The water which holds all land animals in thrall, the water they take into their bodies
for the
maintenance of life, does not look at first sight as though it sprang from the inexhaustible
reservoir of the oceans. For it is fresh: it falls from the sky, gushes from the ground, rises up
from artesian wells, collects in brooks, pools, ponds, marshes, rivers; it irrigates and fertilizes
a
large portion of the land before losing itself in the sea at the end of its long journey. Where
does this fresh water come from?
It is a question that perplexed naturalists and philosophers for centuries. Underground
streams
apparently circulate everywhere below the Earth's crust. Is then the interior of the globe one
immense cistern, a fresh-water sea? Or can there be truth in the old notion of the alchemists
that air or soil changes mysteriously into water within the bowels of the globe?
The story of the discovery of the sources of fresh water is a long succession of mistakes
and
follies. From antiquity onwards there were two rival schools of thought: those who claimed that
fresh and salt water were different substances, and those who declared on the contrary that it
was likely that the ocean was the sole true source of fresh water. With Aristotle, the former
maintained that water, the combination of air and earth, formed within the depths of the earth in
ice-cold caverns. The others claimed, with Plato, that as the ocean flowed through or around
the underworld as the legendary River Styx, the briny water was there filtered and made fresh
before regaining the surface.
In support of their opinions both sides elaborated dazzling theories, masterpieces
of logic and
shrewdness. There were compromises, for example that of Seneca, going as far as to state
that there is some truth on both sides and that water really comes—a
third solution—from
transmuted air or liquefied earth or infiltrated sea- water. Since the authority of the most
celebrated figures of antiquity was behind such doctrines, the only man who might have
discovered the precise origin of fresh water fifteen years before the beginning of the Christian
era was never able to establish his opinion.
This man, Vitruvius, was a military engineer under Caesar and Augustus, and his name
appears in the annals of history less because of his practical achievements than on account of
his De Architectura, a work in ten books in which he assembled
a mass of information about
building, aqueducts, sundials, military engines and the like. In Book VIII Vitruvius deals with the
boring of wells and speculates in this connection upon springs and the provenance of fresh
water. Without bothering about the philosophers' theories he states simply that the water lying
below ground is the same as that which falls from the clouds or comes from the melting of
snow. The water of the rain or the thaw sinks into the ground until the presence of impervious
rocks compels it to seek fissures as a means of continuing its downward course. And that is
exactly how springs start.
The world of the ancients and of the Middle Ages passed, and no scholar or naturalist
paid
attention to the theory of Vitruvius. The first hydrologist worthy of the name, the Brussels
doctor Jean Baptiste von Helmont, was unaware of it. A spiritual descendant of Paracelsus, he
looked upon the world through medical eyes. He had the brilliant and on the whole fairly
accurate idea of comparing the circulation of water inside the Earth to that of blood within a
living entity. The machinery of the blood's circulation had been discovered shortly before, in
1628, by another doctor, the Englishman William Harvey. These two circuits must, for a
disciple of Paracelsus, be brought into harmony: water was for the Earth and the vegetals what
blood stood for with man and the animals.
So far this all seems surprisingly modern, but unfortunately the alchemist in van
Helmont
awoke. The inside of the globe, he pronounced, was a mixture of sand and water, and
mysterious forces were constantly impelling the water into the sand. Purified by the latter, it
found its way through the Earth's crust, bubbled from the rocks, flowed to the sea and came
back to the bowels of the Earth whence, re- filtered, it began all over again. It was but one step
to the hypothesis that the Earth, a living organism, drank in and digested the salt water,
exuding it in fresh form; and van Helmont took it.
The notion of a world drinking up water which it replaced by means of perspiration
met with
scepticism from the more realistic scientists of the period. Nevertheless the old Platonic theory
of salt water being sweetened by means of filtering inside the earth persisted, and the chief
question which bothered men of learning was why the caves and pits where the filtration
supposedly took place were not full of salt left by the sea water.
To settle this point the Science Academy of Bordeaux in 1740 held a competition. Six
years
later the prize was awarded to a certain Professor Kiihn, a native of Danzig and author of a
learned paper entitled Tenable Considerations regarding the Sources
of submarine Water.
Here are some of Kiihn's ' tenable considerations', which were held at the time to be the
quintessence of wisdom:
Sea water is swallowed
up by submarine gulfs and flows thereafter beneath the terra
firma. Here, through countless channels and branches,
it spreads even beneath the
mountain ranges. As it progresses, and being influenced by the heat of the centre of the
earth, it vaporizes gradually and imperceptibly in the grottoes, caverns and
anfractuosities. Through fissures the vapours reach the caves of the higher levels of the
earth, condense and become water, which concentrates gradually in sloping beds of
gravel and loose stones and forms springs at the foot of the mountains. The surplus
water collects in underground basins. Such is the origin of the deeper ground-water. The
water left behind, partially evaporated, in the bowels of the earth is heavier and far more
briny than that of the sea. It constitutes the mother stream, of great saltness, which
returns to the ocean through a network of canals and clefts; being heavy it falls into the
abysses as a gigantic vortex'.
But nearly two centuries before the Science Academy of Bordeaux awarded the prize
to this
'apposite' explanation, an amateur scientist named Bernard Palissy had announced a theory in
keeping with that of Vitruvius: rain and melt-watinto the ground emerge as springs. A potter and
enameller by profession and the inventor of new ceramic processes, Palissy adorned the
gardens of the Tuileries with terracotta and artificial grottoes and, as has been mentioned, was
among the first to offer a correct explanation of the origin of fossils. He was a Protestant at a
period of religious intolerance in France, and because he tried to rouse his fellow citizens from
their obscurantism by his scientific lectures, he finished his days in the Bastille in 1587. His
Excellent Discourse upon the Nature of Water and Fountains, whether
natural or artificial, lay
buried in the archives.
To the credit of science, Palissy was not alone in his opinions. The Dutch scholar
Vossius, for
instance, considered that a river such as the Nile must inevitably be the product of the diluvial
rain of the tropics: while the learned prior of the monastery of St Martin-sous-Beaune, Edme
Mariotte, the first great French physicist, published a treatise about underground water in which
he stated firmly: 'The whole of the water contained in the earth comes only from rain.' Julien de
la Mettrie, physician and atheist philosopher, expressed the same opinion. But it was not until
about 1800 that the true facts began to be accepted by the more enlightened physicists and
geologists: the transformation of salt water into fresh does not take place underground; water
does not come from the infernal regions, as Plato maintained, but from the sky, and the circuit
it follows is infinitely vaster than the philosophers, alchemists and professors of yore could
conceive.
The upper layers of the ocean grow warm under the Sun's radiation and enormous quantities
of
water evaporate, rise up and collect in the form of cloud; then, condensed into rain, they fall
upon the land. The quantity of water evaporated from the oceans amounts to billions of tons, to
which must be added further millions of tons of fresh water evaporating from the surface of the
land. The global volume of precipitation is correspondingly vast.
If the clouds were to release their contents simultaneously upon the land masses all
terrestrial
living things would be submerged, but fortunately the bulk of the rain is shed above the oceans.
Rain falling upon the land works its way in, waters the vegetals, collects in underground
systems, flows on and beneath the surface, emerges afresh and returns to the sea in the form
of streams and minor and major rivers.
It all sounds very simple, but the circulation of water involves a train of complex
phenomena.
Further, it is subject to a variety of influences. To the detriment of farmers, meteorologists and
hydro-logists, the rainfall and the reserves of water are spread unevenly over the surface of the
globe: climatic maps are quite explicit as to that. Side by side with those equatorial, tropical
and temperate zones which are heavily or at least adequately watered because of winds and
currents, and consequently support forests, pasture and crops, there are the deserts that parch
for lack of water; animal and plant life exist there as best they can beneath a never clouded
sky. Such areas have determined or at least modified the fate of human civilization.
Are we in fact slaves of the water cycle, that concatenation of events which begins
with
evaporation, continues in the formation of clouds and the falling of rain, snow and dew, and
ends, with the help of the subterranean systems and the rivers, in the ocean? May there not
be, somewhere in the bowels of the earth, reserves of water untouched by this circuit and to be
broached in need? Sixty or more years ago Eduard Suss, an Austrian geologist and social
reformer, introduced a new element into the discussion—'juvenile'
water. He believed that the
water which he so described might come from magma and reach the upper strata as the
molten rocks beneath the Earth's crust liberated gases.
Some of the water vapour released by volcanoes is, to use Suss's term, in fact 'juvenile',
and
the cooling of magma does introduce a quantity of water into the cycle of nature; but this plays
a mere secondary part in the water economy of the planet. Hopes centred upon exploiting
resources deep within the Earth's mantle are doomed to disappointment; water-hungry man
must still look towards the opening of what the Scriptures call 'the windows of heaven'—the
clouds.
