170 



by the excessive heat prevailing in this ravine. 

 Is this sulphuretted hydrogen mixed with a 

 great proportion of carbonic acid, or of atmos- 

 pheric air ? I am doubtful of the first of these 

 mixtures, though so common in thermal waters 

 (at Aix la Chapelle, Enghien, and Bareges). 

 The gas collected in the tube of Fontana's eudi- 

 ometer had been shaken for a long time with 

 water. The small basins are covered with a 

 light pellicle of sulphur, deposited by the sul- 

 phuretted hydrogen in it's slow combustion in 

 contact with the atmospheric oxygen. A few 

 plants near the springs were incrusted with 

 sulphur. This deposite is scarcely visible, when 

 the water of Mariara is suffered to cool in an 

 open vessel ; no doubt because the quantity of 

 disengaged gas is very small, and is not renewed. 

 The water when cold gives no precipitate with 

 a solution of nitrat of copper ; is destitute of 

 flavour, and very drinkable. If it contain any 

 saline substances, for example, sulphat of soda, 

 or of magnesia, their quantities must be very 

 insignificant. Being almost destitute of chemical 

 tests we contented ourselves with filling two 



* A small case, containing acetat of lead, nitrat of silver., 

 alcohol, prussiat of potash, &c, had been left by mistake at 

 Cumana. I evaporated some of the water of Mariara, and 

 it yielded only a very small residuum., which, digested with 

 nitric acid, appeared to contain only a little silica and 

 extractive vegetable matter. 



