1the 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.
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.
CHAP. XI.
Of Canals; how they are to be kept well ſupplied with Water, and the Uſes
of them not obſtructed.
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
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
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