The Ten Books on Architecture
keep it for a comparatively long time on account of their holding power.
These must not be trusted, but the search must be made in districts and
soils, yet not in depressions, where those signs are found growing not
from seed, but springing up naturally of themselves.
4. If the indications mentioned appear in such places, the following
test should be applied. Dig out a place not less than three feet square
and five feet deep, and put into it about sunset a bronze or leaden bowl
or basin, whichever is at hand. Smear the inside with oil, lay it upside
down, and cover the top of the excavation with reeds or green boughs,
throwing earth upon them. Next day uncover it, and if there are drops
and drippings in the vessel, the place will contain water.
5. Again, if a vessel made of unbaked clay be put in the hole, and
covered in the same way, it will be wet when uncovered, and already
beginning to go to pieces from dampness, if the place contains water. If
a fleece of wool is placed in the excavation, and water can be wrung out
of it on the following day, it will show that the place has a supply.
Further, if a lamp be trimmed, filled with oil, lighted, and put in that
place and covered up, and if on the next day it is not burnt out, but
still contains some remains of oil and wick, and is itself found to be
damp, it will indicate that the place contains water; for all heat
attracts moisture. Again, if a fire is made in that place, and if the
ground, when thoroughly warmed and burned, sends up a misty vapour from
its surface, the place will contain water.
6. After applying these tests and finding the signs described above, a
well must next be sunk in the place, and if a spring of water is found,
more wells must be dug thereabouts, and all conducted by means of
subterranean channels into one place.
The mountains and districts with a northern exposure are the best spots
in which to search, for the reason that springs are sweeter, more
wholesome, and more abundant when found there. Such places face away
from the sun's course, and the trees are thick in them, and the
mountains, being themselves full of woods, cast shadows of their own,
preventing the rays of the sun from striking uninterruptedly upon the
ground and drying up the moisture.
7. The valleys among the mountains receive the rains most abundantly,
and on account of the thick woods the snow is kept in them longer by the
shade of the trees and mountains. Afterwards, on melting, it filters
through the fissures in the ground, and thus reaches the very foot of
the mountains, from which gushing springs come belching out.
But in flat countries, on the contrary, a good supply cannot be had. For
however great it is, it cannot be wholesome, because, as there is no
shade in the way, the intense force of the sun draws up and carries off
the moisture from the flat plains with its heat, and if any water shows
itself there, the lightest and purest and the delicately wholesome part
of it is summoned away by the air, and dispersed to the skies, while the
heaviest and the hard and unpleasant parts are left in springs that are
in flat places.
CHAPTER II
RAINWATER
1. Rainwater has, therefore, more wholesome qualities, because it is
drawn from the lightest and most delicately pure parts of all the
springs, and then, after being filtered through the agitated air, it is
liquefied by storms and so returns to the earth. And rainfall is not
abundant in the plains, but rather on the mountains or close to
mountains, for the reason that the vapour which is set in motion at
sunrise in the morning, leaves the earth, and drives the air before it
through the heaven in whatever direction it inclines; then, when once in
motion, it has currents of air rushing after it, on account of the void
which it leaves behind.
2. This air, driving the vapour everywhere as it rushes along, produces
gales and constantly increasing currents by its mighty blasts. Wherever
the winds carry the vapour which rolls in masses from springs, rivers,
marshes, and the sea, it is brought together by the heat of the sun,
drawn off, and carried upward in the form of clouds; then these clouds
are supported by the current of air until they come to mountains, where
they are broken up from the shock of the collision and the gales, turn
into water on account of their own fulness and weight, and in that form
are dispersed upon the earth.
3. That vapour, mists, and humidity come forth from the earth, seems due
to the reason that it contains burning heat, mighty currents of air,
intense cold, and a great quantity of water. So, as soon as the earth,
which has cooled off during the night, is struck by the rays of the
rising sun, and the winds begin to blow while it is yet dark, mists
begin to rise upward from damp places. That the air when thoroughly
heated by the sun can make vapours rise rolling up from the earth, may
be seen by means of an example drawn from baths.
4. Of course there can be no springs above the vaultings of hot
bathrooms, but the atmosphere in such rooms, becoming well warmed by the
hot air from the furnaces, seizes upon the water on the floors, and
takes it up to the curved vaultings and holds it up there, for the
reason that hot vapour always pushes upwards. At first it does not let
the moisture go, for the quantity is small; but as soon as it has
collected a considerable amount, it cannot hold it up, on account of the
weight, but sprinkles it upon the heads of the bathers. In the same way,
when the atmospheric air feels the heat of the sun, it draws the
moisture from all about, causes it to rise, and gathers it into clouds.
For the earth gives out moisture under the influence of heat just as a
man's heated body emits sweat.
5. The winds are witnesses to this fact. Those that are produced and
come from the coolest directions, the north and northeast winds, blow in
blasts that are rarefied by the great dryness in the atmosphere, but the
south wind and the others that assail us from the direction of the sun's
course are very damp, and always bring rain, because they reach us from
warm regions after being well heated there, and licking up and carrying
off the moisture from the whole country, they pour it out on the regions
in the north.
6. That this is the state of the case may be proved by the sources of
rivers, the majority and the longest of which, as drawn and described in
geographies of the world, are found to rise in the north. First in
India, the Ganges and Indus spring from the Caucasus; in Syria, the
Tigris and Euphrates; in Pontus in Asia, the Dnieper, Bug, and Don; in
Colchis, the Phasis; in Gaul, the Rhone; in Celtica, the Rhine; on this
side of the Alps, the Timavo and Po; in Italy, the Tiber; in Maurusia,
which we call Mauretania, the Dyris, rising in the Atlas range and
running westerly to Lake Heptagonus, where it changes its name and is
called Agger; then from Lake Heptabolus it runs at the base of barren
mountains, flowing southerly and emptying into the marsh called[10]...
It surrounds Meroë, which is a kingdom in southern Ethiopia, and from
the marsh grounds there, winding round by the rivers Astansoba and
Astoboa and a great many others, it passes through the mountains to the
Cataract, and from there it dashes down, and passes to the north between
Elephantis and Syene and the plains of Thebes into Egypt, where it is
called the Nile.
[Note 10: Here something is lost, as also in chapter III, sections 5
and 6.]
7. That the source of the Nile is in Mauretania is known principally
from the fact that there are other springs on the other side of the
Atlas range flowing into the ocean to the west, and that ichneumons,
crocodiles, and other animals and fishes of like nature are found
there, although there are no hippopotamuses.
8. Therefore, since in descriptions of the world it appears that all
rivers of any size flow from the north, and since in the plains of
Africa, which are exposed to the course of the sun in the south, the
moisture is deeply hidden, springs not common, and rivers rare, it
follows that the sources of springs which lie to the north or northeast
are much better, unless they hit upon a place which is full of sulphur,
alum, or asphalt. In this case they are completely changed, and flow in
springs which have a bad smell and taste, whether the water is hot or
cold.
9. The fact is, heat is not at all a property of water, but when a
stream of cold water happens upon a hot place, it boils up, and issues
through the fissures and out of the ground in a state of heat. This
cannot last very long, but in a short time the water becomes cold. If it
were naturally hot, it would not cool off and lose its heat. Its taste,
however, and its smell and colour are not restored, because it has
become saturated and compounded with these qualities on account of the
rarity of its nature.
CHAPTER III
VARIOUS PROPERTIES OF DIFFERENT WATERS
1. There are, however, some hot springs that supply water of the best
taste, which is so delightful to drink that one does not think with
regret of the Fountain of the Muses or the Marcian aqueduct. These hot
springs are produced naturally, in the following manner. When fire is
kindled down beneath in alum or asphalt or sulphur, it makes the earth
immediately over it very hot, and emits a glowing heat to the parts
still farther above it, so that if there are any springs of sweet water
found in the upper strata, they begin to boil in their fissures when
they are met by this heat, and so they run out with their taste
unimpaired.
2. And there are some cold springs that have a bad smell and taste.
They rise deep down in the lower strata, cross places which are on fire,
and then are cooled by running a long distance through the earth, coming
out above ground with their taste, smell, and colour spoiled; as, for
instance, the river Albula on the road to Tivoli and the cold springs of
Ardea, which have the same smell and are called sulphur springs, and
others in similar places. Although they are cold, yet at first sight
they seem to be hot for the reason that when they happen upon a burning
spot deep down below, the liquid and the fire meet, and with a great
noise at the collision they take in strong currents of air, and thus,
swollen by a quantity of compressed wind, they come out at the springs
in a constant state of ebullition. When such springs are not open but
confined by rocks, the force of the air in them drives them up through
the narrow fissures to the summits of hills.
3. Consequently those who think that they have excavated sources of
springs at the height of such hills find themselves mistaken when they
open up their excavations. Suppose a bronze vase filled not to the very
lips, but containing two thirds of the quantity of water which forms its
capacity, and with a cover placed upon it. When it is subjected to a
very hot fire, the water must become thoroughly heated, and from the
rarity of its nature it greatly expands by taking in the heat, so that
it not only fills the vase but raises its cover by means of the currents
of air in it, and swells and runs over. But if you take the cover off,
the expanding forces are released into the open air, and the water
settles down again to its proper level. So it is with the sources of
springs. As long as they are confined in narrow channels, the currents
of air in the water rush up in bubbles to the top, but as soon as they
are given a wider outlet, they lose their air on account of the rarity
peculiar to water, and so settle down and resume their proper level.
4. Every hot spring has healing properties because it has been boiled
with foreign substances, and thus acquires a new useful quality. For