GLOSSARY. 
Coalformation. Coal measures. These terms are considered 
synomynous, and refer to the great deposite of coal in the older 
secondary rocks, which has been called the "independent coal 
formation." There are, however, deposites of carbonaceous mat- 
ter in all the geological periods, and several of them might also 
be called coal formations. 
Conformable. When strata are arranged parallel to each 
other, like the leaves of a book, they are said to be conforma- 
ble. Other strata lying across the edges of these may be con- 
formable among themselves, but unconformable to the first set of 
strata. 
Conglomerate, or Pudding-stone. Rocks composed of rounded 
masses, pebbles and gravel cemented together by a sihcious, cal- 
careous, or argillaceous cement. 
Cretaceous. Belonging to the chalk formation. 
Crop out and out crop. Terms employed by geologists and 
mining engineers to express the emergence of rock, in place, 
on the surface of the earth at the locality where it is said to 
crop out. 
Crystalline. An assemblage of imperfectly defined crystals, 
like loaf sugar ^ind common white marble. 
D. 
Delta. Alluvial land formed at the mouths of rivers. 
Denudation. A term used to express the bare state of the 
rocks over which currents of water have formerly swept, and 
laid the rocks bare, or excavated them to form valleys of denu- 
dation. 
Deoxidize. To separate oxygen from a body. 
Dikes. A kind of vein intersecting the strata, and usually 
filled with some unstratified igneous rock, such as granite, trap, 
or lava. These materials are supposed to have been injected in 
a melted state into great rents or fissures in the rocks. 
Diluvium and Diluvion. Deposites of bowlders, pebbles, and 
gravel, which many geologists have supposed were produced 
by a diluvial wave or deluge sweeping over the surface of the 
earth. 
Dip. Where strata are not horizontal, the direction in which 
their planes sink or plunge is called the direction of the dip, and 
the angle of inclination the angle of dip. 
Dolomite. A magnesian hmestone belonging to the primary 
class. It is usually granular in its structure, and of a friable 
texture. 
Dunes. Sand raised into hills and drifts by the wind. 
E. 
Earth's Crust. The superficial parts of our planet which are 
accessible to human observation. 
