Alberti, Leone Battista, Architecture, 1755

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    <archimedes>
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          <chap>
            <p type="main">
              <s>
                <pb xlink:href="003/01/202.jpg" pagenum="156"/>
              they are not deſigned to ſupport the Weight
                <lb/>
              of a vaulted Roof, but only a flat one of Sum­
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              mers and Rafters. </s>
              <s>Let their Thickneſs there­
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              fore be only one twentieth Part of their Height,
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              and let their Height be only once the Breadth
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              of the Front and an Half, and never more. </s>
              <s>At
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              the Angles of the Iſles come out Pilaſters from
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              the Naked of the Wall, running parallel with,
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              and on a Line with, the Columns, not leſs than
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              twice, nor more than three Times the Thick­
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              neſs of the Wall. </s>
              <s>Others, ſtill more to ſtrength­
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              en the Building, make ſuch a Pilaſter in the
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              Middle of the Row of Columns, in Breadth
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              three of the Diameters of one the Columns, or
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              at moſt four. </s>
              <s>The Columns themſelves too
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              muſt never have the ſame Solidity as thoſe
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              uſed in Temples; and therefore, if we make
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              our Colonades with an Architrave over it, we
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              may obſerve the following Rules. </s>
              <s>If the Co­
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              lumns are to be
                <emph type="italics"/>
              Corinthian,
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              ſubſtract a twelfth
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              Part from their Diameter; if
                <emph type="italics"/>
              Ionic,
                <emph.end type="italics"/>
              a tenth;
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              if
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              Doric,
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              a ninth. </s>
              <s>As for the Compoſition of
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              the other Members, the Capitals, Architrave,
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              Freze, Cornice, and the like, you may proceed
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              in the ſame Manner as in Temples.</s>
            </p>
            <p type="margin">
              <s>
                <margin.target id="marg35"/>
              *</s>
            </p>
            <p type="margin">
              <s>
                <margin.target id="marg36"/>
              †</s>
            </p>
            <p type="margin">
              <s>
                <margin.target id="marg37"/>
              ⤡</s>
            </p>
            <p type="head">
              <s>CHAP. XV.</s>
            </p>
            <p type="main">
              <s>
                <emph type="italics"/>
              Of Colonades both with Architraves and with Arches; what Sort of Columns
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              are to be uſed in Baſiliques, and what Cornices, and where they are to be
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              placed; of the Height and Wedth of Windows and their Gratings; of the
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              Roofs and Doors of Baſiliques, and their Ornaments.
                <emph.end type="italics"/>
              </s>
            </p>
            <p type="main">
              <s>Columns that are to have Arches over
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              them, ought by rights to be ſquare; for
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              if they were round, the Work would not be
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              true, becauſe the Heads of the Arches would
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              not lie plum upon the Solid of the Column
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              underneath; but as much as their Squares ex­
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              ceeded a Circle, ſo much of them would hang
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              over the Void. </s>
              <s>To remedy this Defect, the
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              beſt ancient Maſters placed over the Capitals
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              of their Columns another Abacus or Plinth, in
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              Thickneſs ſometimes one fourth and ſometimes
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              one fiſth Part of the Diameter of the Column;
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              the upper Part of this Plinth, which went off
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              with a Cima-recta, was equal to the greateſt
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              Breadth of the Top of the Capital, and its Pro­
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              jecture was equal to its Height, ſo that by this
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              means the Heads and Angles of the Arches had
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              a ſuller and firmer Seat. </s>
              <s>Colonades with
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              Arches, as well as thoſe with Architraves, are
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              various, ſome being thinner ſet, others cloſer,
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              and ſo on. </s>
              <s>In the cloſer Sort the Height of
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              the Void muſt be three Times and an half the
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              Breadth of the Aperture; in the thin Set, the
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              Height muſt be once the Breadth and two
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              thirds; in the leſs thin, the Height muſt be
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              twice the Breadth; in the cloſeſt of all, the
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              Breadth muſt be one third of the Height. </s>
              <s>We
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              have formerly obſerved, that an Arch is no­
                <lb/>
              thing elſe but a Beam bent. </s>
              <s>We may there­
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              fore give the ſame Ornaments to Arches as to
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              Architraves, according to the different Sorts of
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              Columns over which they are turned; beſides
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              which, if we would have our Structure very
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              rich, over the Heads of our Arches we may
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              run an Architrave, Freze, and Cornice in a
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              ſtraight Line, with the ſame Proportions as we
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              ſhould make them over Columns that ſhould
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              reach to that Height. </s>
              <s>But as the Baſilique is
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              ſometimes encompaſſed only with one ſingle
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              Iſle, and at other Times with two, the Place of
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              the Cornice over the Columns and Arches muſt
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              vary accordingly. </s>
              <s>In thoſe which are encom­
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              paſſed only with one ſingle Portico, having di­
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              vided the Height of your Wall into nine Parts,
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              the Cornice muſt go only to five; or if you
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              divide it into ſeven, to four. </s>
              <s>But in thoſe
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              which are to have double Iſles, the Cornice
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              muſt be placed at one third of the Height of
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              the Wall at leaſt, and at never more than three
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              eighths. </s>
              <s>We may alſo over the firſt Cornice,
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              as well for the greater Ornament as for real
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              Uſe, place other Columns, and eſpecially Pi­
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              laſters, directly plum over the Centers of the
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              Columns which are below them. </s>
              <s>And this
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              indeed is of great Service, as it maintains the
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              Strength and Firmneſs of the Ribs of the Work,
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              and adds Majeſty to it, and at the ſame Time
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              takes off much from the Weight and Expence
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              of the Wall; and over this upper Colonade
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              too we make a regular Entablature, according
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              to the Order of the Columns. </s>
              <s>In Baſiliques
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              with double Side Iſles, we may raiſe three Rows
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              of Columns in this Manner one above another;
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              but in others we ſhould make but two. </s>
              <s>Where </s>
            </p>
          </chap>
        </body>
      </text>
    </archimedes>
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