 ceeded by strata of sandstone, conglomerate, limestone and 

 clay slate, dipping at a gradually decreasing angle of inclination, 

 and this continues until they become nearly horizontal. 



On the east of this spring, the density of the forests is such as 

 rendered it impossible for me to obtain any knowledge of the 

 mineral structure of the subjacent rocks, but this desideratum 

 was supplied by following the road running to the east of the 

 Warm Spring, which, as I have already stated, lies in the same 

 valley. 



^ * In the former part of the paper which is not contained in our present number. 

 —Eds. 



