Archimedes Texts

221
with a Shade, is colder and clearer, but more
undigested, than those warmed by the Sun;
and, on the contrary, Waters too much heated
by the Sun, are brackish and viscous. The
being deep is of Service to either Sort, because
it prevents the latter from being made too hot,
and the former from being too easily affected
by Frost. Lastly it is thought that even the
Marsh is not always to be despised: because
where-ever Eels are found, the Water is reckoned
to be not very bad. Of all Marsh-water that
is accounted the very worst which breeds Horse
leeches, which is so absolutely without Moti
on that it contracts a Scurf on the Top, which
has an offensive Smell, which is of a black or
livid Colour, which being put into a Vessel will
continue soul a great while, which is heavy and
clammy with a mossy Slime, and which being
used in washing your Hands, they are a long
Time before they dry. But as a short Summary
of what has been said of Water, it should be ex
tremely light, clear, thin and transparent, to
which must be added those Particulars which
we have slightly touched in the first Book.
Lastly it will be a strong Confirmation to you
of the Goodness of your Water, if you find that
the Cattle which have washed and drank in it
for several Months together, are in good Con
dition and perfectly healthy; and you have a
sure Way to judge whether they are sound or
not by inspecting their Livers; for what is
noxious injures with Time, and the Injury
which is latest felt is of the worst Consequence.

Having found Water and approved
it to be good, the next Work is to convey
it artfully and accommodate it properly to the
Uses of Men. There are two Ways of convey
ing Water, either by a Trench or Canal, or by
Pipes or Conduits. In either of these Methods,
the Water will not move, unless the Place to
which you would convey it be lower than that
from which it is to be brought. But then there
is this Difference, that the Water which is brought
by a Canal must descend all the Way with a
continued Slope, whereas that which is conveyed
in Pipes may ascend in some Part of the Way.
Of these two Methods we are now to treat.
But first we must premise some Things for the
clearer Explication of our Subject. The
Searchers into Nature tell us, that the Earth is
Spherical, tho' in many Places it rises into
Hills, and in many others sinks into Seas: but
in so vast a Globe this Roughness is not per
ceptible; as in an Egg, which tho' it is far
from being of a smooth Superficies, yet its lit
tle Inequalities bearing but an inconsiderable
Proportion to its whole Circumference, they
are scarce observed. Eratosthenes tells us, that
the Compass of this great Globe is two hun
dred and fifty two thousand Furlongs, or about
thirty one thousand five hundred Miles, and
that there is no Hill so high or Water so deep
as to be above fifteen thousand Cubits perpen
dicular; not even Mount Caucasus, whose Top
enjoys the Sun three Hours in the Night.
There is a prodigious high Mountain in Ar
cadia called Cyllene; and yet those who have
measured its perpendicular, affirm, that it does
not exceed twenty Furlongs. Even the Sea it
self is thought to be no more upon this Globe
of Earth, than the Summer's Dew is upon the
Body of an Apple. Some have wittily said,
that the Creator of the World made use of the
Concavity of the Sea as of a Seal with the Im
pression whereof he stampt the Hills. What
the Geometers teach us upon this Head is very
much to our present Purpose. They say, that
if a straight Line touching the Globe of the
Earth at one End were to be drawn on exactly
horizontal a Mile in Length, the Space be
tween the other End and the Surface of the
Globe would not be above ten Inches. For
this Reason Water will never move on in a
Canal, but stand still like a Lake, unless every
eight Furlongs the Trench has a Slope of one
whole Foot from the Place where the Water
was first found and its Bed cut; which Place
the ancient Lawyers called Incile, from the In
cision which is made either in the Rock or
Bank for conveying the Water: But if in this
Space of eight Furlongs it had a Slope of more
than six Foot, it is supposed that the Rapidity
of its Current would make it inconvenient for
Boats. In order to find whether the Trench
which is to convey the Water be lower than