The casetorwhite sugar is universally known, and its phosphorescence is extremely brilliant, while it is excited by a very moderate friction. In the breaking of the lumps by the common nippers, it is extremely familiar, and it is also readily excited by rubbing two lumps together. No smell is yielded, nor does any circumstance occur by whist. we can be led to conjecture the cause or real nature of the light.
In one instance, not long since, a light analogous to was observed to be produced by ice. This happened in Switzerland, when the Glacier of the Weisshorn fell. As it struck on the valley below, a bright light was given out, respecting which there could be no mistake, as it was witnessed by many persons. It was sug gested that this might be either electrical or phosphoric, but we are rather inclined to rank it under the latter head. More facts of the same nature are hover required, since this is, as yet, as far as we know, a solitary It is well known that the skunk,( Viverra pu:atoria,) the zorrillo of the Spaniards, which inhabits South America, has the power of discharging, to a distance of six feet or more, its urine, as a means of defence against its pur suers. This liquid is so peculiarly offensive as to exceed in that respect all things that can possibly be imagined. It is at the same time so acrid as to inflame the skin, and produce a sensation of burning, which lasts for many hours. Azara,,•ho improperly calls this animal Yagouare, since Jaguar is the American leopard, says, that when this secretion is discharged in the dark, it is phosphorescent. Whatever the cause may be in this case, it is not likely that it will soon he in% estigated more narrowly.
According to M. Dessaignes, whose experiments on this subject are very numerous, it was found that glass and porcelain shone when heated to a temperature of 325° of the centigrade thermometer, as we also notice under the head of mineral phosphorescence. The same happens with respect to many of the alkaline or earthy salts, but at different degrees of temperature. In some of the me tallic oxides, provided they be in a vitrified state, and also in some of the metallic salts, it equally occurs. Among these we may enumerate the sulphate and muriate of soda and of potash, the metallic phosphates, nitrate of lime, and sul phurate of lime, the last familiarly known as the phos phorescent substance of Canton's phosphorus.
The phenomena presented by this latter substance are somewhat remarkable, and require a little additional no tice. It shines equally, whether it has been exposed to the light of the sun, or to any of the coloured rays of the prism, or to the light of the moon, or that of a lamp. Most other substances which shine by absorbing light require that of the sun.
The property of phosphorescing by the application of heat has also been observed in some vegetable and animal substances; and we have thought fit to separate these cases from the former, as appearing to be of a different nature, and to proceed from a different cause.
If linseed oil be heated to 125° of the centigrade ther mometer, although that should be in a vacuum, or under water, it becomes luminous ; but when the light ceases, it does not recover again in the same circumstances. If it be heated in the open air to the boiling point, or near it, a very bright light is produced. This, however, appears to be of a different natut e, since it is extinguished by carbonic acid, and restored by the access of atmospheric air. The first appears to be a simple phosphorescence, similar to that of mineral substances; whereas the latter is probably a species of combustion, analogous to the slow burning of phosphorus.
Mr. Heinrich, one of the latest writers on this subject, has remarked, that many other vegetable substances became phosphorescent by exposure to light. His method was, to remain himself in a perfectly dark room for half an hour or more, and to expose the substances under experi ment to the light of the day for about ten seconds, taking care not to expose them to the rays of the sun, in order to prevent them from being heated. They were then ob served in the dark chamber, where his eyes had become sensible to the least quantity of light. With respect to woods, he found those of hot climates more luminous than those of our own. The wood of the hazel was amongst those which displayed the most of this property. Cotton was very feebly phosphorescent, as were most dried plants ; and he found that paper and linen, or other bleached ve getable matters, were more luminous than the sante sub stance in a natural state.