PHOSPHORESCENCE OP THE SEA. 219 



the presence of such countless luminous points scattered 

 through the waters of the ocean. Sometimes the whole 

 surface, far as the eye can stretch, seems one sheet of 

 phosphorescent sheen; while looking down into the 

 water close to the ship large globes of fire are seen 

 slowly moving along at various depths. The wake of 

 the vessel, at the same time, displays the most vivid and 

 varied scintillations, and the spray that breaks on her 

 prow falls off like a shower of many-coloured sparks. 

 One scarcely knows on which part of this wonderful dis- 

 play of fire-works to fix th e attention. One after another 

 attracts our gaze, and in its turn appears most beautiful. 

 The phosphorescence is not constant ; it is most vivid 

 when the water is disturbed. Thus the passing of the 

 vessel causes an illumination, long continued in the 

 wake she leaves behind : while a sudden breeze sweeping 

 over the surface will send a stream of light far across 

 the sea, striking similar to the dartings of the aurora 

 through the realms of air. Such are some of the glories 

 that the tropical ocean presents to us ; similar, but less 

 brilliant illuminations are witnessed on our coasts, espe- 

 cially in warm evenings towards the close of summer, at 

 which season vast multitudes of small Medusae frequently 

 swim along the shore, entering into creeks and bays, and 

 sometimes literally converting the shallower inlets into 

 strata of living jelly. At ordinary times many beautiful 

 kinds may be collected by dragging a small gauze net 

 after the boat, just below the surface of the water. In 

 calm weather these little creatures rise to the upper 

 strata of water, and sink again when the sea is troubled. 

 In structure, the Acalephce or Jelly-fishes are exceed- 



