30 THE WORLD OF THE SEA. 
in a square inch there were 25,000,000 individuals. As this 
coloration extended to a considerable depth, it would be impossible 
to calculate the number of living creatures. In the Red Sea this 
coloration is seen under certain circumstances, and hence its name. 
In this case, as in the other, the colour is due to a microscopic sea- 
weed. “On the 1oth of December,” says M. Ehrenberg, “I saw 
from Tor, near Mount Sinai, the whole bay, of which the village is 
the port, red as blood; the open sea, beyond the coral reef which 
fringes the shore, kept its ordinary colour. The wavelets carried 
to the shore during the heat of the day a purple mucilaginous 
matter and left it upon the sand, so that in about half an hour the 
whole bay at low tide was surrounded by a red fringe. I took 
some of the water to my tent ina glass. It was easy to see that 
TRICHODESMIUM EHRENBERGII. 
the coloration was due to little flocks, scarcely visible, often 
greenish, and sometimes of an intense green, but for the most part 
a deep red, the water in which they were swimming being per- 
fectly colourless. Upon examining them with a microscope, I found 
that the flocks were formed of bundles of fibres. These bundles 
were rarely as much as one-twelfth of an inch long. They were 
spindle-shaped and were contained in a kind of mucilaginous enve- 
lope. During the day they remained upon the surface of the water, 
but at night they sank to the bottom of the glass; some time 
after they came up again.” This sea-weed is called the Red 
Trichodesmium. M. Evenot Dupont, a noted barrister in the 
Mauritius, recounts that on the 15th of July, 1843, the sea, as 
far as the eye could reach, was tinted with red. The surface 
seemed covered with a material of a brick-dust colour; a 
little mahogany dust would have produced the very effect. 
M. Dupont attached a basket to a cord, and drew up some of 
