24 



It will be recalled that the force of varying mass and pressure 

 tending to produce acceleration by equation (b) is equal to 



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 



d^-db = p (Va-Vb). 



Since AC equals AE, (fig. 7, p. 23), we may substitute (e) and obtain 

 the following: 



da — db = p {Va — V],) =2 CO sin 4> (co — Ci)L (f) 



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 secm-ed 

 from a closed curve ABDC in a plane formed by verticals AC and BD, 

 between stations A and B. First we shall regard the forces tending to 



/\ (Station ZOS). M ETER& or DE:CIBAR.&. g, (pTAmoH Zos). 



_V--- 



-Vs--\-P. 



-y,---\-^^- 



v,-^Ps- 



o- 



- 50 



- 1^5 



fa — 



250. 



.A50 



-ISO 



^o- 



^, 



-__V.,... 



— V3— 



--Vo-- 



D 



- M,— 



Fig. 8.— Two verticals A and B at stations 206 and 205, respectively, and with the observed values 

 of V 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. 



