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Young Folks' Library: Wonders of Earth, Sea and Sky

The Phosphorescent Sea
(From Studies of Animated Nature.)
By
W.S. DALLAS.
It is not merely on land that this phenomenon of phosphorescence is to be seen in living
forms. Among marine animals, indeed, it is a phenomenon much more general, much
more splendid, and, we may add, much more familiar to those who live on our coasts.
There must be many in the British Isles who have never had the opportunity of seeing the
light of the glow-worm, but there can be few of those who have frequented in summer
any part of our coasts, who have never seen that beautiful greenish light which is then so
often visible, especially on our southern shores, when the water is disturbed by the blade
of an oar or the prow of a boat or ship. In some cases, even on our own shores, the
phenomenon is much more brilliant, every rippling wave being crested with a line of the
same peculiar light, and in warmer seas exhibitions of this kind are much more common.
It is now [pg 229] known that this light is due to a minute living form, to which we will afterward
return.
But before going on to speak in some detail of the organisms to which the
phosphorescence of the sea is due, it will be as well to mention that the kind of
phosphorescence just spoken of is only one mode in which the phenomenon is exhibited
on the ocean. Though sometimes the light is shown in continuous lines whenever the
surface is disturbed, at other times, and, according to M. de Quatrefages, more
commonly, the light appears only in minute sparks, which, however numerous, never
coalesce. "In the little channel known as the Sund de Chausez," he writes, "I have seen on
a dark night each stroke of the oar kindle, as it were, myriads of stars, and the wake of the
craft appeared in a manner besprinkled with diamonds." When such is the case the
phosphorescence is due to various minute animals, especially crustaceans; that is,
creatures which, microscopically small as they are, are yet constructed more or less on
the type of the lobster or cray-fish.
At other times, again, the phosphorescence is still more partial. "Great domes of pale gold
with long streamers," to use the eloquent words of Professor Martin Duncan, "move
slowly along in endless succession; small silvery disks swim, now enlarging and now
contracting, and here and there a green or bluish gleam marks the course of a tiny, but
rapidly rising and sinking globe. Hour after hour the procession passes by, and the
fishermen hauling in their nets from the midst drag out liquid light, and the soft sea
jellies, crushed and torn piecemeal, shine in every clinging [pg 230] particle. The night grows
dark, the wind rises and is cold, and the tide changes; so does the luminosity of the sea.
The pale spectres below the surface sink deeper, and are lost to sight, but the increasing
waves are tinged here and there with green and white, and often along a line, where the
fresh water is mixing with the salt in an estuary, there is a brightness so intense that boats
and shores are visible.... But if such sights are to be seen on the surface, what must not be
the phosphorescence of the depths! Every sea-pen is glorious in its light, in fact, nearly
every eight-armed Alcyonarian is thus resplendent, and the social Pyrosoma, bulky and a
free swimmer, glows like a bar of hot metal with a white and green radiance."
Such accounts are enough to indicate how varied and how general a phenomenon is the
phosphorescence of the sea. To take notice of one tithe of the points of interest summed
 
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