Alberti, Leone Battista, Architecture, 1755

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    <archimedes>
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        <body>
          <chap>
            <p type="main">
              <s>
                <pb xlink:href="003/01/072.jpg" pagenum="56"/>
              Beams ought alſo to be related to one another;
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              that is, they ſhould be of the ſame Kind of
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              Timber, and raiſed in the ſame Wood, ex­
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              poſed if poſſible to the ſame Winds, and fell'd
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              the ſame Day; that being endued with the
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              ſame natural Strength, they may bear their
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              Shares equally in the Service. </s>
              <s>Let the Beds for
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              the Beams be exactly level, and perfectly firm
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              and ſtrong; and in laying them take care
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              that the Timber does not touch any Lime,
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              and let it have clear and open Vents all about
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              it, that it may not be tainted by the Contact
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              of any other Materials, nor decay by being
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              too cloſe ſhut up. </s>
              <s>For a Bed for the Beams,
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              ſpread under them either Fern, a very dry
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              Kind of Herb, or Aſhes, or rather Lees of
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                <arrow.to.target n="marg9"/>
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              Oil with the bruiſed Olives. </s>
              <s>But if your Tim­
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              ber is ſo ſhort, that you cannot make a Beam
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              of one Piece, you muſt join two or more to­
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              gether, in ſuch a Manner as to give them the
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              Strength of an Arch; that is to ſay, ſo that
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              the upper Line of the compacted Beam, can­
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              not poſſibly by any Preſſure become ſhorter;
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              and on the contrary, that the lower Line can­
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              not grow longer: And there muſt be a Sort
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              of Cord to bind the two Beams together,
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              which ſhove one another with their Heads,
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              with a ſtrong Ligature. </s>
              <s>The Rafters, and all
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              the reſt of the Wood-work, depend upon the
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              Goodneſs and Soundneſs of the Beams; being
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              nothing elſe but Beams ſplit. </s>
              <s>Boards or Planks
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              are thought to be inconvenient if too thick, be­
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              cauſe whenever they begin to warp they throw
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              out the Nails; and thin Boards, eſpecially in
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              Coverings expoſed to the Air, they ſay, muſt
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              be faſtened with Nails in Pairs, ſo as to ſe­
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              cure the Corners, the Sides and the Middle.
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              </s>
              <s>They tell us, that ſuch Nails as are to bear any
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              tranſverſe Weight, muſt be made thick; but as
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              for others, it matters not if they are thinner;
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              but then they muſt be longer, and have
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              broader Heads.</s>
            </p>
            <p type="margin">
              <s>
                <margin.target id="marg9"/>
              *</s>
            </p>
            <p type="main">
              <s>BRASS Nails are moſt durable in the Air, or
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              in wet; but I have found the Iron ones to be
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              ſtronger under Cover. </s>
              <s>For fattening of the
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              Rafters together, wooden Pins are much uſed.
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              </s>
              <s>Whatever we have here ſaid of Coverings of
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              Wood, muſt be obſerved alſo with relation to
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              thoſe of Stone; for ſuch Stones as have Veins,
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              or Faults running croſſways, muſt be rejected
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              for the making of Beams, and uſed in Columns;
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              or if there are any ſmall inconſiderable Faults,
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              the Side of the Stone in which it appears,
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              when it is uſed, muſt be laid downwards,
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              Veins running longways in Beams of any Sort,
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              are more excuſable than tranſverſe ones.
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              </s>
              <s>Tables, or Scantlings of Stones alſo, as well
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              for other Reaſons, as upon Account of their
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              Weight, muſt not be made too thick. </s>
              <s>Laſtly,
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              the Beams, Rafters, and Planks that are uſed
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              in Coverings, whether of Wood, or Stone,
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              muſt be neither ſo thin, nor ſo few as not to
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              be ſufficient for upholding themſelves, and their
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              Burthens; nor ſo thick, or ſo crouded as to
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              take from the Beauty, and Symmetry of the
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              Work; but thoſe are things we ſhall ſpeak of
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              elſewhere. </s>
              <s>And thus much for Coverings of
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              ſtraight Lines; unleſs it may be proper to men­
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              tion one Thing which is in my Opinion tobe neg­
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              lected in no Sort of Structure. </s>
              <s>The Philoſophers
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              have obſerved, that Nature in forming the Bo­
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              dies of Animals, always takes care to finiſh her
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              Work in ſuch a Manner, that the Bones ſhould
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              all communicate, and never be ſeperate one
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              from the other: So we alſo ſhould connect the
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              Ribs togther, and faſten them together well
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              with Nerves and Ligatures; ſo that the Com­
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              munication among the Ribs ſhould be ſo con­
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              tinued, that if all the reſt of the Structure
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              failed, the Frame of the Work ſhould yet
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              ſtand firm and ſtrong with all its Parts and
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              Members.</s>
            </p>
            <p type="head">
              <s>CHAP. XIII.</s>
            </p>
            <p type="head">
              <s>
                <emph type="italics"/>
              Of Coverings, or Roofs of Curve Lines; of Arches, their Difference and Con­
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              ſtruction, and how to ſet the Stones in an Arch.
                <emph.end type="italics"/>
              </s>
            </p>
            <p type="main">
              <s>We come now to ſpeak of Roofs made
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              of Curve Lines, and we are firſt to
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              conſider thoſe Particulars wherein they exactly
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              agree with Coverings of ſtrait Lines. </s>
              <s>A curvili­
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              near Roof is compoſed of Arches; and we have
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              already ſaid that an Arch is nothing but a
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              Beam bent. </s>
              <s>We might alſo here mention the
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              Ligatures, and thoſe Things which muſt be
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              uſed for filling up the Vacuities; but I would
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              be underſtood more clearly, by explaining
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              what I take to be the Nature of an Arch, and
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              of what Parts it conſiſts.</s>
            </p>
            <p type="main">
              <s>I SUPPOSE then, that Men learnt at firſt to turn
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              Arches from this: They ſaw that two Beams
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              </s>
            </p>
          </chap>
        </body>
      </text>
    </archimedes>
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