SCIENTIFIC TRACTS

AND

FAMILY LYCEUM.

MAY 15, 1834.

[Furnished for the Scientific Tracts and Family Lyceum.]

LUMINOUS APPEARANCE OF THE SEA.

BY CAPT. J. P. COUTHOUY.

"THEY that go down to the sea in ships, and do business in the great waters, these see the works of the LORD, and his wonders in the deep.' To the truth of this remark of the Psalmist, every person who has gone down to the sea' can bear witness. That mighty and unfailing reservoir is in itself, for sublimity and grandeur, a spectacle to which the land has no parallel. Whether its vast expanse is spread out calm and mirror-like, undisturbed, save by the long and heavy swell whose undulations have not ceased since at the word of their Creator, 'the waters were gathered together unto one place,' or broken up into liquid mountains by the breath of the fierce stormit is alone in the severe majesty of its beauty,

'Unchanged, unchangeable, the eternity of Earth!'

But it is not for itself alone that the ocean is wonderful; wild and strange shapes people its depths and sweep over its surface. Glorious creatures replete with life and loveliness, beautiful in form and in hue more manifold than the rainbow, sport in its recesses and gladden the wide waste of waters by their presence. There the huge whale sluggishly heaves his mammoth form above the yielding element, marking his path by sheets of snowy foam, while out of his nostrils goeth smoke as out of a

seething caldron.' Sullen and slow the shark glides past the fearful beholder, like a foul spirit unwillingly brought to the light of day; while the dolphin darts through the waves like a beam of molten gold, or the silver and azure flying fish speeds like an arrow over their crests; and far down where the purple mullet and gold-fish rove,'

There, with its waving blade of green,

The sea-flag streams through the silent water,
And the crimson leaf of the dulse is seen
To blush like a banner bathed in slaughter;

There, with a light and easy motion,

The fan-coral sweeps through the clear, deep sea;
And the yellow and scarlet tufts of ocean

Are bending like corn on the upland lea.'

Among all the strange and wonderful sights however, which present themselves to the view of a stranger journeying over the ocean, there are perhaps none which excite greater surprise, or afford more pleasure, than the phenomenon which forms the subject of the present article. Who, that has witnessed this beautiful appearance, does not remember the inquiring wonder, the fanciful speculations, that arose in his mind, as he gazed for the first time, upon the flood of light which streamed off from the sides of the vessel, interspersed with gems of living lustre in every hue and shade of brilliance? Now, flashing far down in the dark blue water, like a gush of regal diamonds, now gleaming on the surface through the shadow of darkness like the torch of a fairy. Who has not hastened with almost childish eagerness, to examine the minute and glittering particles thrown within his reach by the spray, and too often regretted the inability or indifference of those to whom he turned for information? And who among the bravest, has not felt at least a momentary sensation of awe steal over, and his heart shrink within him, when, from one boundary of the wide horizon to the other, he has seen the ocean seemingly changed in its nature, and rolling like the fabled Phlegethon of the ancients, in waves of liquid flame.

The solution of these singular phenomena has long excited the research of the philosopher, and attracted the attention of the voyager. Many theories have been started to account satisfactorily for their origin. Silberschlag

believed that their nature was phosphoric. Professor J. Mayer supposed the light to be imbibed by, and subsequently evolved from, the surface of the sea. By Gentil it was conjectured to arise from the presence of the electric fluid, because it was occasionally produced by friction. Others attributed it to the putrefaction of marine animals and plants. It is unnecessary at present, to examine the grounds for these opinions, as they are contradicted by all the later observations of naturalists. It is now generally conceded, that the luminous appearance of the ocean is attributable to the presence of innumerable small animals of a gelatinous substance, which emit their light by means of some secretion, the nature of which is, as yet, unknown. These animalculæ are mostly included under the generic term of medusa. Their form and size vary from the refulgent Medusa pellucens, or transparent medusa, which sometimes measures eight inches in diameter, to the sparkling Nereis noctiluca, or night-shining nereis, which is so minute as to be scarcely perceptible to the unassisted eye. The Cancer fulgens, or lightning crab, a small species of shrimp, also possesses this property in a high degree.

The following, it is believed, are the principal varieties of luminous marine animals enumerated by naturalists:Medusa pellucens, discovered by Sir Joseph Banks, during his passage from Madeira to Rio de Janeiro with Capt. Cook, on his first voyage. Medusa noctiluca, described by Forskal, is of an hemispheric form, near three inches in diameter, semi-transparent, of a reddish color with brown spots, the margin scalloped, and it has several broad tentacula depending from the interior. Medusa densa, also described by Forskal, seems rather to be a Beroe. Medusa lucida, discovered by Mr. Macartney an English naturalist, on the coast of England. His description states that it was about half an inch in diameter, the margin undivided, and surrounded on the inside by a row of pale brown spots, with numerous twisted feelers. Four dark lines crossed from the circumference to the centre, from which an irregularly shaped process hung down. When this was examined with a strong lens, it was found to be inclosed in a sheath, and that its extremity

was covered with small cups or suckers, like those on the tentacula of the cuttle-fish. Medusa scintillans, first noticed by the same person, very small, transparent, and of a globular form; their motion slow and graceful, without any apparent contraction. Medusa phosphorea, found by Spallanzani in the Mediterranean, and from his descrip tion, similar to the M. pellucens. He represents it as extremely luminous, shining like a bright flame, and visible at the depth of six or seven fathoms. Pyresoma atlanticum, and Beroe fulgens, both found in the Atlantic ocean, and described hereafter. Pennatula phosphorea, commonly called the sea-pen, found in the Mediterranean. This animal's light is said, by Dr. Shaw, in his History of Algiers, to be so powerful that the fishermen are directed by it in arranging their tackle. The luminous effect is confined to the feather of the pen, or that part which is inhabited by the polyps. Spallanzani affirms that it is only visible when the sea-pen is moving about. The P. grisea, P. grandis, and P. argentea are also said to possess this quality. The Pholas dactylus, a bivalve shell-fish, found on the coasts which border the Mediterranean sea, is well known for its powers of evolving light. As long as eighteen hundred years ago, Pliny observed that every part of its body was filled with a fluid which, like phosphorus, illuminated everything on which it was rubbed. Reaumur confirms the above, and also noticed that the luminous property was communicated to water or any other liquid in which the animal was placed. Limulus noctilucus; this insect was found by Capt. Horsburg, author of the East India Directory, in the Arabian Sea. He compares it, in appearance, to a wood-louse, and says it was covered by a thin shell, from beneath which protruded a number of antennæ, or horns, like mi nute bristles. Cancer fulgens, discovered by Sir Joseph Banks at the same time with the M. pellucens. He remarked that its whole body was frequently illuminated, and emitted very brilliant scintillations. Cancer pulex, sometimes denominated sea-louse. The fact of this insect giving light is doubted by some, but the French academicians Thules and Bernard, assert that they met with

it entirely luminous; and Hablitz, a German writer, states that on examination of a cable which sparkled on being drawn from the sea, he found it covered with the Cancer pulex. Nereis noctiluca: to the presence of this small creature the light of the sea has been very often ascribed, even by persons who never saw it. It is now however, believed to be a rare species, at least in the northern seas. It was first described by Vianelli, in 1749. To the naked eye it appears of a yellowish color, and about the size of an eye-lash. Under the microscope it exhibits many joints; the head has two short feelers, with a sort of horn between them. From the sides project a number of processes, transparent and containing a bunch or tuft of hair, and on the under side are similar processes, resembling the feet of the caterpillar. The above it is believed, are nearly all the marine animals which it is well ascertained are possessed of the faculty of exhibiting light. It will be seen that they are all of the simplest and lowest order of organization. It is not intended to give a full account of all these varieties, but merely to select a few of the most remarkable found in the northern seas, and mention some of the wonderful effects which beings so minute, are enabled by their great numbers to produce.

Perhaps in the whole tribe of luminous creatures, there are none more brilliant than the one designated by the discoverer M. Peron, as the Pyresoma atlanticum. It is from one to three inches in length, of a cylindrical figure, one of its extremities of a conical form, and the other truncated. The body is hollow, and destitute of any organs, except a very delicate structure resembling net-work, which lines the interior of the cavity. The exterior is covered with numerous small tubercles, which are the principal seat of the light, which is reflected in an almost incredible degree in the dark. At a small distance below the surface, the Pyresoma appears similar to a large ruby, giving out the same rich rosy tints for which that gem is remarkable. This creature is not unfrequently met with in clusters of the size of a man's head, when the appearance is extremely beautiful, not unlike the globes frequently placed for show in the windows of druggists.