“Brilliant:” reflecting or refracting the light in rays and flashes. “Vitreous:” glassy in its texture. “Conchoidal:” convex, like the outside of a shell. “Momentum:” the result of the combined weight and velocity of a body in motion. GEOLOGICAL STRATA referred to in this Volume, arranged in their _descending_ order. _Names of Strata._ _Mineral products._ Lava Pumice-stone, which is its froth or scum. Granite Corundum, sapphires, felspar. Old Red Sandstone Fossil ichthyolites. Carboniferous Series Coal, lignites, jet. New Red Sandstone Jaspers, fossilized wood. Lias of the Oolite Fossil “Saurians.” Wealden Fossil reptiles and mammals. Gault } Crystals, flint-nodules, choanites, Greensand } echini, cray-fish, lignites. Chalk } Tertiary Sands } Amber, carnelians, fossil shells. Clays } GLOSSARY of GASES, MINERALS, GEMS, CRYSTALS, and FOSSILS, named in this Volume. _Simple Substances._ Oxygen: a gas. Silicon } Boron } Elements allied to the gases. Carbon } Alumina } Magnesia } Soluble in acids. Sulphur } Manganese } Iron } Metals. Gold } “Steel” is Iron which has been “carbonized.” _Derived or Compounded._ Diamond } Sapphire } Ruby } Emerald } Topaz } Amethyst } Aquamarine } These are termed “gems” or “precious stones.” Garnet } Pearl } Turquoise } Jargoon } Onyx } Sardonyx } Quartz } Rock-crystal } Tourmaline } These are crystallizations. Spar } Asbestos } Jasper } Chalcedony } Agate } Carnelian } These are concretions. Flint } Bloodstone } Moss-agate } Weed-agate } Mocha-stone } Jet } Amber } Clay } These are exudations, depositions, or fossils. Chalk } Coal } Rock-salt: a chloride of sodium. Kaolin: this is from “felspar.” Echinus } Ammonite } These are fossil Alcyonite } animals, for Troglodyte } the most part Choanite } belonging to Ventriculite } extinct species Icthyolite } of “zoophytes.” Cray-fish } Sharks’ teeth } Sand of the Desert: this is powdered quartz. Sand of the Sea-shore: sandstone dust, mixed and penetrated with salt. Sea-weed: a compound of vegetable carbon, salt, and siliceous particles. MINERALOGICAL AND CHEMICAL KEY to the GLOSSARY. OXYGEN. This is a pure gas, and the most universally diffused substance in nature.