With respect to animal matters, he found many to be phosphorescent, in which this property had not before been suspected. Such of the harder substances of this nature as contained carbonate of lime, were observed to possess this quality in a higher degree than those which contained the phosphate. Thus, egg shells, corals, and the shells of fish, gave a more striking light than bones. Other vege table and animal substances, which did not phosphoresce became luminous after drying or burning; and the same in exposure to light, acquired that property by being cooled or heated. Thus, flesh, tendons, bones, and the yolks of eggs, was observed with regard to toasted cheese. Among ve getable matters, coffee, pease, chesnuts, and other sub stances, became also phosphorescent after roasting.
We remarked above, that a light had been observed on the falling of a glacier, and that it was questioned whe ther it was of an electrical nature, or to be referred to this class of phenomena. As Mr. Heinrich has remarked that ice phosphoresces on exposure to light, it is probable that these appearances are both of the same nature. Ile re marked also in this case. that heat augmented the inten sity and diminished the duration of the light, and that cold had a contrary effect. In no case did he succeed in causing transparent fluids to shine.
In Dessaigncs' experiments we find no fluid recorded as phosphorescent but linseed oil ; and, in Mr. Heinrich's, this branch of the subject has also, as we have this moment seen, been passed by. Here Dr. Brewster assists us with a catalogue by which we may enlarge this enumeration of the miscellaneous phosphorescences, for the present, as we are unable to do much towards generalizing or ar ranging them, for want of a sufficient number of sub stances, exhibiting this property, to admit of an useful clas sification. His experiments were performed by heating the different fluids on a hot iron, in the manner practised with the minerals that were thus treated.
Saliva, the white of egg diluted in water, and the so lution of isinglass, were thus found to be phosphorescent. So was a solution of soap, and also one of rhubarb ; there appearing to be little analogy between any of these, ex cept the saliva and the solution of albumen. Oil of olives, like the linseed oil in M. Dessaignes' trials, was found to be possessed of the same property, as was the essential oil of Dill. The phosphorescence of tallow was so obvi ous as to be visible in extinguishing a candle. Of saline solutions he found those of common salt, nitre, and alum, to he luminous ; and it is probable, that this catalogue might be considerably extended. Lastly, alcohol exhibit ed a beautiful light on the heated iron, on which it never inflames, but it is probable that this is an instance of slow combustion, analogous to that of phosphorus, and resem bling the second kind of light which is shown by linseed oil, when it is heated up to near the boiling point.
But we must terminate this part of our subject, on which much information is still wanted, and proceed to consi der the phosphorescence of mineral substances.
Phosphorescence of Minerals.
That phosphorescence was a property belonging to va rious minerals had long been known ; but it was not till the experiments of Dessaignes in France, and those of Dr. Brewster in our own country, that we were acquaint ed either with the numerous circumstances by which it is excited or modified, or with the minerals in which it ex ists. But as those of the former philosopher apply chiefly to general principles, affecting not only minerals but many other substances, we shall reserve an account of them for the end of this article, except where they may particular ly apply to any of the cases now to be mentioned.
Dr. Brewster thinks that the phosphorescent property of minerals was first remarked by the noted Benvenuto Cellini. In his essays on Orificeria, he says, that he had seen a carbuncle (garnet) shine in the dark, and that one of these stones had been found near Rome by means of the light which it emitted in the night. Mr. Boyle, some time after this, observed that a diamond emitted a light in the dark, equal to that of a glow-worm, either when heat ed or rubbed, or sometimes when simply pressed. Other authors have remarked, that a diamond acquired this pro perty only in consequence of a previous exposure to the sun's rays; while many persons have repeated the same experiment without success. In our own trials, we have been uniformly unsuccessful ; and it has now indeed been observed, that a very few diamonds only are possessed of this property ; although, by what particular circumstances in the crystallization or aspect of this stone it is indicated, is not yet known. But this is equally true of many other minerals ; since, among the tremolites, for example, where the eye can trace no reason for the difference, some are found to phosphoresce and others not. In consulting the subjoined list, therefore, which we have borrowed from Dr. Brewster, (Edin. Phil. Journal, vol. i. p. 3830 it is necessary to remember this circumstance, lest an inac curacy should be suspected in the reporter. With regard to this very mineral, tremolite, nothing can be more noto rious, or generally believed, than that it phosphoresces by friction ; yet among the numerous specimens we have ex amined from Glen Tilt, we have never yet in one instance observed it.