være rigtigst for de midterste og dybeste Dele af Havet. 
Henimod Kysterne vil den være mindre rigtig, men her 
blive Dybderne mindre og Tyngdens Tilvæxt selv mere og 
mere forsvindende. 
Tyngdens Tilvæxt med Tilnærmelsen til Jordens Cen- 
trum beregnes saaledes 
| / 
For Atmosfæren g, = 9, | JL, 9 Å 
~ IB 
Havet Op SW i + 1.45 z 
R 
» Continent 4g, = 9. KE 2 
R 
Angaaende den Nøjagtighed, hvormed Factoren b er 
fundet, kan anstilles følgende Beregninger. Vi have 
d, 
03 peo 
dR så d,  ddD 
altsaa db = — b. R 3p D + 3 Sp pe 
Settes d R= +500 Meter (den halve Forskjel mel- 
lem Clarke’s og Listings Jordradius), dd, = + 0.00005 og 
dD=+0.1, saa faar man med NS til Beregningen af b 
brugte Constanter 
ah) = ae 
Vi faa saaledes følgende Udtryk for Tyngdens Stor- 
relse i Bredden g og Dybden h 
Gon = 94 (1 — Pecos 2 9) (1 + 0. h). 
Havvandets Tæthed i Dybet er større end i Over- 
fladen, da Vandet sammentrykkes noget af Vægten af de 
overliggende Vandlag. Er Trykket i et Punkt i Dybet p 
Atmosfærer og Sovandets Sammentrykkelighedscoefficient 
for en Atmosfære 7, saa er, naar dets Tæthed under al- 
mindeligt Luftryk, 1 Atmosfære, er S, (tidligere betegnet 
0.000 000 002 829. 
som Sy dets Tæthed S, under Trykket p 
S, 
ee np 
Det rene Vands Sammentrykkelighedscoefficient er 
afhængig af Temperaturen og af Trykket. Herom henvises 
til IV Del af denne Afhandling “Om Piezometret som 
Dybdemaaler og Vandets Sammentrykkelighed”. Antager 
man, at Søvandet følger de samme Love for Sammentryk- 
ning, kan man sætte 7 under Formen 
—0.159 t —0.000314 1?) (1—0.00009325 p), 
j= (No 
hvorter Vandets Temperatur, p Vandtrykket 1 Atmosfærer 
og 1, Coefficienten ved 0° og almindeligt Lufttryk. 
Regnault! fandt Sammentrykkelighedscoefficienten for 
Sovand af en Temperatur af 17°.5 og specifisk Vægt 1.0264 
! Moussons Physik, I, S. 253. 
temperature and on pressure. 
and for continental attraction. It will prove most accurate 
for the middle and the deepest parts of the sea. On 
approaching the coast, it will be less accurate; but there 
the depths are less, and consequently the increase of gravity 
itself becomes more and more insensible. 
The increase of gravity with the approach to the 
centre of the earth is accordingly computed as follows: — 
For the Atmosphere g, = 4, f JG al 
Oh, = Wo iL + 1.45 al 
Ocean 
| EN 
Continental Se ee 
R 
Concerning the precision with which the factor bd has 
been found, the following COM UAB NS can be made. We 
have 
SV z d 
p= De ON 
) 3 a 
hence db = — b dik , Å a LAD 
Meat ho oD! nr 
Putting d R = + 500 metres (half the difference 
between Clarke's and Listing's values of the earth’s radius), 
dd, = + 0.00005, andd D= + 0.1, with the con- 
stants made use of for calculating 0, 
db = + 0.000 000 002 829. 
we get, 
Thus we have the following expression for the force 
of gravity in latitude q and depth Å 
Yon = Yas (LP cos 2 p) (1 + 0. h). 
The density of sea-water in the deep is greater than 
at the surface, the water being compressed to some extent 
by the weight of the superincumbent strata. * Assuming the 
pressure at a given point in the deep to be p atmospheres, and 
the coefficient of compression of sea-water for one at- 
mosphere to be 1, then, provided its density under ordinary 
atmospheric pressure, | atmosphere, be S, (previously denoted 
£2 
k Y On SOE 5 å a IG 
by Sr) its density, S,, under the pressure p, IS 
The coefficient of compression of pure water depends on 
As to this subject, the reader 
is referred to Part IV of the present Memoir, viz., “The Piez- 
ometer as a Depth-Meter and the Compressibility of Water.” 
Now, assuming sea-water subject to the s 
ing compression, we can put 
» = (y,—0.159 t —0.000314 #2) (1—0.00009325 p), 
in which f is the temperature of the water, p the water- 
pressure in atmospheres, and 1, the coefficient at 0° and 
ordinary atmospheric pressure. 
Regnault! found the coefficient of compression for 
a temperature of 1795 and a specific 
same laws regard- 
sea-water with 
! Moussons Physik, I, p. 253. 
