OCEAN TEMPEEATVEES 



41] 



TABLE 17 



Mean horizontal salinity gradient per meter during the summer for a series 



of depths 



Our salinity data indicate that (A$') is practically zero in winter, 

 hence the mean annual value would be about half of that entered in 

 the table. 



Owing to the small value of (F x V 2 ) compared to the mean 

 value V and because A$' = (A$) 2 (A/S)j equation (209) can be 

 written in the form 



(210) 



(211) 



//*2/2 

 V(S)dA= I T 

 ft 



From equations (207, 208, and 210) we have finally 



SE-VJ(z) I (Ls") e -i/cos fj ^1 d 2/ 

 W =- Jo _ V 7 



r.Ofif. fl) 



In order to check the above results the same principle will be 

 applied to a different volume (fig. 19). The stream lines (fig. 17) 

 being traces of surfaces of flow on a plane perpendicular to the coast, 

 two such planes, two surfaces of flow, and two horizontal planes 

 inclose a volume such that the component of the velocity along a line 

 parallel to the coast is the same for each vertical plane. Hence the 

 vertical flux through a horizontal section of this volume must be 

 independent of the depth of the section, in order that the total quantity 

 of water inclosed by these surfaces may be constant. Consider the 

 volume inclosed by two surfaces of flow, two vertical faces perpen- 

 dicular to the coast and parallel to the plane of the paper at unit 

 distance apart (fig. 19), and two horizontal sections at the depths y z 

 and y 1 of which the upper forms the base of a rectangular prism 

 extending upward to the surface of the water. 



Let r l W 1 be the mean vertical velocity at the depth y l , and r,W 1 

 that at the depth y 2 , then r l W 1 B 1 must equal r 2 W^B 2 where B, nnd 

 B 2 are the areas of the upper and lower sections respectively, whence 

 the section areas B l and B 2 must satisfy the equation 



B, 



(214) 



