124+ 
NATURE FOR ITS OWN SAKE 
Harbor 
bottoms. 
Deep-sea 
color. 
red mud bottoms have reddish waters and 
others with sandy bottoms have yellow waters. 
Black streaks in the water are often indicative 
of hidden rocks or dark masses of seaweed, and 
a sunken mud-bank will occasionally produce a 
silver-gray stripe for miles across an inlet. 
But however the bottom may change the local 
color in shallow waters, it has little or no effect 
upon the great seas. Their coloring is produced 
largely by particles of salt and other substances 
held in the water. The dust and moisture par- 
ticles floating in the atmosphere are productive 
of the blue sky, and if we regard the waters of 
the sea as colored by similar phenomena, we 
shall not go far astray, though the analogy may 
not be quite exact in every way. It is doubtless 
the salt-particles in sea-water having the power 
of reflecting blue that make the Mediterranean 
such a dark ultramarine; and the rock-par- 
ticles carried down from the Alps by the Rhone 
make the water of that stream assume a beauti- 
ful green-blue tone even when the reflecting 
blue sky is shut out by clouds. Again, the ef- 
fect of the Blue Grotto, near Capri, is produced 
by light shining through the water from beneath 
and striking particles that apparently turn to 
blue and produce that tone throughout the cave. 
