No. 200.] 
377 
Dip, The angle which a stratum or series of strata make with the plane 
of the horizon. The direction of dip j is the point of compass towards 
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 se- 
ries 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 lime. 
Drift,) a horizontal passage into a mine. 
Dunes J or downs. Sand raised into hills and drifts by the wind. 
Dykes ^ or dikes. Yeins of stony or rocky matter, belonging to the un- 
stratified class, as granite, greenstone, lava, &c. which intersect tha 
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 formino- a 
o 
dyke, are supposed to have been injected in a melted state from be- 
neath, 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 
earthquakes. 
EartJi'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 dawn. 
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. 
Exiivice. 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. 
FeldspathiCj of or belonging to feldspar. 
Ferruginous^ containing iron. 
Fluviatikj 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 me- 
talliferous compounds in any vein. 
Garnet, A hard reddish or brownish mineral usually crystallized in the 
form of a solid having twelve rhombic or diamond shaped faces or 
planes. 
[ Assem. No. 200. J 44 
