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seen at fabulous depths. The waves of the sea usually present 

 three principal tints — blue, green, and yellow. The waters which 

 are of an indigo blue are the purest and deepest of all ; those which 

 are yellow contain solid matters, fine sand, mud, &c., in suspension ; 

 green indicates water less charged or of a medium depth. In the 

 most profound depths the ocean is almost black. As Tyndall says 

 " You go to bed surrounded by the deep blue of the Atlantic, and 

 wake in the morning and find the sea a bright green, and rightly 

 conclude you are passing over the shallow banks of Newfoundland." 

 But how is it these variously-coloured and minute particles of solid 

 matter produce the same invariable tints of blue, green, or yellow ? 

 They form myriads of mfinitely small mirrors, reflecting back to 

 the surface the light which has penetrated the body of the liquid. 

 We know, of course, the apparent colour of any object depends not 

 on the rays it absorbs, but on those which, as it were, it rejects or 

 sends back to the eye. Thus a thin layer of sea water absorbs all 

 the rays of the spectrum, except the yellow or light green, which 

 are reflected back to the eye. If the water contains no solid 

 particles, or is of a great depth, tbe sea appears a deep blue, i.e., 

 only the rays from the extreme indigo end of the spectrum are 

 reflected. It is for the same reason sea-foam appears white, al- 

 though composed of transparent molecules of water and air. The 

 reflecting surfaces are so numerous that nearly all the rays are sent 

 back to the eye, thus producing the impression of white on the 

 retina. If we take a piece of the most transparent crystal, and 

 pound it into fine fragments, the powder will, for the same reason, 

 appear white, and the self-same cloud in the sky, composed, as you 

 know, of minute molecules of water, may appear the deepest black 

 or the purest white, as it absorbs or reflects the light. Perfectly 

 black surfaces may reflect white light as one often notices, on the 

 huU of some distant ship, which appears white from reflected light. 

 The pure silvery light reflected from the moon is a still better 

 example, giving us an impression of the purest white, although her 

 surface is in reality covered with jagged rocks and mountains of a 

 hue closely approaching to black. Of course these general laws do 

 not apply to instances where the sea is coloured by the presence of 

 sea- weeds, minute animal organisms, or vast quantities of coloured 

 sohd matter discharged into it, as, for example, the Yellow Sea of 

 China, whose waters are discoloured by the great rivers which flow 

 into it from the interior, laden with coloured mud. One sees here 

 the reason of the same Yellow Sea, but many seas have been 

 named apparently in reference to their colour where the reason is 

 less easy to trace. The White Sea was no doubt so called from its 

 ice ; the Black Sea from its frequent tempests, and the Vermilion 

 Sea of the Oalifomian coast from its waters stained by the influx 



