1each other, like the Teeth of a Comb; as a Man
locks his right Hand Fingers into his left; and
the Interſpaces they filled up with any common
Stone, and eſpecially with Pumice Stone, which
is univerſally agreed to be the propereſt of all,
for the ſtuffing Work of Vaults. In building
either Arches or Vaults, we muſt make uſe of
Centres. Theſe are a Kind of Frames made
with the Sweep of an Arch of any rough Boards
juſt clapt together for a ſhort Service, and
covered either with Hurdles, Ruſhes, or any
ſuch common Stuff, in order to ſupport the
Work till it is ſettled and hardened. Yet there
is one ſort of Vault which ſtands in no Need
of theſe Machines, and that is the perfect
Cupola; becauſe it is compoſed not only of
Arches, but alſo, in a Manner, of Cornices.
And who can conceive the innumerable Liga
tures that there are in theſe, which all wedge
together, and interſect one another both with
equal and unequal Angles? So that in whatſo
ever Part of the whole Cupola you lay a Stone,
or a Brick, you may be ſaid at the ſame time
to have laid a Key-ſtone to an infinite Number,
both of Arches, and Cornices. And when
theſe Cornices, or Arches are thus built one
upon the other, if the Work were inclined to
ruinate, where ſhould it begin, when the Joints
of every Stone are directed to one Centre with
equal Force and preſſure? Some of the Ancients
truſted ſo much to the Firmneſs of this Sort of
Structure, that they only made plain Cornices
of Brick at ſtated Diſtances, and filled up the
Interſpaces with Rubble. But I think, thoſe
acted much more prudently, who in raiſing
this Sort of Cupola, uſed the ſame Methods as
in Walling, to cramp and faſten the under
Cornices to the next above, and the Arches
too in ſeveral Places, eſpecially if they had not
plenty of Pit Sand to make very good Cement,
or if the Building was expoſed to South Winds,
or Blaſts from the Sea. You may likewiſe
turn the Angular Cupolas without a Centre,
if you make a perfect one in the Middle of the
Thickneſs of the Work. But here you will
have particular Occaſion for Ligatures to faſten
the weaker Parts of the outer one tightly to
the ſtronger Parts of that within. Yet it will
be neceſſary when you have laid one or two
Rows of Stone to make little light Stays, or
Catchers jutting out, on which, when thoſe
Rows are ſettled, you may ſet juſt Frame-work
enough to ſupport the next Courſes above, to
the Height of a few Feet, till they are ſufficiently
hardened; and then you may remove theſe
Frames, or Supports, higher and higher to
the other Courſes till you have finiſh'd the
whole Work. The other Vaults, both plain and
mixed, or camerated, muſt needs be turn'd
upon Centres. But I would have the firſt
Courſes, and the Heads of their Arches be
placed upon very ſtrong Seats; nor can I ap
prove the Method of thoſe who carry the
Wall clear up firſt, only leaving ſome Mould
ings, or Corbels, upon which, after a Time,
they turn their Arches; which muſt be a very
infirm and periſhable Sort of Work. The
true Way is to turn the Arch immediately,
and equally with the Courſes of the Wall
which is to ſupport it, that the Work may
have the ſtrongeſt Ligatures that is poſſible,
and grow in a Manner all of one Piece. The
Vacuities which are left between the Back of
the Sweep of the Arch, and the Upright of
the Wall it is turn'd from, call'd by Work
men, the Hips of the Arch, ſhould be fill'd
up, not with Dirt, or old Rubbiſh, but rather
with ſtrong ordinary Work, frequently knit
and jointed into the Wall.
locks his right Hand Fingers into his left; and
the Interſpaces they filled up with any common
Stone, and eſpecially with Pumice Stone, which
is univerſally agreed to be the propereſt of all,
for the ſtuffing Work of Vaults. In building
either Arches or Vaults, we muſt make uſe of
Centres. Theſe are a Kind of Frames made
with the Sweep of an Arch of any rough Boards
juſt clapt together for a ſhort Service, and
covered either with Hurdles, Ruſhes, or any
ſuch common Stuff, in order to ſupport the
Work till it is ſettled and hardened. Yet there
is one ſort of Vault which ſtands in no Need
of theſe Machines, and that is the perfect
Cupola; becauſe it is compoſed not only of
Arches, but alſo, in a Manner, of Cornices.
And who can conceive the innumerable Liga
tures that there are in theſe, which all wedge
together, and interſect one another both with
equal and unequal Angles? So that in whatſo
ever Part of the whole Cupola you lay a Stone,
or a Brick, you may be ſaid at the ſame time
to have laid a Key-ſtone to an infinite Number,
both of Arches, and Cornices. And when
theſe Cornices, or Arches are thus built one
upon the other, if the Work were inclined to
ruinate, where ſhould it begin, when the Joints
of every Stone are directed to one Centre with
equal Force and preſſure? Some of the Ancients
truſted ſo much to the Firmneſs of this Sort of
Structure, that they only made plain Cornices
of Brick at ſtated Diſtances, and filled up the
Interſpaces with Rubble. But I think, thoſe
acted much more prudently, who in raiſing
this Sort of Cupola, uſed the ſame Methods as
in Walling, to cramp and faſten the under
Cornices to the next above, and the Arches
too in ſeveral Places, eſpecially if they had not
plenty of Pit Sand to make very good Cement,
or if the Building was expoſed to South Winds,
or Blaſts from the Sea. You may likewiſe
turn the Angular Cupolas without a Centre,
if you make a perfect one in the Middle of the
Thickneſs of the Work. But here you will
have particular Occaſion for Ligatures to faſten
the weaker Parts of the outer one tightly to
the ſtronger Parts of that within. Yet it will
be neceſſary when you have laid one or two
Rows of Stone to make little light Stays, or
Catchers jutting out, on which, when thoſe
Rows are ſettled, you may ſet juſt Frame-work
enough to ſupport the next Courſes above, to
the Height of a few Feet, till they are ſufficiently
hardened; and then you may remove theſe
Frames, or Supports, higher and higher to
the other Courſes till you have finiſh'd the
whole Work. The other Vaults, both plain and
mixed, or camerated, muſt needs be turn'd
upon Centres. But I would have the firſt
Courſes, and the Heads of their Arches be
placed upon very ſtrong Seats; nor can I ap
prove the Method of thoſe who carry the
Wall clear up firſt, only leaving ſome Mould
ings, or Corbels, upon which, after a Time,
they turn their Arches; which muſt be a very
infirm and periſhable Sort of Work. The
true Way is to turn the Arch immediately,
and equally with the Courſes of the Wall
which is to ſupport it, that the Work may
have the ſtrongeſt Ligatures that is poſſible,
and grow in a Manner all of one Piece. The
Vacuities which are left between the Back of
the Sweep of the Arch, and the Upright of
the Wall it is turn'd from, call'd by Work
men, the Hips of the Arch, ſhould be fill'd
up, not with Dirt, or old Rubbiſh, but rather
with ſtrong ordinary Work, frequently knit
and jointed into the Wall.
*
I AM pleaſed with thoſe who, to avoid over
burthening the Arch, have ſtuffed up theſe
Vacuities with earthen Pots, turn'd with their
Mouths downwards, that they might not con
tain any wet, if it ſhould gather there, and
over theſe thrown in Fragments of Stone not
heavy, but perfecty ſound. Laſtly, in all Man
ner of Vaults, let them be of what Kind they
will, we ought to imitate Nature, who, when
ſhe has knit the Bones, faſtens the Fleſh with
Nerves, interweaving it every where with Li
gatures running in Breadth, Length, Height
and circularly. This artful Contexture is what
we ought to imitate in the joining of Stones
in Vaults. Theſe Things being compleated,
the next, and laſt Buſineſs is to cover them
over; a Work of the greateſt Conſequence in
Building, and no leſs difficult than neceſſary;
in effecting, and compleating of which, the
utmoſt Care and Study has been over and over
employed. Of this we are to treat; but firſt,
it will be proper to mention ſomething neceſ
ſary to be obſerved in working of Vaults; for
different Methods are to be taken in the Exe
cution of different Sorts: Thoſe which are
turn'd upon Centres muſt be finiſh'd out of
hand, without Intermiſſion; but thoſe which
are wrought without Centres muſt be diſcon
tinued, and left to ſettle Courſe by Courſe,
left new Work being added to the firſt before
it is dry, ſhould ruin the Whole. As to thoſe
burthening the Arch, have ſtuffed up theſe
Vacuities with earthen Pots, turn'd with their
Mouths downwards, that they might not con
tain any wet, if it ſhould gather there, and
over theſe thrown in Fragments of Stone not
heavy, but perfecty ſound. Laſtly, in all Man
ner of Vaults, let them be of what Kind they
will, we ought to imitate Nature, who, when
ſhe has knit the Bones, faſtens the Fleſh with
Nerves, interweaving it every where with Li
gatures running in Breadth, Length, Height
and circularly. This artful Contexture is what
we ought to imitate in the joining of Stones
in Vaults. Theſe Things being compleated,
the next, and laſt Buſineſs is to cover them
over; a Work of the greateſt Conſequence in
Building, and no leſs difficult than neceſſary;
in effecting, and compleating of which, the
utmoſt Care and Study has been over and over
employed. Of this we are to treat; but firſt,
it will be proper to mention ſomething neceſ
ſary to be obſerved in working of Vaults; for
different Methods are to be taken in the Exe
cution of different Sorts: Thoſe which are
turn'd upon Centres muſt be finiſh'd out of
hand, without Intermiſſion; but thoſe which
are wrought without Centres muſt be diſcon
tinued, and left to ſettle Courſe by Courſe,
left new Work being added to the firſt before
it is dry, ſhould ruin the Whole. As to thoſe