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

Table of Notes

< >
[Note]
Page: 228
[Note]
Page: 229
[Note]
Page: 230
[Note]
Page: 232
[Note]
Page: 234
[Note]
Page: 235
[Note]
Page: 240
[Note]
Page: 241
[Note]
Page: 245
[Note]
Page: 248
[Note]
Page: 249
[Note]
Page: 259
[Note]
Page: 259
[Note]
Page: 259
[Note]
Page: 266
[Note]
Page: 269
[Note]
Page: 277
[Note]
Page: 278
[Note]
Page: 280
[Note]
Page: 281
[Note]
Page: 283
[Note]
Page: 284
[Note]
Page: 285
[Note]
Page: 289
[Note]
Page: 290
[Note]
Page: 291
[Note]
Page: 291
[Note]
Page: 293
[Note]
Page: 295
[Note]
Page: 296
< >
page |< < (285) of 438 > >|
    <echo version="1.0RC">
      <text xml:lang="fr" type="free">
        <div xml:id="echoid-div596" type="section" level="1" n="298">
          <pb o="285" file="301" n="301" rhead="POUR LA NAVIGATION. Liv. VII. Ch. IV."/>
        </div>
        <div xml:id="echoid-div597" type="section" level="1" n="299">
          <head xml:id="echoid-head428" style="it" xml:space="preserve">Des Cartes reduites.</head>
          <p>
            <s xml:id="echoid-s9040" xml:space="preserve">L A Planche vingt-uniéme repreſente une Carte réduite. </s>
            <s xml:id="echoid-s9041" xml:space="preserve">Mais
              <lb/>
            avant que d'en donner la conſtruction & </s>
            <s xml:id="echoid-s9042" xml:space="preserve">les uſages, il faut fça-
              <lb/>
            voir que tant qu'un Vaiſſeau eſt pouſſé par un même vent, il doit
              <lb/>
            toûjours faire le même angle avec tous les Méridiens qu'il rencon-
              <lb/>
            tre ſur la ſurface du Globe terreſtre.</s>
            <s xml:id="echoid-s9043" xml:space="preserve"/>
          </p>
          <p>
            <s xml:id="echoid-s9044" xml:space="preserve">Si le Vaiſfeau court Nord & </s>
            <s xml:id="echoid-s9045" xml:space="preserve">Sud, il fait un angle infiniment ai-
              <lb/>
            guavec le Méridien qu'il décrit, c'eſt-à-dire, qu'il lui eſt parallele,
              <lb/>
            ou plûtôt qu'il le ſuit & </s>
            <s xml:id="echoid-s9046" xml:space="preserve">ne s'en écarte point.</s>
            <s xml:id="echoid-s9047" xml:space="preserve"/>
          </p>
          <p>
            <s xml:id="echoid-s9048" xml:space="preserve">S'il court Eſt & </s>
            <s xml:id="echoid-s9049" xml:space="preserve">Oüeſt, il coupe à angles droits tous les Méridiens,
              <lb/>
            car il décrit ou l'Equateur ou un des cercles qui lui ſont paralle-
              <lb/>
            les. </s>
            <s xml:id="echoid-s9050" xml:space="preserve">Mais ſi ſa courſe eſt moyene entre ces 2, alors il ne décrira plus
              <lb/>
            un cercle, parce qu'un cercle tracé de cette maniere couperoit tous
              <lb/>
            les Méridiens à angles inégaux, ce que le Vaiſſeau ne doit pas faire.
              <lb/>
            </s>
            <s xml:id="echoid-s9051" xml:space="preserve">Il décrit donc une autre courbe, dont la condition eſſentille eſt de
              <lb/>
            couper tous les Méridiens ſous le même angle. </s>
            <s xml:id="echoid-s9052" xml:space="preserve">On la nomme Loxo-
              <lb/>
            dromique, ou fimplement Loxodromie; </s>
            <s xml:id="echoid-s9053" xml:space="preserve">c'eſt une eſpece de ſpirale
              <lb/>
            qui fait une infinité de tours ſans pouvoir arriver à un certain point,
              <lb/>
            qui eſt le Pole où elle tend, & </s>
            <s xml:id="echoid-s9054" xml:space="preserve">dont elle s'approche à chaque pas.</s>
            <s xml:id="echoid-s9055" xml:space="preserve"/>
          </p>
          <p>
            <s xml:id="echoid-s9056" xml:space="preserve">La route d'un Vaiſſeau, à l'exception des 2 premicres que nous
              <lb/>
            av ons marquées, eſt donctoûjours une courbe Loxodromique. </s>
            <s xml:id="echoid-s9057" xml:space="preserve">Elle
              <lb/>
            eſt l'hypotenuſe d'un triangle rectangle ſpherique, dont les 2 côtez
              <lb/>
            ſont le chemin du Vaiſſeau en longitude & </s>
            <s xml:id="echoid-s9058" xml:space="preserve">en latitude.</s>
            <s xml:id="echoid-s9059" xml:space="preserve"/>
          </p>
          <p>
            <s xml:id="echoid-s9060" xml:space="preserve">On a d'ordinaire la latitude par obſervation; </s>
            <s xml:id="echoid-s9061" xml:space="preserve">on a par la Bouſſole
              <lb/>
            l'angle de la Loxodromie, avec l'un ou l'autre des deux côtez, & </s>
            <s xml:id="echoid-s9062" xml:space="preserve">ce
              <lb/>
            qu'on cherche par le calcul de la Trigonométrie, c'eſt la valeur de
              <lb/>
            la longitude parcouruë & </s>
            <s xml:id="echoid-s9063" xml:space="preserve">de la Loxodromie ou route du Vaiſſeau.</s>
            <s xml:id="echoid-s9064" xml:space="preserve"/>
          </p>
          <p>
            <s xml:id="echoid-s9065" xml:space="preserve">Mais comme cette ligne courbe eſt embaraſſante pour les calculs,
              <lb/>
            on a voulu avoir la route en ligne droite, & </s>
            <s xml:id="echoid-s9066" xml:space="preserve">il a fallu conſerver à
              <lb/>
            cette ligne droite l'eſſence de la Loxodromie, qui eſt de couper toû-
              <lb/>
            jours le Méridens ſous le même angle. </s>
            <s xml:id="echoid-s9067" xml:space="preserve">Or cela eſt abſolument im-
              <lb/>
            poſſible tant que les Méridiens ne ſont point paralleles entr'eux,
              <lb/>
            comme eneffet ils ne le ſont pas. </s>
            <s xml:id="echoid-s9068" xml:space="preserve">Il a donc fallu ſuppoſer les Méri-
              <lb/>
            diens paralleles, dont s'eſt enſuivi que les degrez de longitude iné-
              <lb/>
            galement éloignez de l'Equateur ont été ſuppoſez de même gran-
              <lb/>
            deur, quoique réellementils diminuent toûjours depuis l'Equateur,
              <lb/>
            ſelon une certaine proportion connuë; </s>
            <s xml:id="echoid-s9069" xml:space="preserve">mais pour reparer cette er-
              <lb/>
            reur, les degrez de latitude, qui par la nature de la Sphere ſont égaux
              <lb/>
            par tout, ſont augmentez dans les Cartes hydrograp hiques, en mê-
              <lb/>
            </s>
          </p>
        </div>
      </text>
    </echo>
Impressum