HOT SPRINGS AT THEKMOPOLIS, WYOMING 



199 



that if the water was not thrown out by geyser action, it at least 

 flowed in large volume. 



Source of the water. — The source of the water in the Thermopolis 

 springs is difficult to ascertain, but undoubtedly the flow is not 

 derived from the adjacent Red beds, nor from the underlying Embar 

 limestone. Probably the strata are somewhat fractured in the 



Fig. 4. — Hot Spring deposits on old terraces at various heights in western part of 

 l.'hermopolis, Wyoming. Looking south across Bighorn River. 



crest of the arch and permit the escape of the water from deep- 

 seated sources. One of the most likely of these might be thought 

 to be the porous Tensleep sandstone which outcrops high on the 

 mountain slopes southward. It undoubtedly carries a water supply 

 which passes beneath the syncline south of ThermopoHs, and 

 retains sufficient head to rise to and above the surface in any 

 vent to the northward. If the water is from no greater depth than 

 this horizon, there is difficulty in accounting for the high tempera- 

 ture, for the top of the sandstone does not lie at a greater depth 

 than 500 feet at the spring and 2,000 feet in the bottom of the syn- 

 cline a short distance south. Assuming that the mean annual 

 temperature at Thermopolis is 50°, and that the temperature of 

 water increases one degree for every 50 feet underground below 



