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Show 66 GJ.OSSARY. CRETACEous. Belonging to chalk. Elym., Creta, chalk. CRoP OuT. A miner's or mineral surveyor's term, to expres~ the rising up or exposure at the surface of a stratum or senes of strata. CRUST oF THE EARTH. See Earth's crust. . . CRUSTACEA. Animals having a shelly coatmg or crust wh1ch they cast periodically. Crabs, shrimps, and lobsters ar~ exa~ples. CRYPTOGAMIC. A name applied to a class of plants m winch the fructification, or organs of reproduction are concealed. Etym., "PV7rTO!:, kryptos, concealed, and yapo!:, gamo~, marriage. CRYSTALS. Simple minerals are frequently found m r~gular forms, with facets like the drops of cut glass of chandeliers. Quartz being often met with in rocks in such forms, and beautifully transparent like ice, was called rock-crystal, ,;pvura'A'Aor;, crystallos, being Greek for ice. Hence the regular forms of other minerals are called crystals, whether they be clear or opake. CRYSTALLIZED. A mineral which is found in regular forms or crystals is said to be crystallized. CRYSTAJ:LINE. The internal texture which regular crystals exhibit when broken, or a confused assemblage of ill-defined crystals. Loaf-su<Tar and statuary-marble have a crystalline texture. Sugar-c~ndy and calcareous spar are crystallized. CYCA.DE..E. An order of plants, which are natives of warm climates, mostly tropical, although some are found at the Cape of Good Hope. They have a short stem, surm~unted ~y a peculi~r foliage, termed pinnated fronds by botamsts, winch spreads m a circle. The growth of these plants is by a cluster of fresh fronds shooting from the top of the stem, and pusl1ing the former fronds outwards. These last decay down to their bases, which are broad, and remain covering the sides of the stem. The term is derived from KvKa{;, cycas, a name applied by the ancient Greek naturalist Theophrastus to a palm, said to grow in Ethiopia. CYPERACEA. A tribe of plants answering to the English sedges ; they are distinguished from grasses by their stems being solid and generally triangular, instead o~ being hollo.w and round. Together with graminete they constitute what wnters on botanical geography often call glumacete. DEBACLE. A great rush of waters, which breaking down all opposing barriers, carries forward the broken fragments of rocks, and spreads them in its course. Etym., deb.acler, French, to u~bar, to break up as a river does at the cessatron of a long-contmued frost. GLOSSARY. 67 DELTA. When · a great riVer before it enters the sea divides into serarate streams, they often divero-e and form two sides of a triangle the sea bei tl b 0 · . ' ng 1e ase. The land mcluded by the three lmes, and which is invariably alluvial, is called a delta from its resemLlance to the letter of the Greek alphabet which goes by that nam.e A· Geolo g1·s t s ext en d t l1 e boundart.e s of the delta, so as to mclude all the alluvial land outside the triangle which has been formed by the river. ' DENUDATION. The carrying away of a portion of the solid materials of the land, by which the inferior parts are laid bare. Elym., denudo, to lay bare. DEsiCCATION. The act of drying up. Etym., desicco, to dry up. DIAGONAL STRATIFICATION. For an explanation of this term, see vol. iii. p. 174. DICOTYLEDONous. A grand division of the vegetable kingdom founded on the plant having two cotyledons or seed-lobes: Etym., Ot!:, dis, double, and cotyledon. DIKES. :When a mass of the unstratified or igneous rocks, such as gran~te, trap, and lav~ appears as if injected into a great rent in the stratified rocks, cuttmg across the strata, it forms a dike; and ~s t~1py a~e sometimes seen running along the ground, and proJCCtmg, hke a wall, from the strata on both sides of them being worn away, they are called in the north of England and in Scotland ~ikes, the pruvi.ncial name fur wall. It is not easy to draw the lme b~twee~ d1kes and veins. The former are generally of larger thmensJOns, and have their sides parallel for conside~ able distances ; while veins have generally many ramificatiOns, anu these often thin away into slender threads. DILUVJUl\1. Those accumulations of gravel and loose materials which, ~y some ~eol.ogists, are said to have been produced by the actiOn of a dliuvmn wave or deluge sweeping over the surface of the earth. Etym, diluvium, deluge. DIP. ~Vhen a stratum does not lie horizontally, but is inclined, the pomt of the compass towards which it sinks is called the dip of the stratum, and the angle it makes with the horizon is called the angle of dip or inclination. DIPTERA .. An order of insects, comprising those which l1ave only two wmgs. Etym., Ot~, dis double, and 7rTEpov, pteron, wing. DoLERITE. One of the varieties of the trap-rocks, composed of augite and felspar. DoLOl\~ITE. A crystalline limestone, containing magnesia as a conetltuent part: Named after the French geologist Dolomieu. DuNEs. Low lulls of blown sand that skirt the shol'es of Holland , c2 |