PARLEY DESCRIBES VOLCANOES, EARTHQUAKES, AND HOT SPRINGS.
You have no doubt often heard of Volcanoes and Earthquakes, for almost
everybody in all ages has felt a deep interest in them, and a curiosity
to know what they are caused by. If you will listen to me, while I
merely describe them as they really exist, without "drawing the long
bow," as people say, I will then tell you how I think they are produced.
It is quite certain that there is an important connexion between
Volcanoes and Earthquakes; and we may safely take this for granted, and
at once call the cause of both, whatever it may be, _volcanic agency_.
It has been discovered by extensive observations, that this agency
does not exert itself in individual spots, so as to produce here a
Volcano and there an Earthquake; but its operations take place over
long tracts of country in which the Volcanoes are placed, and, in the
spaces between them, Earthquakes are more or less frequent.
These tracts are called Volcanic bands; one of them extends nearly
parallel with the West Coast of South America, along the chain of
mountains called the Andes, which you will see marked on the map; and
another much smaller extends from Mount Vesuvius to Mount Etna, with
the Volcanic Island Stromboli, and several extinct Volcanoes lying
between them, and then turns to the East, through several of the Greek
Islands, and passes on to Syria, where Earthquakes are frequent.
Earthquakes in their simplest form are nothing more than violent
shakings of the ground; but sometimes the earth is split open;
sometimes it is raised; and sometimes it is depressed.
I shall tell you of some of the changes which took place in the great
Earthquake of Calabria, which lies in the smaller volcanic band I
mentioned to you between Vesuvius and Etna.
EARTHQUAKE OF CALABRIA.
The shocks began in 1783, and lasted for nearly four years, till the
end of 1786. During this time the King of Naples sent persons to take
correct notes and representations of all that was going on, and we
have therefore got a better account of it than we have of any other
Earthquake that ever occurred.
The convulsion of the earth, sea, and air, extended as far as Naples,
and over the whole of Sicily; but the district over which it was so
violent as to excite intense alarm, was about five hundred miles in
circumference.
"The first shock of February 5th, 1783, threw down, in two minutes,
the greater part of the houses in all the cities, towns, and villages,
from the western sides of the Apennines in Calabria Ultra, to Messina
in Sicily, and convulsed the whole surface of the country. Another
occurred on the 28th of March, with almost equal violence. The chain of
granite mountains which passes through Calabria from north to south,
and attains the height of many thousand feet, was shaken but slightly;
but it is said that a great part of the shocks which were spread with
a wave-like motion through the recent strata from west to east, became
very violent when they reached the point of junction with the granite,
as if a reaction was produced where the wave-like movement of the soft
strata was suddenly arrested by the more solid rocks. The surface of
the country often heaved like the billows of a swelling sea, which
produced a swimming in the head like sea-sickness. It is particularly
stated, in almost all the accounts, that just before each shock the
clouds appeared motionless; and although no explanation is offered of
this phenomenon, it is obviously the same as that observed in a ship
at sea when it pitches violently. The clouds seem arrested in their
career as often as the vessel rises in a direction contrary to their
course; so that the Calabrians must have experienced precisely the same
motion on the land."
At Messina in Sicily, the shore was rent; and the soil along the port,
which before the shock was perfectly level, was inclined towards the
sea, and the sea itself was considerably deeper, which showed that the
inclination must have been occasioned by the bottom's sinking. The quay
also sunk down 14 inches below the level of the sea, and the houses in
the neighbourhood were much cracked.
In one town there was a large round tower of great strength, which was
divided by a perpendicular rent, and one-half was raised up several
feet, so as to show the foundations. Those who saw it, said that it
looked like a great tooth half extracted, showing the fangs. Along the
line of the crack, the walls were found to fit so exactly together,
that you would not have known they had even been divided if the courses
of the stones had not been disturbed.
[Illustration]
There was a very curious difference between some of the walls which
had been thrown down, or very much shaken by some of the shocks. In
some of them, the separate stones were parted from the mortar, so as to
leave an exact mould where they had rested; and in others, the mortar
was ground to dust between the stones. It was not less strange to see
the effect of what must have been whirling movements in the ground.
In some streets, one house would be thrown down, and leave the rest
uninjured; while in others, all the houses but one were thrown down,
and that one remained firm and unmoved. Two obelisks were twisted
round, so that the stones of which they were composed, stood at cross
purposes. This cut represents one of the two, as it stood after the
earthquake, and before.
[Illustration]
"It appears evident that a great part of the rending and splitting of
the ground was the effect of a violent motion from below upwards; and
in a multitude of cases where the rents and chasms opened and closed
alternately, we must suppose that the earth was by turns heaved up,
and then let fall again. We may conceive the same effect to be produced
on a small scale, if, by some mechanical force, a pavement composed
of large flags of stone should be raised up and then allowed to fall
suddenly, so as to resume its original position. If any small pebbles
happened to be lying on the line of contact of two flags, they would
fall into the opening when the pavement rose, and be swallowed up, so
that no trace of them would appear after the subsidence of the stones.
In the same manner, when the earth was upheaved, large houses, trees,
cattle, and men were engulfed in an instant in chasms and fissures; and
when the ground sunk down again, the earth closed upon them, so that
no vestige of them was discoverable on the surface. In many instances
individuals were swallowed up by one shock, and then thrown out alive,
together with large jets of water, by the shock which immediately
succeeded."
The district called Jerocarne, was torn in a surprising manner, and in
one spot the cracks resembled those in a starred pane of glass; and as
these cracks remained open when the earthquake was over, it seemed as
if the middle had been permanently lifted up.
[Illustration]
"In the vicinity of Oppido, the central point from which the earthquake
diffused its violent movements, many houses were swallowed up by the
yawning earth, which closed immediately over them. In the adjacent
district also of Cannamaria, four farm-houses, several oil-stores,
and some spacious dwelling-houses were so completely engulphed in one
chasm, that no vestige of them was afterwards discernible."
Amongst the many fissures that were opened, there was one, a mile long,
a hundred feet wide, and thirty feet deep; and another, three quarters
of a mile long, one hundred and fifty feet wide, and one hundred feet
deep; and a third, about a quarter of a mile long, which was two
hundred and twenty-five feet deep.
A mountain was cleft completely in two; and a lake of considerable size
was formed by the opening of this great chasm, and springs bursting
out at the bottom. The inhabitants of the neighbourhood were afraid
that the pool of nearly stagnant water which was thus formed would
injure their health, and were at great expense in trying to drain it;
but it was all in vain, for the springs that fed it at the bottom were
inexhaustible.
A great mass of earth, or hill, two hundred feet high, and four hundred
feet in diameter, was moved nearly four miles out of its place, with
trees growing upon it; and another similar mass, with a house on it,
which was not at all injured. Some olive and mulberry trees travelled
a full mile. These great movements were aided by springs under the
masses of earth, which made a slimy sort of road for them; and, of
course, the whole distance was down hill.
"Great agitation was frequently observed in the bed of the sea during
the shocks, and, on those parts of the coast where the movement was
most violent, all kinds of fish were taken in greater abundance, and
with much greater facility. Some rare species, which usually lie buried
in the sand, were taken on the surface of the waters in great quantity.
The sea is said to have boiled up near Messina, and to have been
agitated as if by a copious discharge of vapours from its bottom. The
Prince of Scilla had persuaded a great part of his vassals to betake
themselves to their fishing-boats for safety, and he himself had gone
on board. On the night of the 5th of February, when some of the people
were sleeping in the boats, and others on a level plain, slightly
elevated above the sea, the earth rocked, and suddenly a great mass
was torn from the contiguous Mount Jaci, and thrown down with a
dreadful crash upon the plain. Immediately afterwards, the sea rising
thirty palms above the level of this low tract, rolled foaming over it,
and swept away the multitude. It then retreated, but soon rushed back
again with greater violence, bringing with it some of the people and
animals it had carried away. At the same time every boat was sunk or
dashed against the beach, and some of them were swept far inland. The
aged Prince, with one thousand four hundred and thirty of his people,
was destroyed. The number of persons who perished during the earthquake
is estimated at about forty thousand, and about twenty thousand more
died by diseases which were caused by insufficient nourishment,
exposure to the atmosphere, and malaria, arising from the new stagnant
lakes and pools. By far the greater number were buried under the ruins
of their houses; while some were burnt to death in the conflagrations
which almost invariably followed the shocks, and consumed immense
magazines of oil and other provisions. A small number were engulfed
in chasms and fissures, and their skeletons are perhaps buried in the
earth to this day, at the depth of several hundred feet, for such was
the profundity of some of the openings which did not close in again."
There is a fine description of the Earthquake and this melancholy
result, in Cowper's Task, which we shall quote.
Alas for Sicily! rude fragments now
Lie scatter'd where the shapely column stood.
Her palaces are dust. In all her streets
The voice of singing and the sprightly chord
Are silent. Revelry, and dance, and show
Suffer a syncope and solemn pause;
While God performs upon the trembling stage
Of his own works his dreadful part alone.
The rocks fall headlong, and the valleys rise,
The rivers die into offensive pools,
And charged with putrid verdure, breathe a gross
And mortal nuisance into all the air.
What solid was, by transformation strange,
Grows fluid; and the fix'd and rooted earth,
Tormented into billows, heaves and swells,
Or with vortiginous and hideous whirl
Sucks down its prey insatiable. Immense
The tumult and the overthrow, the pangs
And agonies of human and of brute
Multitudes, fugitive on every side,
And fugitive in vain. The sylvan scene
Migrates uplifted; and, with all its soil
Alighting in far distant fields, finds out
A new possessor, and survives the change.
Ocean has caught the frenzy, and upwrought
To an enormous and o'erbearing height,
Not by a mighty wind, but by that voice
Which winds and waves obey, invades the shore
With force resistless. Where now the throng,
That press'd the beach, and, hasty to depart,
Look'd to the sea for safety? They are gone,
Gone with the refluent wave into the deep--
A prince with half his people!
You will find a great many other astonishing effects of this Earthquake
described in Mr. Lyell's Work on Geology, from which I have extracted
some parts of the preceding account.
VOLCANOES.
The word Volcano comes from Vulcan, the name of the God of fire in the
Greek mythology. You have read how the poets used to represent him as
engaged underground in forging thunderbolts for Jupiter, and other
work of the same kind, with the assistance of his one-eyed journeymen
the Cyclopes. They feigned that Volcanoes were the chimneys of his
workshops, and that when an eruption took place he was busy forging his
iron.
Others pretended that when Jupiter had overcome the giants named
Titans, who had rebelled against him, instead of putting them in the
stocks, he placed mountains upon them, and that when the imprisoned
monsters turned themselves from one side to the other, earthquakes and
eruptions were the consequence.
However, we don't believe any of these stories now, neither perhaps did
the ancients. But you must learn all about them and their meaning,
(where they have any,) from your schoolmaster. My business now is to
tell you what Volcanoes are.
They are openings in the surface of the earth, from whence ignited
matter of various kinds, smoke, and ashes, are sent forth by some
subterranean agency.
For the most part they do not always keep in activity, but have long
intervals of rest for months, and sometimes for very many years,
between the eruptions.
One of the few that always keeps in eruption, is Stromboli, one of the
Lipari Islands off the coast of Sicily, which there is good reason to
think, has been active for nearly 1600 years. This Volcano is merely
a mountain or rock, standing out of the sea, and the melted matter,
that occasionally runs down its sides, flows directly into the water,
and at once kills and parboils the fish that happen to be near it, and
they are thus sometimes taken and eaten by the poor fishermen who live
about the base of the mountain.
The way in which an eruption takes place in a Volcano of the other
kind, when it has been quiet for a long time, is as follows.
Great noises are heard about the foot of the mountain, and earthquakes
frequently occur for several days before any change is seen in the
opening or _crater_, as it is called. The springs in the neighbourhood
often disappear, and as you may suppose all these forebodings make the
people who live near gloomy enough.
After a time a dreadful burst takes place, and the crater is in an
instant cleared of the stones and earth that may have fallen into it
during the period of repose; ashes and cinders, rocks and stones, are
thrown up to an immense height in the air, and a great cloud of smoke
and steam accompanies them.
In perfectly still weather, this vapour is seen to shape itself in
a very beautiful manner. The immense impulse from beneath sends it
up to a vast height as straight and almost as distinct as a pillar.
At a certain elevation, it spreads abroad and assumes the appearance
represented in the plate. When this occurs on Vesuvius, the Italians
call it the _pine tree cloud_, from the resemblance its form bears to
that of a pine tree.
As the eruption goes on the cloud of smoke which is always copiously
charged with electricity, sends out brilliant lightnings; its form
becomes disturbed, and the dark volumes of vapour are angrily sent
forth in shapeless masses. Red-hot stones are sent into the air to a
stupendous height; the melted matter boils up inside the crater and
rolls down the sides of the mountain, setting fire to the trees that it
meets with, and destroying or enveloping whatever else remains in its
way.
You will see their effect as they appear by night, in the other plate.
I should tell you that the Volcano represented in both the pictures is
Mount Vesuvius.
[Illustration: PLATE V.
VESUVIUS N^o. 1]
The melted matter that boils up in the crater, and flows down the
mountain, is called Lava. I dare say most of you have seen some pieces
of this substance when polished and worked into ornaments. It is found
in great variety, and is sometimes black, porous, and light like
cinders; sometimes it consists of crystallized particles of quartz,
felspar, and other minerals, so as closely to resemble granite; and not
unfrequently it is a solid dark-coloured mass, heavy and hard as the
stone that our streets are paved with.
It issues from the crater in a melted state, bubbling and boiling like
water in a tea-kettle, but you must not therefore suppose that it runs
down the declivity of the mountain like water. On the contrary, its
motion is mostly very slow, seldom being faster when it gets at some
distance from the crater, than four miles an hour, which is about as
fast as a man can walk. When it has run still further from its source
it does not travel more than a few yards in a day.
The motion of a stream of Lava is very peculiar, for the surface
exposed to the air is immediately formed into a crust, and hence it
constantly moves with a crackling noise, and when the stream is quite
fresh no light is seen except in the cracks that are constantly being
formed at the extremity.
In this way a current will sometimes go drawling on for months after
the eruption which gave rise to it has ceased.
A very curious effect is produced when the lava runs in a certain state
of fluidity down a steep descent. A thick, strong crust forms on the
outside, and it is one of the qualities of lava when it has become
hard, like most other stony substances, to present great opposition
to the passage of heat. In consequence of this the liquid lava in the
inside of the current is kept hot, and continues to run on for a long
time after the supply from the crater has ceased, and leaves the crust
in the form of an arched passage.
From what I have told you about lava streams, you will see that there
is not much danger from them to living creatures, who may always get
out of their way fast enough: but sometimes houses and even towns are
enveloped in them.
[Illustration: PLATE VI.
VESUVIUS N^o. 2]
However, from the peculiar mode in which they travel there is often a
way of preventing this, and on one occasion it was resorted to, and
the town of Catania thereby saved. A current of lava from Mount Etna
was making its way straight towards the town, but a body of fifty bold
strong fellows went out to meet it, armed with crow bars; with these
they broke great holes in the crust at the side, and thus the stream
was turned into another course, and pursued its way on one side of the
town.
Throughout an eruption, a great quantity of dust is produced by the
rubbing of the stones against each other which are thrown out from the
crater, and often fall back and are thrown up again several times.
This dust is driven over a great extent of country, and a gentleman
whom I visited, who lived about fourteen miles from Mount Vesuvius,
told me that during the great eruption of 1822, his garden was covered
with them, to the depth of full six inches.
But in more violent eruptions they are carried much further than this.
In an eruption of a Volcano in Sumbawa, an island which lies some miles
to the East of Java, the ashes were carried to a distance of 270 miles
in such quantities as to darken the air, and in another direction
they were found 300 miles off. They fell so heavily 40 miles away
from the Volcano that they broke into many houses, and rendered them
uninhabitable.
Quantities of liquid lava are thrown upwards, and shape themselves into
nearly the forms of fish by their passage through the air. These are
called bombs by the inhabitants, and the fall of them is very justly
dreaded, as they come with great violence.
The size of the largest of those from which the following picture was
taken, was six inches long, two inches and a quarter wide, and one
inch and three quarters thick; but there are much larger sometimes.
[Illustration]
If you should have a chance of examining any of these, you may observe
how wisely the living principle, which gives the figure to fish, has
been ordained by their Creator to provide the best form to assist their
motions, in a medium in which they are suspended, and do not move on
ground as the beasts do; seeing that it is precisely the same sort
of figure as the laws of inanimate matter impress upon it, when in a
yielding state, and being impelled to move under similar circumstances.
I must give you a notion of the quantity of lava sometimes sent out in
a single eruption.
The Volcano called Skapta Jokul, in Iceland, in the year 1794, sent
out two great streams, one of which was 50 miles in length, from 10 to
15 in breadth, and the ordinary depth about 100 feet, but in some deep
valleys it was more than 500 feet. The other was forty miles long,
seven wide on the average, and about the same depth as the first.
These streams were not cold in the year 1805, eleven years after they
had issued from the earth, so that you may judge how long the hardened
lava keeps in the heat.
During the eruption in which this immense mass of melted matter was
thrown out, twenty villages were destroyed, more than nine thousand
persons killed, and an immense number of cattle.
The vapour which rises at first in immense clouds, when the eruption
slackens, or when it gets out of the reach of the heat, condenses, and
mingled with the dust thrown up with it, forms mud, which rushes in
torrents down the mountain. These streams of mud are called alluvions,
and are very much more dreaded by the inhabitants than the lava
streams, because they are so much quicker in their movement.
It was one of these, and not a stream of lava which enveloped the
Roman City Pompeii; and which entered the modern town of Torre del
Greco, and so raised the ground that the lower rooms of the houses were
converted into cellars, and the people were obliged to make the street
doors on what had before been the second story.
THE GREAT VOLCANO KIRAUEA, IN THE ISLAND OF HAWAII.
There is a very remarkable Volcano in the Island of Hawaii, where
Captain Cook was killed.
The crater, instead of being at the top of a mountain like those of
most other Volcanoes, is a large plain, seven miles in circumference,
sunk below the surface of the surrounding country, and walled in by
rugged cliffs more than seven hundred feet high.
On this plain there are fifty-one conical hillocks, which are almost
constantly sending out vapour and lava, and red hot stones. The
surrounding banks consist entirely of sulphur and lava.
The islanders, before they were taught the truths of Christianity,
believed it to be the abode of their deities, the chief of whom they
call Pelé, and to her, they say, that everything which grows near the
Volcano is sacred. When some missionaries were going to visit it, and
plucked some juicy berries from the shrubs that grew there to quench
their thirst, the native guides begged them to desist till they had
made an offering to Pelé. When they got to the edge of the crater, they
threw some of the berries in, and said, "Pelé, here are your berries,
and I am now going to eat some." They then ate fast enough, and were
willing that the missionaries should do the same.
The following are extracts from the account of our countryman, Mr.
Stewart's visit to this terrific place.
"I can compare the general aspect of the bottom of the crater, to
nothing that will give a livelier image of it to your mind, than to
the appearance the Otsego Lake would present, if the ice with which
it is covered in winter, were suddenly broken up by a heavy storm,
and as suddenly frozen again, while large slabs and blocks were still
toppling, and dashing, and heaping against each other, with the motion
of the waves. Just so rough and distorted was the black mass under
our feet, only a hundred-fold more terrific, independently of the
innumerable cracks, fissures, deep chasms and holes, from which the
sulphureous vapour, steam, and smoke were exhaled, with a degree of
heat that testified the near vicinity of fire.
"At an inconsiderable distance from us, was one of the largest of the
conical craters, whose laborious action had so greatly impressed our
minds during the night, and we hastened to a nearer examination of it.
On reaching its base, we judged it to be one hundred and fifty feet
high, a huge, irregularly shapen, inverted funnel of lava, covered
with clefts, orifices, and tunnels, from which bodies of steam escaped,
while pale flames, ashes, stones, and lava, were propelled with equal
force and noise, from its ragged mouth.
"The chattering of the islanders around our cabins, and the occasional
sound of voices in protracted conversation among our own number,
had scarcely ceased long enough to admit of sound sleep, when the
volcano again began roaring and labouring with redoubled activity.
The confusion of noises was prodigiously great. These sounds were not
fixed or confined to one place, but rolled from one end of the crater
to the other; sometimes seeming to be immediately under us, when a
sensible tremor of the ground on which we lay took place; and then
again rushing to the farthest end with incalculable velocity. The whole
air was filled with the tumult; and those most soundly asleep were
quickly roused by it to thorough wakefulness. One of our party sprang
up in his cot, exclaiming, 'We shall certainly have an eruption; such
power must burst through everything;' He had barely ceased speaking,
when a dense column of heavy black smoke was seen arising from the
crater directly in front of us; the subterranean struggle ceased,
and immediately after, flames burst from a large cone, near which we
had been in the morning, and which then appeared to have been long
inactive. Red-hot stones, cinders, and ashes, were also propelled to a
great height with immense violence; and shortly after, the molten lava
came boiling up, and flowed down the sides of the cone, and over the
surrounding scoria, in two beautiful curved streams, glittering with
indiscribable brilliance.
"At the same time a whole lake of fire opened in a more distant part.
This could not have been less than two miles in circumference; and its
action was more horribly sublime than anything I ever imagined to
exist, even in the ideal vision of unearthly things. Its surface had
all the agitation of an ocean; billow after billow tossed its monstrous
bosom in the air, and occasionally those from different directions
burst with such violence, as in the concussion to dash the fiery spray
forty and fifty feet high. It was at once the most splendidly beautiful
and dreadfully fearful of spectacles."
OF THE FORMATION OF NEW ISLANDS.
You must know that most of the volcanic mountains bear evident traces
of having been built up of matter thrown out, in the first place,
from a crack or hole in the ground, and afterwards from the _crater_
or _cup_, which would thus soon be formed. At every eruption a new
layer of dust, and cinders, and lava, is added, and thus a mountain is
gradually produced.
In some instances, the successive layers may be seen is the crater,
as is the case with Vesuvius, of the summit of which this would nearly
represent the section, if we could cut it in two.
[Illustration]
Volcanic operations can go on very nearly as well at the bottom of the
sea, as upon dry land; and if you remember what I told you before,
respecting the mode in which the currents of lava flow, you will not be
much surprised to hear that their progress is not stopped by the water,
though it may be somewhat impeded. It is certain that the streams often
travel a great way at the bottom of the sea.
When a Volcano breaks out under the sea, if the eruption send out a
sufficient quantity of lava, and stones and dust, it gets above the
surface and makes such a Volcano as Stromboli.
If the Volcano should afterwards become quiet, then an island is the
result, and if large enough, it may be inhabited.
A great many of the islands of the South Sea, and some of the Greek
islands, originated in this manner; and, only two or three years ago,
an island suddenly rose up off the coast of Sicily, and was taken
possession of in due form by a British captain, in the name of the king
of England; but, as the land consisted of loose earth, and had not much
lava to bind it together, it soon sunk down, and now no trace of it is
to be seen.
OF THE GEYSERS OF ICELAND.
There are many Volcanoes in Iceland, and the whole island seems to have
been the produce of Volcanic agency. I am going to describe to you one
of the most singular proofs of this.
Geysers are springs which spout out at intervals great streams of
hot water. The name is taken from the Icelandic word, _geysa_, which
signifies, _to rage_, or, _burst forth violently_.
[Illustration: PLATE VII.
GEYSERS OF ICELAND]
The Icelanders are a very simple, excellent people, and exceedingly
kind and hospitable to strangers. This is not the place for me to tell
you how much kindness I experienced among them; but if I were to do
so, you would have as high a regard for them as I have. They have in
general a considerable degree of intelligence, but I was surprised to
find that a great many of them did not know where the Geysers were, or
anything about them.
There are many springs of the same kind in several parts of Iceland;
but those that are generally known as _the Geysers_, are near the town
of Haukadal, in the south-west part of Iceland. To these I went in
company with four other persons, and a guide.
After a dreary ride through a wild volcanic looking country, we left
our horses in a safe place, and then, proceeding some distance on foot,
we saw clouds of steam arising over the hills before us. A little
further on we got into the plain, where the Geysers are situated, which
is full of boiling springs and holes sending out steam like the valve
of a steam-boiler.
The great Geyser is at the top of a hillock, which seems to have been
formed in the course of years by the substances which the hot water
holds in solution, and deposits as it cools.
At the top of this mound we found a pond of the shape of a saucer,
lined with the most curious incrustations of spar, which exactly
resembled the heads of cauliflowers. It was then about half full of the
most beautiful hot water, as clear as crystal, which was just stirred
in gentle waves by the steam that rose up from the opening at the
bottom of the basin.
We took advantage of this tranquil state of the spring, to examine this
opening. We let down a line, with a weight at the end, to the depth
of about eighty feet, and as nearly as we could judge, it went down
perpendicularly.
The hole was nearly round, and about nine feet in diameter, but it got
gradually wider towards the top like a funnel. The inside showed the
same kind of flinty incrustation as the hillock was composed of, worn
as smooth as glass by the forcible passage of the water. The water was
then at a temperature of two hundred degrees.
The saucer-shaped reservoir was fifty feet across, and four feet deep.
I ought to tell you that the waters of the Geysers have a petrifying
property, and hence the ground all around them is covered with what was
once grass, moss, and sticks, converted into stone, of which we brought
away many beautiful specimens.
It was very late in the evening when we had completed this examination,
and fixed our tent where we intended to pass the night. The springs
still continued quiet, and you may judge how impatient we were for
something to be going on. However, as it was dark, and we were very
tired, having had a great deal of fatigue during the day, we lay down
in the tent and went to sleep.
About midnight we were suddenly called up by one of our party, to
witness the great Geyser in its full glory. It threw up several jets,
should think of at least ninety feet high, and sent off vast clouds of
steam. There was only just light enough for us to distinguish the water
and steam; but the effect was very grand, and such as we shall never
forget, though it did not leave much behind in our minds to talk about,
as everything seemed indistinct and confused.
The next morning, as soon as it was light, there was a beautiful
eruption of the _New Geyser_, as it is called. The column of water was
eight feet in diameter, and full sixty feet high, and the clouds of
steam were prodigious. The sun was just then rising, and the effect
of his rays through the water and stream, was exquisitely beautiful,
producing many little rainbows. When the water had sunk down, its place
was taken by a tremendous jet of spray and steam, rushing out with a
deafening roar to nearly the same height as the water.
When we threw some large stones into the pipe, the steam instantly
carried them up to an amazing height; and in several instances, when
they went up quite perpendicularly, kept them within its influence for
some minutes, throwing them upwards several times successively, in a
very strange manner; the Geyser seemed to play with them as a boy plays
with his ball when he throws it up and catches it again and again.
We were not yet satisfied, because we had not seen an eruption fairly
from beginning to end; so we waited some time longer. At about seven
o'clock in the morning, we heard low grumbling sounds near the great
Geyser, and the water in the basin bubbled up a little more actively.
We then had an hour and a half of anxious expectation, during which
we kept walking round the hillock; there were then about a dozen loud
reports which made the earth tremble, and the water rose to near the
top of the basin, and became so restless that many of the waves washed
over the edge.
A little while afterwards, the reports became as loud as the firing of
artillery; the ground shook violently under our feet; we ran down the
mound, and had hardly got upon the level ground before the water rushed
up the pipe with such thick clouds of steam, as completely to conceal
the stream. These bursts took place in this manner to the height of
about twenty feet.
There was then a rest for a few seconds, which was followed by several
jets from forty to sixty feet high; and after them a column was thrown
up eighty feet high, and ten feet in diameter. But the last jet was the
most remarkable, for it was more than ninety feet high, and lasted for
seven minutes.
This great effort seemed to have wearied the Geyser, for the water
instantly sunk down out of the basin into the pipe, quite out of sight;
but in a few minutes it rose again to within a foot of the edge of the
basin, and then remained stationary.
Besides the great perpendicular jets, there were many little ones
curling and twisting about in all directions; and we were taught to be
careful of these by one of my companions getting badly scalded in the
leg, for they were very sudden and uncertain in their movements.
When we were quite sure it was all over, we tried the temperature of
the water in the basin, and found it to be twenty degrees cooler than
before the eruption, which was probably caused by the exposure of the
water which had been thrown up into the air.
It seems there are generally about five or six eruptions of each of
the two great Geysers, within twenty-four hours. But while we were on
the spot, many of the smaller springs spouted up much oftener, and one
bustling little thing darted out its waters in all directions, three or
four times in an hour.
We did not see any jet from the great Geyser above one hundred feet
high; but some travellers have asserted that they are at times two or
three hundred feet in height. It would appear that the force of the
Geysers varies considerably, and in some instances is affected by the
earthquakes which often happen here; some of which seem to cripple, and
others to strengthen them.
Some of the water of the great Geyser falls over the edge of the basin
into a deep hole in the rock below, which makes a capital warm bath,
for by the time the water reaches it, it is of the desirable coolness.
I can assure you, we enjoyed a bathe in it very much indeed.
There are several other springs in Iceland of nearly the same
character, and the most remarkable are the Hot Springs of Reykium.
The largest of these has two openings, from one of which the water
is incessantly flowing to the height of six or eight feet; the other
opening is about ten feet distant, and is surrounded by an incrusted
brim, like that of the great Geyser. The eruptions take place from this
about fifteen times in twenty-four hours, to the height of about thirty
feet, accompanied with a great deal of steam.
There is also a most wonderful spring in Reykium, called the Badstofa.
It flows into a great cave, from the bottom of which the water keeps on
retreating and flowing like the waves of the sea, with a deep rumbling
sound for some time before the eruption, when the water rushes up to
the height of nearly twenty feet.
About half a mile from this place, there are some Hot Springs that rise
in the bed of a river, and force themselves quite through the cold
water which covers them.
THE SULPHUR MOUNTAINS AND SULPHUR SPRINGS.
There is a wonderful place in Iceland, which I am sure you would like
to hear about. It is in the south-west part of the island nearer the
sea than the Geysers. Nearly the whole region consists of sulphur, and
hot clay, and hot dirty water, and it contains some mountains, called
the _Sulphur Mountains_, from which great quantities of sulphur are
collected by the peasants, and sent to the continent of Europe for sale.
The vapour that is always rising from this wretched-looking country,
makes a sort of crust over the hot clay; and you will sometimes come to
a spot that appears solid, and as you go over it, your horse's hoofs
will make holes which will send out steam like little cauldrons. A
gentleman who would go over one of these on foot, got terribly scalded
by the crust breaking away under him.
There is here a sort of hut, from the bottom of which much steam rises,
and it is used as a vapour bath. People that are affected with various
diseases, come to it from the surrounding country in considerable
numbers.
At a little distance from this you come to the brink of a cliff, and
looking over it, you see twelve large ponds or basins of black mud,
boiling, and splashing, and raging perpetually, with large volumes
of vapour rolling off their surfaces. Beyond these some dismal
black-looking mountains make a back ground. Can you imagine any thing
more fearful to look upon?
Besides these, there is a kind of Geyser of mud, which just resembles
the real Geysers in its action; but instead of sending up beautiful
clear water, it throws out black unsightly mud, as thick as porridge,
which is caught in a nearly round reservoir of more than one hundred
feet in diameter. It is situated near the summit of a mountain called
_Krabla_ and the reservoir seems to have been in time past a volcanic
crater.
HOW THE GEYSERS MAY BE CAUSED.
Of course there cannot be hot water without some source of heat, and
there must, therefore, be a source of heat taken into consideration
in the action of the Geysers. Now, I do not wish to speak of this
here, I only wish to make you understand how it seems likely that the
eruptions of the Geysers are occasioned, supposing there was a supply
of hot water.
[Illustration]
This cut is intended to represent what may be a section of the
subterranean reservoir, S W, of the great Geyser, and the pipe, P,
connected with the saucer-shaped basin, B, at the top of the mound. You
see the cracks in the rock through which you must suppose hot water
constantly trickling into the reservoir.
The space S will be constantly full of steam, and the space below, W,
will be always full of water. The water will continue to rise till it
gets to A, and it will then quite stop up the escape of the steam.
The steam in S will then press upon the surface of the water, and
force it up the pipe P with more or less violence, according to the
supply of heat; but when enough of the steam has escaped to render the
pressure less, and the water has sunk to near I, the eruption will
cease.
If you will take the trouble to understand this section, you will see
how reasonable it is that the Geyser should be so constructed; and I
have seen a little apparatus made of glass, which showed exactly the
same sort of operations.
Some little variation in the shape of the reservoir and pipe, may
perhaps be needed to account for all that takes place; but the
principle of the activity being produced by the agency of steam, acting
in a space which may be enclosed by the water in its rising to a
certain height, seems to be certain and satisfactory.