Principles of Geology Part 101

QUA-QUA-VERSAL DIP. The dip of beds to all points of the compa.s.s around a centre, as in the case of beds of lava round the crater of a volcano. _Etym._, _qua-qua-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.

QUARTZITE or QUARTZ ROCK. An aggregate of grains of quartz, sometimes pa.s.sing into compact quartz.

RED MARL. A term often applied to the New Red Sandstone.

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 ma.s.ses or beds, in different formations, extensively in the New Red Sandstone formation, as in Ches.h.i.+re; and it is then called _rock_-salt.

RUBBLE. A term applied by quarry-men to the upper fragmentary and decomposed portion of a ma.s.s of stone.

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 loaf-sugar. _Etym._, sa??a?, _sacchar_, sugar, and e?d??, _eidos_, form.

[Ill.u.s.tration: Fig. 100.]

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.

SALT SPRINGS. Springs of water containing a large quant.i.ty of common salt. They are very abundant in Ches.h.i.+re and Worcesters.h.i.+re, 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._, sa??a, _saura_, a lizard.

SAXICAVOUS. Hollowing out stone.

SCHIST is often used as synonymous with slate; but it may be very useful to distinguish between a schistose and a slaty structure. The hypogene or primary _schists_, as they are termed, such as gneiss, mica-schist, and others, cannot be split into an indefinite number of parallel laminae like rocks which have a true slaty cleavage. The uneven schistose layers of mica-schist and gneiss are probably layers of deposition, which have a.s.sumed a crystalline texture. See "Cleavage." _Etym._, _schistus_, adj. Latin, that which may be split.

SCHISTOSE ROCKS. See "Schist."

SCORIae. 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_.

SECULAR REFRIGERATION. The periodical cooling and consolidation of the globe from a supposed original state of fluidity from heat.

_Saeculum_, 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 b.a.l.l.s of stone, generally a kind of iron-stone, which, on being split, are seen to be separated in their interior into irregular ma.s.ses. _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 color, 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.

Sh.e.l.l MARL. A deposit of clay, peat, and other substances mixed with sh.e.l.ls, which collects at the bottom of lakes.

s.h.i.+NGLE. The loose and completely water-worn gravel on the sea-sh.o.r.e.

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 acc.u.mulated by currents in banks. Thus the mouth of a river is silted up when its entrance into the sea is impeded by such acc.u.mulation 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 a.n.a.lysis, 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.

SINTER, CALCAREOUS OR SILICEOUS. A German name for a rock precipitated from mineral waters. _Etym._, _sintern_, to drop.

SLATE. See "Cleavage" and "Schist."

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

SPORULES. The reproductory corpuscula (minute bodies) of cryptogamic plants. _Etym._, sp??a, _spora_, a seed.

STALACt.i.tE. 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 _stalact.i.tes_. _Etym._, sta?a??, _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 sta?a?a, _stalagma_, a drop, in opposition to _stalact.i.te_, which see.

STATICAL FIGURE. The figure which results from the equilibrium of forces. From stat??, _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 ma.s.s 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 ma.s.s 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 ca.n.a.l, affords a perfect ill.u.s.tration both of the form and origin of stratification. A large portion of the ma.s.ses const.i.tuting the earth's crust are thus stratified, 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.