On Luminous Marine Animals.
There are few phenomena in nature much more striking than the luminous appearance exhibited by the water of the ocean, particularly in tempestuous weather ; terrific, in particular, to landsmen in these cases, as it is splendent and beautiful in the calms of summer. It has accordingly not only been an object of much remark among common observers, but has excited the attention of naturalists at all times, so as to have led to much discussion. From the time of Pliny downwards, frequent inquiries have been made respecting the cause, and accordingly many different theories have been proffered. Some of these, as usual, have been pure hypotheses, even in modern times, where experiment was easy, and its necessity in all such cases acknowledged. Were this not a frequent resource of philosophers in many other departments of natural science, we might be surprised that such explanations should have been offered, even within a few years, and in a case in which investigation was so easy.
With these persons, as with naturalists in general, it was long taken for granted, at it is even yet by some, that this property belonged to the water itself, not to any bodies contained in it. Hence, instead of examining into its real seat, they were induced to speculate on its cause. A Lew of these theories deserve notice, because we are fully sen sible that they have not yet been quite abandoned, in spite of the evidence respecting the real cause wino, has been Produced, and which ought to satisfy the most or incredulous.
_Mayer, and others who followed him, considered that this phenomenon depended on the same cause as the light emitted by the diamond and other substances after expo sure to the sun's rays. He supposed that the sea-water absorbed light which it afterwards gave out. Others were content with calling the light phosphoric, and with sup posing that sea-water was endowed with the property of phosphorescence ; a solution just as satisfactory as all those in which words are substituted for meaning, or in which one term is changed for another. As if these hy potheses were not unintelligible eneigh, this phenomenon was also attributed to electricity, although thc slightest at tention to the nature of this power might have shown that, under no circumstances, could the electric action be ex cited within a body of water, and by the mutual collision of its own parts. Another party attributed the light to the putrefaction of sca-water, although it was not explain ed what the connection was between putrefaction and phosphorescence. But the least knowledge of sea-water
might have shown, that, except in some few rare cases, such as in calms in the tropical latitudes, where many animals are present, the waters of the sea are not subject to this change. On the contrary, and for reasons as ob vious as on the land, nature has made ample provision in the sea, as she has done in the atmosphere, for the speedy decomposition and dissipation of all such dead animal matter as might render that element noxious to its inha bitants. The waves, the tides, the currents, and probably other causes, effect in the ocean what storms do in the air, a renewal of a perpetual state of purity. The ex periments of Dr. Hulme made a nearer approximation to the true cause, by showing that the luminous secretion, or matter attached to the mucus of certain fishes, was diffusible in water. But that even this is not the true one, we shall shortly show.
The luminous appearance of the sea has, by mariners and fishermen, as by philosophers, been attributed to some inherent property in the water itself, and, like all splendid and striking phenomena, has been supposed to arise from some mysterious and recondite quality which it was fruitless to inquire further about. Hence they have neglected inves tigations more within their reach than in that of philoso phers, or they might long since have not only shown what the real seat and origin of this appearance was, but have assisted us at this moment in the enumeration we shall attempt to make of-those bodies in which the property really does reside. To mariners, professionally and hereditarily superstitious, the light elicited by water has been a fruitful source of prognostics, as all meteoric phe nomena arc respecting changes in the weather. That a high degree of phosphorescence in the sea is the fore runner of a storm, is a creed as firmly fixed among them as it is, that changes in the weather are governed by pe riods in lunation, are directed by the moon, although every day's experience contradicts them—not less in the one case than in the other. That it may be fortuitously connected with peculiar states of the atmosphere we do not however deny ; and thus therefore it may really some times forerun changes of weather sufficiently, when added to the prevailing prejudices, to perpetuate this common error.