VIII 
PHOSPHORESCENCE OF THE SEA 
173 
the whole surface sparkled as brightly as when first taken out 
of the water. It does not appear probable in this case that 
the particles could have remained so long alive. On one 
occasion having kept a jelly-fish of the genus Diansea till it 
was dead, the water in which it was placed became luminous. 
When the waves scintillate with bright green sparks, I believe 
it is generally owing to minute Crustacea. But there can be 
no doubt that very many other pelagic animals, when alive, are 
phosphorescent. 
On two occasions I have observed the sea luminous at 
considerable depths beneath the surface. Near the mouth of 
the Plata some circular and oval patches, from two to four 
yards in diameter, and with defined outlines, shone with a 
steady but pale light ; while the surrounding water only gave 
out a few sparks. The appearance resembled the reflection of 
the moon, or some luminous body ; for the edges were sinuous 
from the undulations of the surface. The ship, which drew 
thirteen feet water, passed over, without disturbing these 
patches. Therefore we must suppose that some animals were 
congregated together at a greater depth than the bottom of 
the vessel. 
Near Fernando Noronha the sea gave out light in flashes. 
The appearance was very similar to that which might be 
expected from a large fish moving rapidly through a luminous 
•fluid. To this cause the sailors attributed it ; at the time, 
however, I entertained some doubts, on account of the frequency 
and rapidity of the flashes. I have already remarked that the 
phenomenon is very much more common in warm than in cold 
countries ; and I have sometimes imagined that a disturbed 
electrical condition of the atmosphere was most favourable to 
its production. Certainly I think the sea is most luminous 
after a few days of more calm weather than ordinary, during 
which time it has swarmed with various animals. Observing 
that the water charged with gelatinous particles is in an impure 
state, and that the luminous appearance in all common cases 
is produced by the agitation of the fluid in contact with the 
atmosphere, I am inclined to consider that the phosphorescence 
is the result of the decomposition of the organic particles, by 
which process (one is tempted almost to call it a kind of 
respiration) the ocean becomes purified. 
