. 67.

Supposed section of Barren Island, in the Bay of Bengal.]

MUD VOLCANOES.

_Iceland._--Mr. R. Bunsen, in his account of the pseudo-volcanic
phenomena of Iceland, describes many valleys where sulphurous and
aqueous vapors burst forth with a hissing sound, from the hot soil
formed of volcanic tuff. In such spots a pool of boiling water is seen,
in which a bluish-black argillaceous paste rises in huge bubbles. These
bubbles on bursting throw the boiling mud to a height of fifteen feet
and upwards, accumulating it in ledges round the crater or basin of the
spring.

_Baku on the Caspian._--The formation of a new mud volcano was witnessed
on the 27th of November, 1827, at Tokmali, on the peninsula of
Abscheron, east of Baku. Flames blazed up to an extraordinary height for
a space of three hours, and continued for twenty hours to rise about
three feet above a crater, from which mud was ejected. At another point
in the same district where flames issued, fragments of rock of large
size were hurled up into the air, and scattered around.[616]

[Illustration: Fig. 68.

Mud cones and craters of Hinglaj near Beila, district of Lus, 120 miles
northwest of mouth of Indus. From original drawing by Capt. Robertson.
(See Map, p. 460.)]

_Sicily._--At a place called Macaluba, near Girgenti in Sicily, are
several conical mounds from ten to thirty feet in height, with small
craters at their summits, from which cold water, mixed with mud and
bitumen, is cast out. Bubbles of carbonic acid and carburetted hydrogen
gas are also disengaged from these springs, and at certain periods with
such violence, as to throw the mud to the height of 200 feet. These "air
volcanoes," as they are sometimes termed, are known to have been in the
same state of activity for the last fifteen centuries; and Dr. Daubeny
imagines that the gases which escape may be generated by the slow
combustion of beds of sulphur, which is actually in progress in the blue
clay, out of which the springs rise.[617] But as the gases are similar
to those disengaged in volcanic eruptions, and as they have continued to
stream out for so long a period, they may perhaps be derived from a more
deep-seated source.

_Beila in India._--In the district of Luss or Lus, south of Beila, about
120 miles N. W. of Cutch and the mouths of the Indus (see Map, fig. 71,
p. 460), numerous mud volcanoes are scattered over an area of probably
not less than 1000 square miles. Some of these h