Efter disse Verdier for dh er Kartet over Tet- 
hedsfladen, Pl. XLII, construeret. Der er optrukket Linier 
for ligestore Hojder over eller under Niveaufladen (Grund- 
fladen) for hver Tiendedel Meter. Ved Hjelp af Observa- 
tioner fra Pommerania-Expeditionen, i den nordlige Del af 
Nordsøen, udenfor Skotland, og fra de danske Fyrskibe 
Horns Rev og Skagens Rev er Tæthedsfladen forsøgt 
opeonstrueret over Nordsøen indtil Kartets Sydgrændse. 
Kartet viser, at Tæthedsfladen har Fordybninger 
nordenfor Færøerne, østenfor Island, østenfor Jan Mayen, 
vestenfor Beeren Filand og i Østhavet. Disse Fordybninger 
hidrøre fra saltere Vand og lavere Temperatur. De ligge 
ligesom i en Dalsænkning, der strækker sig langs de nævnte 
Strøg. Fra dette Strog af løfter Tethedsfladen sig mod 
Kysterne, hvor det ferskere Vand i Overfladen forhøjer 
Vandspejlet, selv henimod Grønlands Østkyst, hvor Tempe- 
raturen er lav. Fra det laveste Punkt, Station No. 48, 1 
Øst for Island, hvor dh = —0.112 Meter, stiger Tætheds- 
fladen under Grønlands Kyst til 0.46 Meter over Grund- 
planet, altsaa ialt henimod 60 Centimeter, under Spidsbergens 
Vestkyst til 0.49 Meter, altsaa ialt over 60 cm, under det 
sydlige Norges Vestkyst og i Skagerak samt ved Jyllands 
Vestkyst til 0.55 m og derover, altsaa ialt 66 em. 
Nordenfor Island, mellem denne Ø og Grønland, ligger 
en Indsænkning paa Ordinaten 0. Denne opstaar deraf, 
at Vandet, navnlig i Overfladen, er forholdsvis lidet salt 
saavel under Grønlands Kyst, som under Islands. Ved 
den første virke smeltende Drivis og Smeltevand fra det 
glacierede Land til at forringe Saltholdigheden i de øvre 
Vandlag, paa den sidste Islands mægtigste Bræ-Elve, der 
alle udmunde paa Nordkysten. Fordelingen i Dybet af 
Søvandets Tæthed under Grønland har jeg opconstrueret 
efter Observationerne fra *Germania” i 1869-—70 fra den 
74.—75. Breddegrad og fra “Sofia” i 18831 Danmarkstrædet. 
Tæthedernes Fordeling under Island, hvorfra Obser- 
vationer ikke have været mig tilgjængelige, har jeg con- 
strueret overensstemmende med den, som vore Observationer 
have givet udenfor Norges Vestkyst mellem den 60. og 62. 
Breddegrad. Her udmunde ingen synderlig store Elve, saa 
at det nok kan hænde, at Tæthedens Tilvæxt med Dybet 
nordenfor Island er i Virkeligheden sterkere, end jeg har 
antaget. I saa Fald skulde Tæthedsfladen skraane fra 
Islands Kyst mod Nord endnu sterkere, end Kartet viser. 
Sovandets Tæthed er betinget af dets Saltholdighed, 
Temperatur, Nedbør, Isdannelse, Issmeltning, For- 
dunstning. 
dets 
Den Teethedsflade, jeg har fremstillet, er den, 
som følger af Sovandets virkelige Tæthed, saaledes som 
den fremgaar af Iagttagelserne. Idet vi anvende Tætheds- 
fladen til Beregningen af Havets gjennemsnitlige Strøm- 
ninger, er der altsaa taget Hensyn til de Forandringer 1 
164 
In acccordance with these values for dh, the Map 
of the Surface of Density, Pl. XLIT, has been constructed. 
Lines of equal height above or below the surface of level 
(the base) are drawn for every tenth of a metre. By 
means of observations taken on the *Pommerania” Hxpe- 
dition in the northern part of the North Sea, off Scotland, 
and at the Danish light-ships Horns Rev and Skagens 
Rev, I have sought to construct the surface of density for 
the North Sea to the southern extremity of the map. 
The map shows that the surface of density has depres- 
sions north of the Færoe Islands, east of Iceland, east of 
Jan Mayen, west of Beeren Hiland, and in the Barents 
Sea. These depressions arise from salter water and lower 
temperature. They extend, as it were, down the hol- 
low of a valley, stretching along the said tracts. From 
this region the surface of density rises in the direction of 
the coasts, where the comparatively fresh water at the 
surface raises the level of the sea, even towards the east 
coast of Greenland, where the temperature is low. From 
the lowest point, Station No. 48, east of Iceland, where 
dh = —0,112 metre, the surface of density rises off the 
coast of Greenland to 0.46 metre above its base, accordingly 
in all about 60 centimetres; off the west coast of Spitz- 
bergen to 0.49 metre, or in all more than 60 cms.; 
off the west coast of Southern Norway and in the Skage- 
rak, as also along the west coast of Jutland, to 0.55 
metre and above; therefore in all upwards of 66 cms. 
North of Iceland, between that island and Greenland, 
lies a depression on the ordinate 0. It arises from the 
water, particularly at the surface, being less salt alike off 
the coast of Greenland and that of Iceland. In the former 
locality, melting drift-ice and water from the glaciated 
land tend to diminish the amount of salt in the upper 
strata of water; in the latter, the largest of Iceland’s glacier- 
rivers, which all disembogue on the north coast. The distribu- 
tion in the deep of the density of the sea-water off the coast 
of Greenland, I have constructed from observations taken by 
the “Germania,” 1869—70, on the 74th and 75th parallels 
of latitude, and the “Sofia,” 1883, in Denmark Strait. 
The distribution of density off the coast of Iceland, 
a locality whence observations were not obtainable, I 
have constructed in accordance with that given us by 
our observations off the West Coast of Norway, between 
the 60th‘ and the 62nd parallels of latitude. There, no 
rivers of any magnitude empty their water into the 
sea, and hence perhaps, north of Iceland, the increase of 
density with depth is in reality greater than assumed. In 
that case, the surface of density should slope, from the 
coast of Iceland northwards, at a greater angle than shown 
by the map. | 
The density of sea-water depends on the amount of 
salt, on temperature, precipitation, the formation of ice, the 
melting of ice, evaporation. The surface of density I have 
represented, is that which results from the actual density 
of the sea-water as found from observation. Hence, when 
applying the surface of density to compute the general 
currents of the ocean, regard has been paid to the changes 
