24 
It will be recalled that the force of varying mass and pressure 
tending to produce acceleration by equation (b) is equal to 
D=p% 
and the accelerating force in a closed curve ABDC between stations 
A and B, in the plane formed by the verticals AC and BD, is equal to 
da—dy=p Va—Vp). 
Since AC equals AE, (fig. 7, p. 23), we may substitute (e) and obtain 
the following: 
da—dy=p (a—Vp) =2 w sin $ (@9—C1) L.----------@) 
Thus finally we are furnished with an expression which includes the 
forces due to the distribution of mass and pressure tending to accele- 
rate a current moving on a rotating earth, and moreover, it is formed 
of terms which readily lend themselves to the requirements of practical 
oceanography. 
THE PRACTICAL METHODS AND FORM OF COMPUTATIONS GEN- 
ERALLY FOLLOWED IN DYNAMIC PHYSICAL OCEANOGRAPHY 
We may now continue by describing the manner in which the un- 
known terms of (f) are determined by observational data secured 
from a closed curve ABDC in a plane formed by verticals AC and BD, 
between stations Aand B. First we shall regard the forces tending to 
A (STATION 206). METERS OR DECIBARS. B (Station 205), 
& 0 — 
50 ———_—_—_—__ 8. —_---v--- 
125 ——____——_ 8, —---V3--- 
250 —__—_—_—— 8, +] ---Vg--- 
AS ©) ee Rs So 
wre) ——————F, --- V--- 
Fic. 8.—Two verticals A and B at stations 206 and 205, respectively, and with the observed values 
of » and p at depths expressed in decibars or meters as follows: 0, 50, 125, 250, 450, and 750 
accelerate the particles as a result of varying degrees of stability in the 
water columns of any given area. The abstract exposition, further- 
more, has been supplemented by a practical example wherein stations 
A and B are replaced by stations 206 and 205, respectively. (See com- 
putations, p.28.) These stations were taken by the International Ice 
Patrol in 1922, the sectional line forming approximately a right angle 
with the northern edge of the Gulf Stream south of the Grand Banks. 
