HOT WATER SUPPLY OF THE HOT SPRINGS 447 



and similar in. chemical composition, it seems likely that they have 

 a common origin. Special hypotheses are invalidated by this 

 probability. 



The meteoric hypothesis then suffers from two main defects: 

 (i) A possible lack of head to force the water through the postu- 

 lated structure; (2) the very special association of uncooled rock 

 with the structure. 



The hypothesis of juvenile origin for the waters when examined 

 is perhaps more satisfactory, but suffers from conspicuous defects. 



This hypothesis may take two forms: (i) That there is a 

 buried mass of uncooled igneous rock which is discharging water 

 due to cooling and crystallization; (2) that a fracture or fissure 

 extends from the springs into the deep interior of the earth, similar 

 in character to the great fault fractures and through this fracture 

 deep-seated waters, juvenile or of mixed origin, rise to the surface. 



A mass of uncooled igneous rock discharging juvenile water is 

 a hypothesis of the same special character as the uncooled body 

 postulated under the meteoric hypothesis. It is no more unreason- 

 able to assume that it is still crystallizing and discharging water, 

 than that it is not crystallizing, but is still hot enough to heat the 

 water by contact. Moreover, the nearby igneous bodies are of 

 Cretaceous age and there is no other evidence of igneous activity 

 in the general region. 



That a deep fracture or fissure exists is also a special hypothesis 

 but only special in that it provides that the water rising in this 

 .fissure is warm at the surface. A source of heated water is every- 

 where present in the deeper crust and in regions of disturbance 

 there is a rise in the geotherms and in some instances at least 

 invasion of batholithic bodies. Deep fissures in this general region, 

 though their position is now almost wholly concealed by erosion, 

 must have occurred as late as the Pleistocene epoch during which 

 time the principal uplift is thought to have occurred. Under a 

 hypothesis of recent faulting the position of the springs at the 

 nose of Hot Springs Mountain anticline is purely accidental 

 except that the rising waters have taken advantage of the pre- 

 existing fracture by overthrust of the Hot Springs sandstone and 

 the two underlying shales. 



