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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 infinitely 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, the sea appears a deep blue, 7.e., 
only the rays from the extreme indigo end of the spectrum are 
reflected. Itis 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 
hull of some distant ship, which appears white from reflected light. 
The pure silvery light reflected from the moon isa 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 
solid matter discharged into it, as, for example, the Yellow Sea of 
ina, 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 
‘ofthe Californian coast from’ its “Watérs stained by the influx 
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