"The earths constitute the bases of the fossil kingdom. Though they have frequently been suspected to be compound bodies, and several attempts have been made to decompose them, it does not yet appear but that they are simple or elementary substances. Some of the earths possess alkaline properties; others are without such... but they all partake of the following characters: 1. They are incombustible, or do not unite with oxygen; 2. they are inferior to the metals in lustre and opacity; 3. they are sparingly soluble in water; 4. they are difficultly fusible, or resist great heat with out alteration; 5. they combine with acids; 6. they combine with each other, and with metallic oxides; and, 7. their specific gravities are from 1 to 5."