71 



mestr opveies af den Forøgelse af samme, der skyldes de 

 der herskende lavere Temperaturer. 



Det fremgaar altsaa, at Differentserne mellem Salt- 

 gehalten i de atlantiske Overfladelag og de paa Bunden 

 hvilende iskolde Vandmasser gjennemsnitlig kun ere megei 

 smaa, om de end paa de Puncter, hvor Vandel i de dybere 

 Lag besidder en overveiende polar Karakter, turde vaie 

 adskilligt mere fremtrædende. Disse Differentser af hen- 

 imod 0.02% ere dog niere end tilstrækkelig sture til i de 

 nederste niere afkjølede Lau af det atlantiske Vand at 

 fremkalde et, sum det vil sees af Tabellen, meget tydeligt 

 om end svagt Maximum af den specifiske Vægt, hvad der 

 nærmest bevirkes derved, at Søvandet ved Afkjøling under 

 0° nærmer sig sit Tæthedsmaximum og derfor i Nærheden 

 af dette for mindre Temperaturvariationer kun forandrer 

 sit Volum med næsten umærkelig smaa ' Værdier, saaledes 

 at en selv meget ringe Forøgelse af Saltgehalten under 

 disse < Imstændigheder taar en overveiende Indfiydelse lige- 

 overfor en Grads Forandring af Temperaturen. 



Det er' saaledes saa langt fra Tilladde, at der i de 

 specifiske Vægter af de forskjellige Vandlag ligger nogen 

 Hindring for Antagelsen af, at det atlantiske Vand skulde 

 synke gjennem det koldere Polarvand, at man tvertom af 

 disse maa slutte, at saa maa være Tilfælde, dersom ikke 

 andre i Havet herskende Strømme virke hemmende paa en 

 saadan Bevægélse. Man tænke sig f. Ex. ved Siden af 

 hinanden i Havet to Vandsøiler af 2000 Favnes (3658 

 Meters) Dybde, hvori Temperaturens Yariation med Dybden 

 for Simpelheds Skyld kan antages at være den samme. 

 hvorimod Saltgehalten i den Iste helt igjennem sættes til 

 3.52 °/o, medens den i den 2den paa Strøget fra Overfladen , 

 til 500 Favnes (1114 Meters) Dyb gives Værdien 3.52°/ 

 fra ."mil til 2000 (914 til 3658) Værdien 3.50 °/ , saa- 

 ledes som Forholdet ifølge < Mbservationerne virkelig synes 

 at stille siu paa enkelte Steder i det imdersogte Hav. Det 

 er da umiddelbart indlysende. at en saadan Fordeling af 

 Saltgehalten vil have en Synkning i den Iste Søile til Følge, 

 saaledes at Våndet i denne vil soge at udbrede sig langs 

 Bunden og fordrive det omliggende speeitisk lettere Vand. 

 Den Hastiglied. hvormed en saadan Bevægélse foregaar, 

 vil naturligvis rette sig efter Differentsen mellem Trykkene 

 i samme Niveau i begge Soiler. en Differents, som ved 

 Bunden i 2000 Favnes (3658 Meters) Dyb efter Beregning 

 beløber sig til henimod 32""" Kviksolvsoile. 



For nærmere at begrunde den forhen fremsatte Hypo- 

 these. om at det paa Bunden hvilende iskolde Vand paa 

 de i Kartet med rød Farve betegnede Steder skulde have 

 atlantisk Oprindelse, vil jeg benytte mig af de i en tidligere 

 Athandling 1 beskrevne Observationer over de i Sovandet 

 indeholdte Kvælstofinrengder. hvis Anvendelse i saadant 

 Øiemed allerede paa det Sted løselig er bleven antydet. 



Som bekjendt herskede der i ældre Tider den An- 

 skuelse, at de i Sovandet i de storre Dyb indeholdte Luft- 

 mængder paa Grund af det der herskende Tryk maatte 



1 -Om Luften i Søvandet.' 



by a decrease in the amount of salt. is almost compensated 

 by the rise resulting from the low temperatures prevailing 

 there. 



It appears, therefore, that the différences between the 



amount of salt in the warm upper strata and that in the 

 cold water at the bottom, are. on an average, exceedinglj 

 small, tbougb more striking perhaps in localities where the 

 water of the deeper strata to a verv great extent is Polar 

 in origin. These différences — about 0.02 per cent — are. 

 however. as will be seen from the Table. more than suffi- 

 cient in the deepest and coldest strata of Atlantic water 

 to occasion an appreciable. though a low. maximum of 

 specific gravitv. which is explained by the fact, that sea- 

 water below bas very nearly reached its maximum of 

 density, and the increase in volume then resulting from 

 trilling variations in tempera ture. is a, well nigh inappreci- 

 able magnitude: hence, under such circumstances, the in- 

 rluence of a very slight addition to the amount of salt 

 with but one degree's difference in temperature will be ex- 

 ceedingly great. 



Such being the case. there is nothing in the specitic 

 gravities observed in the different strata of water to dis- 

 favour the assumption that the comparatively warm At- 

 lantic water should sink through the cold water of Polar 

 origin: nay, from these specific gravities we may inter its 

 correctness. provided only that such descending motion 

 he not counteracted by the effect of ocean currents. To 

 give an illustration. Let us imagine two columns of 

 water. ^(H ii i fathoms (3658 metres) deep, in both of 

 which, for convenience' sake. the variation in temperature 

 with the depth is assumed to be equal ; the amount of salt 

 on the other hand. being put at 3.52 per cent throughout 

 the whole of the first, but in the second. at 3.52 per cent 

 from the surface to a depth of 500 fathoms (914 metres). 

 at 3.50 per cent from 500 to 2ooo fathoms (914—3658 

 metres). — a ratio of distribution actually observed in some 

 localities. This given, it is obvious that such a distribution 

 must cause the water in the first ■ coluimi to sink. and spread 

 itself over the bottom, displacing as it does so the speci- 

 tically lighter. The rapidity of tliis downward motion will 

 of course be proportionate with the difference in pressure 

 at the same le vel in the two columns. a difference which, 

 at the depth of 2000 fathoms (3658 metres). has been 

 computed equal to that of a column of mercury 32""" in 

 height. 



With a view to furnish additional eonfirmation of 

 the hypothesis brought forward, above. which assumes the 

 cold bottom-water in the red-coloured sections of the 

 Plate to be of Atlantic origin. I sball have recourse to 

 my observations on the amount of nitrogen in sea-water, 

 published in a former paper, 1 where their application to 

 such a purpose was briefly alluded to. 



The opinion formerk entertained. that the quantity 

 of air contained in sea-water at great depths must be ex- 

 ceedingly great, by reason of the immense pressure pre- 



1 (in the Air in Sea-Water.'' 



