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-s8547" xml:space="preserve">
              <pb o="272" file="288" n="288" rhead="CONSTRUCT. ET USAGES DES INSTRUMENS"/>
            entre le point où il ſe leve & </s>
            <s xml:id="echoid-s8548" xml:space="preserve">le vrai Eſt; </s>
            <s xml:id="echoid-s8549" xml:space="preserve">& </s>
            <s xml:id="echoid-s8550" xml:space="preserve">l'amplitude Occidentale
              <lb/>
            eſt l'arc de l'horiſon compris entre le point où il ſe couche & </s>
            <s xml:id="echoid-s8551" xml:space="preserve">le vrai
              <lb/>
            Oüeſt</s>
          </p>
          <p>
            <s xml:id="echoid-s8552" xml:space="preserve">Les Aſtres dont la déclinaiſon eſt Septentrionale, ont auſſi leur
              <lb/>
            amplitude Septentrionale, & </s>
            <s xml:id="echoid-s8553" xml:space="preserve">ceux qui l'ont Méridionalc ont leur
              <lb/>
            amplitude du même côté. </s>
            <s xml:id="echoid-s8554" xml:space="preserve">Plus les Aſtres ont de déclinaiſon, plus
              <lb/>
            ils ont d'amplitude; </s>
            <s xml:id="echoid-s8555" xml:space="preserve">les obliquitez de la Sphere augmentent auſſi les
              <lb/>
            amplitudes des Aſtres; </s>
            <s xml:id="echoid-s8556" xml:space="preserve">car dans la Sphere droite les amplitudes
              <lb/>
            des Aſtres ſont préciſément égales à leurs déclinaiſons, & </s>
            <s xml:id="echoid-s8557" xml:space="preserve">dans la
              <lb/>
            Sphere oblique elles ſont plus grandes.</s>
            <s xml:id="echoid-s8558" xml:space="preserve"/>
          </p>
          <p>
            <s xml:id="echoid-s8559" xml:space="preserve">On aura par chaque obſervation une autre amplitude de l'Aſtre,
              <lb/>
            que l'on peut nommer l'amplitude obſervée, qui eſt la diſtance de
              <lb/>
            l'Eſt de la Bouſſole, juſqu'au point de l'horiſon où l'Aſtre ſe leve, ou
              <lb/>
            la diſtance de l'Oüeſt de la Bouſſole, juſqu'au point où il ſe couche.</s>
            <s xml:id="echoid-s8560" xml:space="preserve"/>
          </p>
          <p>
            <s xml:id="echoid-s8561" xml:space="preserve">Cette amplitude s'obſerve en regardant par les ouvertures ou par
              <lb/>
            les pinules du compas de variation le lever ou le coucher de l'Aſtre;
              <lb/>
            </s>
            <s xml:id="echoid-s8562" xml:space="preserve">& </s>
            <s xml:id="echoid-s8563" xml:space="preserve">comme le ſil qui traverſe & </s>
            <s xml:id="echoid-s8564" xml:space="preserve">paſſe par le centre de l'inſtrument, re-
              <lb/>
            preſente le raïon de l'Aſtre, les degrez de la roſe compris depuis ce
              <lb/>
            fil juſqu'à l'Eſt ou l'Oüeſt du Compas ou Bouſſole, marquent les de-
              <lb/>
            grez de l'amplitude obſervée; </s>
            <s xml:id="echoid-s8565" xml:space="preserve">enſuite comparant l'amplitude de la
              <lb/>
            table calculée avec l'amplitude obſervée, on connoîtra la variation
              <lb/>
            de l'éguille, ſi elle en a, de la maniere que nous allons expliquer.</s>
            <s xml:id="echoid-s8566" xml:space="preserve"/>
          </p>
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        <div xml:id="echoid-div573" type="section" level="1" n="283">
          <head xml:id="echoid-head410" xml:space="preserve">EXEMPLE.</head>
          <p>
            <s xml:id="echoid-s8567" xml:space="preserve">Etanten Mer le 15
              <emph style="sub">me</emph>
            jour de Mai de l'année 1715, à 45 d. </s>
            <s xml:id="echoid-s8568" xml:space="preserve">de la-
              <lb/>
            titude Seprentrionale, je connois par une Table calculée que la dé-
              <lb/>
            clinaiſon du Soleil eſt de 19 d. </s>
            <s xml:id="echoid-s8569" xml:space="preserve">Septentrionale, & </s>
            <s xml:id="echoid-s8570" xml:space="preserve">ſon amplitude O-
              <lb/>
            rientale de 27 d. </s>
            <s xml:id="echoid-s8571" xml:space="preserve">25 m. </s>
            <s xml:id="echoid-s8572" xml:space="preserve">Septrionale. </s>
            <s xml:id="echoid-s8573" xml:space="preserve">Je l'obſerve à ſon lever avec
              <lb/>
            les pinules du Compas de variation, & </s>
            <s xml:id="echoid-s8574" xml:space="preserve">je trouve qu'il paroît ſe lever
              <lb/>
            entre le 62 & </s>
            <s xml:id="echoid-s8575" xml:space="preserve">le 63 d. </s>
            <s xml:id="echoid-s8576" xml:space="preserve">compté du Nord, allant ves l'Eſt de la roſe;
              <lb/>
            </s>
            <s xml:id="echoid-s8577" xml:space="preserve">c'eſt-à-dire, entre le 27 & </s>
            <s xml:id="echoid-s8578" xml:space="preserve">le 28
              <emph style="sub">me</emph>
            d. </s>
            <s xml:id="echoid-s8579" xml:space="preserve">compté de l'Eſt, & </s>
            <s xml:id="echoid-s8580" xml:space="preserve">comme en
              <lb/>
            ce cas l'àmplitude obſervée eſt égale à l'amplitude calculée, je con-
              <lb/>
            clus qu'en cet endroit & </s>
            <s xml:id="echoid-s8581" xml:space="preserve">en ce tems là l'éguille n'a point de décli-
              <lb/>
            naiſon.</s>
            <s xml:id="echoid-s8582" xml:space="preserve"/>
          </p>
          <p>
            <s xml:id="echoid-s8583" xml:space="preserve">Mais ſile Soleil a paru ſe lever entre le 52 & </s>
            <s xml:id="echoid-s8584" xml:space="preserve">53
              <emph style="sub">me</emph>
            degré compté
              <lb/>
            du Nord à l'Eſt, ſon amplitude obſervée ſera de 37 à 38 deg. </s>
            <s xml:id="echoid-s8585" xml:space="preserve">c'eſt-
              <lb/>
            à-dire, de 10 d. </s>
            <s xml:id="echoid-s8586" xml:space="preserve">plus grande que celle de la Table calculée, par où
              <lb/>
            l'on connoít que l'éguille aimantée décline du Nord à l'Eſt de 10
              <lb/>
            d. </s>
            <s xml:id="echoid-s8587" xml:space="preserve">Si au contraire l'amplitude Orientale obſervée étoit moindre
              <lb/>
            que la calculée, leur difference marqueroit la déclinaiſon de l'éguil-
              <lb/>
            le du Nord à l'Oüeſt. </s>
            <s xml:id="echoid-s8588" xml:space="preserve">Car ſi l'amplitude obſervée eſt plus grande
              <lb/>
            </s>
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