LUMINOSITY. 4u 



flash and die like gas-jets on a festive gala night." The pheno- 

 menon is most frequently witnessed when the surface of the sea 

 is ruffled by some gentle breeze, dead calms and very rough 

 weather being alike unfavourable to its production. 



It is well described, as seen around our own shores, by Sir 

 "Walter Scott in his " Lord of the Isles :" 



" Awaked before the rushing prow, 

 The mimic fires of ocean glow, 



Those lightnings of the wave ; 

 Wild sparkles crest the broken tides, 

 And, flashing round the vessel's sides, 



With elfish lustre lave, 

 While far behind, their livid light 

 To the dark billows of the night 



A gloomy splendour gave." 



Over all parts of the ocean alike the waves are lit up at times 

 with these animated fires ; but in the warmer latitudes the 

 spectacle assumes an aspect of extraordinary sublimity and splen- 

 dour. " Between the tropics," says Humboldt, " the ocean simul- 

 taneously develops light over a space of many thousand square 

 miles. Here the magical effect of light is owing to the forces of 

 organic nature. Foaming with light, the eddying waves flash in 

 phosphorescent sparks over the wide expanse of waters, where 

 every scintillation is the vital manifestation of an invisible 

 animal world/ According to the enthusiastic accounts of voy- 

 agers, the appearance of the ocean on these occasions is grand and 

 beautiful as it is possible to conceive. Far as the eye can reach, 

 the crest of every wave, which during the day is white with 

 foam, becomes transformed by darkness into a swelling ridge of 

 light, while here and there, where the billows dash with greater 

 violence, the spray flies up, sparkling and glittering like a 

 shower of stars, and falling again, is lost in a sea of effulgence. 

 Occasionally, too, while the more minute forms of the Acalepha? 

 produce this diffused luminosity at the surface of the ocean, the 

 larger kinds are seen below, illuminating its m) r stic depths 

 some gleaming through the water with a pale and steady light, 

 like submerged moons, others glowing with dazzling brightness, 

 like balls of molten metal, or shooting by like the fiery meteors of 

 the heavens above. 



