364 REPORT UNITED STATES GEOLOGICAL SURVEY. 



Stanley,* no less than thirty-five spouting springs made their appear- 

 ance, many of which afterwards diminished in activity. After an earth- 

 qualie in 1789 Old Strokhr, one of the geysers of Haukadal, gradually 

 became a quiet spring, and the one now known as Strokhr began to 

 ernpt.t 



Coming down to the nineteenth century we find that in Chili, after 

 the earthquake of 1822, the hot springs of Cauquenes ceased flowing 

 for a time, and after the earthquake of 1835 were temporarily lowered 

 in temperature from 118° F. to 92° F. 



The spring of Rita, in Ischia, increased in temperature during the 

 earthquake of February 2, 1828, and the earthquake of 1837, in Syria, 

 caused new hot springs to appear at Tabereah. 



These are a few of the many instances that might be enumerated, but 

 they are sufficient to prove that springs may either be brought into exist- 

 ence or may be destroyed by earthquakes, or made cold or hot, as the case 

 may be. 



According to Hoffman | numerous hot springs act as safety valves 

 and serve as a protection from earthquakes, as at Sciacca, in Sicily, 

 which is rarely disturbed by them, in comparison with other j^arts of 

 the island. 



In some cases the hot springs may become clogged or stopped up, and 

 when the pent-ui) stream bursts out earthquake shocks may be caused. 

 The shocks we experienced at Steamboat Point, on Yellowstone Lake, 

 in 1871 § were probably due to inadequacy of the steam vents. 



CHAPTER III. 



CLASSIFICATION AND THERAPEUTICS. 



Classification. — A few remarks upon the classification of thermal 

 waters should perhaps be included here, although it is manifestly be- 

 yond our pi-eseut scope to enter upon the subject in its completeness. 



Thermal waters are subject to the same laws of classification as ordi- 

 nary mineral waters, whether a chemical, therapeutical, geological, or 

 geographical system be adopted. They may be alkaline, saline, sul- 

 l)hureted, carbonated, or chalybeate, according to their various ingre- 

 dients which will usually be found present in less proportion than in 

 ordinary mineral waters. There is, however, one exception — the pro- 

 portion of silica is apt to be greater, especially if the springs have 

 water at or near the boiling temperature. Of course, if the hot water 

 does not have access, in the depths below the surlace, to siliceous rocks, 

 it may contain but a small percentage of silica. 



As we shall have to do more with siliceous waters in the chapters 

 upon the analyses, especially with those of the Yellowstone National 

 Park, we shall refer to this subject of classification more particularly 

 as it concerns the three great regions in which this class of thermal 

 springs is found. 



So few of the springs of the Yellowstone National Park have had 



* Account of the Hot Springs of Iceland, p. 41. 



t/ftirf., p. 32. 



X Poggeudorf's Annalen, V. XXIV., p. 70, cited by Biscliof. 



§ Report for 1871, p. 190. 



