162 
Tæthedsfladens Form, det er dens verticale Coordi- 
nater over Niveaufladen, beregnes saaledes. Efter Formelen 
P300 = 94.6438 + 53.23 (I — 1.02783) 
beregnes Trykket, i Atmosfærer, af Vandsøjlen paa 300 
Favnes Højde, regnet fra Overfladen af, for en Række Sta- 
tioner i Nordhavet. Ved de Stationer, hvor Dybden er 
mindre end 300 Favne, har jeg tænkt mig et Rør lagt 
langs Bunden fra Stationens Vertical til det nærmeste 
Punkt i 800 Favnes Dyb og taget i dette, efter Tversnit- 
tene Pl. XXXIX—XLLden midlere Tæthed for Lagene 
mellem 300 Favne og 200 Favne, mellem 200 Favne og 
100 Fv. o.s.v. De saaledes extrapolerede Værdier ere i 
Tabellerne Side 189—1483 merkede med en Stjerne. Paa 
denne Maade har jeg ført Tæthedsfladen ind til Kysterne. 
De saaledes beregnede Værdier for Trykket af en 
Vandsøjle af 300 Favnes Højde blive af forskjellig Størrelse. 
Jo større XS, desto større Tryk. Til Grundplan for Tet- 
hedsfladen har jeg taget Niveaufladen gjennem Overfladen 
paa et Sted, hvor det beregnede Tryk i 800 Favnes Dyb 
er 54.6438 Atmosfærer. Trykket ide andre Stationer er dels 
større, dels mindre end dette. Da nu Trykket i Grændse- 
fladen skal være constant 54.6438 Atmosfærer i alle Sta- 
tioner, saa betegner et mindre Tryk end dette, at Vand- 
søjlen paa 300 Fayne er for kort til at frembringe det 
Tryk, som Grændsefladen skal have. Til de 300 Favnes 
Højde maa lægges en Vandsøjle at en saadan Højde, at 
dennes Tryk er ligt det manglende. Overfladen kommer 
altsaa over 300 Favne højere end Grændsefladen. 
Ligesaa betegner en større Værdi af ps, end 54.6438 
Atmosfærer, at den tilsvarende Vandsøjle er for tung. Den 
maa forkortes saameget, at dens Tryk bliver 54.6438 Atm., 
det er, der maa fradrages den en liden Vandsøjle, hvis 
Tryk er ps9 — 54.6438.  Overfladen kommer saaledes at 
ligge mindre end 300 Favne over Grændsefladen. Da Af- 
standen mellem Grændsefladen og Niveaufladen for Over- 
fladen i Station 247 er 300 Favne, vil i første Tilfælde 
Tæthedsfladen ligge højere, i sidste Tilfælde lavere end Ni- 
veaufladen gjennem Overfladen i Station 247. Den til Tryk- 
forskjellen svarende Højdeforskjel findes af Formelen 
ato Sy (L—P cos 2) (1 + bh) 
i) = S eg dh 
Å dp l—mnp 1 
/oraf = —- : 
hvoraf dh iS, Ua LPen 
For 300 Favne er S, wat - = 1.0305 og, da 1 Favn 
4) 
er = 1.82877 Meter, faar man 
10.027 
i Wier = === hp, 
dh i Meter T=5 sd 
The form of the surface of density, 1. e., its vertical 
co-ordinates above the surface of level, was computed as 
follows. According to the formula 
P300 = 54.6438 + 53.23 (3 — 1.02783), 
the pressure is computed, in atmospheres, of the column 
of water of a height of 300 fathoms, reckoned from the 
surface, for a series of Stations in the North Ocean. At 
the Stations where the depth is less than 300 fathoms, I 
have supposed a tube laid down along the bottom from 
the vertical of the Station to the nearest point at a depth of 
300 fathoms, and have taken in the said tube, from the trans- 
verse sections Pl. XX XIX to Pl. XLI, the mean density 
for the strata between 300 and 200 fathoms, between 200 
and 100 fathoms, ete.. These extrapolated values are marked 
with an asterisk in the Tables, page 139 to 143. In this 
way I have carried the surface of density up to the coasts. 
The values thus computed for the pressure of a column 
of water 300 fathoms in height will of course be different. 
The greater XS, the greater the pressure. As the base for the 
surface of density, I have takén the surface of level through 
the top-surface, in a locality where the computed pres- 
sure at a depth of 300 fathoms is 54.6458 atmospheres. 
The pressure at the other Stations is partly greater, partly 
less. Now, since the pressure at the limiting surface has 
to be 54.6438 atmospheres at all Stations, a pressure less 
than this will indicate that the column of water of a depth of 
300 fathoms is too short to produce the pressure which the 
limiting surface requires. To the height of 300 fathoms 
must be added a column of water of such a height that 
its pressure will equal that which is wanting. The sur- 
face of the sea must accordingly lie more than 300 fathoms 
above the limiting surface. In like manner, a value of poo 
greater than 54.6438 atmospheres indicates that the corre- 
sponding column of water is too heavy. It must, therefore, 
be shortened to such an extent as will make its pressure 
54.5438 atmospheres, i. e., from off it has to be taken a short 
column of water whose pressure IS 3, — 54.6458. The sur- 
face will accordingly lie less than 300 fathoms above the limit- 
ing surface. As the distance between the limiting surface 
and the surface of level for the top-surface at the 
Station 247 is 300 fathoms, the surface of density must 
in the former case lie higher, in the latter case lower than 
the surface of level passing through the top-surface at 
Station 247. The difference in height corresponding to the 
difference in pressure is found from the formula 
Y BE Ov 2 , 
i= a, S, (1 — cos 2 |) (1 + bh) Al 
1— 9p | 
1— yp Dd 
whence le = A tor Too peed e 
For 300 fathoms S, ae = 1080s ancl ag I 
ad 
fathom = 1.82877 metre, we get 
10.027 
id, DH Dons = === 4 
1 — Poos2 
