Archimedes Texts

229
the slowest Current will be the most lasting:
Which may be somewhat illustrated by the
Comparison of a Man that descends from a
steep Hill, and who comes down not direct
and as fast as he can, but fetching different
Compasses about the Sides, sometimes to the
right Hand, and sometimes to the Left. The
Rapidity of the Stream proceeds from the Steep
ness of the Channel. A Current either too
swift or too slow, is inconvenient. The for
mer demolishes the Banks; the latter produ
ces Weeds, and is easily frozen. Making the
River narrower may perhaps force the Water
to rise higher, and another Way to make it
deeper is digging the Channel, lower. Deep
ening the Channel, removing Impediments,
and clearing the River are all done by the
same Methods and for the same Purposes,
whereof we shall speak presently: But deepen
ing the Bottom of a River will be in vain, un
less we go on to do it quite away to the Sea,
in order to give the Stream its due Slope all
the Way.

Of Canals; how they are to be kept well supplied with Water, and the Uses
of them not obstructed.

We now proceed to speak of Canals.
What we are to provide for in these,
is that they be well supplied with Water, and
that the Uses for which they are intended be
not obstructed. There are two Ways of prevent
ing their failing. The first is to have a large
Quantity of Water constantly running into them
from some other Stream; the second is to con
trive that they keep what does come into them
as long as can be. The Water is to be brought
into Canals in the manner above set down: and
our Diligence must prevent their Uses from be
ing obstructed, by often cleaning them, and
removing whatever Incumbrances may be
brought into them. A Canal is said to be a
sleeping River; and it should therefore have
all the same Properties which a River has, and
especially its Bottom and Sides should be per
fectly sound, that the Water may neither be
sucked up, nor run out at any Cracks. It
should be more deep than broad, as well for the
better carrying off all Sorts of Vessels, as that it
may be less exhausted by the Sun and breed the
fewer Weeds. A great many Canals were cut
from the Euphrates to the Tygris, because the
Channel of the former lay higher than that of
the Latter. Lombardy lying between the Po
and the Adige, is every where navigable by
Canals; an Advantage which it gains by ly
ing all upon a Flat. Diodorus tells us, that
when Ptolomey went out of the Mouth of the
Nile, he opened a Canal on Purpose, and had
it stopp'd up as soon as he was got through it.
The Remedies for the several Faults of either
Canals or Rivers are confining, clearing and
stopping them. Rivers are confined by arti
ficial Banks. The Line of such Banks should
not restrain the River at once, but by degrees,
by means of an easy Slope. When you would
set it at Liberty again from a narrow Channel
into a wider Breadth, you must observe the
same Method, not let it out at once, but gently,
lest upon too sudden an Enlargment it does
Mischief by Eddies and Whirlpools. The River
Melas used of old to run into the Euphrates;
but King Artanatrix, perhaps out of a Desire
to make his Name famous, stopp'd it up and
overslowed the Country all round: but soon
afterwards the Waters return'd with such Ed
dies and so much Fury that they tore up all
that resisted them, washed away a great many
Estates, and laid Waste a great Part of Phrygia
and Galatia. The Roman Senate fined the
King for this audacious Attempt, in thirty Ta
lents. Nor is it foreign to our Purpose just to
mention what we read of Iphicrates the A
thenian, that when he was besieging Stymphalus
in Arcadia he attempted with a vast Quantity
of Spunge to stop up the River Erasinus which
enters into the Hill and rises up again in the
Country of Arges; but by the Admonition of
Jupiter he laid aside the Design. I advise
therefore, that your artificial Bank be made as
strong as possible. This Strength must be
owing to the Solidity of your Materials, your
Method of putting them together, and the
Breadth of the whole Work. Where it is ne
cessary that the Water should run over this
Bank, do not let the Outside of it be a Per
pendicular, but fall in an easy Slope, that the
Water may run down it easily and not form
any Eddies. If in its Fall it begins to dig up