THERMAL SPRINGS. 189 



to the springs, in proportion as they have a deeper origin." 

 With the learned bishop Plato's Pyriphlegethon was the hell 

 of sinners ; and as though he desired at the same time to re- 

 mind one of the cold hells of the Buddhists, an aqua gelidissi- 

 ma concrescens in glaciem is admitted, somewhat unphysically 

 and notwithstanding the depth, for the nunquam jiniendum 

 suppliciu?7i impiorum. 



Among hot springs, those which, approaching the boiling 

 heat of water, attain a temperature of 194° F. are far more 

 rare than is usually supposed, in consequence of inexact ob- 

 servations ; least of all do they occur in the vicinity of still 

 active volcanoes. I was so fortunate, during my American 

 travels, as to investigate two of the most important of these 

 springs, both between the tropics. In Mexico, not far from 

 the rich silver mines of Guanaxuato, in 21° N. lat., and at 

 an elevation of about 6500 feet above the surface of the sea, 

 near Chichemequillo,* the Aguas de Comangillas burst forth 

 from a mountain of basalt and basaltic breccia. In Septem- 

 ber, 1803, I found their temperature to be 205°-5 F. This 

 mass of basalt has broken in the form of veins through a 

 columnar porphyry, which again rests upon a white syenite 

 rich in quartz. At a greater elevation, but not far from 

 this nearly boiling spring, near Los Joares, to the north of 

 Santa Rosa de la Sierra, snow falls from December to April 

 even at an elevation of 8700 feet, and the inhabitants pre- 

 pare ice the whole year round by radiation in artificial ba- 

 sins. On the road from Nueva Valencia, in the Valles de 

 Aragua, toward the harbor of Porto Cabello (in about 101° 

 of latitude), on the northern slope of the coast chain of Ven- 

 ezuela, I saw the aguas calientes de las Trincheras springing 

 from a stratified granite, which does not pass at all into 

 gneiss. I foundf the springs, in February, 1800, at 194°-5 

 F., while the Banos de Mariara, in the Valles de Aragua, 

 which belong to the gneiss, showed a temperature of 138°-7 

 F. Twenty-three years later, and again in the month of 

 February, Boussingault and Riverof found in the Mariara 



* Humboldt, Essai Politique sur la Nouvelle Espagne^ ed. 2, t. iii. 

 (1827), p. 190. • 



t Relation Ilistoriqne, t. ii., p. 98 ; Cosmos, vol. i., p. 222. The hot 

 springs of Carlsbad also originate in the granite (Leop. von Buch, in 

 Foggend., Anmlen, bd. xii., s. 230), just like the hot springs of Mo- 

 may, in Thibet, visited by Joseph Hooker, which break forth near 

 Changokhang, at an elevation of 16,000 feet above the sea, with a 

 temperature of 115° (IIi?nalai/an Journal, a'oI. ii., p. 133). 



t Boussingault, " CoHsiderations sur les eaux thermales des Cor- 



