1treat of the Stone-Bridge, the Parts whereof
are theſe: The Banks of the Shore, the Piers,
the Arches, and the Pavement. Between the
Banks of the Shore and the Piers, is this Diffe
rence, that the Banks ought to be by much the
ſtrongeſt, inaſmuch as they are not only to ſup
port the Weight of the Arches like the Piers,
but are alſo to bear the Foot of the Bridge, and
to bear againſt the Weight of the Arches, to
keep them from opening in any Part. We
ought therefore to be very careful in the Choice
of our Shore, and to find out, if poſſible, a
Rock of ſolid Stone, ſince nothing can be too
ſtrong that we are to intruſt with the Feet of
the Bridge; and as to the Piers, they muſt be
more or leſs numerous in Proportion to the
Breadth of the River. An odd Number of Ar
ches is both moſt pleaſant to the Sight, and
conduces alſo to Strength; for the farther the
Current of the River lies from the Shore, the
freer it is from Impediment, and the freer
it is the ſwifter and eaſier it flows away;
for this therefore we ought to leave a Paſſage
perfectly free and open, that it may not ſhake
and prejudice the Piers by ſtruggling with the
Reſiſtance which it meets with from them.
The Piers ought to be placed in thoſe Parts of
the River, where the Water flows the moſt
ſlowly, and (to uſe ſuch an Expreſſion) the
moſt lazily: And thoſe Parts you may eaſily
find out by means of the Tides: Otherwiſe
you may diſcover them in the following Man
ner: Imitate thoſe who threw Nuts into a
River, whereby the Inhabitants of a Town be
ſieged, gathering them up, were preſerved
from ſtarving; ſtrew the whole Breadth of the
River, about fifteen hundred Paces above the
Place which you intend for your Bridge, and
eſpecially when the River is fulleſt, with ſome
ſuch light Stuff that will eaſily float: And in
thoſe Places where the Things you have
thrown in Cluſters thickeſt together, you may
be ſure the Current is ſtrongeſt. In the Situ
ation of your Piers therefore avoid thoſe Places,
and chuſe thoſe others to which the Things
you throw in come the ſloweſt and thinneſt.
are theſe: The Banks of the Shore, the Piers,
the Arches, and the Pavement. Between the
Banks of the Shore and the Piers, is this Diffe
rence, that the Banks ought to be by much the
ſtrongeſt, inaſmuch as they are not only to ſup
port the Weight of the Arches like the Piers,
but are alſo to bear the Foot of the Bridge, and
to bear againſt the Weight of the Arches, to
keep them from opening in any Part. We
ought therefore to be very careful in the Choice
of our Shore, and to find out, if poſſible, a
Rock of ſolid Stone, ſince nothing can be too
ſtrong that we are to intruſt with the Feet of
the Bridge; and as to the Piers, they muſt be
more or leſs numerous in Proportion to the
Breadth of the River. An odd Number of Ar
ches is both moſt pleaſant to the Sight, and
conduces alſo to Strength; for the farther the
Current of the River lies from the Shore, the
freer it is from Impediment, and the freer
it is the ſwifter and eaſier it flows away;
for this therefore we ought to leave a Paſſage
perfectly free and open, that it may not ſhake
and prejudice the Piers by ſtruggling with the
Reſiſtance which it meets with from them.
The Piers ought to be placed in thoſe Parts of
the River, where the Water flows the moſt
ſlowly, and (to uſe ſuch an Expreſſion) the
moſt lazily: And thoſe Parts you may eaſily
find out by means of the Tides: Otherwiſe
you may diſcover them in the following Man
ner: Imitate thoſe who threw Nuts into a
River, whereby the Inhabitants of a Town be
ſieged, gathering them up, were preſerved
from ſtarving; ſtrew the whole Breadth of the
River, about fifteen hundred Paces above the
Place which you intend for your Bridge, and
eſpecially when the River is fulleſt, with ſome
ſuch light Stuff that will eaſily float: And in
thoſe Places where the Things you have
thrown in Cluſters thickeſt together, you may
be ſure the Current is ſtrongeſt. In the Situ
ation of your Piers therefore avoid thoſe Places,
and chuſe thoſe others to which the Things
you throw in come the ſloweſt and thinneſt.
KING Mina, when he intended to build the
Bridge of Memphis, turned the Nile out of its
Channel, and carried it another Way among
ſome Hills, and when he had finiſhed his Build
ing brought it back again into its old Bed.
Nicore Queen of the Aſſyrians, having pre
pared all the Materials for building a Bridge,
dug a great Lake, and into that turned the
River; and as the Channel grew dry as the
Lake filled, ſhe took that Time to build her
Piers. Theſe mighty Things were done by
thoſe great Princes: As for us, we are to pro
ceed in the following Manner: Make the
Foundations of your Piers in Autumn, when
the Water is loweſt, having firſt raiſed an In
cloſure to keep off the Water, which you may
do in this Manner: Drive in a double Row of
Stakes, very cloſe and thick ſet, with their
Heads above the Top of the Water, like a
Trench; then put Hurdles within this double
Row of Stakes, cloſe to that Side of the Row
which is next the intended Pier, and fill up
the Hollow between the two Rows with Ruſhes
and Mud, ramming them together ſo hard
that no Water can poſſibly get through. Then
whatever you find within this Incloſure, Water,
Mud, Sand, and whatever elſe is a Hindrance
to you, throw out. For the reſt of your Work,
you muſt obſerve the Rules we have laid down
in the preceding Book. Dig till you come to
a ſolid Foundation, or rather make one of
Piles burnt at the End, and driven in as cloſe
together as ever they can ſtick. And here I
have obſerved that the beſt Architects uſed to
make a continued Foundation of the whole
Length of the Bridge, and not only under each
Pier; and this they did, not by ſhutting out
the whole River at once by one ſingle Inclo
ſure, but by firſt making one Part, then another,
and ſo joyning the whole together by degrees;
for it would be impoſſible to withſtand and
repulſe the whole Force of the Water at once;
we muſt therefore, while we are at work with
one Part, leave another Part open, for a Paſ
ſage for the Stream.
Bridge of Memphis, turned the Nile out of its
Channel, and carried it another Way among
ſome Hills, and when he had finiſhed his Build
ing brought it back again into its old Bed.
Nicore Queen of the Aſſyrians, having pre
pared all the Materials for building a Bridge,
dug a great Lake, and into that turned the
River; and as the Channel grew dry as the
Lake filled, ſhe took that Time to build her
Piers. Theſe mighty Things were done by
thoſe great Princes: As for us, we are to pro
ceed in the following Manner: Make the
Foundations of your Piers in Autumn, when
the Water is loweſt, having firſt raiſed an In
cloſure to keep off the Water, which you may
do in this Manner: Drive in a double Row of
Stakes, very cloſe and thick ſet, with their
Heads above the Top of the Water, like a
Trench; then put Hurdles within this double
Row of Stakes, cloſe to that Side of the Row
which is next the intended Pier, and fill up
the Hollow between the two Rows with Ruſhes
and Mud, ramming them together ſo hard
that no Water can poſſibly get through. Then
whatever you find within this Incloſure, Water,
Mud, Sand, and whatever elſe is a Hindrance
to you, throw out. For the reſt of your Work,
you muſt obſerve the Rules we have laid down
in the preceding Book. Dig till you come to
a ſolid Foundation, or rather make one of
Piles burnt at the End, and driven in as cloſe
together as ever they can ſtick. And here I
have obſerved that the beſt Architects uſed to
make a continued Foundation of the whole
Length of the Bridge, and not only under each
Pier; and this they did, not by ſhutting out
the whole River at once by one ſingle Inclo
ſure, but by firſt making one Part, then another,
and ſo joyning the whole together by degrees;
for it would be impoſſible to withſtand and
repulſe the whole Force of the Water at once;
we muſt therefore, while we are at work with
one Part, leave another Part open, for a Paſ
ſage for the Stream.
YOU may leave theſe Paſſages either in the
Channel itſelf, or if you think it more conve
nient, you may frame wooden Dams, or hang
ing Channels, by which the ſuperfluous Wa
ter may run off. But if you find the Expence
of a continued Foundation for the whole Bridge
too great, you may only make a ſeparate Foun
dation for every particular Pier, in the Form
of a Ship with one Angle in the Stern, and an
other in the Head, lying directly even with the
Current of the Water, that the Force of the
Water may be broken by the Angle. We are
to remember that the Water is much more
dangerous to the Stern, than to the Head of
the Piers, which appears from this, that at
the Stern the Water is in a more violent Mo
tion than at the Head, and forms Eddies,
which turn up the Ground at the Bottom;
while the Head ſtands firm and ſafe, being
guarded and defended by the Banks of Sand
thrown up before it by the Channel. Now
Channel itſelf, or if you think it more conve
nient, you may frame wooden Dams, or hang
ing Channels, by which the ſuperfluous Wa
ter may run off. But if you find the Expence
of a continued Foundation for the whole Bridge
too great, you may only make a ſeparate Foun
dation for every particular Pier, in the Form
of a Ship with one Angle in the Stern, and an
other in the Head, lying directly even with the
Current of the Water, that the Force of the
Water may be broken by the Angle. We are
to remember that the Water is much more
dangerous to the Stern, than to the Head of
the Piers, which appears from this, that at
the Stern the Water is in a more violent Mo
tion than at the Head, and forms Eddies,
which turn up the Ground at the Bottom;
while the Head ſtands firm and ſafe, being
guarded and defended by the Banks of Sand
thrown up before it by the Channel. Now