194 cosmos. 



A thermal spring which gives rise to an entire river of 

 water acidified by sulphur, the Vinegar River {Rio Vinagre), 

 called Pusambio by the aborigines, is a remarkable phenom- 

 enon to which I first called attention. The Rio Vinagre 

 rises at an elevation of about 10,660 feet on the northwest- 

 ern declivity of the volcano of Purace, at the foot of which 

 the city of Popayan is situated. It forms three picturesque 

 cascades,* of one of which I have given a representation, 

 falling over a steep trachytic wall probably 320 feet in per- 

 pendicular height. From the point where the small river 

 falls into the Cauca, this great river, for a distance of 2 — 3 

 miles (from 8 to 12 English miles) downward, as far as the 

 junctions of the Pindaraon and Palace, contains no fish; 

 which must be a great inconvenience to the inhabitants of 

 Popayan, who are strict observers of fasts! According to 

 Boussingault's subsequent analysis, the waters of the Pusam- 

 bio contain a great quantity of sulphureted hydrogen and 

 carbonic acid, with some sulphate of soda. Near the source, 

 Boussingault found the temperature to be 163°. The up- 

 per part of the Pusambio runs underground. Degenhardt 

 (of Clausthal, in the Harz), whose early death has caused a 

 great loss to geognosy, discovered a hot spring in 1846 in 

 the Paramo de Ruiz, on the declivity of the volcano of the 

 same name, at the sources of the Rio Guali, and at an alti- 

 tude of 12,150 feet, in the water of which Boussingault 

 found three times as much sulphuric acid as in the Rio 

 Vinagre. 



The equability of the temperature and chemical constitu- 

 tion of springs, as far as we can ascertain from reliable ob- 

 servations, is far more remarkable than the instability! which 



* One of these cascades is represented in my Vues dcs Cordilleres, 

 pi. xxx. On the analysis of the water of the Rio Vinagre, see Bous- 

 singault, in the Annales de Chimie et de Physique, 2e se'rie, t. hi., 1833, 

 p. 397, and Dumas, 3e serie, t. xviii., 1846, p. 503; on the spring in 

 the Paramo de Ruiz, see Joaquin Acosta, Viajes Cientijicos d los Andes 

 Ecuatoriales, 1849, p. 89. 



t The examples of alteration of temperature in the thermal springs 

 of Mariara and Las Trincheras lead to the question whether the Styx 

 water, whose source, so difficult of access, is situated in the wild 

 Aroanic Alps of Arcadia, near Nonacris, in the district of Pheneos, 

 has lost its pernicious qualities by alteration in the subterranean fis- 

 sures of supply ? or whether the waters of the Styx have only occasion- 

 ally been injurious to the wanderer by their icy coldness ? Perhaps 

 they are indebted for their evil reputation, which has been transmitted 

 to the present inhabitants of Arcadia, only to the awful wildness and 

 desolation of the neighborhood, and to the myth of their origin from 



