The influence of light on the colours of organised creation is well shown in the sea. Near the shores we find seaweeds of the most beautiful hues, particularly on the rocks which are left dry by the tides; and the rich tints of the actiniæ which inhabit shallow water must often have been observed. The fishes which swim near the surface are also distinguished by the variety of their colours, whereas those which live at greater depths are gray, brown, or black. It has been found that after a certain depth, where the quantity of light is so reduced that a mere twilight prevails, the inhabitants of the ocean become nearly colourless.—Hunt’s Poetry of Science.
ACTION OF LIGHT ON MUSCULAR FIBRES.
That light is capable of acting on muscular fibres, independently of the influence of the nerves, was mentioned by several of the old anatomists, but repudiated by later authorities. M. Brown Séquard has, however, proved to the Royal Society that some portions of muscular fibre—the iris of the eye, for example—are affected by light independently of any reflex action of the nerves, thereby confirming former experiences. The effect is produced by the illuminating rays only, the chemical and heat rays remaining neutral. And not least remarkable is the fact, that the iris of an eel showed itself susceptible of the excitement sixteen days after the eyes were removed from the creature’s head. So far as is yet known, this muscle is the only one on which light thus takes effect.—Phil. Trans. 1857.
LIGHT NIGHTS.
It is not possible, as well-attested facts prove, perfectly to explain the operations at work in the much-contested upper boundaries of our atmosphere. The extraordinary lightness of whole nights in the year 1831, during which small print might be read at midnight in the latitudes of Italy and the north of Germany, is a fact directly at variance with all that we know, according to the most recent and acute researches on the crepuscular theory and the height of the atmosphere.—Biot.
PHOSPHORESCENCE OF PLANTS.
Mr. Hunt recounts these striking instances. The leaves of the œnothera macrocarpa are said to exhibit phosphoric light when the air is highly charged with electricity. The agarics of the olive-grounds of Montpelier too have been observed to be luminous at night; but they are said to exhibit no light, even in darkness, during the day. The subterranean passages of the coal-mines near Dresden are illuminated by the phosphorescent light of the rhizomorpha phosphoreus, a peculiar fungus. On the leaves of the Pindoba palm grows a species of agaric which is exceedingly luminous at night; and many varieties of the lichens, creeping along the roofs of caverns, lend to them an air of enchantment by the soft and clear light which they diffuse. In a small cave near Penryn, a luminous moss is abundant; it is also found in the mines of Hesse. According to Heinzmann, the rhizomorpha subterranea and aidulæ are also phosphorescent.—See Poetry of Science.
PHOSPHORESCENCE OF THE SEA.
By microscopic examination of the myriads of minute insects which cause this phenomenon, no other fact has been elicited than that they contain a fluid which, when squeezed out, leaves a train of light upon the surface of the water. The creatures appear almost invariably on the eve of some change of weather, which would lead us to suppose that their luminous phenomena must be connected with electrical excitation; and of this Mr. C. Peach of Fowey has furnished the most satisfactory proofs yet obtained.[13]