1with their Backs againſt each other, joining
perpendicularly. The third Stone which is
laid upon theſe ſecond ones, muſt be ſet
by the Plum-lines, as we directed in raiſing
the Wall, with even Joinings, ſo that they
may ſerve both the Arches, and be a Binding
to both their Wedges. Let the Lines of the
Joinings of all the Stones in the Arch point
exactly to the Centre of that Arch.
perpendicularly. The third Stone which is
laid upon theſe ſecond ones, muſt be ſet
by the Plum-lines, as we directed in raiſing
the Wall, with even Joinings, ſo that they
may ſerve both the Arches, and be a Binding
to both their Wedges. Let the Lines of the
Joinings of all the Stones in the Arch point
exactly to the Centre of that Arch.
THE moſt skillful Workmen always make
the Key-ſtone of one ſingle Piece, very large
and ſtrong; and if the Breadth of the Top is
ſo great, that no one Stone will ſuffice, it will
then be no longer only an Arch, but a vaul
ted Roof.
the Key-ſtone of one ſingle Piece, very large
and ſtrong; and if the Breadth of the Top is
ſo great, that no one Stone will ſuffice, it will
then be no longer only an Arch, but a vaul
ted Roof.
CHAP. XIV.
Of the ſeveral Sorts of Vaults, and wherein they differ; of what Lines they
are compoſed, and the Method of letting them ſettle.
are compoſed, and the Method of letting them ſettle.
There are ſeveral Sorts of Vaults; ſo
that it is our Buſineſs here to enquire
wherein they differ, and of what Lines they
are compoſed; in doing of which, I ſhall be
obliged to invent new Names, to make myſelf
clear and perſpicuous, which is what I have
principally ſtudied in theſe Books. I know
Ennius the Poet calls the Arch of the Heavens
the mighty Vaults; and Servius calls all Vaults
made like the Keel of a Ship, Caverns: But I
claim this Liberty; that whatever in this Work,
is expreſſed aptly, clearly, and properly, ſhall
be allowed to be expreſſed right. The differ
ent Sorts of Vaults are theſe, the plain Vault,
the Camerated, or mixed Vault, and the he
miſpherical Vault, or Cupola; beſides thoſe
others which partake of the Kind of ſome of
theſe. The Cupola in its Nature is never
placed but upon Walls that riſe from a cir
cular Platform: The Camerated are proper for
a ſquare one; the plain Vaults are made over
any quadrangular Platform, whether long or
ſhort, as we ſee in all ſubterraneous Porticoes.
Thoſe Vaults too which are like a Hill bored
through, we alſo call plain Vaults; the plain
Vault therefore, is like a Number of Arches
join'd together Sideways; or like a bent Beam
extended out in Breadth, ſo as to make a Kind
of a Wall turn'd with a Sweep over our
Heads for a Covering. But if ſuch a Vault
as this, running from North to South, hap
pens to be croſs'd by another which runs from
Eaſt to Weſt, and interſects it with equal
Lines meeting at the Angles like crooked
Horns, this will make a Vault of the Camer
ated Sort. But if a great Number of equal
Arches meet at the Top exactly in the Centre,
they conſtitute a Vault like the Sky, which
therefore we call the Hemiſpherical, or com
pleat Cupola. The Vaults made of Part of
theſe, are as follows: If Nature with an even
and perpendicular Section, were to divide the
Hemiſphere of the Heavens in two Parts, from
Eaſt to Weſt, it would make two Vaults,
which would be proper Coverings for any
ſemi-circular Building. But if from the Angle
at the Eaſt, to that at the South, and from the
South to the Weſt, thence to the North, and
ſo back again to the Eaſt, if Nature were to
break and interrupt this Hemiſphere by ſo
many Arches turn'd from Angle to Angle,
ſhe would then leave a Vault in the Middle,
which for its Reſemblance to a ſwelling Sail,
we will venture to call a Velar Cupola. But
that Vault which conſiſts of a Number of
plain Vaults meeting in a Point at Top, we
ſhall call an Angular Cupola.
that it is our Buſineſs here to enquire
wherein they differ, and of what Lines they
are compoſed; in doing of which, I ſhall be
obliged to invent new Names, to make myſelf
clear and perſpicuous, which is what I have
principally ſtudied in theſe Books. I know
Ennius the Poet calls the Arch of the Heavens
the mighty Vaults; and Servius calls all Vaults
made like the Keel of a Ship, Caverns: But I
claim this Liberty; that whatever in this Work,
is expreſſed aptly, clearly, and properly, ſhall
be allowed to be expreſſed right. The differ
ent Sorts of Vaults are theſe, the plain Vault,
the Camerated, or mixed Vault, and the he
miſpherical Vault, or Cupola; beſides thoſe
others which partake of the Kind of ſome of
theſe. The Cupola in its Nature is never
placed but upon Walls that riſe from a cir
cular Platform: The Camerated are proper for
a ſquare one; the plain Vaults are made over
any quadrangular Platform, whether long or
ſhort, as we ſee in all ſubterraneous Porticoes.
Thoſe Vaults too which are like a Hill bored
through, we alſo call plain Vaults; the plain
Vault therefore, is like a Number of Arches
join'd together Sideways; or like a bent Beam
extended out in Breadth, ſo as to make a Kind
of a Wall turn'd with a Sweep over our
Heads for a Covering. But if ſuch a Vault
as this, running from North to South, hap
pens to be croſs'd by another which runs from
Eaſt to Weſt, and interſects it with equal
Lines meeting at the Angles like crooked
Horns, this will make a Vault of the Camer
ated Sort. But if a great Number of equal
Arches meet at the Top exactly in the Centre,
they conſtitute a Vault like the Sky, which
therefore we call the Hemiſpherical, or com
pleat Cupola. The Vaults made of Part of
theſe, are as follows: If Nature with an even
and perpendicular Section, were to divide the
Hemiſphere of the Heavens in two Parts, from
Eaſt to Weſt, it would make two Vaults,
which would be proper Coverings for any
ſemi-circular Building. But if from the Angle
at the Eaſt, to that at the South, and from the
South to the Weſt, thence to the North, and
ſo back again to the Eaſt, if Nature were to
break and interrupt this Hemiſphere by ſo
many Arches turn'd from Angle to Angle,
ſhe would then leave a Vault in the Middle,
which for its Reſemblance to a ſwelling Sail,
we will venture to call a Velar Cupola. But
that Vault which conſiſts of a Number of
plain Vaults meeting in a Point at Top, we
ſhall call an Angular Cupola.
IN the Conſtruction of Vaults, we muſt
obſerve the ſame Rules as in that of the Walls,
carrying on the Ribs of the Wall clear up to
the Summit of the Vault; and according to
the Method preſcribed for the Former, obſerv
ing the ſame Proportions and Diſtances: From
Rib to Rib, we muſt draw Ligatures croſſways,
and the Interſpaces we muſt fill up with Stuf
fing. But the Difference between the Work
ing of a Vault and a Wall, lies in this; that
in the Wall the Courſes of Stone are laid even
and perpendicular by the Square and Plum
line; whereas, in the Vault the Courſes are
laid by a curve Line, and the Joints all point
to the Centre of their Arch.
obſerve the ſame Rules as in that of the Walls,
carrying on the Ribs of the Wall clear up to
the Summit of the Vault; and according to
the Method preſcribed for the Former, obſerv
ing the ſame Proportions and Diſtances: From
Rib to Rib, we muſt draw Ligatures croſſways,
and the Interſpaces we muſt fill up with Stuf
fing. But the Difference between the Work
ing of a Vault and a Wall, lies in this; that
in the Wall the Courſes of Stone are laid even
and perpendicular by the Square and Plum
line; whereas, in the Vault the Courſes are
laid by a curve Line, and the Joints all point
to the Centre of their Arch.
THE Ancients hardly ever made their Ribs
of any but burnt Bricks, and thoſe generally
about two Foot long, and adviſe to fill up the
Interſpaces of our Vaults with the lighteſt
Stone, that they might not oppreſs the Wall
with too great a Weight. But I have obſerved
that ſome have not always thought themſelves
obliged to make continued ſolid Ribs, but in
their ſtead, have at certain Diſtances, ſet Bricks
lying Sideways, with their Heads jointing into
of any but burnt Bricks, and thoſe generally
about two Foot long, and adviſe to fill up the
Interſpaces of our Vaults with the lighteſt
Stone, that they might not oppreſs the Wall
with too great a Weight. But I have obſerved
that ſome have not always thought themſelves
obliged to make continued ſolid Ribs, but in
their ſtead, have at certain Diſtances, ſet Bricks
lying Sideways, with their Heads jointing into