I:\KTFLV 259 



EARTHS. 



LIME BARYTA STRONTIA MAGNESIA SILICA ALUMINA GLU- 



CINA ZIRCONIA AND YTTRIA. 



Introductory Remarks. 



In the plan of this work, and in connexion with the alkalies, some 

 objections have been stated to the prevailing mode of arranging most 

 of them, and all the earths, under the metals. With . respect to the 

 earths, this course, though highly inconvenient, would perhaps be 

 somewhat less so than in relation to the alkalies ; but I decidedly pre- 

 fer to preserve the old division of earths, notwithstanding the inter- 

 esting discovery that most, if not all,* of them are metallic oxides. 

 Here, as in the case of the fixed alkalies, there can be no difficulty in 

 pursuing the analytical course, by proceeding from the compound to 

 its principles, first describing the earth, and then its composition ; 

 and reverting again to the metallic bases of the earths, when we 

 come to the metals. The great advantage proposed in pursuing this 

 course is, that we are, as early as possible, put in possession of a 

 knowledge of the properties of these important bodies, and that the 

 natural order of earths will remain unbroken ; for, as Dr. Ure (Diet.) 

 very justly remarks, " whatever may be the revolutions of chemical 

 nomenclature, mankind will never cease to consider as earths, those 

 solid bodies composing the mineral strata, which are incombustible, 

 colorless, not convertible into metals by all the ordinary methods of 

 reduction, or when reduced by scientific refinements, possessing but 

 an evanescent metallic existence, and which either alone, or at least 

 when combined with carbonic acid, are insipid, and insoluble in 

 water." 



Nearly the whole crust of our planet is composed of these bodies ; 

 for, the combustibles, and alkalies, and the metals, properly so called, 

 form but a very small proportion of the whole. Nine bodies have been 

 distinguished by chemists, to which the name earth has been given ; 

 they are, as enumerated at the head of this division, Lime, Baryta, 

 Strontia, Magnesia, Silica, Alumina, Glucina, Zirconia, and Yttria. 



The three latter are of little consequence, either in a scientific or 

 practical view, and seem chiefly important in determining the con- 

 stitution of some few gems, and of a few other minerals, most of 

 them rare. Of the remaining six, the most abundant is silica ; lime, 

 is in this respect, the next ; then follows alumina, and then magnesia ; 



* The base of silica seems to have no claim to be called a metal ; should it be 

 melted it may, perhaps, exhibit metallic properties. 



