The base of _lime_ is CALCIUM. This metal was satisfactorily obtained first by Sir H. Davy. It is of a whiter color than the two last mentioned metals; and like them decomposes the air and water, and thus becomes lime, which is an _oxide of calcium_. The _base_ of common _limestone is_, of course, _a metal_. The base of _magnesia_ is MAGNESIUM. This metal was discovered by Sir H. Davy, but in very small quantities; sufficient, however, to determine its strong affinity for oxygen, so as to decompose water, and thus oxidize, and become the earth magnesia, which is a metallic oxide. The base of common magnesia is, of course, a metal. 3. The bases of the five earths, _alumina_, _glucina_, _yttria_, _zirconia_, and _silica_. The base of _alumina_ is ALUMINIUM. The existence of this metal was pretty satisfactorily ascertained by Sir H. Davy, and subsequently _established_ by Wöhler. It is very difficult to obtain it, as the preparation is attended with intense heat and light. When obtained it is generally in small scales of a metallic lustre. It requires a great heat to fuse it; and when heated to redness in the open air, it burns with a bright light, and the product is an _oxide of aluminium_, which is _pure clay_, of a white color, and quite hard. This oxide, or pure clay, is very abundant in the composition of the earth, though generally very much adulterated. It is found in all countries and used for making bricks, porcelain ware, pipes, &c. When pure it sometimes crystallizes. Hence it is capable of forming some of the most beautiful _gems_: as the sapphire and ruby, which are pure crystallized clay. _Clay, then, has a metallic base._ The base of _glucina_, is GLUCINIUM. Glucina was first discovered by Vauquelin in 1798, and by analogy its base was _supposed_ to be metallic, which has since been confirmed by Dr. Wöhler, who has obtained the base in the form of a metal. _An. de ch. et de ph. Sept. 1828, as quoted by Dr. Bache, Turner’s Chem. p. 303._ The base of _yttria_ is YTTRIUM. This metal was obtained in a separate state by Dr. Wöhler, (See last quoted authority,) though its existence was inferred by Godolin who discovered the earth which is an oxide of this metal. The base of _zirconia_ is ZIRCONIUM. The earth was discovered by Klaproth in 1789, and its metallic base clearly established by Berzelius 1824.