Harriot, Thomas, Mss. 6788

List of thumbnails

< >
941
941 (471r) 		942
942 (471v)
943
943 (472r) 		944
944 (472v)
945
945 (473r) 		946
946 (473v)
947
947 (474r) 		948
948 (474v)
949
949 (475r) 		950
950 (475v)
< >
page |< < (485r) of 1134 > >|
    <echo version="1.0RC">
      <text xml:lang="eng" type="free">
        <div type="section" level="1" n="1">
          <pb file="0969.jpg" o="485r" n="969"/>
          <head xml:space="preserve"> 1. Some remembrances of taking
            <emph style="super">the</emph>
          altitude of sonne
            <lb/>
          by the Astrolabe and Sea </head>
          <p>
            <s xml:space="preserve"> There are three instruments used at sea for taking of altitude, the
              <lb/>
            Astrolabe, The ring, & the staffe.
              <emph style="st">Seamen use the Astrolabe</emph>
            The
              <lb/>
            Astolabe hath here most ancient & is used commonly & only for the
              <lb/>
            sonne; and serveth the seamans turne most specially when the sonne is
              <lb/>
            [???] becuase then they
              <emph style="st">if the</emph>
            find the staffe very uncertayne. And when
              <lb/>
            the sea is wrought it is very hard to make any observation by it
              <lb/>
            also; because of his agitation & unquiet </s>
          </p>
          <p>
            <s xml:space="preserve"> But howsoever when there is need you must do as well as you may.
              <lb/>
            and therefore when you have your Astrolabe guaging as quietly as the time
              <lb/>
            will permit with his side toward the sonne according to the usual order,
              <lb/>
            you are to fit the Judex by moving it so long up & downe till the former
              <lb/>
            shine thourough the holes of both the sights at the same time. Or you finding by reason
              <lb/>
            of his agitation that the sonne will not passe iustly thourough the lower sights but be
              <lb/>
              <emph style="st">[???]</emph>
            sometme higher & sometime lower. where you finde the lyst of the syghts
              <lb/>
            now as much over as under: then your Judex standeth as precisely as if the
              <lb/>
            Astrolabe had hong quietly; & sheweth the true altitude of the center of the </s>
          </p>
          <p>
            <s xml:space="preserve"> But if you doubt of the true guaging of the AStrolabe, you may move
              <lb/>
            your Judex quickly to the same signe on the other side & hold it towards the sonne.
              <lb/>
            If you find the sonne shine thourough as before your Astrolabe hangeth well.
              <lb/>
            Otherwise you are also to move
              <emph style="st">your</emph>
              <emph style="super">the</emph>
            Judex, till you have also the altitude on
              <lb/>
            that side. Which had, compare with the other & note the difference. The half of that
              <lb/>
            difference added to the lesse altitude or detract from the greater; And you have
              <lb/>
            the altitude of the sonne as exacte as if your Astrolabe had hung truly </s>
          </p>
          <p>
            <s xml:space="preserve"> The other instrument called
              <emph style="super">Sea Ring</emph>
            is of late yeares in great use with the
              <lb/>
            Portingalls & Spaniards, The making whereof & use they had about 40
              <lb/>
            yeares
              <emph style="super">past</emph>
            of a country man of their owne a learned mathematician called
              <lb/>
            Petrus Nonius who also hath written [???] of the arte of Navigating
              <lb/>
            as well in Latin as in Spanish. And is only for taking the altitude of the
              <lb/>
            sonne as the Astrolabe. but for ease & space it much excelleth it
              <lb/>
            as also for exactnesse. for the degrees are as large agayne as in an
              <lb/>
            Astrolabe of the same signes. And in the use, there is no
              <emph style="st">noe</emph>
            troublesome
              <lb/>
            moving up & downe any Judex as in an Astrolabe; but it guaging as the
              <lb/>
            Astrolabe,
              <emph style="st">the</emph>
            & that side which hath a small
              <emph style="super">be of</emph>
            bing holden towards
              <lb/>
            the sonne; the light passing
              <emph style="st">thh</emph>
              <emph style="super">presently</emph>
            sheweth upon the degrees noted
              <lb/>
            within the ring the altitude of the sonne you desire. you are to note
              <lb/>
            that the middle of the light be it round or long is your true marke.
              <lb/>
            And if the light play by reason of his unquiet hanging; then the
              <lb/>
            middle of the play is the
              <emph style="st">th</emph>
            hight. This instrument is continued
              <lb/>
            together for your use the last viadge with the Astrolabe , And upon your
              <lb/>
            returne it was geven to your servant Cap. Whidden, who now
              <emph style="st">hath</emph>
              <lb/>
            also hath it redy for your use. By our last practice
              <emph style="st">[???]</emph>
            I
              <lb/>
            found
              <emph style="super">it</emph>
            much lighter then it ought to be, which is a fault also in all
              <lb/>
            the Astrolabes I have seene. By reason of
              <emph style="st">[???]</emph>
            speedy
              <emph style="st">setting</emph>
              <lb/>
            setting forth it cnnot more be remedied; but is to be used as </s>
          </p>
        </div>
      </text>
    </echo>
Impressum