226 THE SEAS 



the rays of light from the sun were cut off immediately 

 and completely by the surface water, no plants could 

 survive there and it is likely that our oceans would not 

 contain that wealth of animal life in which they all abound. 

 The amount of light to be found at any depth in the sea 

 depends upon the altitude and strength of the sun, on the 

 weather conditions, and upon the amount of sand and 

 sediment present in the water, that is to say its turbidity. 

 Much light is reflected from the sea surface especially if 

 there are waves, because the light rays glance off the sloping 

 sides of the waves. It is often almost impossible to look 

 towards the setting sun over the sea because of the dazzling 

 path of reflected light, and we must realize that this light 

 is not being reflected only along the path between us and 

 the sun, but all over the sea surface, because from whatever 

 place we look towards the sun we shall always find this 

 path of light. The lower the sun is in the heavens the more 

 its rays are reflected. Thus we see that it is seldom that 

 all the light from the sun penetrates the actual sea surface ; 

 such a thing only happens when the sun is vertically over- 

 head and the sea itself is as calm as glass. But the rays 

 of light that do pass through the surface cannot penetrate 

 right to the bottom in very deep water. Out in the great 

 oceans the darkness on the sea floor thousands of fathoms 

 beneath the surface is absolute. This is because the light 

 itself is absorbed by the w^ater. But all the different 

 colours of which white light is composed are not absorbed 

 to an equal extent. The red rays for instance are absorbed 

 very quickly indeed. It is a matter of several fathoms 

 only before all the red light has gone. It is the blue and 

 violet light that penetrates farthest and in clear ocean waters 

 William Beebe has noticed, on one of his bathysphere dives, 

 that every trace of visible light had vanished at 2,000 feet. 

 Some years ago experiments made in the Sargasso Sea showed 



