20 



THE UNIVERSE. 



drink. If with the aid of the microscope we were to 

 scrutinize everything that a single drop of water contains, 

 there would be enough to frighten many people. 



Every one who has sailed at night upon the sea, or passed 

 along its shore, is acquainted with the phenomenon of 

 phosphorescence, which for a long time puzzled the sagacity 

 of the learned. It was attributed to very different causes, 

 but is now known to depend upon the presence of a mul- 



!). Medusa campanidaTia. 



titude of animals. Sometimes, when of small extent, it is 

 caused by fish traversing the waves like a flaming arrow; 

 at other times it is owing to the presence of Medusae, the 

 brilliant disks of which are seen calm and motionless in 

 the depths of the waters; or to the Physsophora, dragging 

 behind them their trains all spangled Avith stars like that 

 of Berenice in the firmament. Certain molluscs too, though 

 enveloped in their shells, are nevertheless phosphorescent. 

 Pliny had previously remarked that the mouths of persons 

 who had eAten Pholades were quite luminous. 



This phenomenon, however, is most frequently seen in 

 places where the sea is in movement; every wave then rolls 

 with luminous foam against the prow of the ship, and the 

 billows gleam like the starry sky. These myriads of phos- 



