ancient group of secondary strata; but any bed containing coal may
be said to be carboniferous. _Etym._, _carbo_, coal, and _fero_, to
bear.

CATACLYSM. A deluge. _Etym._, [Greek: kataklyzo], _catacluzo_, to
deluge.

CEPHALOPODA. A class of molluscous animals, having their organs of
motion arranged round their head. _Etym._, [Greek: kephale],
_cephale_, head, and [Greek: poda], _poda_, feet.

CETACEA. An order of vertebrated mammiferous animals inhabiting the
sea. The whale, dolphin, and narwal are examples. _Etym._, _cete_,
whale.

CHALCEDONY. A siliceous simple mineral, uncrystallized. Agates are
partly composed of chalcedony.

CHALK. A white earthy limestone, the uppermost of the secondary
series of strata.

CHERT. A siliceous mineral, nearly allied to chalcedony and flint,
but less homogeneous and simple in texture. A gradual passage from
chert to limestone is not uncommon.

CHLORITIC SAND. Sand colored green by an admixture of the simple
mineral chlorite. _Etym._, [Greek: chlorys], _chlorus_, green.

CLEAVAGE. Certain rocks, usually called Slate-rocks, may be cleaved
into an indefinite number of thin laminae which are parallel to each
other, but which are generally not parallel to the planes of the
true strata or layers of deposition. The planes of cleavage,
therefore, are distinguishable from those of stratification.

CLINKSTONE, called also phonolite, a felspathic rock of the trap
family, usually fissile. It is sonorous when struck with a hammer,
whence its name.

COAL FORMATION. This term is generally understood to mean the same
as the Coal Measures, or Carboniferous group.

COLEOPTERA. An order of insects (Beetles) which have four wings, the
upper pair being crustaceous and forming a shield. _Etym._, [Greek:
koleos], _coleos_, a sheath, and [Greek: pteron], _pteron_, a wing.

[Illustration: Fig. 98.

CONFORMABLE. When the planes of one set of strata are generally
parallel to those of another set which are in contact, they are said
to be conformable. Thus the set _a_, _b_, Fig. 98, rest conformably
on the inferior set _c_, _d_; but _c_, _d_ rest unconformably on E.]

CONGENERS. Species which belong to the same genus.

CONGLOMERATE, or PUDDINGSTONE. Rounded water-worn fragments of rock
or pebbles, cemented together by another mineral substance, which
may be o