, Geography of the Sea. 14T 



The theory of this circulation from the Polar seas is greatly 

 strengthened by the facts appearing from the investigation of the 

 bathymetric isotherms in inclosed seas, i. e., seas which are 

 separated from the deep oceans by submarine barriers. In such 

 seas the temperature decreases slowly from the surface down to 

 the depth of the barrier, and from there on remains constant to 

 the bottom. 



The influence of currents on the surface temperature is very 

 marked, cold currents bending the isothermal lines towards the 

 equator, and warm currents bending them towards the poles. 

 The seasonal changes in surface temperatures are considerable, 

 being the least in the tropical zones. 



In the Atlantic Ocean the maximum surface temperature lies 

 near the coast of South America, between Para and Cayenne, and 

 another maximum occurs near the west coast of Africa, between 

 Freetown and Cape Coast Castle. 



The Pacific Ocean shows the peculiarity that the surface tem- 

 peratures on the western side are lower than those on the eastern 

 side. Between 45° N. and 45° S. the temperature does not fall 

 below 50°, but between those parallels and the poles it remains 

 most always below that figure. 



The warmest water is found in the Hed Sea where the surface 

 temperature has been recorded as high as 90°. North of the 

 equator the mean annual temperature is considerably above 80°, 

 but south of it, to about the parallel of 25°, it varies from 80° 

 to 70°. 



Chemical Composition, Salinity and Density of Sea Water. 



In this branch of inquiry great progress has been made, and 

 sea water is now known to contain at least 32 elementary bodies. 

 Its chief constituents are found to consist of the chlorides and 

 sulphates of sodium, magnesium, potassium and calcium. It also 

 contains air and carbonic acid. 



The salinity and density of sea water have been investigated 

 very thoroughly, particularly in the Atlantic. As the salinity 

 of the sea water is an index of its density, changes in the former 

 naturally affect the latter. The salinity has been found generally 

 to decrease in the neighborhood of coasts, where rivers discharge 

 their water into the sea, and it is a maximum in the trade zones, 

 and a minimum in the equatorial rain belt. The salinity is 

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