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

Table of Notes

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            <s xml:id="echoid-s5426" xml:space="preserve">
              <pb o="168" file="182" n="182" rhead="CONSTRUCT. ET USAGES DE LA BOUSSOLE"/>
            n'y en ait de caché, car le fer change entierement la direction de
              <lb/>
            l'Eguille aimantée.</s>
            <s xml:id="echoid-s5427" xml:space="preserve"/>
          </p>
          <p>
            <s xml:id="echoid-s5428" xml:space="preserve">Je ſuppoſe que le Pivot ſur lequel eſt poſée la chape de l'Eguille
              <lb/>
            eſt au centre d'un cercle diviſé en 360 deg. </s>
            <s xml:id="echoid-s5429" xml:space="preserve">ou 4 fois 90, dont le
              <lb/>
            premier degré eſt dans la ligne qui tend du Septentrion au Midi, & </s>
            <s xml:id="echoid-s5430" xml:space="preserve">
              <lb/>
            que la Bouſſole eſt quarrée, comme elle eſt ici repreſentée.</s>
            <s xml:id="echoid-s5431" xml:space="preserve"/>
          </p>
          <p>
            <s xml:id="echoid-s5432" xml:space="preserve">Appliquez le long du Mur le côté de la Bouſſole où eſt la marque
              <lb/>
            du Septentrion; </s>
            <s xml:id="echoid-s5433" xml:space="preserve">le nombre des degrez où s'arrêtera l'éguille aiman-
              <lb/>
            tée, marquera la déclinaiſon du Mur, & </s>
            <s xml:id="echoid-s5434" xml:space="preserve">dequel côté. </s>
            <s xml:id="echoid-s5435" xml:space="preserve">Si, par exem-
              <lb/>
            ple, la pointe de l'éguille qui marque le Septentrion tend vers le
              <lb/>
            Mur, c'eſt une marque qu'il peut être éclairé du Soleil à midi; </s>
            <s xml:id="echoid-s5436" xml:space="preserve">& </s>
            <s xml:id="echoid-s5437" xml:space="preserve">ſi
              <lb/>
            elle s'arrête ſur le 30 deg. </s>
            <s xml:id="echoid-s5438" xml:space="preserve">compté du Septentrion vers l'Orient, la
              <lb/>
            déclinaiſon eſt d'autant de degrez du Midi à l'Orient. </s>
            <s xml:id="echoid-s5439" xml:space="preserve">Si elle s'ar-
              <lb/>
            rête ſur le 30 degré compté du Septentrion vers l'Occident, la dé-
              <lb/>
            clinaiſon eſt d'autant de degrez du Midi à l'Occident.</s>
            <s xml:id="echoid-s5440" xml:space="preserve"/>
          </p>
          <p>
            <s xml:id="echoid-s5441" xml:space="preserve">Mais comme l'Eguille aimantée décline preſentement à Paris
              <lb/>
            d'environ 12 deg & </s>
            <s xml:id="echoid-s5442" xml:space="preserve">15 min. </s>
            <s xml:id="echoid-s5443" xml:space="preserve">au Nord Oüeſt; </s>
            <s xml:id="echoid-s5444" xml:space="preserve">pour corriger ce dé-
              <lb/>
            faut on doit les ajoûter au nombre des degrez marquez par l'Eguil-
              <lb/>
            le lorſque la déclinaiſon eſt vers l'Orient. </s>
            <s xml:id="echoid-s5445" xml:space="preserve">Il faut au contraire les ô-
              <lb/>
            ter lorſque la déclinaiſon eſt du côté d'Occident.</s>
            <s xml:id="echoid-s5446" xml:space="preserve"/>
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          <p>
            <s xml:id="echoid-s5447" xml:space="preserve">Ainſi ſuppoſant, comme nous venons de faire, que l'Eguille ſoit
              <lb/>
            arrêtée ſur le 30
              <emph style="sub">me</emph>
            degré vers l'Orient; </s>
            <s xml:id="echoid-s5448" xml:space="preserve">la déclinaiſon du Mur ſera
              <lb/>
            de 42 deg. </s>
            <s xml:id="echoid-s5449" xml:space="preserve">15 min. </s>
            <s xml:id="echoid-s5450" xml:space="preserve">du Midi vers Orient. </s>
            <s xml:id="echoid-s5451" xml:space="preserve">Mais ſi l'Eguille s'arrête
              <lb/>
            du côté d'Occident ſur le 30
              <emph style="sub">me</emph>
            degré, la déclinaiſon du Mur ſera
              <lb/>
            de 17 deg. </s>
            <s xml:id="echoid-s5452" xml:space="preserve">45 min. </s>
            <s xml:id="echoid-s5453" xml:space="preserve">du Midivers l'Occident.</s>
            <s xml:id="echoid-s5454" xml:space="preserve"/>
          </p>
          <p>
            <s xml:id="echoid-s5455" xml:space="preserve">Que ſi la pointe de l'Eguille aimantée qui marque le Midi,
              <lb/>
            tend vers le Mur, c'eſt une marque que le Midi eſt de l'autre côté
              <lb/>
            du Mur, & </s>
            <s xml:id="echoid-s5456" xml:space="preserve">par conſequent que la face dont on veut trouver la dé-
              <lb/>
            clinaiſon, ne ſera point éclairée du Soleil à midi; </s>
            <s xml:id="echoid-s5457" xml:space="preserve">c'eſt pourquoi ſa
              <lb/>
            déclinaiſon ſera du Septentrion à l'Orient, ou à l'Occident ſelon
              <lb/>
            qu'il ſera tourné vers l'une ou l'autre de ces Parties du Monde. </s>
            <s xml:id="echoid-s5458" xml:space="preserve">Ceci
              <lb/>
            ſera plus amplement expliqué en parlant des Cadrans Solaires.</s>
            <s xml:id="echoid-s5459" xml:space="preserve"/>
          </p>
        </div>
        <div xml:id="echoid-div445" type="section" level="1" n="212">
          <head xml:id="echoid-head322" xml:space="preserve">USAGE II.</head>
          <head xml:id="echoid-head323" style="it" xml:space="preserve">Pour meſurer un angle ſur la terre avec la Bouſſole.</head>
          <p>
            <s xml:id="echoid-s5460" xml:space="preserve">SOit l'angle DAE propoſé à meſurer. </s>
            <s xml:id="echoid-s5461" xml:space="preserve">Appliquez le long d'une
              <lb/>
              <note position="left" xlink:label="note-182-01" xlink:href="note-182-01a" xml:space="preserve">Fig. 2.</note>
            deslignes qui forment l'angle, comme lelong de la ligne AD, le
              <lb/>
            côté dela Bouſſole où eſt la marque du Septentrion; </s>
            <s xml:id="echoid-s5462" xml:space="preserve">faites en ſorte
              <lb/>
            quel' Eguille tourne librement ſur ſon pivot, & </s>
            <s xml:id="echoid-s5463" xml:space="preserve">quand elle ſera ar-
              <lb/>
            rêtée, prenez garde quel nombre de degrez répond à la pointe de l'é-
              <lb/>
            </s>
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