1this being ſo, this Part ought of the whole
Structure to be beſt fortified againſt the
Violence of the Waters; and nothing will
conduce more to this, than to make the Pile
work deep and broad every Way, and eſpeci
ally at the Stern, that if any Accidents ſhould
carry away any of the Piles, there may be enow
leſt to ſuſtain the Weight of the Pier. It will
be alſo extremely proper to begin your Foun
dation at the upper Part of the Channel, and
to make it with an eaſy Deſcent, that the
Water which runs over it may not fall upon
it violently as into a Precipice, but glide over
gently, with an eaſy Slope; becauſe the Water
that ruſhes down precipitately, routs up the
Bottom, and ſo being made ſtill rougher carries
away every Thing that it can looſen, and is
every Moment undermining the Work.
Structure to be beſt fortified againſt the
Violence of the Waters; and nothing will
conduce more to this, than to make the Pile
work deep and broad every Way, and eſpeci
ally at the Stern, that if any Accidents ſhould
carry away any of the Piles, there may be enow
leſt to ſuſtain the Weight of the Pier. It will
be alſo extremely proper to begin your Foun
dation at the upper Part of the Channel, and
to make it with an eaſy Deſcent, that the
Water which runs over it may not fall upon
it violently as into a Precipice, but glide over
gently, with an eaſy Slope; becauſe the Water
that ruſhes down precipitately, routs up the
Bottom, and ſo being made ſtill rougher carries
away every Thing that it can looſen, and is
every Moment undermining the Work.
BUILD the Piers of the biggeſt and longeſt
Stones, and of ſuch as in their Nature are beſt
adapted for ſupporting of Froſts, and as do
not decay in Water, nor are eaſily ſoftened by
any Accident, and will not crack and ſplit
under a great Weight; and build them ex
actly according to the Square, Level and Plum
line, omitting no Sort of Ligature Length
ways, and placing the Stones Breadth-ways in
alternate Order, ſo as to be a Binding one to
another; abſolutely rejecting any ſtuffing with
ſmall Pieces of Stone. You muſt alſo faſten
your Work with a good Number of Braſs
Cramps and Pins, ſo well fitted in, that the
Joynts of the Structure may not ſeparate, but
be kept tight and firm. Raiſe both the Fronts
of the Building angular, both Head and Stern,
and let the Top of the Pier be ſure to be
higher than the fulleſt Tide; and let the Thick
neſs of the Pier be one fourth of the Heighth
of the Bridge. There have been ſome that
have not terminated the Head and Stern of
their Piers with an Angle, but with an half
Circle; induced thereto, I ſuppoſe, by the
Beautifulneſs of that Figure. But though I
have ſaid elſewhere, that the Circle has the
ſame Strength as an Angle, yet here I approve
better of an Angle, provided it be not ſo ſharp
as to be broken and defaced by every little Acci
dent: Nor am I altogether diſpleaſed with thoſe
which end in a Curve, provided it be very much
lengthened out, and not left ſo obtuſe as to re
ſiſt the Force and Weight of the Water. The
Angle of the Pier is of a good Sharpneſs, if it
is three Quarters of a Right Angle, or if you
like it better, you may make it two thirds.
And thus much may ſuffice as to the Piers. If
the Nature of your Situation is ſuch, that the
Sides or Banks of the Shore are not as you
could wiſh; make them good in the ſome Man
ner as you build your Piers, and indeed make
other Piers upon the Shore, and turn ſome
Arches even upon the dry Ground; to the
Intent, that if in Proceſs of Time, by the con
tinual waſhing of the Water, and the Force of
the Tides, any Part of the Bank ſhould be
carried away, your Paſſage may ſtill be pre
ſerved ſafe, by the Production of the Bridge
into the Land. The Arches ought upon all
Accounts, and particularly becauſe of the con
tinual violent ſhaking and Concuſſion of Carts
and other Carriages, to be extreamly ſtout and
ſtrong. Beſides, as ſometimes you may be
obliged to draw immenſe Weights over them,
ſuch as a Coloſſus, an Obelisk or the like; you
ſhould provide againſt the Inconvenience which
happened to Scaurus, who when he was re
moving that great Boundary Stone, alarmed all
the publick Officers, upon Account of the
Miſchief that might enſue. For theſe Reaſons,
a Bridge both in its Deſign, and in its whole
Execution, ſhould be well fitted to bear the
continual and violent Jars which it is to re
ceive from Carriages. That Bridges ought to
be built of very large and ſtout Stones, is very
manifeſt by the Example of an Anvil, which,
if is large and heavy, ſtands the Blows of the
Hammer unmoved; but if it is light, rebounds
and trembles at every Stroke. We have al
ready ſaid, that all vaulted Work conſiſts of
Arches and Stuffing, and that the ſtrongeſt of
all Arches is the Semi-circle. But if by the
Diſpoſition of the Piers, the Semi-circle ſhould
riſe ſo high as to be inconvenient, we may
make uſe of the Scheme Arch, only taking
Care to make the laſt Piers on the Shore the
ſtronger and thicker. But whatever Sort of
Arch you vault your Bridge with, it muſt be
built of the hardeſt and largeſt Stones, ſuch as
you uſe in your Piers; and there ſhould not
be a ſingle Stone in the Arch but what is in
Thickneſs at leaſt one tenth Part of the Chord
of that Arch; nor ſhould the Chord itſelf be
longer than ſix Times the Thickneſs of the
Pier, nor ſhorter than four Times. The Stones
alſo ſhould be ſtrongly faſtened together with
Pins and Cramps of Braſs. And the laſt Wedge,
which is called the Key-ſtone, ſhould be cut
according to the Lines of the other Wedges,
but left a ſmall Matter bigger at the Top, ſo
that it may not be got into its Place without
ſome Strokes of a light Beetle; which will
Stones, and of ſuch as in their Nature are beſt
adapted for ſupporting of Froſts, and as do
not decay in Water, nor are eaſily ſoftened by
any Accident, and will not crack and ſplit
under a great Weight; and build them ex
actly according to the Square, Level and Plum
line, omitting no Sort of Ligature Length
ways, and placing the Stones Breadth-ways in
alternate Order, ſo as to be a Binding one to
another; abſolutely rejecting any ſtuffing with
ſmall Pieces of Stone. You muſt alſo faſten
your Work with a good Number of Braſs
Cramps and Pins, ſo well fitted in, that the
Joynts of the Structure may not ſeparate, but
be kept tight and firm. Raiſe both the Fronts
of the Building angular, both Head and Stern,
and let the Top of the Pier be ſure to be
higher than the fulleſt Tide; and let the Thick
neſs of the Pier be one fourth of the Heighth
of the Bridge. There have been ſome that
have not terminated the Head and Stern of
their Piers with an Angle, but with an half
Circle; induced thereto, I ſuppoſe, by the
Beautifulneſs of that Figure. But though I
have ſaid elſewhere, that the Circle has the
ſame Strength as an Angle, yet here I approve
better of an Angle, provided it be not ſo ſharp
as to be broken and defaced by every little Acci
dent: Nor am I altogether diſpleaſed with thoſe
which end in a Curve, provided it be very much
lengthened out, and not left ſo obtuſe as to re
ſiſt the Force and Weight of the Water. The
Angle of the Pier is of a good Sharpneſs, if it
is three Quarters of a Right Angle, or if you
like it better, you may make it two thirds.
And thus much may ſuffice as to the Piers. If
the Nature of your Situation is ſuch, that the
Sides or Banks of the Shore are not as you
could wiſh; make them good in the ſome Man
ner as you build your Piers, and indeed make
other Piers upon the Shore, and turn ſome
Arches even upon the dry Ground; to the
Intent, that if in Proceſs of Time, by the con
tinual waſhing of the Water, and the Force of
the Tides, any Part of the Bank ſhould be
carried away, your Paſſage may ſtill be pre
ſerved ſafe, by the Production of the Bridge
into the Land. The Arches ought upon all
Accounts, and particularly becauſe of the con
tinual violent ſhaking and Concuſſion of Carts
and other Carriages, to be extreamly ſtout and
ſtrong. Beſides, as ſometimes you may be
obliged to draw immenſe Weights over them,
ſuch as a Coloſſus, an Obelisk or the like; you
ſhould provide againſt the Inconvenience which
happened to Scaurus, who when he was re
moving that great Boundary Stone, alarmed all
the publick Officers, upon Account of the
Miſchief that might enſue. For theſe Reaſons,
a Bridge both in its Deſign, and in its whole
Execution, ſhould be well fitted to bear the
continual and violent Jars which it is to re
ceive from Carriages. That Bridges ought to
be built of very large and ſtout Stones, is very
manifeſt by the Example of an Anvil, which,
if is large and heavy, ſtands the Blows of the
Hammer unmoved; but if it is light, rebounds
and trembles at every Stroke. We have al
ready ſaid, that all vaulted Work conſiſts of
Arches and Stuffing, and that the ſtrongeſt of
all Arches is the Semi-circle. But if by the
Diſpoſition of the Piers, the Semi-circle ſhould
riſe ſo high as to be inconvenient, we may
make uſe of the Scheme Arch, only taking
Care to make the laſt Piers on the Shore the
ſtronger and thicker. But whatever Sort of
Arch you vault your Bridge with, it muſt be
built of the hardeſt and largeſt Stones, ſuch as
you uſe in your Piers; and there ſhould not
be a ſingle Stone in the Arch but what is in
Thickneſs at leaſt one tenth Part of the Chord
of that Arch; nor ſhould the Chord itſelf be
longer than ſix Times the Thickneſs of the
Pier, nor ſhorter than four Times. The Stones
alſo ſhould be ſtrongly faſtened together with
Pins and Cramps of Braſs. And the laſt Wedge,
which is called the Key-ſtone, ſhould be cut
according to the Lines of the other Wedges,
but left a ſmall Matter bigger at the Top, ſo
that it may not be got into its Place without
ſome Strokes of a light Beetle; which will