GLOSSARY. 



Coal formation. 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 maybe 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 silicious, 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 and 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 limestone 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 ar« 

 accessible to human observation. 



