Underground Sounds--Quito--Rio Apure--Guanaxuato--Melida--Nakous.
Not the least remarkable among the phenomena produced by volcanic
forces, are the strange underground noises which are occasionally
heard. For the most part these are the preludes either of shocks of
earthquake or of volcanic eruptions. Those which for months
preceded the upheaval of the volcano of Jorullo, will recur to your
remembrance. For about a month before the great mud eruption from
Tunguragua on 4th February 1797, already described, there proceeded
from the interior of that mountain noises of the most fearful kind.
These would occur suddenly in the midst of perfect silence. They
were heard by Antonio Pineda, the naturalist, who was there at the
time, and they led him to foretell the approach of some great
convulsion. Strange to say, however, the catastrophe itself was
unaccompanied by underground noises any where near the volcano.
But, stranger still, at Quito, which is distant about 200 miles, a
short time after the eruption began, there were heard tremendous
underground thunders. But this distance, between the site of the
underground noises and the probable focus of disturbance, was far
exceeded in another remarkable instance. It is stated by Humboldt
that, in the grassy plains of Calaboso, on the banks of the Rio
Apure, a tributary of the Orinoco, there were heard, over a large
extent of country, loud underground thunders, unaccompanied by any
shaking of the ground; while great streams of lava were being
poured forth from the crater of Morne-Garou, in the Island of St.
Vincent, at the distance of no less than 632 miles in a right line.
This was as though an eruption of Mount Vesuvius were accompanied
by underground thunders in Normandy.
There have, nevertheless, been instances of the existence of such
underground noises, without their having been followed either by an
earthquake, by a volcanic eruption, or any other outward appearance
whatever. One of the most remarkable cases of the kind, was that
mentioned by Humboldt as having occurred at Guanaxuato in Mexico, a
mountain-city situated far from any active volcano. This celebrated
traveller states that these noises began on the 9th of January
1784, and lasted above a month. The sounds were at first neither
very loud nor very frequent; but from the 15th to the 16th of
January they resembled continuous low rolling thunder, alternating
with short loud thunder-claps. The sounds then gradually died away
and nothing came of them, although they excited great terror among
the inhabitants while they lasted. There are mines in the
neighbourhood fifteen hundred and ninety-eight English feet in
depth, yet neither in them nor at the surface could the least
tremor be detected.
A somewhat similar phenomenon occurred in the Island of Melida in
the Adriatic, off the coast of Dalmatia, where underground
rumblings were heard from March 1822 to September 1824; but in this
case the sounds were sometimes accompanied by shocks.
A still more singular phenomenon of this sort occurs on the borders
of the Red Sea, at a place called Nakous, where intermittent
underground sounds have been heard for an unknown number of
centuries. It is situated at about half a mile's distance from the
shore, whence a long reach of sand ascends rapidly to a height of
about three hundred feet. This reach is about eighty feet wide, and
resembles an amphitheatre, being walled in by low rocks. The sounds
coming up from the ground at this place recur at intervals of about
an hour. They at first resemble a low murmur; but ere long there is
heard a loud knocking, somewhat like the strokes of a bell, and
which, at the end of about five minutes, becomes so strong as to
agitate the sand.
The explanation of this curious phenomenon given by the Arabs, is,
that there is a convent under the ground here, and that these
sounds are those of the bell, which the monks ring for prayers. So
they call it "Nakous," which means a bell. The Arabs affirm that
the noise so frightens their camels when they hear it as to render
them furious. Philosophers attribute the sounds to suppressed
volcanic action--probably to the bubbling of gas or vapours
underground.