Principles of Geology Part 100

OPHIDIOUS REPTILES. Vertebrated animals, such as snakes and serpents. _Etym._, ?f??, _ophis_, a serpent.

ORGANIC REMAINS. The remains of animals and plants (_organized_ bodies) found in a fossil state.

ORTHOCERATA OR OHTHOCERae. An extinct genus of the order of molluscous animals, called Cephalopoda, that inhabited a long-chambered conical sh.e.l.l, like a straight horn. _Etym._, ?????, orthos], _orthos_, straight, and ?e?a?, _ceras_, horn.

OSSEOUS BRECCIA. The cemented ma.s.s of fragments of bones of extinct animals found in caverns and fissures. _Osseous_ is a Latin adjective, signifying bony.

OSTEOLOGY. That division of anatomy which treats of the bones; from ?ste??, _osteon_, bone, and ?????, _logos_, a discourse.

OUTLIERS. When a portion of a stratum occurs at some distance, detached from the general ma.s.s of the formation to which it belongs, some practical mineral surveyors call it an _outlier_, and the term is adopted in geological language.

OVATE. The shape of an egg. _Etym._, _ovum_, egg.

OVIPOSITING. The laying of eggs.

OXIDE. The combination of a metal with oxygen; rust is oxide of iron.

OXYGEN. One of the const.i.tuent parts of the air of the atmosphere; that part which supports life. For a farther explanation of the word, consult elementary works on chemistry.

PACHYDERMATA. An order of quadrupeds, including the elephant, rhinoceros, horse, pig, &c., distinguished by having thick skins.

_Etym._, pa???, _pachus_, thick, and de?a, _derma_, skin, or hide.

PACHYDERMATOUS. Belonging to Pachydermata.

PALaeOTHERIUM, PALEOTHERE. A fossil extinct quadruped, belonging to the order Pachydermata, resembling a pig, or tapir, but of great size. _Etym._, pa?a???, _palaios_, ancient, and ??????, _therion_, wild beast.

PALEONTOLOGY. The science which treats of fossil remains, both animal and vegetable. _Etym._, pa?a???, _palaios_, ancient, ??ta, _onta_, beings, and ?????, _logos_, a discourse.

PELAGIAN, PELAGIC. Belonging to the _deep_ sea. _Etym._, _pelagus_, sea.

PEPERINO. An Italian name for a particular kind of volcanic rock, formed like tuff, by the cementing together of volcanic sand, cinders, or scoriae, &c.

PETROLEUM. A liquid mineral pitch, so called because it is seen to ooze like oil out of the rock. _Etym._, _petra_, rock, and _oleum_, oil.

PHaeNOGAMOUS or PHANEROGAMIC PLANTS. A name given by Linnaeus to those plants in which the reproductive organs are apparent. _Etym._, fa?e???, _phaneros_, evident, or fa???, _phaino_, to show, and ?a??, _gamos_, marriage.

PHLEGRaeAN FIELDS. Campi Phlegraei, or "the Burnt Fields." The country around Naples, so named by the Greeks, from the traces of igneous action everywhere visible.

PHONOLITE. See "Clinkstone."

PHRYGANEA. A genus of four-winged insects, the larvae of which, called caddis-worms, are used by anglers as a bait.

PHYSICS. The department of science which treats of the properties of natural bodies, laws of motion, &c.; sometimes called natural philosophy and mechanical philosophy. _Etym._, f?s??, _physis_, nature.

PHYTOLOGY, PHYTOLOGICAL. The department of science which relates to plants--synonymous with, botany and botanical. _Etym._, f?t??, _phyton_, plant, and ?????, _logos_, discourse.

PHYTOPHAGOUS. Plant-eating. _Etym._, f?t??, _phyton_, plant, and fa?e??, _phagein_, to eat.

PISOLITE. A stone possessing a structure like an agglutination of peas. _Etym._, p?s??, _pison_, pea, and ?????, _lithos_, stone.

PISTIA. P. 618. The plant mentioned by Malte-Brun is probably the _Pistia Stratiotes_, a floating plant, related to English duckweed, but very much larger.

PIT COAL. Ordinary coal; called so, because it is obtained by sinking pits in the ground.

PITCHSTONE. A rock of a uniform texture, belonging to the unstratified and volcanic cla.s.ses, which has an unctuous appearance like indurated pitch.

PLASTIC CLAY. One of the beds of the Eocene Tertiary Period; so called, because it is used for making pottery. The formation to which this name is applied is a series of beds chiefly sands, with which the clay is a.s.sociated. _Etym._, p?a.s.s?, _pla.s.so_, to form or fashion.

PLESIOSAURUS. A fossil extinct amphibious animal, resembling the saurian, or lizard and crocodile tribe. _Etym._, p??s???, _plesion_, near to, and sa??a, _saura_, a lizard.

PLIOCENE, OLDER and NEWER. Two divisions of the Tertiary Period which are the most modern, and of which the largest part of the fossil sh.e.l.ls are of recent species. _Etym._, p?e???, _pleion_, more, and ?a????, _kainos_, recent.

PLUTONIC ACTION. The influence of volcanic heat and other subterranean causes under pressure.

PLUTONIC ROCKS. Granite, porphyry, and other igneous rocks supposed to have consolidated from a melted state at a great depth from the surface.

POLIPARIA. CORALS. A numerous cla.s.s of invertehrated animals, belonging to the great division called Radiata.

PORPHYRY. An unstratified or igneous rock. The term is as old as the time of Pliny, and was applied to a red rock with small, angular, white bodies diffused through it, which are crystallized felspar, brought from Egypt. The term is hence applied to every species of unstratifled rock in which detached crystals or felspar or some other mineral are diffused through a base of other mineral composition. _Etym._, p??f??a, _porphyra_, purple.

PORTLAND LIMESTONE, PORTLAND BEDS. A series of limestone strata, belonging to the upper part of the Oolite Group, 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.

POZZUOLANA. Volcanic ashes, largely used as mortar for buildings, similar in nature to what is called in this country Roman cement. It gets its name from Puzzuoli, a town in the Bay of Naples, from which it is shipped in large quant.i.ties to all parts of the Mediterranean.

PRECIPITATE. Substances which, having been dissolved in a fluid, are separated from it by combining chemically and forming a solid, which falls to the bottom of the fluid. This process is the opposite to that of chemical solution.

PRODUCTA. An extinct genus of fossil bivalve sh.e.l.ls occurring only in the older secondary rocks. It is closely allied to the living genus Terebratula.

PTERODACTYL. A flying reptile: species of this genus have been found in the Oolite and Muschelkalk. Some of the finger-joints are lengthened, so as to serve as the expansors of a membranous wing.

Hence the name _wing-fingered_. _Etym._, pte???, _pteron_, a wing, and da?t????, _dactylos_, a finger.

p.u.b.eSCENCE. The soft hairy down on insects. _Etym._, _p.u.b.esco_, the first growth of the beard.

PUDDINGSTONE. See "Conglomerate."

PUMICE. A light spongy lava, chiefly felspathic, of a white color, produced by gases or watery vapor getting access to the particular kind of gla.s.sy lava called obsidian, when in a state of fusion; it may be called the froth of melted volcanic gla.s.s. The word comes from the Latin name of the stone, _pumex_.

PURBECK LIMESTONE, PURBECK BEDS. Limestone strata, belonging to the Wealden Group, which intervenes between the Greensand and the Oolite.

PYRITES. (Iron.) A compound of sulphur and iron, found usually in yellow shining-crystals like bra.s.s, and in almost every rock, stratified and uustratifled. The shining metallic bodies so often seen in common roofing slate are a familiar example of the mineral.

The word is Greek, and comes from p??, _pyr_, fire; because tinder particular circ.u.mstances, the stone produces spontaneous heat, and even inflammation.

PYROMETER. An instrument for measuring intense degrees of heat.

QUADRUMANA. The order of mammiferous animals to which apes belong.

_Etym._, _quadrus_, a derivative of the Latin word for the number four, and _ma.n.u.s_, hand, the four feet of those animals being in some degree usable as hands.