204 REACTION OF THE INTERIOR OF THE EARTH 



volcano of Purace, at the foot of which the town of 

 Popayan stands. It forms three picturesque cascades,( 281 ) 

 of one of which, which falls over a precipice more than 

 300 feet high, I have given a drawing. From the point 

 where this small stream falls into the Cauca, to the 

 mouths of the Pindamon and Palace 10 or 12 miles 

 lower down, no fish are found in that large river, much 

 to the annoyance of the inhabitants of Popayan, who are 

 strict observers of ecclesiastical fasts. The waters of the 

 Pusambio contain, according to Boussingault's later-made 

 analysis, a large quantity of hydrosulphuric acid and 

 carbonic acid gases as well as some sulphate of soda. Near 

 the source Boussingault found the temperature 163. The 

 upper portion of the course of the Pusambio is subter- 

 ranean. In the Paramo de Euiz, on the side of the 

 volcano of the same, name, at the sources of the Eio 

 Gruali, at an elevation of 12,150 feet, Degenhardt (a 

 geologist from Clausthal in the Hartz, whose early death 

 is a loss to geological science,) discovered in 1846 a hot 

 spring in the waters of which Boussingault found three 

 times as much sulphuric acid as in the Eio Vinagre. 



The persistent identity in temperature and chemical 

 composition of much the greater number of thermal 

 springs as far back as can be traced by secure observa- 

 tions, is a more remarkable fact than the variations 

 which have been made out in a few cases. ( 282 ) Thermal 

 springs, whose waters during their long and intricate 

 course take up from the rocks with which they come in 

 contact a variety of ingredients, which they often con- 

 duct to parts where the strata are wholly wanting 

 in such components, exert also another and entirely dif- 

 ferent kind of action, an action at once metamorphic 



