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hand;

quadrus, a derivative of the Latin word for the number four, and manus, the four feet of those animals being in some degree usable as hands. QUA-QUA-VERSAL DIP. The dip of beds to all points of the compass around a centre, as in the case of beds of lava round the crater of a volcano. Etym., quâ-quâ versum, on every side.

QUARTZ. A German provincial term, universally adopted in scientific language for a simple mineral composed of pure silex, or earth of flints: rock-crystal is an example.

RED MARL. A term often applied to the New Red Sandstone, which is the principal member of the Red Sandstone Group. See Table I., K, Vol. II. p. 455. RETICULATE. A structure of cross lines, like a net, is said to be reticulated, from rete, a net.

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, such as the ox, deer, &c. Etym., the Latin verb rumino, meaning the same thing.

SACCHAROID, SACCHARINE. When a stone has a texture resembling that of loafsugar. Etym., anxap, sacchar, sugar, and ados, eidos, form.

SALIENT ANGLE. In a zigzag line,

a a are the salient angles, b b the re-entering angles. Etym., salire, to leap or bound forward.

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SALT SPRINGS. Springs of water containing a large quantity of common salt. They are very abundant in Cheshire and Worcestershire, and culinary salt is obtained from them by mere evaporation.

SANDSTONE. Any stone which is composed of an agglutination of grains of sand, whether calcareous, siliceous, or of any other mineral nature.

SAURIAN. Any animal belonging to the lizard tribe. Etym., σavpa, saura, a lizard. SCHIST is often used as synonymous with slate; but it may be very useful to distinguish between a schistose and a slaty structure. The granitic or primary schists, as they are termed, such as gneiss, mica-schist, and others, cannot be split into an indefinite number of parallel laminæ, like rocks which have a true slaty cleavage. The uneven schistose layers of mica-schist and gneiss are probably layers of deposition which have assumed a crystalline texture. See "Cleavage." Etym., schistus, adj. Latin; that which may be split.

SCHISTOSE ROCKS. See "Schist."

SCORIA. Volcanic cinders. The word is Latin for cinders.

SEAMS. Thin layers which separate two strata of greater magnitude. SECONDARY STRATA. An extensive series of the stratified rocks which compose the crust of the globe, with certain characters in common, which distinguish them from another series below them called primary, and from a third series above them called tertiary. See Vol. II. p. 432; and Table I., Vol. II. p. 454. SECULAR REFRIGERATION. The periodical cooling and consolidation of the globe from a supposed original state of fluidity from heat. Sæculum, age or period. SEDIMENTARY Rocks, are those which have been formed by their materials having been thrown down from a state of suspension or solution in water.

SELENITE. Crystallized gypsum, or sulphate of lime-a simple mineral. SEPTARIA. Flattened balls of stone, generally a kind of iron-stone, which, on being split, are seen to be separated in their interior into irregular masses. Etym., septa, inclosures.

SERPENTINE. A rock usually containing much magnesian earth, for the most part unstratified, but sometimes appearing to be an altered or metamorphic stratified rock. Its name is derived from frequently presenting contrasts of colour, like the skin of some serpents.

SHALE. A provincial term, adopted by geologists to express an indurated slaty clay. Etym., German schalen, to peel, to split.

SHELL MARL. 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. SILICATE. A chemical compound of silica and another substance, such as silicate of iron. Consult elementary works on chemistry.

SILICEOUS. Of or belonging to the earth of flint. 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 the mouth of a river is 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. They are not simple in regard to their nature; for, when subjected to chemical analysis, they are found to consist of a variety of different substances. Pyrites is a simple mineral in the sense we use the term, but it is a chemical compound of sulphur and iron.

SLATE. See "Cleavage" and "Schist."

SOLFATARA. A volcanic vent from which sulphur, sulphureous, watery, and acid vapours and gases are emitted.

SPORULES. The reproductory corpuscula (minute bodies) of cryptogamic plants. Etym., ropa, spora, a seed.

STALACTITE. When water holding lime in solution deposits it as it drops from the roof of a cavern, long rods of stone hang down like icicles, and these are called stalactites. Etym., oraλaw, stalazo, to drop.

STALAGMITE. When water holding lime in solution drops on the floor of a cavern, the water evaporating leaves a crust composed of layers of limestone: such a crust is called stalagmite, from oraλayμa, stalagma, a drop, in opposition to stalactite, which see.

STATICAL FIGURE. The figure which results from the equilibrium of forces. From σratos, statos, stable, or standing still.

STERNUM. The breast bone, or the flat bone occupying the front of the chest. STILBITE. A crystallized simple mineral, usually white, one of the Zeolite family, frequently included in the mass of the trap rocks.

STRATIFIED. Rocks arranged in the form of strata, which see.
STRATIFICATION. An arrangement of rocks in strata, which see.

STRATA, STRATUM. The term stratum, derived from the Latin verb struo, to strew or lay out, means a bed or mass of matter spread out over a certain surface by the action of water, or in some cases by wind. The deposition of successive layers of sand and gravel in the bed of a river, or in a canal, affords a perfect illustration both of the form and origin of stratification. A large portion of the

masses constituting the earth's crust are thus statified, the successive strata of a given rock preserving a general parallelism to each other; but the planes of stratification not being perfectly parallel throughout a great extent like the planes of cleavage, which see.

STRIKE. The direction or line of bearing of strata, which is always at right angles to their prevailing dip. For a fuller explanation, see Vol. II. p. 471. SUBAPENNINES. Low 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. II. p. 478.

SYNCLINAL AXIS. See "Anticlinal." Etym., ovv, syn, together, and xxww, clino, to incline.

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. The term is borrowed from the language of fortification, where talus means the outside of a wall of which the thickness is diminished by degrees, as it rises in height, to make it the firmer.

TARSI. The feet in insects, which are articulated, and formed of five or a less number of joints.

TERTIARY STRATA. A series of sedimentary rocks, with characters which distinguish them from two other great series of strata-the secondary and primarywhich lie beneath them.

TESTACEA. Molluscous animals, having a shelly covering. Etym., testa, a shell, such as snails, whelks, oysters, &c.

THERMAL. Hot. Etym., Sepμos, thermos, hot.

THERMO-ELECTRICITY. Electricity developed by heat.

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 disappear. TRACHYTE. 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 trachyte passes into the varieties of trap called greenstone, basalt, dolorite, &c. The term is derived from rpaxus, trachus, rough, because the rock has a peculiar rough feel.

TRAP and TRAPPEAN ROCKS. Volcanic rocks composed of felspar, augite, and hornblende. The various proportions and state of aggregation of these simple minerals, and differences in external forms, give rise to varieties, which have received distinct appellations, such as basalt, amygdaloid, dolorite greenstone, and others. The term is derived from trappa, a Swedish word for stair, because the rocks of this class sometimes occur in large tabular masses, rising one above another, like steps. For further explanation, see Vol. II. p. 479, 480. TRAVERTIN. A concretionary limestone, usually hard and semi-crystalline, deposited from the water of springs holding lime in solution.-Etym. This stone was called by the ancients Lapis Tiburtinus, the stone being formed in great quantity by the river Anio, at Tibur, near Rome. Some suppose travertin to be an abbreviation of trasteverino from transtiburtinus.

TROPHI, of Insects. Organs which form the mouth, consisting of an upper and under lip, and comprising the parts called mandibles, maxillæ, and palpi.

TUFA, CALCAREOUS. A porous rock deposited by calcareous waters on their exposure to the air, and usually containing portions of plants and other organic subVOL. I.-3 T

stances incrusted with carbonate of lime.

The more solid form of the same

deposit is called " travertin," into which it passes.

TUFA, VOLCANIC. See "Tuff.”

TUFACEOUS. A rock with the texture of tuff or tufa, which see.

TUFF OF TUFA, VOLCANIC. An Italian name for a variety of volcanic rock of an earthy texture, seldom very compact, and composed of an agglutination of fragments of scoriæ and loose matter ejected from a volcano.

TURBINATED. Shells which have a spiral or screw-form structure. Etym., turbinatus, made like a top.

UNCONFORMABLE. See "Conformable."

UNOXIDIZED, UNOXIDATED. Not combined with oxygen.

VEINS, MINERAL. Cracks in rocks filled up by substances different from the rock, which may either be earthy or metallic. Veins are sometimes many yards wide; and they ramify or branch off into innumerable smaller parts, often as slender as threads, like the veins in an animal, hence their name. VERTEBRATED ANIMALS. A great division of the animal kingdom, including all those which are furnished with a backbone, as the mammalia, birds, reptiles, and fishes. The separate joints of the back-bone are called vertebra, from the Latin verb verto, to turn.

VESICLE. A small, circular, inclosed space, like a little bladder. Etym., diminutive of vesica, Latin for a bladder.

VITRIFICATION. The conversion of a body into glass by heat.

VOLCANIC BOMBS. Volcanos throw out sometimes detached masses of melted lava, which, as they fall, assume rounded forms (like bomb-shells), and are often elongated into a pear shape.

VOLCANIC FOCI. The subterranean centres of action in volcanos, where the heat is supposed to be in the highest degree of energy.

WACKE. A rock nearly allied to basalt, of which it may be regarded as a soft and earthy variety.

ZEOLITE. A family of simple minerals, including stilbite, mesotype, analcime, and some others, usually found in the trap or volcanic rocks. Some of the most common varieties swell or boil up when exposed to the blow-pipe, and hence the name of (w, zeo, to boil, and λos, lithos, stone.

ZOOPHYTES. Corals, sponges, and other aquatic animals allied to them; so called because, while they are the habitation of animals, they are fixed to the ground, and have the forms of plants. Etym., Cov, zoon, animal, and qurov, phyton, plant.

END OF VOL. I.

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