"The brilliant discovery by Sir H. Davy in 1808, of the metallic bases of , soda, strontia, and lime, subverted the ancient ideas regarding the earths, and taught us to regard them as all belonging, by most probable analogies, to the metallic class. According to an ingenious suggestion of Mr Smithson silica, however, ought to be ranked acids, since it has the power, in native mineral compounds, of neutralizing the alkaline earths, as well as the common metallic oxides. But as this property is also possessed by many metallic oxides, it can afford no evidence against the metallic nature of the siliceous basis. Alumina, by the experiments of Ehrman, may be made to saturate lime, producing a glass; and the triple compounds of magnesia, alumina, and lime, are perfectly neutral in . We might therefore refer alumina, as well as silica, to the same class with the oxides of , , , columbium, , , and . Alumina, however, bears to silica the same relation that oxide of antimony does to that of arsenic; the antecedent pair acting the part of bases, while the consequent pair act only as acids. The compound of the fluoric principle with silica is... mysterious... The almost universal function which silica enjoys, of saturating the alkaline oxides in the native earthy minerals, is exhibited in a very striking manner in Mr Allan's valuable Synoptic Tables. From his fifth to his fifteenth table of analyses, the column of silica is always complete, whatever deficiency or variation may occur in the columns of the earthy bases. At least, only a very few exceptions need be made for the oriental gems, which consist of strongly aggregated alumina."