1G 
THE OCEAN WORLD. 
waves roll and break in a silvery foam. Glittering bodies, which 
might be taken for fire-fishes, seem to pursue and catch each other 
—lose their hold, and dart after each other anew. From time 
immemorial, the phosphorescence of the sea has been observed by 
navigators. The luminous appearance presents itself on the crest of 
the waves, which in falling scatters it in all directions. It attaches 
itself to the rudder and dashes against the bows of the vessel. It 
plays round the reefs and rocks against which the waves beat, and on 
silent nights, in the Tropics, its effects are truly magical. This 
phosphorescence is due chiefly to the presence of a multitude of 
mollusks and zoophytes which seem to shine by their own light; 
they emit a fluid so susceptible of expansion, that in the zigzag 
movement pursued they leave a luminous train upon the water, which 
spreads with immense rapidity. One of the most remarkable of 
these minute mollusks is a species of Pyrosoma, a sort of mucous sac 
of an inch long, which, thrown upon the deck of a ship, emits a light 
like a rod of iron heated to a white heat. Sir John Hersehel noted 
on the surface of calm water a very curious form of this phospho- 
rescence ; it was a polygon of rectilinear shape, covering many square 
feet of surface, and it illuminated the whole region for some moments 
with a vivid light, winch traversed it with great rapidity. 
This phosphorescence may also result from another cause. When 
animal matter is decomposed, it becomes phosphorescent. The bodies 
of certain fishes, when they become a prey to putrefaction, emit an 
intense light. MM. Becquerel and Breschct have noted fine phos- 
phorescent effects from this cause in the waters of the Brenta at 
Yenice. Animal matter in a state of decomposition, proceeding from 
dead fish which floats on the surface of ponds, is capable of producing 
large patches of oleaginous matter, which, piled upon tho water, com- 
municates to a considerable extent the phosphorescent aspect. 
Whatever may be the case elsewhere, there are local causes which 
affect the colour of the waters in certain rivers, and even originate 
their names. The Gua'inia of the Bio Negro, or Black Eiver, is 
of a deep brown, which scarcely interferes with the limpidity of 
its waters. The waters of the Orinoco and the Casiquaire have 
also a brownish colour. The Ganges is of a muddy brown, while the 
Djumna, which it receives, is green or blue. The whitish colour 
