nedad og langs Bassinets Render opad. Den første fore- 
gaar med mindre Friction end den sidste. 
Et Bevægelsessystem som det her beskrevne forud- 
setter en vis Fordeling af Vandets Tæthed, der resulterer 
ien Overflade. som afviger fra Niveaufladen og en Grændse- 
flade i et vist Dyb mellem denne og det dybeste Punkt i 
Havet. Den Fordeling af Havvandets Tæthed, som var den 
oprindelige, vilde imidlertid ved de beskrevne Bevægelser 
forrykkes. Det lettere Vand fra Bredderne vilde efterhaan- 
den af de øvre Strømninger føres til Midten og Midtens 
tungere af de nedre Strømninger mod Renderne. 
Dersom altsaa en oprindelig ulige Fordeling af Tæt- 
hederne var den eneste eller hovedsageligste Aarsag til 
Havets Strømninger, vilde en Udjevning af disse Uligheder 
være Følgen af Bevægelsen, og denne vilde efterhaanden 
tabe sig for at give Plads for Ligevægt. 
Men i Naturen er Forholdet det, at der er andre og 
sterkere Kræfter, som stadig vedligeholde den stedfindende 
Ulighed 1 Tætheden 1 de forskjellige Punkter af Havet. 
Disse Kræfter ere de af Vindene fremkaldte Strømninger 
i Forbindelse med Elvevand og Issmeltning paa Havet, 
Opvarmning og Afkjøling, Nedbør og Fordunstning. Vin- 
dene fore salt Atlanterhavsvand md i vort Nordhay, og 
sprede, langs Kysterne Elvevand, fra de isfyldte Partier 
smeltet Isvand udover det salte. Indførselsvejene ere andre 
end Udførselsvejene, saa at Strømningerne, for en stor Del, 
ikke vende tilbage 1 sine gamle Baner. Men Tilførslerne 
og Udførslerne foregaa paa bestemte Steder, og saaledes 
opretholdes et constant System af Fordelingen af de ulige 
’ Teetheder (Saltholdighed saavel som Temperatur) ved de 
normale Vinde. Disses Virkning er meget sterkere end 
den, der flyder af Tæthedernes Ulighed, og den gaar, i de 
øvre Lag, i samme Retning. 
Den Udjevning af Tæthedernes Ulighed, som de af 
denne fremkaldte Strømninger vilde hidføre, opvejes saa- 
ledes mere end fuldstændig af Vindstrømmene. 
ikke længere end til en Tendents til Udjevning. 
Det kommer 
Tæthedens 
ulige Fordeling bliver et constant System, og de af samme 
resulterende Strømninger ville finde Sted, uden at Tæt- 
hedernes Ulighed udjevnes. 
Overensstemmende med disse Betragtninger, hvis Rig- 
tighed vil fremgaa endnu klarere i det Følgende, naar vi 
beskrive det hele resulterende Strømsystem, sætter jeg Re- 
sultatet af Tæthedernes ulige Fordeling i Havvandet deri, 
at der dannes en Overflade, som afviger fra Niveaufladen. 
Denne kalder jeg Tætheds-Fladen. Dens Form kan 
findes, naar man kjender Dybden af den Flade, jeg kalder 
Grændsefladen. ThiiGrændsefladen, der er en Niveauflade, 
ere Trykkene overalt lige store, og Tæthedsfladens Højde 
over denne bliver omvendt proportional med de, af Obser- 
tionerne givne, midlere Tætheder i de verticale Vandsøjler 
mellem begge Flader. 
Dybden af Grændsefladen er bestemt derved, at denne 
Flade ligger imellem Bevægelser, der gaa i modsatte Ret- 
minimum and upward along the margins of the basin. 
The former has less friction to overcome than the latter. 
A of motion such forth, is 
based upon a certain distribution of the density of the water 
resulting in a top-surface that deviates from the surface of 
level and a limiting surface at a certain depth between the 
latter and the deepest pomt of the sea. The original distri- 
bution of the density of the sea-water, would however be 
disturbed by the motions described. 
system as here set 
The lighter water from 
the shores would gradually be carried by the upper currents 
towards the middle, and the heavier water of the middle 
by the lower currents towards the margins. 
Hence, therefore, assuming that originally an unequal 
distribution of density were the sole or the chief cause of 
ocean-currents, an equalisation of these differences would 
be a necessary consequence of the motion, which must 
gradually yield and give way to equilibrium. 
But in nature the condition is such, that other and 
stronger forces are found to maintain the inequality of the 
density in the various parts of the sea. ‘These forces are 
the currents produced by the winds in conjunction with 
river-water and the melting of ice in the sea, also heating 
and cooling, precipitation, and evaporation. The winds carry 
salt Atlantic water into our North Ocean; they spread 
along the coasts river-water, and from the ice-covered parts 
melted ice-water above the salt-water. The passages of 
inlet differ from those of outlet; and hence the currents, 
to a great extent, do not return by their original courses. 
But the imflow and outflow take place definite 
localities; and thus a constant system is maintained of the 
distribution of unequal densities (amount of salt as well 
as temperature) by means of the normal winds. The 
effect of the winds greatly exceeds that produced by 
unequal density, and it goes throughout the upper strata 
in the same direction. 
in 
The equalisation of unequal density, to which the 
currents occasioned by it would give rise, is accordingly 
more than counterbalanced by the wind-currents. It does not 
go farther than a tendency to equalisation. The unequal 
distribution of density becomes a constant system, and the 
currents resulting from it will be produced without equalis- 
ing the differences of density. 
In accordance with these views, the correctness of 
which will appear still more clearly in the sequel, on giving 
a description of the whole resulting system of currents, I put 
the issue of the unequal distribution of density throughout 
the water of the sea in the forming of a top-surface dif- 
fering from the surface of level. This surface I call the Swr- 
face of Density. Its form may be found on knowing the depth 
of the surface whith I call the limiting surface. For at 
the limiting surface, which is a surface of level, the pres- 
sure is everywhere the same, and the height of the surface 
of density above it will be inversely proportional to the 
mean density of the vertical columns of water between 
both surfaces given by the observations. 
The depth of the limiting surface is determined by 
its lying between motions proceeding in opposite. directions. 
