198 REACTION OF THE INTERIOR OF THE EARTH 



heat, " which occasions the fiery eruptions of Etna and 

 Vesuvius," and " renders springs so much the warmer as 

 their origin is deeper." He considered the Pyriphlege- 

 thon of Plato to be the hell of sinners ; and further, as if 

 he would have recalled one of the cold hells of the 

 Buddhists, supposed, somewhat unscientifically, for the 

 " nunquam finiendum supplicium impiorum," notwith- 

 standing the depth, an " aqua gelidissima concrescens in 

 glaciem." 



Among hot springs, those which attain a temperature 

 of 194 Fahr. (approaching the boiling point of water, 

 212) are much more rare than, from inexact observa- 

 tions, is commonly believed, and least of all are they to be 

 looked for in the neighbourhood of still active volcanoes. 

 In my American journey, I was able to examine two of 

 the most Important of such springs, both within the 

 tropics. In Mexico, not far from the rich silver mines 

 of G-uanaxuato, in 21 north latitude, at an elevation of 

 fully 6400 feet above the level of the sea, ( 27 ) the 

 Aguas de Comangillas gush forth from a mountain of 

 basalt and basaltic breccia. I found their temperature, 

 in September 1803, 205-5 Fahr. This basaltic mass 

 has been broken through by a dyke of columnar por- 

 phyry, which itself rests on a white quartzose syenite. 

 Higher up, but not far from this almost boiling spring, 

 at los Joares, north of Santa Eosa de la Sierra, snow 

 falls from December to April at an elevation of only 

 8700 feet ; and throughout the year the natives prepare 

 ice, by means of radiation, in artificial basins. In the 

 route from Nueva Valencia in the Valles de Aragua to 

 the harbour of Portocabello (in about 10 \ north la- 

 titude), on the northern declivity of the Venezuelan 



