Torrents of Hot Water, AirWolcanocs, and Cold-Spi'ings, 315 
and flame and smoke rushed from it to the height of more than 
three hundred feet. Great masses of dried mud were projected 
from it to great distances, and it vomited forth currents of o, bi- 
tuminous mud or slime, to the amount of one hundred thousand 
cubic fathoms. Humboldt describes air-volcanoes which he 
saw in the middle of an elevated plain, in the province of Car- 
thagena in South America, There were twenty small cones, 
having an elevation of from twenty-one to twenty-seven feet in 
height, and formed of bluish coloured clay. Their summits 
were hollow or crater-like, filled with water, from the surface of 
which air arose, and burst with an explosion, and often threw 
out mud. In the Island of Trinidad and also in Java, there 
are considerable air or mud volcanoes. 
5. Rocks forined from Cold-Springs. 
Many cold or common perennial springs throw out great 
quantities of earthy matter, principally calcareous, and thus 
give rise to extensive depositions of ^ calcareous tuffa and sinter. 
Independent of the thick incrustation formed on the surfaces 
of craggs and cliffs, and rents of rocks, by the water of such 
springs, and of which we have a fine example at Starlyburn in 
Fifeshire, we find that when the water flows into hollows and 
forms lakes, that then very thick and extensive calcareous for- 
mations take place. Thus in Thmangia there are very exten- 
sive lake-deposites of calcareous tuffa and sinter. In some dis- 
tricts in that part of Germany, the tuffa rests upon gravel, or on 
some of the solid strata of the country, and forms beds some- 
times fifty feet thick, and which are composed of alternate 
strata of compact and friable tuffa, with occasional thin beds of 
bituminous matter; It is in this calcareous formation, that the 
remains of fossil elephants, rhinoceri, &c. are found in diffe- 
rent parts of Germany. It is an important fact, as connected 
with these fossil animal remains, that the tuffa in which they 
are envelloped, contains fresh-water shells, analogous to those at 
present met with in the country where the tuff* occurs, but no 
sea-shells, which proves that these elephants, rhinoceri, &c. 
could not have been brought from a distance, but must have 
lived and died in the spot where they are at present found. 
* An account of the mud volcanoes in Trinidad, Dr Ferguson,^\vill be 
found in the Edin^ Trans. Vol. IX., p. 93., now in the press. 
’ X 2 
