Alberti, Leone Battista, Architecture, 1755

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              <s>
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              each other, like the Teeth of a Comb; as a Man
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              locks his right Hand Fingers into his left; and
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              the Interſpaces they filled up with any common
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              Stone, and eſpecially with Pumice Stone, which
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              is univerſally agreed to be the propereſt of all,
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              for the ſtuffing Work of Vaults. </s>
              <s>In building
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              either Arches or Vaults, we muſt make uſe of
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              Centres. </s>
              <s>Theſe are a Kind of Frames made
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              with the Sweep of an Arch of any rough Boards
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              juſt clapt together for a ſhort Service, and
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              covered either with Hurdles, Ruſhes, or any
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              ſuch common Stuff, in order to ſupport the
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              Work till it is ſettled and hardened. </s>
              <s>Yet there
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              is one ſort of Vault which ſtands in no Need
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              of theſe Machines, and that is the
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              perfect
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              Cupola;
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              becauſe it is compoſed not only of
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              Arches, but alſo, in a Manner, of Cornices.
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              </s>
              <s>And who can conceive the innumerable Liga­
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              tures that there are in theſe, which all wedge
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              together, and interſect one another both with
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              equal and unequal Angles? </s>
              <s>So that in whatſo­
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              ever Part of the whole Cupola you lay a Stone,
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              or a Brick, you may be ſaid at the ſame time
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              to have laid a Key-ſtone to an infinite Number,
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              both of Arches, and Cornices. </s>
              <s>And when
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              theſe Cornices, or Arches are thus built one
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              upon the other, if the Work were inclined to
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              ruinate, where ſhould it begin, when the Joints
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              of every Stone are directed to one Centre with
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              equal Force and preſſure? </s>
              <s>Some of the Ancients
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              truſted ſo much to the Firmneſs of this Sort of
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              Structure, that they only made plain Cornices
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              of Brick at ſtated Diſtances, and filled up the
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              Interſpaces with Rubble. </s>
              <s>But I think, thoſe
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              acted much more prudently, who in raiſing
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              this Sort of Cupola, uſed the ſame Methods as
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              in Walling, to cramp and faſten the under
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              Cornices to the next above, and the Arches
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              too in ſeveral Places, eſpecially if they had not
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              plenty of Pit Sand to make very good Cement,
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              or if the Building was expoſed to South Winds,
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              or Blaſts from the Sea. </s>
              <s>You may likewiſe
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              turn the Angular Cupolas without a Centre,
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              if you make a perfect one in the Middle of the
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              Thickneſs of the Work. </s>
              <s>But here you will
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              have particular Occaſion for Ligatures to faſten
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              the weaker Parts of the outer one tightly to
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              the ſtronger Parts of that within. </s>
              <s>Yet it will
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              be neceſſary when you have laid one or two
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              Rows of Stone to make little light Stays, or
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              Catchers jutting out, on which, when thoſe
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              Rows are ſettled, you may ſet juſt Frame-work
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              enough to ſupport the next Courſes above, to
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              the Height of a few Feet, till they are ſufficiently
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              hardened; and then you may remove theſe
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              Frames, or Supports, higher and higher to
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              the other Courſes till you have finiſh'd the
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                <arrow.to.target n="marg10"/>
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              whole Work. </s>
              <s>The other Vaults, both plain and
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              mixed, or camerated, muſt needs be turn'd
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              upon Centres. </s>
              <s>But I would have the firſt
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              Courſes, and the Heads of their Arches be
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              placed upon very ſtrong Seats; nor can I ap­
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              prove the Method of thoſe who carry the
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              Wall clear up firſt, only leaving ſome Mould­
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              ings, or Corbels, upon which, after a Time,
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              they turn their Arches; which muſt be a very
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              infirm and periſhable Sort of Work. </s>
              <s>The
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              true Way is to turn the Arch immediately,
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              and equally with the Courſes of the Wall
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              which is to ſupport it, that the Work may
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              have the ſtrongeſt Ligatures that is poſſible,
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              and grow in a Manner all of one Piece. </s>
              <s>The
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              Vacuities which are left between the Back of
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              the Sweep of the Arch, and the Upright of
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              the Wall it is turn'd from, call'd by Work­
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              men, the
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              Hips
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              of the Arch, ſhould be fill'd
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              up, not with Dirt, or old Rubbiſh, but rather
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              with ſtrong ordinary Work, frequently knit
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              and jointed into the Wall.</s>
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              *</s>
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            <p type="main">
              <s>I AM pleaſed with thoſe who, to avoid over­
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              burthening the Arch, have ſtuffed up theſe
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              Vacuities with earthen Pots, turn'd with their
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              Mouths downwards, that they might not con­
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              tain any wet, if it ſhould gather there, and
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              over theſe thrown in Fragments of Stone not
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              heavy, but perfecty ſound. </s>
              <s>Laſtly, in all Man­
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              ner of Vaults, let them be of what Kind they
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              will, we ought to imitate Nature, who, when
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              ſhe has knit the Bones, faſtens the Fleſh with
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              Nerves, interweaving it every where with Li­
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              gatures running in Breadth, Length, Height
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              and circularly. </s>
              <s>This artful Contexture is what
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              we ought to imitate in the joining of Stones
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              in Vaults. </s>
              <s>Theſe Things being compleated,
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              the next, and laſt Buſineſs is to cover them
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              over; a Work of the greateſt Conſequence in
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              Building, and no leſs difficult than neceſſary;
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              in effecting, and compleating of which, the
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              utmoſt Care and Study has been over and over
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              employed. </s>
              <s>Of this we are to treat; but firſt,
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              it will be proper to mention ſomething neceſ­
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              ſary to be obſerved in working of Vaults; for
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              different Methods are to be taken in the Exe­
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              cution of different Sorts: Thoſe which are
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              turn'd upon Centres muſt be finiſh'd out of
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              hand, without Intermiſſion; but thoſe which
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              are wrought without Centres muſt be diſcon­
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              tinued, and left to ſettle Courſe by Courſe,
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              left new Work being added to the firſt before
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              it is dry, ſhould ruin the Whole. </s>
              <s>As to thoſe
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              </s>
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