81 



The thermal waters have only a temperature of 

 43-2° cent, (the atmosphere being 27°) ; they 

 flow first to the distance of forty toises over the 

 rocky surface of the ground ; are then precipi- 

 tated into a natural cavern ; and pierce through 

 the limestone, to issue out at the foot of the 

 mountain, on the left bank of the little river 

 Narigual. The springs, while in contact with 

 the oxygen of the atmosphere, deposit a good 

 deal of sulphur. I did not collect, as I had 

 done at Mariara, the bubbles of air, that rise 

 in jets from these thermal waters. They no 

 doubt contain a large quantity of azot, because 

 the sulphuretted hydrogen decomposes the mix- 

 ture of oxygen and azot dissolved in the spring. 

 The sulphurous waters of San Juan, which issue 

 from calcareous rock like those of Bergantin, 

 have also but a weak temperature (31'3°) ; while 

 in the same region, the temperature of the sul- 

 phurous waters of Mariara and las Trincheras 

 (near Portocabello), which gush immediately 

 from gneiss-granite, is 58* 9° the former, and 

 90*4° the latter *. It would seem as if the heat, 

 which these springs acquire in the interior of 

 the globe, diminishes in proportion as they pass 

 from primitive to secondary superposed rocks. 



* L. c. Vol. iv, p. 52, 195, 272. J am ignorant of the 

 temperature of the hot, and hydrosulphurous springs of 

 Provisor, near San Diego, half a league distant from Nueva 

 Barcelona, toward the south. 



VOL. VI. G 



