275 



tion upon one that the waters of the springs owe their temperature to 

 passing over hot rocks or the vapor from such in some part of their under- 

 ground course. 6 The fact that these are practically 7 the only hot springs 

 within the Ouachita area, though there are scores of cold springs issuing 

 from the same formations and under practically the same geologic rela- 

 tions, gives this suggestion great weight ; but inasmuch as some of the 

 springs are said to be unusually radio-active, there is the alternative sug- 

 gestion that atomic decomposition in igneous rocks (which may have lost 

 their magmatic heat) is the source of the high temperature of the water. 

 Fayetteville, Ark. 



6 Dr. J. C. Branner has already called attention to this as the probable source of the heat. 

 See Geol. Surv. of Ark., Report on Mineral Waters, pp. 9 and 10. 



7 Recently a spring, said to have a temperature of 98° to 100° F., has been discovered 

 issuing from the Arkansas novaculite in the bed of the Caddo River, at Caddo Gap, Mont- 

 gomery County. 



