Bion, Nicolas, Traité de la construction et principaux usages des instruments de mathématique, 1723

Table of Notes

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          <p>
            <s xml:id="echoid-s5463" xml:space="preserve">
              <pb o="169" file="183" n="183" rhead="POUR LEVER LES PLANS. Liv. IV. Ch. VII."/>
            guille qui indique le Septentrion; </s>
            <s xml:id="echoid-s5464" xml:space="preserve">& </s>
            <s xml:id="echoid-s5465" xml:space="preserve">le trouvant, par exemple, de
              <lb/>
            80 deg. </s>
            <s xml:id="echoid-s5466" xml:space="preserve">la déclinaiſon de ladite ligne ſera d'autant de degrez. </s>
            <s xml:id="echoid-s5467" xml:space="preserve">Pre-
              <lb/>
            nez enſuite de la même maniere la déclinaiſon de la ligne AE, que
              <lb/>
            je ſuppoſe de 215 deg. </s>
            <s xml:id="echoid-s5468" xml:space="preserve">ôtez le petit nombre 80, du plus grand 215,
              <lb/>
            reſtera 135, qu'il faut ſouſtraire de 180 ce dernier reſte ſera 45 d.
              <lb/>
            </s>
            <s xml:id="echoid-s5469" xml:space="preserve">pour la valeur de l'angle propoſé à meſurer.</s>
            <s xml:id="echoid-s5470" xml:space="preserve"/>
          </p>
          <p>
            <s xml:id="echoid-s5471" xml:space="preserve">Mais ſi la déclinaiſon de la ligne AD n'étoit, par exemple, que
              <lb/>
            de 30 deg. </s>
            <s xml:id="echoid-s5472" xml:space="preserve">& </s>
            <s xml:id="echoid-s5473" xml:space="preserve">que celle de la ligne AE fût de 265, la difference de
              <lb/>
            ces deux déclinaiſons qui eſt de 235, ſeroit trop grande pour être
              <lb/>
            ôtée de 180; </s>
            <s xml:id="echoid-s5474" xml:space="preserve">c'eſt pourquoi en ce cas il faudroit ôter 180 du plus
              <lb/>
            grand nombre 235, le reſte 55 ſera la valeur de l'angle propoſé.</s>
            <s xml:id="echoid-s5475" xml:space="preserve"/>
          </p>
          <p>
            <s xml:id="echoid-s5476" xml:space="preserve">Quand on meſure des angles avec la Bouſſole, il n'eſt pas neceſ-
              <lb/>
            ſaire d'avoir aucun égard à la variation de l éguille aimantée, puiſ-
              <lb/>
            que cette variation ſera toûjours la même en toutes les differentes
              <lb/>
            poſitions de l'éguille, pourvü toutefois qu'il n'y ait pas de fer qui la
              <lb/>
            faſſe dévoïer; </s>
            <s xml:id="echoid-s5477" xml:space="preserve">& </s>
            <s xml:id="echoid-s5478" xml:space="preserve">lorſqu'on ne peut poſer la Bouſſole proche du plan,
              <lb/>
            par quelque empêchement, il ſuffira de la placer bien parallelement,
              <lb/>
            comme la figure le montre, elle fera le même effet.</s>
            <s xml:id="echoid-s5479" xml:space="preserve"/>
          </p>
        </div>
        <div xml:id="echoid-div447" type="section" level="1" n="213">
          <head xml:id="echoid-head324" xml:space="preserve">USAGE III.</head>
          <head xml:id="echoid-head325" style="it" xml:space="preserve">Pour lever le Plan d'une Forêt, d'un Marais ou d'un Chemin
            <lb/>
          avec ſes détours.</head>
          <p>
            <s xml:id="echoid-s5480" xml:space="preserve">SOit propoſé à lever le Plan d'un Marais ou Etang ABCDE,
              <lb/>
              <note position="right" xlink:label="note-183-01" xlink:href="note-183-01a" xml:space="preserve">Fig. 3.</note>
            dans lequel on ne peut entrer. </s>
            <s xml:id="echoid-s5481" xml:space="preserve">Pour ces ſortes d'operations il faut
              <lb/>
            qu'il y ait ſur la Bouſſole 2 pinules immobiles attachées ſur la li-
              <lb/>
            gne qui tend du Septentrion au Midi. </s>
            <s xml:id="echoid-s5482" xml:space="preserve">Faites planter des piquets aſ-
              <lb/>
            ſez longs & </s>
            <s xml:id="echoid-s5483" xml:space="preserve">bien à plomb, de maniere qu'ils ſoient dans les lignes
              <lb/>
            paralleles aux côtes qui ſont l'enceinte du Marais; </s>
            <s xml:id="echoid-s5484" xml:space="preserve">placez la Bouſſo-
              <lb/>
            le ſur ſon pied dans une ſituation horiſontale; </s>
            <s xml:id="echoid-s5485" xml:space="preserve">bornaiez deux de ces
              <lb/>
            piquets par les fentes des pinules, mettant toûjours auprès de l'œil
              <lb/>
            celle qui eſt ſur la partie méridionale de la Bouſſole; </s>
            <s xml:id="echoid-s5486" xml:space="preserve">puis ayant tra-
              <lb/>
            cé ſur du papier une figure qui repreſente à peu près le plan du Ma-
              <lb/>
            rais, écrivez ſur chaque ligne le nombre des degrez que marquera
              <lb/>
            l'éguille lorſqu'elle ſera arrêtée. </s>
            <s xml:id="echoid-s5487" xml:space="preserve">Faites en même tems meſurer avec
              <lb/>
            la toiſe la longueur exacte de chaque côté du Marais, & </s>
            <s xml:id="echoid-s5488" xml:space="preserve">marquez-en
              <lb/>
            la valeur ſur chaque ligne correſpondante de vôtre mémorial. </s>
            <s xml:id="echoid-s5489" xml:space="preserve">Lorſ-
              <lb/>
            que vous aurez fait tout le tour du Marais, les degrez marquez par
              <lb/>
            l'éguille de la Bouſſole ſerviront à former les angles de la figure, & </s>
            <s xml:id="echoid-s5490" xml:space="preserve">la
              <lb/>
            longueur de chaque ligne déterminera tout le plan du Marais pro-
              <lb/>
            poſé.</s>
            <s xml:id="echoid-s5491" xml:space="preserve"/>
          </p>
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