11 4 M. Humboldt on the Waters of the Rio Vinagre 



opening communicated with a basin full of boiling water. 

 The vapours which escape with so much violence are of the 

 sulphurous acid, which is indicated by their suffocating smell. 

 We shall soon see that the water of the subterraneous lake 

 is charged with sulphuretted hydrogen ; but the odour of this 

 gas is not smelt at the summit of the volcano, because it is 

 disguised by the much stronger smell of the sulphurous acid 

 vapours. 1 had not any means of determining the tempera- 

 ture of these vapours, which seem to undergo a prodigiously 

 strong pressure in the interior of the volcano. As the Indians 

 pretend that the opening has several compartments which are 

 not all filled with water, and that the noise which is heard at 

 times in the interior of the crevice is the forerunner of flames, 

 I introduced, by means of a long pole, some pa}iers coloured 

 with ihe tincture of violet, under the vault, where I could be 

 sure of not touching the surface of the water. Drawing back 

 the pole, I found the papers strongly reddened, but not at all 

 inflamed, as was easy to be fojeseen. 



We succeeded after several vain attempts in obtaining some 

 water from the crevice : thisawas by tying a tutuma (the fruit of 

 the Crelcentia Cujete) to a stick 8 feet long. The water was 

 directly poured into a bottle hermetically stopped. We ex- 

 amined it on our return to the village of Purace : it exhaled a 

 strong smell of sulphuretted hj-drogen ; it had no acid taste, 

 but some weak precipitates caused by the nitrate of silver 

 showed the presence of muriatic acid. The crust of sulphur 

 which forms above the mouth arises without doubt from the 

 contact of the vapours of sulphurous acid with the sulphuretted 

 hydrogen which the subterraneous lake disengages. Even the 

 water of this lake is covered with a coat of sulphur, which dis- 

 appeared in the places where we threw the stones. It results 

 from these observations, that only the presence of the muriatic 

 acid, or of combinations of this acid with salifiable bases, indi- 

 cates a feeble analogy between the waters of Rio Vinagre and 

 those of the lakes, 'rhe first, which spring much lower, at the 

 declivity of the volcano of Purace, are charged with free sul- 

 phuric acid : the others, which are found at the summit of the 

 volcano, contain sulphuretted hydrogen. As the upper mouths 

 are found at very different heights above the level of the sea, 

 it may be supposed that their subterraneous waters are owing 

 to the melting of the snows, and that they do not communicate. 

 The Rio Vinagre receives its acid in the interior of a volcano 

 which abounds in sulphur, and the temperature of which ap- 

 pears extremely elevated, although for centuries no luminous 

 phoenomenon has been perceived at its summit. 



The 



