Cyclone (sī´klōn).—A violent storm, often of vast extent, characterized by high winds rotating about a calm center of low atmospheric pressure. This center moves onward, often with a velocity of twenty or thirty miles an hour.
Denudation (dĕn´û-dā´shŭn or dē´nū-).—The laying bare of rocks by the washing away of the overlying earth, etc.; or the excavation and removal of them by the action of running water.
Deposit.—A body of ore distinct from a ledge; pocket of gravel or pay dirt.
Diplacanthus (dip-lä-kăn´thus).—A fish, belonging to Acanthodii, known only by fossil remains in Old Red Sandstone.
Drifts.—Tunnels leading off from the main shaft, or from other tunnels or levels, through and along the vein.
Drift Matter.—Earth, pebbles and bowlders that have been drifted by water, and deposited over a country while submerged.
Druse (drṳs).—A cavity in a rock, having its interior surface studded with crystals and sometimes filled with water.
Elephas (el´e-fas).—The Latin name for Elephant. The primitive elephant was what is known as the Mammoth.
Fata Morgana (fä´tȧ môr-gä´nȧ).—A kind of mirage by which distant objects appear inverted, distorted, displaced, or multiplied. It is noticed particularly at the Straits of Messina, between Calabria and Sicily, Italy.
Fire-damp.—An explosive carburetted hydrogen of coal mines.