34. _Alumine_ is a kind of earth, so called from its forming the basis of alum (197). It is soft, compact, and tenacious; about twice the weight of water, and, when breathed upon, has a smell which is peculiar to all clayey productions. In the fire it shrinks, and becomes so hard as even to yield sparks when struck against steel. It readily absorbs water, and is dissolved by most acids. Some writers state that pure alumine has been discovered in a native state near Halle, in Germany. It is found in a crystallized form, and nearly in a state of purity, in the Oriental ruby and sapphire. The name of _argil_, or clay, has sometimes been applied to it; but, in mineralogy, this name has usually been given to a mixture of alum, quartz, and other substances. Sir H. Davy has obtained from alumine a metallic basis, called _aluminum_. 35. _Zircon_, when freed from those substances with which it is combined, is a white and somewhat rough powder, insipid to the taste, insoluble in water, and about four times as heavy as that fluid. It is found in the two kinds of precious stones called jargoon and hyacinth, and has not hitherto been applied to any useful purpose. 36. _Glucine_ is a kind of earth of peculiar nature, which is found in the emerald and beryl, and, when purified, forms a soft and white powder, without smell, and of sweetish taste. To the last of these qualities it is indebted for its name, which is derived from a Greek word signifying sweet. It is somewhat unctuous to the touch, and about three times as heavy as water. The uses of this earth, whatever they may be, are not known. 37. _Yttria_ is an earth which, among other particulars, differs from glucine by its weight, as it is nearly five times heavier than water. In a natural state it occurs as the basis of a black Swedish mineral, called gadolinite. When cleansed, by chemical process, from all its impurities, it is a fine, white, and inodorous powder. 38. _Barytes_ is a white, porous, and very heavy earth, which can only be obtained pure by chemical process. It is easily reduced to powder, and is soluble in all kinds of acids. To the taste it is harsh and caustic; and, if taken into the stomach, proves an extremely virulent poison. In some respects it agrees with the alkalies (42), particularly in its property of changing blue vegetable colours to green, and in corroding, like them, though with less energy, all kinds of animal substances. From these circumstances it has sometimes been denominated an alkaline earth. Saturated with sulphuric (24) and carbonic acid (26), it constitutes the minerals denominated sulphat and carbonat of barytes (196). It has been discovered to have a metallic base, which is called _barium_.