in bodies, a property directly opposite to fluidity, and by which they resist the impression of any other substance, sometimes in an extreme degree. Quist and others have constructed tables of the hardness of different substances. The method pursued in constructing these tables was by observing the order in which the articles tried were capable of cutting or making an impression upon one another. The following table, extracted from Magellan's edition of Cronstedt's *Mineralogy*, was taken from Quist, Bergman, and Kirwan. The first column shows the hardness, and the second the specific gravity.

| Substance | Hardness | Specific Gravity | |----------------------------|----------|------------------| | Diamond from Ormus | 20 | 3.7 | | Pink diamond | 19 | 3.4 | | Bluish diamond | 19 | 3.3 | | Yellowish diamond | 19 | 3.3 | | Cubic diamond | 18 | 3.2 | | Ruby | 17 | 4.2 | | Pale ruby from Brazil | 16 | 3.5 | | Ruby spinell | 13 | 3.4 | | Deep blue sapphire | 16 | 3.8 | | Ditto paler | 17 | 3.8 | | Topaz | 15 | 4.2 | | Whitish ditto | 14 | 3.5 | | Bohemian ditto | 11 | 2.8 | | Emerald | 12 | 2.8 | | Garnet | 12 | 4.4 | | Agate | 12 | 2.6 | | Onyx | 12 | 2.6 | | Sardonyx | 12 | 2.6 | | Occidental amethyst | 11 | 2.7 | | Crystal | 11 | 2.6 | | Cornelian | 11 | 2.7 | | Green jasper | 11 | 2.7 | | Reddish yellow ditto | 9 | 2.6 | | Schoerl | 10 | 3.6 | | Tourmaline | 10 | 3.0 | | Quartz | 10 | 2.7 | | Opal | 10 | 2.6 | | Chrysolite | 10 | 3.7 | | Zeolite | 8 | 2.1 | | Fluor | 7 | 3.5 | | Calcareous spar | 6 | 2.7 | | Gypsum | 5 | 2.8 | | Chalk | 3 | 2.7 |