18 



paa Kartet, der er fremstillet ved Hojdekurver 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 tåget 

 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 tåget lykkets mig at tilvejebring.e en god 

 Overensstemmelse mellem Skitserne og de tagne Vinkelmaal. 



Øens geografiske Beliggenhed er aflagt efter vniv 

 astronomiske og geodetiske Observationer. 1 



Ved Sammenligning mellem de ældre Karter og vort 

 vil man tinde adskillige Afvigelser. Jeg skal her vise de 

 vigtigste af disse. 



Scoresbys Bredder stemme gjermemgaaende godt med 

 vore. Efter Udmaaling af 11» Punkter tinder jeg. at Sco- 

 resbys Bredder i Gjennemsnit er et halvt Minut større 

 end vore, og den største Forskjel er 2 Minuter. Scoresby's 

 Længder ere derimod gjenaemsnitlig 28 Bueminuter mindre 

 end vore. Afvigelserne variere mellem 20 og 33 Minuter. 

 Med andre Ord. Jan Mayen ligger efter vor Bestemmelse 

 lidt over 9 Kvartmil hengere Vest end i Scoresby's Kart 

 og i de bidtil brugte Søkarter. Da vor Længdebestemmelse 

 ikke er usikker paa mere end nogle faa Tidssekunder. bliver 

 Jan Mayens geografiske Beliggenhed at rette i Karterne. 

 I >usaa den, hollandske Expedition med Skonnerten -W* illem 

 Barendsz" i 1878 fandt Jan Mayens vestlige Lærigde større 

 end Karterne angive. Scoreshy'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" hegger .lan Mayen mellem Bredderne 

 71° 0' og 71" 30', altsaa en 15 Minuter for langt mod 

 Xord, og Øens Midte paa Meridianen af ( 'ap Landsend,- 

 eller 5° 40' Vest fur Greenwich, det er næsten 3 Grader 

 for langt mod Ost. 



Den nordlige Del af (len og den midterste lave 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 freragaar saavel 

 af vore Vinkelmaalinger som af de. med Loggemaskinen 

 bestemte, udsejlede Distancer. 



Efter alle vore Vinkelmaalinger, saavel horizontale 

 som verticale, og efter alle Skitser ligger Beerenbergs Kegle 

 og Krater niere ceritralt paa Nordlandet end hos Scoresby 

 og Vogt. Vi fandt Hojden af Beerenberg den 3die August 

 at være 1945 Meter, medens Scoresby angiver den til iiS7<» 



1 Sc II, Mohn. Ast!-. aiske Observationer Side 23. 



the island. in particular as regards their vertical extent. 

 The relief of the land — shown on theMap 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 every where bad to the ten- 

 dency exhibited in the sketches, as confirmed too by the tri- 

 gonometri cal 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 astroilomical and geodetical observations. 1 



On comparing the earlier niaps of Jan Mayen with 

 that we have now eonstructed. ours will be found to differ 

 in many respects. I will point out the most important. 



Scoresby's latitudes agree on the whole satisfactorily 

 with those determined by ourselves. By direct measure- 

 ment of 19 points, I found Scoresby's latitudes on an aver- 

 age to exceed ours liv halta minute; the greatest difference 

 is 2 minutes. Scoresby's longitudes, however. are on an 

 average 28 minutes of are 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 Scoresby '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 Jan Mayen 

 on maps and charts will henceforth have to be rectiiied. The 

 Dutch Expedition, too, despatched in 1878 with the schooner 

 "AYillem Barendsz." found the west longitude of Jan Mayen 

 to be greater than that given in the charts. Scoresby '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 compnted. 



The "Zeespiegel" places Jan Mayen between the par- 

 allels 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, w<e found 

 to be shorter and broader than it is given on the earlier 

 maps. a result derived alike from our trigonometrical obser- 

 vations and the extent of the coast as determined liv the 

 water-log. 



According to all our trigonometrical measurements. 

 lioth 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 



H. .Mohn. Astronomical Observations, p. 



