149 
0.000139 Atmosfære eller 0.106mm Kviksølvtryk. En saa 
sterk Tilvæxt eller Aftagen med Dybden som den, vi have 
regnet med, forekommer ikke i de større Dyb. Man kan 
saaledes trygt regne med constant 3 
Ved Studiet af Vandets Bevægelse i Havets Dyb 
gjælder det at kjende Trykket i forskjellige Punkter af 
samme Niyeauflade. Havets Overflade vilde en Ni- 
veautlade, naar det var i Hvile og der paa hvert Punkt af 
Overfladen var samme absolute Lufttryk. Den vilde da staa 
lodret paa Tyngdens Retning i ethvert Punkt, men Tyng- 
dens Størrelse vilde aftage fra Polerne mod Æquator. 
Igjennem hvert Punkt i Havet kan lægges en Niveauflade, 
der er characteriseret derved, at der paa alle dens Punkter | 
hviler samme Tryk. I Forbindelse hermed staar, at Af- 
standen mellem to paa hinanden følgende Niveauflader, maalt | 
langs Verticallinien, er omvendt proportional med Tyngdens | 
Størrelse. | 
være 
Antages Lufttrykket constant, Havvandets Tæthed lig 
X er py» Vandtrykket i Bredden p og Dybden h, og pin 
Vandtrykket 1 45° Bredde og Dybden H, saa er | 
~(1— @cos2 y) (14 $0. hy) 
the error will equal 0.000139 atmosphere, or 0.106 mm. 
mercury-pressure. So considerable an increase or 
tion with depth as that we have assumed, 
at great depths. 
constant. 
For investigating the motion of the water in the depths 
diminu- 
does not occur 
Hence, we can safely compute with I as 
of the ocean, we must know the pressure at the various points 
of the same surface of level. The surface of the sea would 
be a surface of level were it at rest, and were each of 
the points of the surface subjected to the same absolute 
atmospheric pressure. It would then stand perpendicular 
to the direction of gravity at every point; but the force 
of gravity would diminish from the poles to the equator. 
Through every point of the sea can be laid a surface of level, 
characterized by its having the same pressure at all of its 
points. In connexion herewith we have the corollary, that 
the distance between two consecutive 
measured along the vertical line, 
of gravity. 
surfaces of level, 
is inversely as the force 
Assuming the atmospheric pressure constant, the den- 
sity of the sea-water equal to 3, the water-pressure p oft 
in the latitude and at the depth h, and the water-pressure 
Pin On the 45th parallel of latitude and at the depth 
H, then 
h 
p On = == 1 as 
a, S(1 + 
z b. H) 
3 r) p ph 
H 
Psn= 
| = 3 YP 454 
Skulle begge disse Punkter tilhøre samme Niveautlade, | 
MAN OO eee ler, 
(l—fcos2g) +30 A)h=U +50. H) H 
Jal 1+ 3bH 
L—Pes2@@ VI 206 | 
Da den midlere Tyngde i Bredden | (9mp) er (ig 
gs, (1 — Poos2g) (LL 1 bh) og i 45° Bredde (g,,45) lg 
h= 
Tyngden. Da b er en meget liden Størrelse, kan man | 
seette 
1+140 H , 7 
dg = 1 bh — +62) i 
ew 1+30H— :bh beh H+ 4 
idet man udelader Leddene med de højere Potenser af b. | 
es H 
Indsætter man her den tilnærmede Værdi af h = ——> 33 | 
1 — pPcos2p 
faar man I 
\ 
H Jal 
LEG Topesta ve neal 
For det extreme Tilfælde g=80°, H= 2000 Favne, | 
bliver det sidste Led = 0.00202 Favne, der svarer til | 
Gas (1 — 
‘surface of the sea, inversely as the force of gravity. 
we substitute here the approximate value of h= 
— (> COS 2 rs 
the last term will = 0.00202 fathoms, 
If both of these points are to belong to the same 
surface of level, we must have py, = Pin Or 
(1—feos2g) (1 4 3bh) h= (I +30 H) H, 
tt fal I1+40H 
1B cos 2 LL LOB 
The mean gravity in latitude p (9,4) being equal to 
Pcos2g)(1 + 46h), and in latitude 45° (9,45) 
b= 
Q P h m45 ° 
gs; (1 +30 H), har man y= == eller Niveautladens Afstand equal to gu (1+ 46H), we get H=% = or hedie 
på | | | | Gap 
fra Overfladens Niveauflade omvendt proportional med | stance of the surface of level in the deep from that of the 
Since 
b is but a small quantity, we can put 
(pe (pe DE SGD DB = =1+4b(H—h), 
Now, if 
H 
1 —Bcos2p 
excluding all terms with the higher powers of b. 
we get 
H 
4 EH? pb cos 2 9 
1 > Pecos 2'—p 
es. 3 cos 2 TEN 
In the extreme case that gy = 80°, H= 2000 tathoms, 
which corresponds 
