322 Dzvellers of the Sea and Shore 



shore. From this It is generally concluded to be by 

 far the shallowest of all oceans. 



The deep transparent blue of the ocean has been 

 celebrated in the literature of every age. In just what 

 way the sea assumes its remarkable color does not seem 

 to be well understood. That the depth of the water is 

 in some manner associated with this phenomenon 

 would appear from the fact that the purest blues are 

 mostly far from land, whereas, it is well known, the 

 shallows of the tropics are always green. On the other 

 hand, it may be pointed out that the Rhone, at its 

 emergence from Lake Geneva, and indeed the lake It- 

 self, exhibits an Intensity of blue which surpasses that 

 of any sea. Then, there is also no doubt but that a 

 distinct relationship exists between the color of the 

 water and Its purity, or transparency. Water that con- 

 tains fewer small floating organisms is more blue than 

 Is otherwise the case. An Increase In the turbidity Is 

 generally accompanied by an increasing cast of green. 

 The transparency of sea water has often been measured 

 in different parts of the globe, and It was found that 

 great differences exist between various regions. In the 

 Sargasso Sea a white disk six feet in diameter could be 

 observed 216 feet below the surface; the same disk in 

 the equatorial currents and the cold currents of the 

 north was visible only in about half that depth. The 

 purest oceanic blues are found In the warm regions of 

 the Pacific and the Indian oceans and In the Sargasso 

 Sea of the Atlantic. The optical property of sea water 

 is of considerable biological importance, as it affects 

 the penetration of sunlight and Its consequent Influence 

 on the growth of vegetation. Every plant, of course. 



