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18
paa Kartet, der er fremstillet vecl Højdekurver for ’hver
100 Meter, beror paa vort fælles Arbejde, saaledes at de
store Træk ere udkastede af Capt. Wille, medens jeg har
nærmere udarbejdet Detaljen. Herved er stadig taget
Hensyn til, at Skitserne gjerne, som ogsaa de udførte
Vinkelmaalinger vise, overdrive de verticale i Forhold til
de horizontale Dimensioner. Efter mange gjentagne Forsøg
er det i det Hele taget lykkets mig at tilvejebring! en god
Overensstemmelse mellem Skitserne og de tagne Vinkelmaal.
Øens geografiske Beliggenhed er aflagt efter vore
astronomiske og geodetiske Observationer.1
Ved Sammenligning mellem de ældre Karter og vort
vil man finde adskillige Afvigelser. Jeg skal her vise de
vigtigste af disse.
Scorésby’s Bredder stemme gjennemgaaende godt meel
vore. Efter Udmaaling af 19 Punkter finder jeg, at
Sco-resbys Bredder i Gjennemsnit er et halvt Minut større
end vore, og clen største Forskjel er 2 Minuter. Scorésby’s
Længder ere derimod gjennemsnitlig 28 Bueminuter mindre
end vore. Afvigelserne variere mellem 20 og 33 Minuter.
Med andre Ord, .Tan Mayen ligger efter vor Bestemmelse
lidt over 9 Kvartmil længere Vest end i Scorésby’s Kart
og i de hidtil brugte Søkarter. Da vor Længdebestemmelse
ikke er usikker paa mere end nogle faa Tidssekunder, bliver
Jan Mayens geografiske Beliggenhed at rette i Karterne.
Ogsaa den. hollandske Expedition med Skonnerten •’Willem
Barendsz" i 1878 fandt Jan Mayens vestlige Længde større
end Karterne angive. Scorésby’s Bestemmelse er fra Au-
-gust 1817 ; han havde, da været i Søen fra Vaaren af, og
det er ikke at undres over, at hans Chronometers beregnede
Stand kunde afvige betydeligt fra den rigtige.
•’Zeespiegel-’ lægger Jan Mayen mellem Bredderne
71° 0’ og 71° 30’, altsaa en 15 Minuter for langt mod
Nord, og Øens Midte paa Meridianen af Cap
Landsend,-eller 5° 40’ Vest for Greenwich, det er næsten 3 Grader
for langt mod Øst.
Den nordlige Del af Øen og den midterste låve Del
stemme i sine større Omrids vel overens paa alle Karter.
Den sydlige Del derimod have vi fundet kortere og bredere
end paa de ældre Karter, et Resultat, der fremgaar saavel
af vore Vinkelmaalinger som af de, med Loggemaskinen
bestemte, udsejlede Distancer.
Efter alle vore Vinkelmaalinger, saavel horizontals
som verticale, og efter alle Skitser ligger Beerenbergs Kegle
og Krater mere centralt paa Nordlandet end hos Scoresby
og Vogt. Vi fandt Hojden af Beerenberg den 3die August
at være 19-45 Meter, medens Scoresby angiver den til 6870
1 Se H. Mohn. Astronomiske Observationer Side 23.
the island, in particular as regards their vertical extent.
The relief of the land — shown on the Map by contour lines for
every 100 metres, — is the result of our joint labours. Capt. Wille
having laid down the general features while I worked out
the details. Regard has been everywhere had to the
tendency exhibited in the sketches, as Confirmed too by the
trigonometrical measurements, of increasing the vertical and
lessening the horizontal extent. After numerous re-iterated
attempts I at length succeeded in attaining satisfactory
agreement between the sketches and the trigonometrical
measurements.
The geographical position of the island is that found
from our astronomical and geodetical observations.1
On comparing the earlier maps of Jan Mayen with
that we have now constructed, ours will be found to differ
in many respects. I will point out the most important.
Scorésby’s latitudes agree on the whole satisfactorily
with those determined by ourselves. By direct
measurement of 19 points, I found Scorésby’s latitudes on an
average to exceed ours by half a minute; the greatest difference
is 2 minutes. Scorésby’s longitudes, however, are on an
average 28 minutes of arc less than ours. The difference
varies between 20 and 33 minutes. In short, Jan Mayen,
according to our determination., lies a little more than 9
miles farther west than it does on Scorésby’s map and the
charts in use up to the present time. As the error of our
determination of longitude does not amount to more than
a few seconds in time, the geographical position of Jau Mayen
on maps and charts will henceforth have to be rectified. The
Dutch Expedition, too, despatched in 1878 with the schooner
"Willem Barendsz," found the west longitude of Jan Mayen
to be greater than that given in the charts. Scorésby’s
determination dates from August 1817. As captain of, a
whaler, Scoresby had then been at sea since the spring of
the year; and hence it. is not surprising that the true error
of his chronometer should have deviated considerably from
that computed.
The ^Zeespiegel" places Jan Mayen between the
parallels 7!° 0’ and 71° 30’, thus 15 minutes too far north,
and the middle of the island on the meridian of Land’s
End, or 5° 40’ west of Greenwich — nearly 3 degrees too
far east.
The northern part of the island and the low-lying
central tract agree well in their general contours on all
the maps. The southern part, on the other hand, we found
to be shorter and broader than it is given on the earlier
maps, a result derived alike from our trigonometrical
observations and the extent of the coast as determined by the
water-log.
According to all our trigonometrical measurements,
both horizontal and vertical, as also the numerous sketches,
the cone and crater of Mount Beerenberg should have a
more central position in the northern part of the island than
has been given them by -Scoresby and Vogt.’ We found
1 H. Mohn. Astronomical Observations, p. 2:5.-
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