(a), a peculiar earth discovered by Vauquelin in the beryl and the emerald. Its general properties are as follows: 1. It is white; 2. Insipid; 3. Insoluble in water; 4. Adhesive to the tongue; 5. Insoluble; 6. Soluble in the fixed alkalis; 7. Insoluble in ammonia; 8. Soluble in the carbonate of ammonia; 9. Soluble in almost every one of the acids (except the carbonic and phosphoric acids), and forming salts of a saccharine taste; 10. Fusible with borax into a transparent glass; 11. Absorbs one fourth of its weight of carbonic acid; 12. Decomposes the alumino-silicates; 13. Is not precipitated by well-saturated hydro-sulphurates.

The specific characters of glucina, which are united in none of the other known earths, are: 1. Its salts are saccharine, and slightly astringent; 2. It is very soluble in the sulphuric acid by excess; 3. It decomposes the alumino-silicates; 4. It is soluble in the carbonate of ammonia; 5. Is completely precipitated from its solutions by ammonia; 6. Its affinity for the acids is intermediate between magnesia and alumine.

One hundred parts of beryl contain 16 of glucina; but for the best method of analyzing the beryl, and of course obtaining the earth, we must refer our readers to the article Mineralogy in this Supplement; and shall conclude this short article with a valuable and judicious remark of Vauquelin's.

"It almost always happens (says this able chemist), in the sciences of observation, and even in the speculative sciences, that a body, a principle, or a property, formerly unknown, though it may often have been used, or even held in the hands, and referred to other simple species, may, when once discovered, be afterwards found in a great variety of situations, and be applied to many useful purposes. Chemistry affords many recent examples of this truth. Klapproth had no sooner discovered the different substances with which he has enriched the science, but they were found in various other bodies; and if I may refer to my own processes, it will be seen, that after I had determined the characters of chrome, first found in the native red lead, I easily recognized it in the emerald and the ruby. The same has happened with regard to the earth of the beryl. I have likewise detected it in the emerald; in which, nevertheless, it was overlooked both by Klapproth and myself in our first analysis: so difficult it is to be aware of the presence of a new substance, particularly when it possesses some properties resembling those already known!"