74 



sernes Vedkommende af saadan Størrelse, at de i Sammen- 

 ligning med de smaa Differentser, som det lier gjælder at 

 paavise, lettelig paa sine Steder kunne gjøre sig gjældende 

 og frembringe Uoverensstemmelser, hvor de i Tilfælde af 

 absolut nøiagtige ( Ibservationer ikke vilde lindes. 



Hvilken Vægt man nu end vil tillægge disse faa For- 

 skjelliglieder mellem de to Karter, saa meget er dog sikkert, 

 at de kun optræde som Undtagelser. medens den langt stær- 

 keré frémtrædende Regel er Overensstemmelser af saadan 

 Art. at de ikke uden videre kunne tilskrives Tilfældiglieder. 

 1 >er existerer uimodsigeligt en paa mange Puncter næsten 

 til Proportionalitet grændsende lovmæssig Forbindelse mel- 

 lem Saltgehalten og Kvælstofmængderne, som muligens ikke 

 turde lade sig forklare paa anden Maade end netop gjen- 

 nem den før omtalte Hypothese, som saaledes maa ansees 

 for at indeholde ialfald en stor Del Sandbed, idet den 

 samtidig bestyrkes af to af hinanden fuldstændig uafhængige, 

 uensartede Observationsrækker. der i alt Væsentligt give 

 det samme Resultat. 



Den, som det synes, største Vanskeligbed ved denne 

 Hypothese bestaar i at forklare, hvorledes det i de store 

 Dyb frydende atlantiske Vand skulde have antaget en saa 

 lav Temperatur, som det ifølge Observationerne viser sig 

 at besidde. Dette turde dog maaske ikke synes saa urime- 

 ligt, uaar man betænker, at den varme, søndenfra kommende 

 Atlauterhavsstrom ved at flyde henover det underliggende 

 meget koble Vand paa de nærmest til dette grændsende 

 Lag maa blive udsat for en meget stærk Afkjoling neden- 

 fra, og' at det først gjennem en saadan Afkjøling til om- 

 kring 0° opnaar den høie specifiske Vægt, der er den nød- 

 .vendige Betingelse for, at det skal kunne synke tilbunds. 

 Det atlantiske Vand har altså a, allerede førend det begyn- 

 der at synke, antaget en meget lav Temperatur og vil 

 desforuden under selve Synkningen, idet det da kanske i 

 et meget langt Tidsrum bebuder sig paa alle Sider omgivet 

 af polart Vand, end yderligere blive Gjenstand for Afkjø- 

 ling. førend det naar Bunden. Det fremgaar forøvrigt 

 ogsaa af de endnu ikke offentliggjorte Temperaturobserva- 

 tioner. som jeg desuagtet ved Velvillie af Professor Molm 

 har faaet Anledning til at gjore mig bekjendt med. at 

 Temperaturen i de store Dyb paa de med rød Farve be- 

 tegnede Partier er noget bøiere end der, hvor Kartet er 

 lurvet blaat, saaledes at i Virkeligheden ogsaa Temperatur- 

 forholdene tale for den opstillede Hypothese. 



Det vilde dog være paa urette Sted paa dette Sta- 

 dium at forsøge udredet alle Vanskelighe<ler. saalænge de 

 paa Expeditionen udførte tafrige Temperaturbestemmelser 

 endnu ikke ere forelagte Offentligheden, da man alene ved 

 at taue tilhørligt Hensyn til det hele foreliggende 1 Materiale 

 af Observationer vil kunne vente at faa det bedst mulige 

 Indblik i de mere indviklede Spørgsmaal om Strømforhol- 

 dene. Det er dog meget saudsyuligt. at man senerehen 

 ved at combinere alle Data vil kunne kaste Lys uvei- me- 

 get, sum nu maa synes dunkelt. 



Uheldigvis var det ved Expeditionens L' dreise ikke 

 inuligt at forudse, at, de chemiske . Obåervationer skulde 

 kunne fore til Slutninger af saadan Art S de her paa- 



of the computations. they might easily affect the result, 

 and give rise to discrepancies which, with perfectly accurate 

 observations, there would be no fear of. 



Whatever weight may be attached to these differences, 

 they must unquestionably be regarded as exceptional: the 

 rule is agreement. aud of a character precliidmg the possi- 

 bility of ascribing it to chance. Many of the observations 

 prove incontestibly the existence of a definite. well nigh 

 proportional connexion between the amount of salt and 

 that of nitrogen, a counexion difbcult. perhaps, to explain 

 without having recourse to the aforesaid hypothesis. which 

 cannot but come near the truth. contirmed as it is by 

 two widely different series of observations. leading, each 

 independently of the other. in all essential points. to the 

 same result. 



The greatest apparent difticulty in vol ved in this hypp- 

 thesis consists in explaining the low temperature of the 

 xAtlantic water in the deeper strata. We must. however. 

 bear in mind that the warm Atlantic current. in flowing 

 over the cohl water of the lower strata, is necessarily 

 made to part with a very considerable amount of heat; 

 aud that the high specinc gravity, without which it could 

 not sink to the bottom, involves a temperature of about 

 0°. Hence, the Atlantic water will have acquired a very 

 low temperature before beginning to siuk. and moreover, 

 beirig surrounded during its downward passage, possibly 

 for a considerable period. by Polar water, give off a further 

 amount of heat ere it reacbes the bottom. For the rest, 

 it appears from the independent series of temperature 

 observations, not yet in print, with which Professor Mohn 

 bas kindly made me acquainted. that the temperature at 

 great depths in the sections coloured red in the Plate, 

 is somewhat higher-than in those coloured blue; and hence 

 the hypothesis adopted bere derives additional support from 

 the variation in temperature. 



Meanwhile, it would he premature to attempt dis- 

 posiug of all difticulties. till the numerous temperature 

 determinations performed on the Expedition shall have 

 been made public, since to elucidate fully the more intri- 

 cate questions c&nnected with ocean currents. the wbole 

 stock of materials must he dealt with. We may however 

 venture to hope, that. at a. later stage of this interesting 

 inquiry, a geheral combination of data will tbrow light 

 upon mueli that is at present involved in obscuritv. 



Unfortunately. it was not possible to foresee on the 

 departure of the Expedition, that such iuferences as those 

 bere pointed out would be drawn from the chemical ob 



