“On the 8th of June,” he observes, “being then in lat. 30° S., and
long. 27° 5′ W., having fine weather and a fresh south-easterly
trade-wind, and the range of the thermometer being from 78° to 84°,
late at night, the mate of the watch came and called me to witness
a very unusual appearance in the water, which he, on first seeing
it, considered to be breakers. On arriving upon deck, this was found
to be a very broad and extensive sheet of phosphorescence, extending
in a direction from east to west, as far as the eye could reach. The
luminosity was confined to the range of animals in this shoal, for
there was no similar light in any other direction. I immediately cast
the towing-net over the stern of the ship, as we approached nearer the
luminous streak, to ascertain the cause of this extraordinary and so
limited phenomenon. The ship soon cleaved through the brilliant mass,
from which, by the disturbance, strong flashes of light were emitted;
and the shoal, judging from the time the vessel took in passing through
the mass, may have been a mile in breadth. The passage of the vessel
through them increased the light around to a far stronger degree,
illuminating the ship. On taking in the towing-net, it was found half
filled with _Pyrosoma_ (_Atlanticum?_), which shone with a beautiful
pale-greenish light; and there were also a few shell-fish in the net at
the same time. After the mass had been passed through, the light was
still seen astern, until it became invisible in the distance; and the
whole of the ocean then became hidden in the darkness as before this
took place. The scene was as novel as beautiful and interesting; more
so from my having ascertained, by capturing luminous animals, the cause
of the phenomenon.
“The second occasion of my meeting these creatures was not exactly
similar to the preceding; but though also limited, was curious, as
occurring in a high latitude, during the winter season. It was on the
19th of August, the weather dark and gloomy, with light breezes from
north-north-east, in lat. 40° 30′ S., and long. 138° 3′ E., being then
distant about 368 miles from King’s Island (at the western entrance of
Bass’s Straits). It was about eight o’clock P.M. when the ship’s wake
was perceived to be luminous; and scintillations of the same light
were also abundant around. As this was unusual, and had not been seen
before, and it occasionally, also, appeared in larger and smaller
detached masses, giving out a high degree of brilliancy, to ascertain
the cause, so unusual in high latitudes during the winter season, I
threw the towing-net overboard, and in twenty minutes succeeded in
capturing several _Pyrosomata_, giving out their usual pale-green
light; and it was, no doubt, detached groups of these animals that were
the occasion of the light in question. The beautiful light given out by
these molluscous animals soon ceased to be seen emitted from every part
of their bodies; but by moving them about it could be reproduced for
some length of time after. As long as the luminosity of the ocean was
visible (which continued most part of the night), a number of _Pyrosoma
Atlanticum_, two species of _Phyllosoma_, an animal apparently allied
to _Leptocephalus_, as well as several crustaceous animals (all of
which I had before considered as intertropical species), were caught
and preserved. At half-past ten P.M. the temperature of the atmosphere
on deck was 52°, and that of the water 51½°. The luminosity of the
water gradually decreased during the night, and towards morning was no
longer seen, nor on any subsequent night.”[156]