A boat containing dead mackerel often presents the appearance of being loaded with coals of fire, each fish gleaming with a soft phosphorescent light, that seems to arise in the greasy mucus which covers them. Place one of these luminous fishes in the water, and the latter will soon assume a like appearance. Vegetables piled in cellars often appear phosphorescent, especially potatoes and cantaloupes. In a case of the former, a servant seeing the brilliant light gave an alarm of fire, arousing the neighborhood. The men rushed in, and the cellar was well flooded before it was discovered that some unoffending potatoes were the cause of the alarm. CHAPTER XIX. LUMINOUS SHOWERS. In many old works, accounts are found of so-called showers of fire, during which the entire heavens seemed filled with gleaming drops, that threatened to burn every living thing, but were in reality harmless; the exhibition being merely another instance of this strange phenomenon of heatless light. Some years ago a party of peasants were making the ascent of one of the high peaks of the Alps, when they were caught in a rain-storm, which produced a demoralizing effect upon them. As the rain fell, it seemed to become luminous, and drops of fire apparently ran from their clothing and beards. Their attempts at brushing it away, while adding to the startling nature of the phenomenon, showed, however, that it was perfectly harmless. Dr. Phipson records some interesting instances of this kind of phosphorescence, of which the following may be cited:-- M. de Thielan observed on Jan. 25, 1822, near Freyburg, a most extraordinary spectacle. A heavy snow had been falling during the early part of the evening, and the trees, branches, limbs, and leaves quivered and scintillated with a resplendent bluish light, while the drops of rain upon the grass left golden trains as they dripped to the ground. [Illustration: PLATE XXIII. DEEP SEA ANGLER. (_Melanocetus johnstoni, Gth._)] Arrago records similar occurrences: In 1731 a priest named Hallai, who lived at Lessay, near Constance, states that he observed one evening during a severe thunder-storm, rain falling which looked like _drops of red-hot liquid metal_. Bergman, the eminent Swedish chemist, communicated to the Royal Society of London, in 1761, that late in the afternoon upon two occasions, though hearing no thunder, he had seen rain which glittered as it fell upon the ground, making it look as if covered with waves of fire. M. Pasumot, on May 3, 1768, was overtaken, while walking near Arnay-le-Duc, on an open plain, by a very heavy storm. The rain collecting on the brim of his hat, he stooped his head to allow it to run off, when to his astonishment, as it encountered that which fell from the clouds, at about twenty inches from the ground, _sparks were emitted_ between the two portions of liquid.