PHOSPHORESCENCE. OF THE SEA. -tf 



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 algae (Trichodesmium erythr<zum\ 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 ot 

 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 of a 

 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, medusae, 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 Noctiluca. The motion of a vessel or the splash of 



