SALSES. 221 



la Tour), with its harmless exhalations, has nothing to do 

 with these fatal actions. 77 



I conclude this section on the salses and steam and gas 

 springs, with the description of an eruption of hot sulphu- 

 rous vapours, which may attract the interest of geognosists 

 on account of the kind of rock from which they are evolved. 

 During my delightful, but somewhat fatiguing passage over 

 the central Cordillera of Quindiu, (it took me 14 or 15 days 

 on foot, and sleeping constantly in the open air, to get over 

 the mountain crest of 11.500 feet from the valley of the Rio 

 Magdalena into the Cauca valley), when at the height of 

 6810 feet I visited the Azufral to the west of the station el 

 Moral. In a mica-schist of a rather dark colour, which, re- 

 posing upon a gneiss containing garnets, surrounds, with the 

 latter, the elevated granite domes of la Ceja and la Garita 

 del Paramo, I saw hot sulphurous vapours flowing out from 

 the clefts of the rocks in a narrow valley (Quebrada del 

 Azufral). As they are mixed with sulphuretted hydrogen 

 gas and much carbonic acid, a stupefying dizziness is expe- 

 rienced on stooping down to measure the temperature, and 

 remaining long in their vicinity. The temperature of the 

 sulphurous vapours was 117 7 ; that of the air 69 ; and 

 that of the sulphurous brook, which is probably cooled in 

 the upper parts of its course by the snow-waters of the 

 volcano of Tolima, 84. 6. The mica-schist, which contains 

 some pyrites, is permeated by numerous fragments of sul- 

 phur. The sulphur prepared for sale is principally obtained 

 from an ochre-yellow loam, mixed with native sulphur and 

 weathered mica-slate. The operatives (Mestizoes) suffer 

 from diseases of the eyes and muscular paralysis. When 

 Boussingault visited the Azufral de Quindiu, 30 years after 

 me (1831), the temperature of the vapours which he ana- 

 lysed 78 had so greatly diminished, as to fall below that of the 

 open air (7 1!~6), namely to 66 68. The same excellent 

 observer saw the trachytic rock of the neighbouring volcano 

 of Tolima, breaking through the mica-schist, in the Quebrada 

 de Aguas calientes : just as I have very distinctly seen the 



77 Blume, Rumphia sire Comment, lotanicce, t. i (1835), pp. 4759. 



" s Humboldt, Essai r/eognostique sur le gisement des Roches dans les 

 deux Hemispheres, 1823, p. 76 ; Boussingault, in the Annales de Chimie 

 tt de Physique, t. Hi, 1S33, p. 11. 



