Charles Lyell

“ Etym., silex, which see, A siliceous rock is one mainly composed of silex.
Silicified. Any substance that is petrified or mineralized by siliceous earth.
Silt. The more comminuted sand, clay, and earth, which is transported by running water. It is often accumulated by currents in banks. Thus we speak of the mouth of a river being silted up when its entrance into the sea is impeded by such accumulation of loose materials.
Simple mineral. Individual mineral substances, as distinguished from rocks, which last are usually an aggregation of simple minerals. ”

“ Lava. The stone which flows in a melted state from a volcano.
Leucite. A simple mineral found in volcanic rocks, crystallized, and of a white colour. Etym.,leucos, white.
Lias. A provincial name, adopted in scientific language, for a particular kind of limestone, which being characterized, together with its associated beds, by peculiar fossils, is formed in this work into a particular group of the secondary strata. See Table II. I, p. 392.
Ligniperdous. A term applied to insects which destroy wood. Etym., lignum, wood, and perdo, to destroy. ”

“ Statum, Strata. When several rocks lie like the leaves of a book, one upon another, each individual forms a stratum; - strata is the plural of the word. Etym., stratum, part of a Latin verb signifying to strew or lay out. ”

“ A simple mineral, having a shining silvery surface, and capable of being split into very thin elastic leaves or scales. It is often called talc in common life, but mineralogists apply the term talc to a different mineral. The brilliant scales in granite are mica. Etym., mico, to shine. ”

“ Crag. A provincial name in Norfolk_ and Suffolk for a deposit, usually of gravel, belonging to the Older Pliocene period. See Table II. C, p. 389.
Crater. The circular cavity at the summit of a volcano, from which the volcanic matter is ejected. Etym., Crater, a greatcup or bowl.
Cretaceous. Belonging to chalk. Etym., Creta, chalk.
Crop Out. A miner's or mineral surveyor's term, to express the rising up or exposure at the surface of a stratum or series of strata.
Crust of the Earth. See Earth's crust.
Crustacea. Animals having a shelly coating or crust which they cast periodically. ”

“ Marsupial animals. A tribe of quadrupeds having a sack or pouch under the belly, in which they carry their young. The kangaroo is a well-known example. Etym., marsupium, a purse.
Mastodon. A genns of fossil extinct quadrupeds allied to the elephant. So called from the form of the hind teeth or grinders, which have their surface covered with conical mammillary crests. Etym., mastos, mammilla or litttle pap, and odon, tooth.
Matrix. If a simple mineral or shell, in place of being detached, be still fixed in a portion of rock, it is said to be in its matrix. Matrix, womb. ”

“ Thin out. When a stratum, in the course of its prolongation in any direction, becomes gradually less in thickness, the two surfaces approach nearer and nearer; and when at last they meet, the stratum is said to thin out, or dissapear.
Trachite. A variety of lava essentially composed of glassy felspar, and frequently having detached crystals of felspar in the base or body of the stone, giving it the structure of porphyry. It sometimes contains hornblende and augite; and when these last predominate, the trachite passes into the varieties of trap called greenstone, basalt, dolorite, etc. ”

“ Etym., German schalen, to peal, to split.
Shell mar. A deposit of clay, peat, and other substances mixed with shells, which collects at the bottom of lakes.
Shingle. The loose and completely water-worn gravel on the sea-shore.
Silex. The name of one of the pure earths, being the Latin word for flint, which is wholly composed of that earth. French geologists have applied it as a generic name for all minerals composed entirely of that earth, of which there are many of different external forms.
Silica. One of the pure earths. Etym., silex, flint, because found in that mineral. ”

“ A body that resembles or corresponds with another body. A recent shell of the same species as a fossil-shell, is the analogue of the latter.
Anoplothere, Anoplotherium. A fossil extinct quadruped belonging to the order Pachydermata, resembling a pig. It has received its name because the animal must have been singularly wanting in means of defence, from the form of its teeth and the absence of claws, hoofs, and horns. Etym., anoplos, unarmed, and therion, a wild beast. ”

“ Etym., kryptos, concealed, and gamos, marriage.
Crystals. Simple minerals are frequently found in regular 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-crytal, krystallos, being Greek for ice. Hence the regular forms of other minerals are called crystals, whether they be clear or opake. ”

“ Two powers in nature, the action of the one counteracting that of the other, by which a kind of equilibrium or balance is maintained, and the destructive effect prevented that would be produced by one operating without a check. ”

“ Fauna. The various kind of animals peculiar to a country constitute its Fauna, as the various kinds of plants constitute its Flora. The term is derived from the fauni, or rural deities in Roman Mythology.
Felspar. A simple mineral, which constitutes the chief material of many of the unstratified or igneous rocks. The white angular portions in granite are felspar. It is originally a German miner's term. Etym., feld, field, and spath, a very old mineralogical word in Germany, _which seems to have been at first specially applied to a transparent kind of gypsum called selenite. ”

“ Bitmumen. Mineral pitch, of which the tar-like substance which is, often seen to ooze out of the Newcastle coal when on the fire and which makes it cake, is a good example. Etym., Bitumen,pitch.
Bituminous shale. An argillaceous shale, much impregnated with bitumen, which is very common in the coal measures.
Blende. A metallic ore, a compound of the metal zinc with sulphur. It is often found in brown shining crystals, hence its name among, the German miners, from the word blenden, to dazzle. ”

“ Lime combines with great avidity with carbonic acid, a gaseous acid only obtained fuid when united with water, _and all combinations of it with other substances are called carbonates. All limestones are carbonates of lime, and quick lime is obtained by driving off the carbonic acid by heat. ”

“ Ophidious reptiles. Vertebrated animal, such as snakes and serpents. Etym., ophis, a serpent.
Organic remain. The remains of animals and plants; organized bodies, found in a fossil state.
Orthocerata. An extinct genus of the order of Molluscous Animals, called Cephalopoda, that inhabited a long chambered, conical shell, like a straight horn. Etym., orthos, straight, and ceras, horn.
Osseous breccia. The cemented mass of fragments of bones of extinct animals found in caverns and fissures. Osseus is a Latin adjective, signifying bony. ”

“ Subapennines. Loww hills which skirt or lie at the foot of the great chain of the Apennines in Italy. The term Subapennine is applied geologically to a series of strata of the Older Pliocene period.
Syenite. A kind of granite, so called because it was brought from Syene in Egypt. For geological acceptation of the term, see vol. iii. p. 358.
Synclinal axis. See explanation of this term, vol. iii. p. 293.
Talus. When fragments are broken off by the action of the weather from the face of a steep rock, as they accumulate at its foot, they form a sloping heap, called a talus. ”

“ Clayey, composed of clay. Etym., argilla, clay.
Aragonite. A simple mineral, a variety of carbonate of lime, go called from having been first found in Arragon, in Spain.
Augite. A simple mineral of a dark geen, or black colour, which forms a constituent part of many varieties of volcanic rocks.
Avalanches. Masses of snow which, being detached from great heights in the Alps, acquire enormous bulk by fresh accumulations as they descend; and when they fall into the valleys bellow often cause great destruction. They are also called lavanges, and lavanches, in the dialects of Switzerland.
Basalt. ”

“ The term is hence applied to every species of unstratified rock, in which detached crystals of felspar are diffused through a base of other mineral composition. Etym., porphyra, purple.
Portland limestone, Portland beds. A series of limestone strata belonging to the upper part of the Oolite group (see Table II'.H, p. 39l.) , found chiefly in England, in the Island of Portland on the coast of Dorsetshire. The great supply of the building stone used in London is from these quarries. ”

“ Rock salt. Common culinary salt, or muriate of soda, found in vast solid masses or beds, in different formations, extensively in the New Red Sandstone formation, as in Cheshire, and it is then called rock-salt.
Ruminantia. Animals which ruminate or chew the cud. Etym., the Latin verb rumino, meaning the same thing.
Saccharoid, Saccharine. When a stone has a texture resembling that of loaf-sugar. Etym., sacchar, sugar, eidos, form. ”

“ A white earthy limestone, the uppermost of the secondary series of strata. See Table II. F, p. 390.
Chert. A siliceous mineral, approaching in character to flint, but less homogeneous and simple in texture.
Chloritic Sand. Sand coloured green by an admixture of the simple mineral chlorite. Etym.,chloros, green.
Coal Formation. This term is generally understood to mean the same as the Coal Measures. See Table II. _, p. 393. There are, however, “coal formations” in all the geological periods, wherever any of the varieties of coal form a principal constituent part of a group of strata. ”

“ A shining substance like black-lead ; a species of mineral charcoal. Etym.,anthrax,coal.
Anthracotherium. A name given to an extinct quadruped, supposed to belong to the Pachydermata, the bones of which were found in lignite and coal of thertiary strata. Etym.,anthrax, coal, and therion, wild beast.
Anthropomorphous. Having a form resembling the human. ”