As if to still further carry out the idea of the miner, the animal bears its own light, which, though vivid, could but little more than illumine the stony prison into which the Pholas has willingly ensconced itself. In Borneo, a freshwater form has been found boring in the dead trunks of trees. Pliny was probably among the first to place on record the luminosity of this little borer, having stated that it shone in the mouths of those who ate it; and its phosphorescence has been studied by Réaumur, Beccaria, Marsilius, Galeatus, Montius, and others in modern times. One of Beccaria’s experiments was to ascertain how the light affected certain colors. He secured a Pholas in a dark spot, and placed in its light ribbons of various colors. The white ribbon shone most brilliantly, the yellow next, and the green next, while others were so indistinct as to be hardly noticeable. Substituting liquids for the ribbons, the result was the same. Beccaria also made one of the first practical applications of the phosphorescent Pholas, demonstrating that it could be used as a lamp. This was accomplished by placing one in seven ounces of milk, which rendered the latter so luminous that print could have been read by it, the milk appearing almost transparent. So it is within the bounds of possibility to write a _post-mortem_ description of the Pholas by its own light. It is evident from these simple experiments that the discovery of the secret of phosphorescence, and its practical application to the wants of mankind, would result in revolutionizing present systems,--a heatless, inexpensive, unextinguishable light being the perfection of possibilities in this direction,--and it is not improbable that the experimentalists of olden times may have had this in view when making their investigations. Both Réaumur and Beccaria attempted to render the light of this animal lamp permanent. By placing one in honey, the luminosity was apparently preserved for a year, the light re-appearing whenever the mollusk was placed in warm water. Brandy extinguishes the light, and Galeatus and Montius found that vinegar and wine produced the same result. If the body of Pholas is heated slowly, the light gradually becomes more and more intense, until, finally, at 45° Réaumur, or 56° Centigrade, it disappears, and cannot be restored. The secure position of the Pholas in its impregnable fortress would hardly seem to require a warning or attractive light; and its use must remain a mystery, though theory could, of course, suggest explanations.