PHOSPHORESCENCE OF THE SEA. IT 
At other times coloured animal or vegetable bodies give to the 
water a particular tint. The Red Sea owes its colour to a minute 
microscopic alge (Zrichodesmium erythreum), which was examined 
under the microscope by Ehrenberg; but various other causes of 
its colouration have been suggested. Some microscopists maintain’ 
that it is imparted to it by the presence of minute Infusoria ; others, 
again, ascribe its colour to the fact that the evaporation which goes 
on unceasingly in that riverless district produces reddish salt rocks 
on a great scale all round its shores. In the same manner sea water,’ 
concentrated by the action of the solar rays in the salt marshes of 
the south of France, when they arrive at a certain stage of concentra- 
tion, take a fine red colour, which, however, is due to the presence ofa 
species of red-shelled Entomostracon which only appear in sea water of 
this strength. The red saline lakes on the Great Thibetian watersheds 
are also said to be due to this cause. Strangely enough, these minute 
creatures die when the waters attain greater density by further con- 
centration, and also if it becomes weaker from the effects of rain. 
Navigators often traverse long patches of green, red, white, or 
yellow coloured waters, their colouration being consequent on the 
presence of microscopic crustaceans, medusze, zoophytes, and marine 
plants—the Vermilion Sea on the Californian coast is probably due 
to the latter cause. 
The phenomenon known as Phosphorescence of the Sea is due to 
analogous causes. ‘This wonderful sight is observable in all seas, 
but is most striking in the Indian Ocean, the Arabian Gulf, and 
other tropical seas. In the Indian Ocean, Captain Kingman, of the 
American ship Shooting Star, traversed a zone twenty-three miles 
in length so filled with phosphorescent matter, that a little before 
eight o’clock at night, the water was seen rapidly assuming a white, 
milky appearance, and during the night it presented the appear- 
ance of a vast field of snow. ‘There was scarcely a cloud in the 
heavens,” he continues, “yet the sky, for about 10° above the hori- 
zon, appeared as black as if a storm were raging ; stars of the first 
magnitude shone with a feeble light, and the ‘Milky Way’ of the 
heavens was almost entirely eclipsed by that through which we were 
sailing.” Some of the animals which produced this appearance were 
thought to be about six inches long, and appeared formed of a 
gelatinous and translucent matter. At times, the sea was one blaze 
of light, produced by countless millions of those minute globular 
creatures, called (Voctiluca. The motion of a vessel or the splash of 
