COLOUR OP THE SEA. 93 



reflects the hue of the superincumbent sky, and 

 appears to be of the same colour. Thus, if the 

 day be cloudy and rainy the surface of the sea 

 is more or less of a leaden or grey tinge ; if the 

 sky is cloudless or a smart breeze blows to the shore, 

 the waters appear blue, the depth of the colour 

 varying under certain modifications of its causes. 



But the sea has other colours besides those 

 occasioned by its reflecting the hues of the sky. 

 It has colour essential to itself. In shallow places 

 along our shores its colour cannot be very accu- 

 rately observed. In such places it is modified by 

 the reflection of the bottom : if the bottom be, on 

 the one hand of fine white sand, or on the other 

 of dark rocks, the water assumes more or less of 

 the light or a dark hue. It is in the wide ocean 

 that the colour of its waters is best observed. 

 The colour of the sea waters varies in different 

 parts of the ocean from light green to dark blue, 

 independently altogether of atmospheric reflec- 

 tion. The waters of the North Sea and of the 

 Polar regions are light green : those of the 

 regions of the trade wind, and especially of the 

 Indian Ocean, are dark blue. The waters of the 

 great current in the ocean called the Grulf Stream, 

 which flows from the Grulf of Mexico towards the 

 Arctic Seas, are of an indigo blue, and afford a 

 striking contrast with the green of the Atlantic 

 through which they take their course. 



The causes of this dissimilarity are not yet fully 

 understood. But probably one of the chief causes 

 is a difference in the chemical constitution of the 



