beauty by the springs of the ancient Ionian city of Hierapolis (holy
city), which at the present time flow in the solitary plateau called
Panbouk-Kelessi (Castle of Cotton), on account of the cotton-like
aspect of the white masses of travertin of which it is composed. On
reaching this spot from Smyrna, something like an immense cataract
may be seen in the distance, 328 feet high and 2½ miles wide; this
is formed by the walls which the water has gradually constructed,
column after column, and layer after layer, by flowing over the
edges of the plateau and gushing out on the slopes. Here and there,
real cascades glitter in the sun, and their sparkling surfaces
light up the dead whiteness of the crystal walls. As a spectator
ascends the declivities, the masses deposited and carved out by the
water appear in all their strange beauty; one might fancy that they
were colonnades, groups of figures, and rude bas-reliefs which the
chisel had not yet perfectly set free from their rough coverings of
stone. And all these calcareous deposits which have been fashioned
by the cascades during a succession of ages open a multitude of
cup-like hollows with fluted edges fringed with stalactites; these
graceful reservoirs--some of which are shaded with yellow or veined
with red, brown, and violet, like jasper or agate--are filled with
pure water. Higher still follow two steps of the plateau on which
stood the ancient thermal edifice and the Necropolis of Hierapolis.
There whitish masses cover the ancient tombstones and fill up the
conduits. The ground is crossed in various directions by the former
beds of rivulets, which have gradually stopped up their own courses
by depositing concretions upon them. Above one of the widest of
these dried-up channels, the magnificent span of a natural bridge
displays its graceful form, like an arch of alabaster, streaming with
innumerable stalactites. At what date did this majestic structure
take its rise, and how many years and centuries did the process of
its formation last? No one knows. According to Strabo, the channels
of the baths of Hierapolis were soon filled up by solid masses, and
if Vitruvius can be believed, when the proprietors of the environs
wished to inclose their domain, they caused a current of water to run
along the boundary-line, and in the space of a year the walls had
risen.
Silica, which is still more important than chalk in the formation
of terrestrial rocks, is also sometimes deposited on the edge of
springs, but in very small quantities.
The various dislocations of the terrestrial strata, the cooling of
the waters, and, perhaps, in many instances, the obstruction of
channels by deposits of ore, explain why, in the present period,
so small a number of thermal springs issue from metalliferous
beds. Nevertheless, many localities might be mentioned where these
phenomena take place at the present time. A spring at Badenweiler,
in the Black Forest, issues forth at a few yards from a vein of
sulphuret of lead. In the granitic plateau of central France other
springs are likewise found to be associated with this metal. Various
thermal waters in the Black Forest, like those of Carlsbad and
Marienbad, are in close connection with veins of iron and manganese.
Oligiste iron is found in the fissures of the springs of Plombières
and Chaude-Fontaine. In Tuscany sulphureous fumaroles proceed from
the veins of antimony. In France and Algeria the waters of Sylvanès
and Hammam R’ira issue forth from beds of copper. Lastly, near
Freyberg, a voluminous thermal spring has been discovered in a vein
of silver.
Among the mineral substances which some springs bring to the surface
of the soil, the most important, in an economical point of view, is
common salt. This substance, being one of those which dissolve most
readily in water, all the liquid veins which pass over saline beds
become saturated with salt; therefore springs of this kind, which
flow in great abundance, give rise to salt-works of more or less
importance. The masses of common salt which make their way every
year from the interior of the earth may be estimated at thousands
of tons. The springs of Halle, which rise on the northern slope of
the Alps of Salzburg (Salt Town), and are managed with the greatest
care, annually produce 15,000 tons of this mineral. The salt springs
of Halle, in Prussia, which have been worked from time immemorial by
a company, furnish 10,000 tons of salt every year. Other parts of
Germany also yield for consumption thousands of tons of white salt,
which is produced by the evaporation of saline springs. The mass
of salt furnished by the single artesian well of Neusalzwerk, near
Minden, in Prussia, represents every year a cube measuring 78 feet on
each side.
Though not so rich as Germany in saline springs thus turned to
account, most of the civilized countries of the world possess
salt-works which are also very important. France enjoys the springs
of Dieuze, Salins, and Salies; Switzerland, those of Bex; Italy has
the springs in the environs of Modena, and many others besides. In
England, near Chester, there are some mines of rock-salt in which
numerous liquid veins issue forth which are impregnated with salt.
Lastly, the United States have the celebrated springs of Syracuse.
Not far from the “spot where Troy once stood” is the valley of
Touzla-sou, which owes its name (Salt Water) to its numerous salt
springs. The mountains which rise around its circumference are
variously shaded with blue, red, and yellow, and the rocks are
incessantly decomposing under the action of the liquid salt which
oozes out from and trickles down their sides. The plain itself
is covered with a variegated crust, while jets of boiling water,
saturated with salt, burst forth in every direction. Here and there
pools are found, the moisture of which, by evaporating in the sun,
leaves upon the soil beds of salt as white as snow. Near the mouth
of the valley springs become more and more numerous. Lastly, in
the place where the cliffs approach near together, so as to form a
defile, a magnificent spout of water jets out from one side of the
rock. This jet is not less than a foot in diameter at the orifice,
and falls again after having described a parabola of more than a
yard and a half. Other springs shoot out on both sides, the constant
temperature of which is more than 212° (Fahr.); these, together with
the principal jet, form a rivulet of boiling and steaming water.
Springs of salt water are used for the treatment of diseases as
well as for the extraction of salt. They constitute one of the most
important groups of medicinal waters, according to the various
substances which they contain in solution. The other springs made
use of, on account of their healing virtues, have been classed under
ferruginous, sulphureous, and acidulous springs. These waters also
contain, in different proportions, a variable quantity of gases and
salts which they have dissolved in their passage over subterranean
beds of every kind.
Mineral springs are most numerous and abundant in mountain valleys,
and there, consequently, the great thermal institutions are
established. In Europe the chain of the Pyrenees is probably the
richest in mineral, sulphureous, saline, ferruginous, and acidulous
springs. According to Francis, the engineer, in 1860 more than 550
mineral springs, 187 of which are used, flowed upon the French
slopes of the Pyrenees. These waters supplied 83 hot baths in 53
localities, the principal of which are Bagnères de Bigorre, Luchon,
Eaux-Bonnes, and Cauterets. The most abundant springs, those of Graus
d’Olette, form a sort of mineral stream, yielding more than four
gallons a second, or 2,322 cubic yards a day. In Algeria the spring
of Hammam-Mes Khoutine yields 6 gallons a second.
There are regions, some volcanic and some not, in which nearly all
the springs are thermal and mineral; springs of pure and fresh
water being so rare, they are there considered to be most precious
treasures. One of these regions comprehends a large part of the
plateau of Utah. In this place numerous thermal springs issue forth,
to which have been given the vulgar names of the Beer, Steamboat,
Whistle Springs, etc., and into one of which the Mormons plunge their
neophytes. The springs which are not thermal are loaded with saline
and calcareous matter. It is only in spring, at the time when the
snow melts, that the springs, which then become very abundant, yield
comparatively pure water. During the dry season, salt and carbonate
of lime become concentrated in the nearly exhausted springs, and give
to the liquid flow an unpalatable taste. Palgrave, the traveler,
informs us that all the springs of the country of Hasa, in Arabia,
are also thermal.
It can readily be understood that when all these substances escape
from the interior of the rocks, together with the water which holds
them in solution, they must leave empty spaces in the earth. During
the course of long centuries whole strata are dissolved, and, under
a form more or less chemically modified, are brought up from the
depths and distributed on the surface of the soil. The thermal waters
of Bath, which are far from being remarkable for the proportion of
mineral substances they contain, bring to the surface of the earth
an annual amount of sulphates of lime and soda, and chlorides of
sodium and magnesium, the cubic mass of which is not less than 554
cubic yards. It has also been calculated that one of the springs of
Louèche, that of Saint Laurent, brings every year to the surface
8,822,400 pounds of gypsum, or about 2,122 cubic yards; this quantity
is enough to lower a bed of gypsum a square mile in extent, more than
five feet in one century. But this is only one spring, and we have
reckoned one century only; if we think of the thousands of mineral
springs which gush from the soil, and of the immensity of time during
which their waters have flowed, some idea may be formed of the
importance of the alterations caused by springs. In time they lower
the whole mass of mountains, and, no doubt, after these sinkings,
violent oscillations of the earth may often have taken place.
In regions where the strata are pierced with wide and deep caverns,
and especially in calcareous countries, the waters sometimes
accumulate in sufficient quantities to form perfect streams with
long subterranean courses. At their issue from the caverns, these
waters form a contrast with the rocks and hills around, all the more
striking because the latter are completely devoid of moisture, and
fearfully sterile, while on the brink of the limpid stream the fresh
verdure of plants and trees is at once developed. Like a captive,
joyous at seeing the light once more, the water which shoots forth
from the sombre grotto of rocks sparkles in the sun, and careers
along with a light murmur between its flowery banks.
Among these subterranean streams, the most celebrated, and doubtless
one of the most beautiful, is the Sorgues of Vaucluse. The vaulted
grotto from which the mighty mass of water escapes opens at the mouth
of an amphitheatre of calcareous rocks with perpendicular sides.
Above the spring rises a high white cliff, bearing on its summit
a ruined tower of the Middle Ages; the rock is everywhere sterile
and bare; there is nothing but a miserable fig-tree, clinging to
the stone like a parasitical plant to the bark of a tree, which has
plunged its roots into the fissure of the cave, and greedily absorbs
with its leaves the moisture which floats like a mist above the
cascades of the spring. After heavy rains, the liquid mass, which is
then estimated at 26 or even 32 cubic yards a second, flows in a wide
sheet high above the entrance to the cavern, which is then altogether
inaccessible. When the waters are low, they flow bubbling across the
barrier of rocky débris which obstructs the entrance; at that time
it is quite possible to penetrate under the arch, and to contemplate
the vast basin in which the blue waters of the subterranean stream
spread out before they leap into the open air. Soon after its issue
from the cave and amphitheatre of Vaucluse, the Sorgues is divided
into numerous irrigation channels, which spread fertility in the
country over an area of more than 77 square miles. The subterranean
course of the affluents which form the stream is not ascertained; but
it is known that most of them commence 12 or 15 miles to the east,
in the plateaus of Saint Christol and Lagarde, which are pierced all
over with _avens_ or chasms, into which the rain-water sinks and
disappears.
In another part of France there is a second important subterranean
stream, which is much less known but no less remarkable than that of
Vaucluse; this is the Touvre of Angoulême, continuing the course of
the Bandiat, the waters of which, like those of the Tardoire, are
swallowed up in several abysses at distances varying from 3 to 7
miles to the east and northeast. The three principal springs of the
Touvre flow slowly out of a deep cave, hollowed out at the base of
an escarped cliff; another spring bubbles up in a basin of rock; the
third emerges from a sort of boggy meadow intersected by drains. At
the outlet of their subterranean courses these three enormous springs
immediately form three streams, which reunite, leaving between them
two long peninsulas of reeds and other aquatic plants. Below the
junction, the Touvre, which is here more than 100 yards wide, passes
round a rugged hill, and, dividing into several branches, turns
the numerous mill-wheels of the important gun-foundry of Ruelle;
then, after a course of five miles, it flows into the Charente at a
small distance above Angoulême. Among the hundreds and thousands of
travelers whom steam annually conveys over the bridge of the Touvre,
there are few who are aware of the curious nature of the source of
the river of limpid water over which the train passes in its noisy
career.
Omitting to mention the streams which accidentally pass under the
strata of rocks during a small part of their course, or of the
subterranean outlets of certain lakes, a multitude of other instances
might be brought forward of masses of water, more or less abundant,
which appear above ground after having traversed a considerable
distance under the earth. Of this kind is the graceful spring of
Nîmes, the blue transparent water of which, reflecting the foliage
of pines and chestnut trees, glides in its gentle ripples over the
semicircular steps of an old Roman staircase. Of this kind, too, is
the spring of Vénéran, near Saintes: this spring, which was formerly
sacred to the Goddess of Love, gushes from the ground in a gorge of
rocks, and, passing through a mill, the wheel of which it turns, it
suddenly disappears, being swallowed up in an abyss; thus it appears
on the earth to work but for an instant.
Numbers of water-courses do not reappear on the surface of the soil
after being swallowed up in the earth, but flow straight to the sea
by means of subterranean channels. On nearly the whole extent of the
continental shores, and principally in localities where the coasts
are of a calcareous nature, the outlets of submarine tributaries may
be noticed, some of which are perfect rivers. Most of the springs of
the department of Bouches du Rhone jet up from the bottom of the sea,
but at various distances from the shore. One of them, that of Porte
Miou, near Cassis, forms on the surface of the sea a considerable
current, which drifts any floating bodies to a great distance.
At Saint Nazaire, Ciotat, Cannes, San Remo, and Spezzia, other
streams also issue from the midst of the salt waves, and attempts
have even been made to measure approximately their discharge. M.
Villeneuve-Flayosc estimates at 24 cubic yards a second the quantity
of water discharged into the sea by all the hidden affluents of the
Mediterranean between Nice and Genoa. Some of the submarine springs
of Provence and Liguria proceed from enormous depths. The orifice of
the spring of Cannes is 531 feet below the level of the sea; that of
San Remo rises from a depth of 954 feet; lastly, at four miles to
the south of Cape Saint Martin, between Monaco and Mentone, another
stream of fresh water empties itself under a bed of salt water, near
2,296 feet deep.
The coasts of Algeria, Istria, Dalmatia, and the Herzegovina also
present numerous instances of submarine streams; on the eastern
shores of the Adriatic the traveler may even have the pleasure of
contemplating the delta of a considerable river, the Trebintchitza,
visible through the sea-water at the depth of a yard. The abundant
springs of fresh water which pour out into the open sea to the
southwest of the Cuban port of Batabano are well known, since
Humboldt described them, and it is observed that the lamantins,
or sea-cows, which dread salt water, delight in frequenting these
parts. Lastly, the Red Sea, which does not throughout its immense
circumference receive a single permanent stream flowing on the
surface of the ground, nevertheless receives some which spring
from the bottom of its bed. The shores of the United States, the
calcareous soil of which is probably pierced with caverns from the
very centre of the continent, perhaps are the coasts which pour into
the sea the most abundant subterranean rivers. Near the mouth of the
stream of St. John, a submarine stream of perfectly pure water spouts
in bubbles as far as one to two yards above the level of the sea.
Off the Carolinas, and Florida, salt water has been known to change
into brackish water under the influence of the sudden increase of its
subterranean affluents. In the month of January, 1857, all that part
of the sea which is adjacent to the southern point of Florida was
the scene of an immense eruption of fresh water. Muddy and yellowish
water furrowed the straits, and myriads of dead fish floated on the
surface and accumulated on the shores. Even in the open sea the
saltness diminished by one-half, and in some places the fishermen
drew their drinking-water from the surface of the sea as if from
a well. It is affirmed by all those who witnessed this remarkable
inundation of the subterranean river that, during more than a month,
it discharged at least as much water as the Mississippi itself, and
spread over all the strait, 31 miles wide, which separates Key West
from Florida.
On the coasts of Yucatan, the fresh waters which take a subterranean
course down to the sea do not appear to flow like rivers which have a
narrow bed and attain considerable speed, but more in the form of a
wide sheet of liquid with a nearly imperceptible current. _Cenotes_
open here and there over the surface of the country; they are a
kind of natural draining-well or hole, not very deep, into which
the inhabitants descend to draw spring water. At Merida and in the
environs the subterranean water is found at a depth of 26 to 30 feet;
but the nearer we approach to the sea the thinner the layer of rock
becomes which covers the liquid veins; on the seashore fresh water
is found nearly on a level with the soil. The height of the veins
varies several inches, according to the quantity of rain; but in
every season the mass of water descending from the plateau of Yucatan
is poured into the sea through innumerable outlets. Over a great
extent of the shore of the peninsula, these hidden springs furnish
collectively a mass sufficiently large to counterpoise the waters of
the sea. Under the pressure of the marine current which runs along
the coast, there is formed, between the open sea and the liquid mass
which has made its way from the land, a littoral bank like those
barriers which the waves construct before the mouths of rivers. This
embankment, which protects the coasts of Yucatan like a breakwater,
is not less than 171 miles long, and is cut through by the sea at
two or three points. The channel, which stretches like a wide river
between the bank of alluvium and the Yucatan coast, is, not without
reason, designated by the inhabitants by the name of stream or _rio_.
Among the remarkable phenomena which perhaps owe their existence to
subterranean water-courses, we must mention the sudden or gradual
appearance of those hillocks of clay (“mud-lumps”) which rise, to
the great danger of navigators, either in the middle of the bar of
the Mississippi, or in the immediate vicinity. Like small volcanoes
of mud, the “mud-lumps” generally appear under the form of isolated
cones, allowing a rill of dirty water to escape from their summits.
Some of them are irregular on their surface, on which lateral
orifices here and there show themselves, some in full activity,
others abandoned by the springs which formerly gushed from them. The
water of some “mud-lumps” is loaded with oxide of iron or carbonate
of lime, which, with the agglutinated sands, form hard masses, having
the consistence of perfect rocks. These hillocks vary both in their
height and shape. The greater part remain hidden at the bottom of the
water, and even their summits do not reach the level of the river
or sea; others hardly raise their heads above the waves; the most
considerable, however, rise to a height of 6, 9, or even 19 feet, and
their base covers an area of several acres. The sudden way in which
most of these water-volcanoes make their appearance, the anchors of
vessels, and the remains of cargoes which have been found on their
surface, their conical form, their terminal craters, and all the
springs, “which seem to spout out as if from a subterranean sieve,”
indicate the existence of a subterranean force always at work to
upheave this band of hillocks.
M. Thomassy is of opinion that the hillocks of these bars are the
orifices of regular artesian wells naturally formed by a sheet of
subterranean water descending from the plateaus of the interior and
flowing below the Mississippi and the clayey levels of Louisiana.
However this may be, the mode in which these mud hillocks are formed
is well enough known to render it easy to clear them away from the
mouths of the Mississippi and to protect the interests of navigation.
When a cone of clay makes its appearance on the bar, a charge of
powder is introduced into it and explodes it. Thus, in the year 1858,
the southwest passage was cleared of a “mud-lump” which formed a
considerable island; a single charge was sufficient to annihilate
the whole. The island suddenly sunk; in its place a wide depression
was formed, the circumference of which resembled that of a volcanic
crater; at the same time an enormous quantity of hydrogen gas was
discharged into the atmosphere.
Above the springs the course of subterranean rivulets is generally
indicated by a series of chasms or natural wells, which disclose
the stream beneath. The arches of caves not being always strong
enough to support the weight of the superincumbent masses, they
necessarily fall in some places, leaving above them other spaces
into which the upper beds successively sink. The débris of the ruin
is afterward cleared away by the water, or dissolved, atom by atom,
by the carbonic acid contained in the stream, and gradually all the
loose rubbish is carried away. In this manner, above the subterranean
rivulets, a kind of well is formed, which is designated in various
countries by very different names.
By means of these natural gulfs it is possible to reach the
subterranean streams, and to give some account of their system, which
is exactly like that of rivulets and rivers flowing in the open air.
These streams also have their cascades, their windings, and their
islands; they also erode or cover with alluvium the rocks which
compose their bed, and they are subject to all the fluctuations of
high and low water. The only important difference which superficial
waters and subterranean currents present in their phenomena is that
these streams in some places fill the whole section of the cave, and
are thus kept back by the upper sides, which compress the liquid
mass. In fact, the spaces hollowed out by the waters in the interior
of the earth are only in a few places formed into regular avenues,
which might be compared to our railway tunnels. Where beds of hard
stone oppose the flow of the rivulet, all it has done during the
course of centuries has been to hew out one narrow aperture. This
succession of widenings and contractions, similar to those of the
valleys on the surface, forms a series of chambers, separated one
from the other by partitions of rock. The water spreads widely in
large cavities, then, contracting its stream, rushes through each
defile as if through a sluice.