24 
NATURAL HOT BATH. 
■with filling at the spring two bottles, which were sent, 
along with the nourishing milk of the tree called polo de 
vaca, to MM. Eourcroy and Vauquelin, by the way of 
Porto Cabello and the Havannah. This purity in hot 
waters issuing immediately from granite mountains is in 
Europe, as well as in the New Continent, a most curious 
phenomenon.* How can we explain the origin of the 
sulphuretted hydrogen? It cannot proceed from the de- 
composition of sulphurets of iron, or pyritie strata. Is it 
owing to sulphurets of calcium, of magnesium, or other 
earthy metalloids, contained in the interior of our planet, 
under its rocky and oxidated crust ? 
In the ravine of the hot waters of Mariara, amidst little 
funnels, the temperature of which rises from 56° to 59°, two 
species of aquatic plants vegetate; the one is membrana- 
ceous, and contains bubbles of air ; the other has parallel 
fibres. The first much resembles the Ulva labyrinthiformis 
of Yandelli, which the thermal waters of Europe furnish. 
At the island of Amsterdam, tufts of lycopodium and mar- 
chantia have been seen in places where the heat of the soil 
was far greater : such is the effect of an habitual stimulus 
on the organs of plants. The waters of Mariara contain no 
aquatic insects. Frogs are found in them, which, being 
probably chased by serpents, have leaped into the funnels, 
and there perished. 
South of the ravine, in the plain extending towards the 
shore of the lake, another sulphureous spring gushes out, 
less hot and less impregnated with gas. The crevice whence 
this water issues is six toises higher than the funnel just 
described. The thermometer did not rise in the crevice 
above 42°. The water is collected in a basin surrounded by 
large trees ; it is nearly circular, from fifteen to eighteen feet 
diameter, and three feet deep. The slaves throw themselves 
into this bath at the end of the day, when covered with 
dust, after baling worked in the neighbouring fields of in- 
digo and sugar-cane. Though the water of this bath (baiio) 
is habitually from 12° to 14° hotter than the air, the negroes 
call it refreshing ; because in the torrid zone this term is 
* Warm springs equally pure are found issuing from the granites 
of Portugal, and those of Cantal. In Italy, the Pisciarelli of the lake 
Agnano have a temperature equal to 93°. Are these pure waters pro- 
duced by condensed vapours ? 
