Archimedes Texts

225
It is incredible the Violence and Impetuosity
of Nature when the Wind in such a Pipe is re
strained and compressed too close. I have read
in the Works of the Physicians, that the Bone of
a Man's Leg has been broken by the sudden
Irruption of a Vapour so confined. The Ar
tists in Hydraulics can force Water to leap up
out of a Vessel, by confining a Quantity of Air
between two Waters.

I now come to speak of Cisterns. A Cistern
is a large Vessel for holding Water, not
unlike the Water-house or Conduit-head. Its
Bottom and Sides therefore must be perfectly
strong and well compacted. There are two
Sorts, one for containing Water for Drinking,
and the other for preserving it for other Uses,
as particularly against sudden Fires. The first
we shall call a Drinking-cistern, the other a
Reservoir. The Drinking-cistern out to pre
serve its Water in the greatest Purity; because
when it is impure it is the Cause of a great many
Inconveniencies. In both we are to take care
that the Water is properly admitted, preserved
and dispensed. Water is brought into the Cis
tern by Pipes from the River or Spring, and
sometimes Rain-water from the House-top or
from the Ground. I was extremely pleased
with the Invention of an Architect, who in a
large bare Rock on the Summit of a Hill cut
a round Bason ten Foot deep, which received
all the Rain-water which ran into it from that
naked Rock. Then in the Plain under the
Hill he erected a Water-house, open on every
Side, and built of Brick and Mortar, thirty
Foot high, forty long and forty broad. Into
this Water-house he brought the Rain-water
from the upper Reservoir by a subterraneous
Conduit of brick Pipe; that Reservoir lying
much higher than the Top of the Water-house.
If you strew the Bottom of your Cistern with
good round Pebbles, or large Gravel from the
River very well washed, or rather fill it with it
to a certain Height, suppose of three Foot, it
will make your Water clear, cool and pure;
and the Higher you make this Strewing, your
Water will be the more limpid. The Water
sometimes runs out at the Joints and Cracks
of the Cistern if it is ill made; and sometimes
the Water is spoiled by Filth. And indeed it
is no easy Matter to keep Water imprisoned,
unless the Reservoir be strongly built, and even
of good square Stone. It is also particularly
necessary, that the Work should be perfectly
dry before you let the Water into it, which
pressing hard upon it with its Weight, and
Sweating through it by means of its Humidi
ty, if it can but make a small Crack, will be
continually working its Way till it has opened
itself a large Passage. The Ancients guarded
against this Inconvenience, and especially in
the Corners of their Reservoirs, by several Coats
of strong Plaistering, and sometimes by Incrus
tations of Marbles. But nothing better pre
vents this oozing out of the Water, than Chalk
close rammed in between the Wall of the Cis
tern and the Side of the Trench in which it is
made. We order the Chalk which we use for
this Purpose to be thoroughly dried and beat
into Powder. Some think, that if you fill a
Glass Vessel with Salt, and stop it up close
with a Plaister of Mortar tempered with Oil,
that no Water may get in, and then hang it
down in the Middle of the Cistern, it will pre
vent the Water from corrupting, let it be kept
ever so long. Some add Quick-silver to the
Composition. Others say, that if you take a
new earthen Vessel full of sharp Vinegar, stopt
up as above, and set it in the Water, it will en
tirely clear it from all Slime. They tell us too,
that either a Ciftern or a Well are purified by
putting some small Fish into them, thinking
that the Fish feed upon the Slime of the Wa
ter and of the Earth. We are told of an old
Saying of Epigenes, that Water which has been
once corrupted, will in Time recover and pu
rify itself, and after that never spoil any more.
Water which is beginning to corrupt, if it is
stirred about, and poured often out of one Ves
sel into another, will lose its ill Smell, which
will also hold good of Wine and Oil that is
mothery. Josephus relates, that when Moses
came to a dry Place, where there was only one
Spring of Water, and that foul and bitter, he
commanded the Soldiers to draw it; and upon
their beating and stirring it about heartily, it
became drinkable. It is certain that Water
may be purified by boiling and straining; and