18 



B. Observationer i Søen og deres Resultater. 



Ved Expeditionens Udrustning var det paatænkt, at 

 der skulde gjøres fuldstændige magnetiske Observationer 

 ombord, naar man var i Soen. Hertil havdes fuldstændigt 

 Apparat i Admiralitets Standard-Kompasset og Fox-Cir- 

 kelen. Med denne sidste foretog jeg i 187G. under Skibets 

 Udrustning, paa, Bergens Observatorium de nødvendige Af- 

 vejninger. Under Expeditionens Opbold i Huso fra den 

 10de til 19de Juni samme Aar gjordes alle de fornødne 

 Basis-Observationer. De magnetiske Elementers Storrelse 

 bestemtes, som ovenfor vist. i Land ved absolute Maalinger. 

 Deviationen bestemtes saavel for Styre-Kompasset som for 

 Fox-Cirkelens Plads og med Fox-Cirkelen maaltes Inkli- 

 nation og Intensitet under forskjellige anlagte Kurser, idet 

 Skibet blev svunget ved Hjælp af Trosser. Der toges 

 Svingnmgs-Observationer til Bestemmelse af Coetficienterne 

 /.i og A. 



Ved Beregningen af de med Fox-Cirkelen ombord 

 maalte Inkliuationer og Intensiteter, fandt Prof. Mobn. at 

 disse ikke kunde bringes til indbyrdes Harmoni, med mindre 

 Indexfejlen for Fox-Cirkelens Naal sattes hele 19 Minuter 

 større, end den fandtes af de Observationer, der var gjorte 

 i Land paa samme Sted og til samme Tid med Fox-Cirke- 

 len og med Inklinatoriet. 



Da vi den '22de Juni 187(3 i meget roligt Vejr og 

 rolig Sø forsøgte Observationer med Fox-Cirkelen. viste det 

 sig, at Skibet. vel nærmest paa Grund af det langsomt 

 virkende Styreapparat, 1 ikke kunde boldes paa Kurs med 

 den Stobed, som udfordredes til at Observationerne kunde 

 gjøres med nogenlunde Nøjagtigbed, ligesom Skibets verti- 

 kale Bevægelser uagtet den rolige Sø viste sig yderst hin- 

 drende i samme Retning. Beregningen af Observationerne 

 gav ogsaa et utilfredsstillende Resultat. Kun en Gang 

 senere forsøgtes, nemlig under Sejladsen ind til Tliorsbavn. 

 Observationer med Fox-Cirkelen. Det yderst urolige Vejr, 

 som Expeditionen havde i 187(3. forbød alle videre Forsøg 

 i dette Aar. 



I 1877 hindrede saavel Vejret. som den Onistændig- 

 hed, at jeg maatte gaa fra Husø til Bergen for at faa ind- 

 sat ny Mellemaxel i Maskinen, mig i at foretage Basis- 

 Observationer. I 1878 var Expeditionen under Rejserne 

 saa ganske optagen af andre mere nødvendige Gjøremaal, 

 at der ikke levnedes Tid til at tåge andre magnetiske Ob- 

 servationer ombord end til Bestemmelse af Misvisningen. 



Saaledes forenede sig Skibets magnetiske Konstitution, 

 om jeg saa maa kalde det, dets langsomtvirkende Styre- 

 apparat. dets Letbevægelighed og ringe Bredde, uroligt 

 Vejr, Keparation af Maskinen og Hensynet til Expeditio- 

 nens Hovedaibejder, Lodninger. Temperaturmaalinger og 

 Skrabninger, til absolute Hindringer mod Fox-Cirkelens 



1 C. YVille. Apparaterne og ilens Brug. Sid,' 4. 



B. Observations at Sea, and their Results. 



The Scbeme of Work approved for the Expedition 

 included complete series of magnetic observations at sea. 

 for which \ve had the Admiralty standard compass and the 

 Fox circle. With the latter instrument, I undertook in 

 1876. at the Bergen Observatory, whilst the ship was 

 fitting out, the necessary weighings. During the stay of 

 the Expedition at Husø. from the 10th to the 19th of June. 

 same year. were tåken all necessary base-observations. The 

 deviation was determined alike for the steering-compass and 

 the position of the Fox circle, and inclination and intensity 

 were observed with the Fox circle bn different courses, the ship 

 being swung the while by means of hawsers. Observations 

 of vibration were tåken to determine the coefticients it and X. 



ln his computations of inclination and intensity ob- 

 served on board with the Fox circle. Professor Mohn could 

 not, he ib und, attain satisfactory agreement for the respec- 

 tive results unless the index-error for the needle of the 

 Fox circle were put as much as 19 minutes greater than 

 the error found from the observations tåken on shor? in 

 the same place and at the same time with the Fox circle 

 and with the dip circle. 



On taking a fe w preliminary observations with the Fox 

 circle, June 22nd 187(3, in very tine weather and a calm 

 sea, it was found impossible, chiéfly no doubt owing to the 

 tardy action of the steering-apparatus, 1 to keep the ship 

 sufficiently steady on her course for observing with com- 

 parative accuracy; moreover, the vertical motion of the 

 vessel. calm as was the sea, proved a serious obstacle to 

 the attainment of anything like trustworthy determinations. 

 The computed results, too, were not to be relied upou. 

 Only once afterwards. viz. when nearing Thorshavn. did 

 we try to observe with the Fox circle; indeed the boister- 

 ous weather encountered by the Expedition throughout the 

 summer of 1870. precluded any further attempt on the 

 first cruise. 



In 1877 I had no opportunity of taking base-obser- 

 vations, both by reason of the weather and the discovery, 

 on arriving at Husø. of a defect in the engine-shaft, necessi- 

 tating our immediate return to Bergen to get a new one 

 put in. In 1878 the prosecution of other and more im- 

 portant exploratory work leit no time for magnetic obser- 

 vations save those required to determine declination. 



Thus. the ship's magnetic properties, so to speak. the 

 slow action of her steering-apparatus, her great mobility 

 aud trining breadth of beam. rough weather. time lost in 

 repairing the engine, and regard to the main objects of 

 the Expedition. viz. sounding, determining temperature. and 

 dredging the bottom. — proved one with the other in- 



1 C. Wille. 'Chr Apparatas, and Ilnw (Jsed, p. I. 



