UTILITY OF PHOSPHORESCENT LIGHT. 51 



his dangers ; especially if we consider that this lumi- 

 nosity is seen only in the night season, is vivid in 

 proportion to the darkness, disappearing even before 

 the feeble light of the moon ; and also that it increases 

 with the agitation of the sea, so that during the pre- 

 valence of storms it greatly diminishes the dense 

 gloom which at such times is often impenetrable to 

 the moon or stars, throws such a light about the ship 

 and rigging as to enable the sailors to execute their 

 allotted tasks with certainty, and at all times points 

 out to the cautious mariner the lurking danger of 

 sunken rocks, shoals, and unknown coasts, by the 

 phosphorescent or snowy appearance which it gives to 

 the breakers, so as to render them visible at a con- 

 siderable distance, or, where certain forms of it appear, 

 lets him know that he is within soundings, and pro- 

 bably at no great distance from some fatal spot." 



