93 Notice of the Thermal Springs of North AQiierica. 



travertine which the springs formerly deposited, is different in 

 color and appearance from what they produce at present ; the for- 

 mer being dark looking, and containing a portion of iron, as well 

 as calcareous matter ; the latter quite white, and consisting en- 

 tirely of carbonate of lime. 



The springs vary considerably in temperature, the hottest being 

 148°, the coolest 118°Fahr., according to my observations.* 



They contain very little mineral matter, a pint evaporated to 

 dryness, yielding no more than 1.8 grains ; of this one half was 

 carbonate of lime, and ^th of a grain, silica. The rest was 

 chiefly common salt, but there was a mere trace of sulphuric acid, 

 when the water had been much concentrated. One of these 

 springs deposited an ochreous precipitate, and gave indications of 

 iron when tested. The remainder were entirely free from that 

 ingredient. 



Most of the springs emitted bubbles of gas, which according to 

 my experiments, consisted of carbonic acid, 4 per cent., nitro- 

 gen, 92.4, oxygen, 7.6. 



The rock which forms the basis of the hill, from which the 

 thermal springs of Washita issue, is a blueish fissile clay slate, 

 dividing into nearly vertical laminse. Incumbent upon it, how- 

 ever, are beds of chert, quartzy sandstone, and flinty slate, from 

 the junction of which, with the clay slate, the springs appear to 

 gush out. 



The prevailing rock, however, in the neighborhood of the 

 springs, so far as my observation extends, is quartz-rock, some- 

 times assuming the character of whetstone slate, and in one local- 

 ity (situated within a few miles of the springs) quarried for houses, 

 but constituting a part of the same extensive formation, which I 

 have represented myself as having followed from Little Rock in 

 Arkansas, to St. Louis in Missouri. 



The chain is regarded by Geographers, as a branch of the 

 Ozark mountains, and is the first elevated land met with on pro- 

 ceeding westward from the Mississippi, though its greatest height 

 is probably not more than 500 or 600 feet above the river. The 

 only circumstance connected with this range of hills, which can 

 throw any light upon the origin of the thermal waters, that issue 



* They are stated, however, in Silliman's Journal, as rising as high as 154° or 

 156°. 



