Alberti, Leone Battista, Architecture, 1755

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            <p type="main">
              <s>
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              drive the lower Wedges cloſer together, and
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              ſo keep them tight to their Duty. </s>
              <s>The filling
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              up, or ſtuffing between the Arches ſhould be
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              wrought with the ſtrongeſt Stone, and with the
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              cloſeſt Joynts that can poſſibly be made, But
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              if you have not a ſufficient Plenty of ſtrong
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              Stone to make your Stuffing of it, you may in
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              Caſe of Neceſſity make uſe of a weaker Sort;
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              ſtill provided that the whole Turn of the Arch,
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              and the Courſe of Work behind both the Sides
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              of it, be built entirely of ſtrong Stone.</s>
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            <p type="main">
              <s>THE next Work it to pave the Bridge; and
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              here we ſhould obſerve, that we ought to
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              make the Ground upon a Bridge as firm and
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              ſolid as the moſt durable Roads; we ſhould
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              raiſe it with Gravel or coarſe Sand, to the
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              Heighth of a Cubit, and then pave it with
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              Stone, filling up the Joints either with River
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              or Sea-ſand. </s>
              <s>But the Subſtrature or Layer
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              under the Pavement of a Bridge ought firſt to
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              be levelled and raiſed quite to the Top of the
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              Arches; with regular Maſonry, and then the
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              Pavement itſelf ſhould be cemented with Mor­
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              tar. </s>
              <s>In all other Reſpects we ſhould obſerve
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              the ſame Rules in paving a Bridge, as in pav­
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              ing a Road. </s>
              <s>The Sides ſhould be made firm
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              with the ſtrongeſt Work, and the reſt paved
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              with Stones, neither ſo ſmall as to be eaſily
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              raiſed and thrown out upon the leaſt Strain;
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              nor ſo large, that the Beaſts of Burden ſhould
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              ſlide upon them as upon Ice, and fall before
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              they meet with any Catch for their Foot. </s>
              <s>And
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              certainly we muſt own it to be of very great
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              Importance what Kind of Stone we uſe in our
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              Pavements, if we conſider how much they
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              muſt be worn by the continual grinding of
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              the Wheels, and the Hoofs of all Manner of
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              Cattle, when we ſee that even ſuch ſmall Ani­
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              mals as Ants, with conſtant paſſing up and
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              down, will wear Traces even in Flints.</s>
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            <p type="main">
              <s>I HAVE obſerved that the Ancients in many
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              Places, and particularly in the Way to
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              Tivoli,
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              paved the Middle of the Road with Flints, and
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              only covered the Sides with ſmall Gravel. </s>
              <s>This
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              they did, that the Wheels might make the leſs
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              Impreſſion, and that the Horſes Hoofs might
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              not want ſufficient Hold. </s>
              <s>In other Places, and
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              eſpecially over Bridges, there was a raiſed Way
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              on each Side, with Stone Steps, for Foot Paſ­
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              ſengers; and the Middle of the Way was leſt
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              for Beaſts and Carriages. </s>
              <s>Laſtly, the Ancients,
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              for this Sort of Work greatly commend Flints,
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              and eſpecially thoſe which are fulleſt of Holes;
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              not becauſe ſuch are the ſtrongeſt, but becauſe
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              they are the leaſt ſlippery. </s>
              <s>But we may make
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              uſe of any Sort of Stone, according to what
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              we have in greateſt Plenty, provided we only
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              uſe the ſtrongeſt we can get, and with thoſe
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              pave at leaſt that Part of the Way which is
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              moſt beaten by Cattle; and the Part moſt
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              beaten by them is always moſt level, becauſe
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              they always avoid all ſloping Ground as much
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              as they can. </s>
              <s>Let the Middle and higheſt Part
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              of the Way be laid with Flints, or whatever
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              other Stone you uſe, of the Thickneſs of a
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              Foot and an half, and the Breadth of at leaſt
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              a Foot, with the upper Face even, and ſo cloſe
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              compacted together that there are no Grevices
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              left in order to throw off the Rain. </s>
              <s>There
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              are three different Slopes for all Streets; either
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              towards the Middle, which is proper for a
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              broad Street, or to the Sides, which is leaſt
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              Hindrance to a narrow one; or elſe Length­
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              ways. </s>
              <s>But in this we are to govern ourſelves
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              according to the Conveniences and Advanta­
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              ges of our Drains and Currents, whether into
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              the Sea, Lake or River. </s>
              <s>A very good Riſe
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              for a Slope is half an Inch in every three Foot.
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              </s>
              <s>I have obſerved that the Riſe with which the
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              Ancients uſed to build their Bridges, was one
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              Foot in every thirty; and in ſome Parts, as
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              particularly at the Summit of the Bridge, four
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              Inches in every Cubit or Foot and an half;
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              but this was only for ſo little a Way, that a
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              Beaſt heavy loaden could get over it at one
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              Strain.</s>
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            <p type="head">
              <s>CHAP. VII.</s>
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            <p type="head">
              <s>
                <emph type="italics"/>
              Of Drains or Sewers, their different Sorts and Uſes; and of Rivers and
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              Canals for Ships.
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              </s>
            </p>
            <p type="main">
              <s>Drains or Sewers are look'd upon as
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              a Part of the Street, inaſmuch as they
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              are to be made under the Street, thro' the
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              Middle of it; and are of great Service, as well
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              in the paving and levelling, as in cleaning the
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              Streets; for which Reaſon they are by no
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              means to be neglected here. </s>
              <s>And indeed, may
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              we not very properly ſay that a Drain is a </s>
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          </chap>
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