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Diluvium, An accumulation of loose sand and gravel, and other mate- 
rials, which some geologists suppose to have been collected or spread 
over a district by the action of a deluge. 
Dip. The angle w^hich a stratum or series of strata make With, the plane 
of the horizon. The direction of djip^ is the point of compass to- 
wards which the strata sink or plunge, and the angle of dip is the 
amount in degrees which the planes of the strata make with the plane 
of the horizon. 
Dislocation. A lateral or vertical displacement of a vein, stratum or 
series of strata, destroying thereby the coincidence of the planes of 
stratification in the same formation, and breaking the continuity of 
veins, dykes, &c. 
Dolerite, one of the trap rocks, composed of feldspar and augite. 
Dolomite, a magnesian carbonate of hme. 
Drift, a horizontal passage into a mine. 
Dunes or doivns. Sand raised into hills and drifts by the wind. 
Dykes or dikes. Veins of stony or rocky matter, belonging to the un- 
stratified class, as granite, greenstone, lava, 6cc. which intersects the 
strata or cut through them, and generally approaching to verticality. 
It is a Scottish term for wall, as the dyke often projects upward above 
the strata in the form of a wall. The materials forming a dyke, are 
supposed to have been injected in a melted state from beneath, into 
cracks and fissures which have been formed by the drying of the 
earth's surface, or by convulsions of a more powerful kind, as earth- 
quakes. 
Earth's crust. The superficial parts of the earth's surface, which are 
accessible to observation. 
Eocene. An era or period which commenced with the present order of 
things, applied with particular reference to the animate creation ; it 
signifies daivn. 
Estuary. An inlet of the sea towards the land. The extent is confined 
to the limits of salt water, or the area in which fresh and salt water 
mingle. 
ExuvicE. Fossil remains of animals. 
Fault. Displacement of veins, dykes and strata commencing first in 
their fracture and ending in their removal in some direction by which 
the continuity of their planes is destroyed. See Dislocation. 
Feldspar, one of the simple minerals, and next to quartz one of the 
most abundant. 
Feldspathic, of or belonging to feldspar. 
Ferruginous, containing iron. 
Fulviatile, belonging to a river. 
Formation. Deposits having a common origin, or formed during the 
same era or period. 
Fossils. Remains of plants and animals buried in the earth. 
Fossiliferous. One of the grand divisions of rocks characterized by the 
presence of fossils. 
Galena. Sulphuret of lead, or sulphur and lead ; one of the common 
ores of lead. 
Gangue. The earthy or rocky material which embraces directly the 
metalliferous compounds in any vein. 
