THE PROPERTIES OF SKA-\VATKK 81 



The specific heat of sea-water at 17*5 C. may be taken from 

 the following table : 



Specific Heat of Sea-Water. 

 Salinity (per 



millc) ... o 5 10 15 20 25 30 35 40 



Specific heat 1*000 0*982 0*968 0*958 0*951 0*945 '939 '93 2 0*926 



The specific heat of sea-water is less than would be expected 

 from the nature and amount of the dissolved salts. 



The heat conductivity of sea-water has not been determined 

 practically, but from theoretical considerations the following 

 table is constructed, compared with fresh water expressed as 

 2,000 (really -0020) : 



Salinity (per mille) o 10 20 30 35 40 



Conductivity 1400 1367 1353 1346 1341 1337 



The Surface Tension of sea-water is of considerable 

 importance to the study of oceanography. Every liquid may 

 be regarded as bounded by a surface film which behaves like 

 a stretched membrane, and sea-water is no exception. The 

 surface tension plays a part in the formation of the smallest 

 waves, and it increases with the salinity. 



Viscosity. 



According to one theory, surface currents due to winds are 

 helped to spread to the deeper layers by the viscosity of the 

 sea-water. The viscosity of salt water is higher than that of 

 fresh, but is considerably diminished at higher temperatures, 

 so much so that in tropical seas of a temperature of 25 C. and 

 upwards the viscosity is only half of that observed at o C. In 

 the deeper layers of ocean waters the viscosity may be higher 

 on account of the increased pressure, but it has not been 

 ascertained experimentally. 



A rise of i per cent, in salinity only causes an increase of 

 2 to 3 per cent, in the viscosity, and since the salinity of sea- 

 water does not vary much it follows that it is the changes of 

 temperature which produce changes in viscosity. 



These changes in viscosity are associated with differences 



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