CHARACTERISTICS OF NEVADA SPRINGS. 257 



must be ascribed to their having neighboring and probably parallel channels along 

 the same fracture zone. Decomposed rock along such a fracture zone would 

 form an effective barrier, preventing currents from mingling the waters and 

 averaging their temperatures. The cool water is evidently vadose, and probably 

 represents a part of the atmospheric waters which fall upon the Silver Peak 

 Range, while the hot waters have a distinct and vastly deeper origin. It is clear, 

 however, that in many similar cases the two currents of water must mingle, 

 appearing at the surface as springs of varying warmth and of composite origin. 

 In seeking to understand the nature of the Silver Peak hot springs the writer 

 learned from the inhabitants of the village a significant fact. According to them 

 the water of the hot springs is much hotter in winter and fall than in summer 

 and spring, so that in the former seasons much more cold water must be added 

 to bring it down to a temperature requisite for bathing. This indicates that the 

 temperature of the hot water is really modified by the cool vadose water, the 

 modifying being characteristic of the seasons when the melting of the snows 

 provides a considerable supply to the shallow underground circulation. 



THE DEVILS PUNCHBOWL. 



Mr. J. L. Butler, the discoverer of Tonopah and an old inhabitant of the 

 region, has described to the writer a hot spring in Monitor Valley, not far from 

 Belmont, which is 45 miles northeast of Tonopah. This spring occupies a cup- 

 shaped depression probably formed by sinter accumulations known as the Devils 

 Punchbowl. This depression is reported to be 30 feet in diameter and to be full 

 of hot water up to a point 30 feet below the top. The level of the water has 

 gone down 3 feet in thirty years and the water has become cooler. Formerly 

 more gas than at present was emitted, and occasional flames were seen. This 

 change is apparently a secular one, strikingly different from the seasonal variations 

 of vadose springs, and suggesting as a cause the diminution of volcanic energy 

 in this region of abundant Tertiary volcanics. 



AMOUNT OF PRESENT AND RECENT HOT-SPRING ACTION. 



Similar hot springs, some of them boiling, abound in the region and surround 

 Tonopah on all sides. Volcanic activity has been great in this province for a 

 prolonged period, lasting from the beginning of the Tertiary to within a few 

 hundred years ago. At Silver Peak is a small, undefaced basalt crater, which is 

 younger than the detritus of the valley, and can hardly be more than a few 

 hundred years old; and there are a number of other craters, such as those in and 

 near Lake Mono described by Russell which are comparatively recent. That 

 many of the hot springs which accompanied or followed the different manifestations 

 16843 No. 4205 17 



