and indeed when the bubbles rise from one of the apertures, the
emission of gas follows instantly from the other three. I could not
succeed in inflaming the small quantities of gas that rise above the
thermal waters, or those I collected in a glass phial held over the
springs, an operation that excited in me a nausea, caused less by the
smell of the gas, than by the excessive heat prevailing in this
ravine. Is this sulphuretted hydrogen mixed with a great proportion of
carbonic acid or atmospheric air? I am doubtful of the first of these
mixtures, though so common in thermal waters; for example at Aix la
Chapelle, Enghien, and Bareges. The gas collected in the tube of
Fontana's eudiometer had been shaken for a long time with water. The
small basins are covered with a light film of sulphur, deposited by
the sulphuretted hydrogen in its slow combustion in contact with the
atmospheric oxygen. A few plants near the springs were encrusted with
sulphur. This deposit 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 nitrate of copper; it is
destitute of flavour, and very drinkable. If it contain any saline
substances, for example, the sulphates of soda or magnesia, their
quantities must be very insignificant. Being almost destitute of
chemical tests,* (* A small case, containing acetate of lead, nitrate
of silver, alcohol, prussiate of potash, etc., 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.) we contented ourselves with filling at the spring two
bottles, which were sent, along with the nourishing milk of the tree
called palo de vaca, to MM. Fourcroy and Vauquelin, by the way of
Porto Cabello and the Havannah. This purity in hot waters issuing