Alberti, Leone Battista, Architecture, 1755

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            <p type="main">
              <s>
                <pb xlink:href="003/01/309.jpg" pagenum="229"/>
              the ſloweſt Current will be the moſt laſting:
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              Which may be ſomewhat illuſtrated by the
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              Compariſon of a Man that deſcends from a
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              ſteep Hill, and who comes down not direct
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              and as faſt as he can, but fetching different
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              Compaſſes about the Sides, ſometimes to the
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              right Hand, and ſometimes to the Left. </s>
              <s>The
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              Rapidity of the Stream proceeds from the Steep­
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              neſs of the Channel. </s>
              <s>A Current either too
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              ſwift or too ſlow, is inconvenient. </s>
              <s>The for­
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              mer demoliſhes the Banks; the latter produ­
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              ces Weeds, and is eaſily frozen. </s>
              <s>Making the
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              River narrower may perhaps force the Water
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              to riſe higher, and another Way to make it
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              deeper is digging the Channel, lower. </s>
              <s>Deep­
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              ening the Channel, removing Impediments,
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              and clearing the River are all done by the
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              ſame Methods and for the ſame Purpoſes,
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              whereof we ſhall ſpeak preſently: But deepen­
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              ing the Bottom of a River will be in vain, un­
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              leſs we go on to do it quite away to the Sea,
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              in order to give the Stream its due Slope all
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              the Way.</s>
            </p>
            <p type="head">
              <s>CHAP. XI.</s>
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            <p type="head">
              <s>
                <emph type="italics"/>
              Of Canals; how they are to be kept well ſupplied with Water, and the Uſes
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              of them not obſtructed.
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              </s>
            </p>
            <p type="main">
              <s>We now proceed to ſpeak of Canals.
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              </s>
              <s>What we are to provide for in theſe,
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              is that they be well ſupplied with Water, and
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              that the Uſes for which they are intended be
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              not obſtructed. </s>
              <s>There are two Ways of prevent­
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              ing their failing. </s>
              <s>The firſt is to have a large
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              Quantity of Water conſtantly running into them
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              from ſome other Stream; the ſecond is to con­
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              trive that they keep what does come into them
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              as long as can be. </s>
              <s>The Water is to be brought
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              into Canals in the manner above ſet down: and
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              our Diligence muſt prevent their Uſes from be­
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              ing obſtructed, by often cleaning them, and
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              removing whatever Incumbrances may be
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              brought into them. </s>
              <s>A Canal is ſaid to be a
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              ſleeping River; and it ſhould therefore have
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              all the ſame Properties which a River has, and
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              eſpecially its Bottom and Sides ſhould be per­
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              fectly ſound, that the Water may neither be
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              ſucked up, nor run out at any Cracks. </s>
              <s>It
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              ſhould be more deep than broad, as well for the
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              better carrying off all Sorts of Veſſels, as that it
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              may be leſs exhauſted by the Sun and breed the
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              fewer Weeds. </s>
              <s>A great many Canals were cut
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              from the
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              Euphrates
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              to the
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              Tygris,
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              becauſe the
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              Channel of the former lay higher than that of
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              the Latter.
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              Lombardy
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              lying between the
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              Po
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                <lb/>
              and the
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              Adige,
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              is every where navigable by
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              Canals; an Advantage which it gains by ly­
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              ing all upon a Flat.
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              Diodorus
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              tells us, that
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              when
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              Ptolomey
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              went out of the Mouth of the
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                <emph type="italics"/>
              Nile,
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              he opened a Canal on Purpoſe, and had
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              it ſtopp'd up as ſoon as he was got through it.
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              </s>
              <s>The Remedies for the ſeveral Faults of either
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              Canals or Rivers are confining, clearing and
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              ſtopping them. </s>
              <s>Rivers are confined by arti­
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              ficial Banks. </s>
              <s>The Line of ſuch Banks ſhould
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              not reſtrain the River at once, but by degrees,
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              by means of an eaſy Slope. </s>
              <s>When you would
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              ſet it at Liberty again from a narrow Channel
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              into a wider Breadth, you muſt obſerve the
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              ſame Method, not let it out at once, but gently,
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              leſt upon too ſudden an Enlargment it does
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              Miſchief by Eddies and Whirlpools. </s>
              <s>The River
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                <emph type="italics"/>
              Melas
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              uſed of old to run into the
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              Euphrates;
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                <lb/>
              but King
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              Artanatrix,
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              perhaps out of a Deſire
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              to make his Name famous, ſtopp'd it up and
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              overſlowed the Country all round: but ſoon
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              afterwards the Waters return'd with ſuch Ed­
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              dies and ſo much Fury that they tore up all
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              that reſiſted them, waſhed away a great many
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              Eſtates, and laid Waſte a great Part of
                <emph type="italics"/>
              Phrygia
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                <lb/>
              and
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              Galatia.
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              </s>
              <s> The
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              Roman Senate
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              fined the
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              King for this audacious Attempt, in thirty Ta­
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              lents. </s>
              <s>Nor is it foreign to our Purpoſe juſt to
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              mention what we read of
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              Iphicrates
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              the
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              A­
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              thenian,
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              that when he was beſieging
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              Stymphalus
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              in
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              Arcadia
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              he attempted with a vaſt Quantity
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              of Spunge to ſtop up the River
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              Eraſinus
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              which
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              enters into the Hill and riſes up again in the
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              Country of
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              Arges;
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              but by the Admonition of
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                <emph type="italics"/>
              Jupiter
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              he laid aſide the Deſign. </s>
              <s>I adviſe
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              therefore, that your artificial Bank be made as
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              ſtrong as poſſible. </s>
              <s>This Strength muſt be
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              owing to the Solidity of your Materials, your
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              Method of putting them together, and the
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              Breadth of the whole Work. </s>
              <s>Where it is ne­
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              ceſſary that the Water ſhould run over this
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              Bank, do not let the Outſide of it be a Per­
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              pendicular, but fall in an eaſy Slope, that the
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              Water may run down it eaſily and not form
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              any Eddies. </s>
              <s>If in its Fall it begins to dig up </s>
            </p>
          </chap>
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      </text>
    </archimedes>
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