blot tilsyneladende, idet Tæthedstladens Heldning fra Ky- 
sten turde være noget sterkere end antaget i Kartet PI. 
XLII. Eller den for den sydgaaende Strøm fornødne 
Vandforsyning hentes fra de dybere liggende og koldere 
Vandlag. Dette vilde bidrage til at forklare de forholdsvis 
lave Temperaturer, som vi træffe paa Skotlands Østkyst 
(Se Pl. XVD. 
For at beregne Vandets Hastighed i Overfladen, gaa 
vi ud fra Formelen 
2osnp 
tang 7 = 7 cos 29) . U 
hvor wu er Hastigheden og 1 Heldningvinkelen af Overfladen 
i et Plan lodret paa Ligetrykslinierne. Kaldes den til 
Afstanden A\x, regnet langs Normalen, svarende Stigning 
af Overfladen /Yh, saa er 
Ah gu (I — 8 cos 2 g) 
Aa 
Regnes Ah i Meter, Az i Kilometer, saa faar man 
w= 
20sin p 
yok 1 gull =poos2y)_ An 1 
~ fg 1000 2 wsin | Aa FB 
Meter per Secund. 
w sin | 
Størrelsen å = 1000. 
net 1 Tabellen Side 126. 
I Kartet Pl. XLIII er Højdeforskjellen mellem Lige- 
højdelinierne, Ah, 0.1 Meter, og man faar 
1 1 
Efter denne sidste Formel er Skalaen paa Pl. XLITI 
beregnet. Til Venstre staar den opstigende Skala for 
Kilometer. Parallel med den vise den hyperboliske Curves 
verticale Ordinater (Ax) de Afstande mellem to Lige- 
hojdelinier, der svare til de forskjellige Hastigheder (w). 
Skalaen for disse er den horizontale Grundlinie, inddelt 
til at angive Hastigheden saavel 1 Meter pr. Secund som 
i Kvartmil i 24 Timer. Den yderste Hyperbel gjælder for 
55° Bredde, den inderste for 80°. Ved Abseissen for 
0.01 m ere, øverst til Højre, Hyperblerne for de mellem- 
liggende 5 til 5 Grader antydede. 
For at finde Strømhastigheden i et Punkt tager man 
altsaa med Passeren Afstanden mellem de to nærmeste 
Ligehøjdelinier, opsøger i Skalaen den verticale Ordinat, 
som passer hertil, Bredden taget 1 Betragtning, og aflæser 
paa Horizontalskalaen Hastigheden i Meter pr. Secund 
eller 1 Kvartmil i 24 Timer. 
inclination of the surface would appear to point north- 
ward, whereas the motion must proceed along the coast 
southward. This may indeed only apparent, since 
the slope of the surface of density from the coast is pos- 
sibly somewhat steeper than assumed in the map, Pl. XLII. 
Or the supply of water necessary for the current setting 
south is derived from the deeper-lying and colder strata. 
This would go far to explain the comparatively low temper- 
ature met with off the east coast of Scotland (See Pl. XVI). 
For computing the velocity of the water at the sur- 
face, we have recourse to the following formula: — 
be 
2 w sin | 
gis (1 — B cos 2 9) 
tan 7 = Yb, 
in which w represents the velocity and 7 the angle of in- 
clination of the surface in a plane perpendicular to the 
lines of equal pressure. Now, if we call Yh the rise of 
the surface corresponding to the distance Ax, reckoned 
along the normal, then 
a Me = tan 7 
Bea," 
and 
Ah  o5(1 — B cos 2 9) 
Aa 
If Ah be taken in metres, Ax in kilometres, we 
shall get 
Ul 
2 wsin p 
ee Ah 1 gus (1 — P cos 2 @) _A h Å 
~ We 00 Vosng Ay 2k 
metres per second. 
SE will be 
5 i P= OOO, 
The CEE) == MOOD gas (1 — BS cos 2 9) 
found computed in the Table, p. 126. 
In the map, Pl. XLIIT, the difference in height be- 
tween the lines of equal height, Ah, is 0.1 metre; hence 
1 1 
we get u= or Da’ Lap = SO oO 
According to this last formula, the scale, Pl. X LITT, has 
been computed. To the left, we have the ascending scale for 
kilometres. Parallel with this scale, the hyperbolical curve’s: 
vertical ordinates (Ax) show the distances between two 
lines of equal height that correspond to the different 
velocities (w). The scale for these velocities is the hori- 
zontal base-line, graduated to indicate the velocity both in 
metres per second and in nautical miles per 24 hours. 
The outermost hyperbola refers to the 5dth parallel of 
latitude, the innermost to the 80th. At the abscissa for 
0.01 m., in the upper corner to the right, the hyperbolas 
for the interjacent 5 to 5 degrees are marked off. 
To find the velocity of the current at any given 
point, we measure accordingly, with the compasses, the 
distance between the two nearest lines of equal height, 
seek out on the scale the vertical ordinate corresponding 
to it — taking the latitude into account — and read off on 
the horizontal scale the velocity in metres per second or 
in nautical miles per 24 hours. 
