Page:Cyclopaedia, Chambers - Supplement, Volume 2.djvu/453

 S E L

S E L

SELEN7E, EsXwmm, in antiquity, a kind of cakes ufed in fa- crifices, and fo called from their being broad and horned, in imitation of the new moon. Potter, Tom. I. p. 214. SELENDERS, in the manege, are chops or mangy fores in the bending of a horfe's hough, as the malenders are in the knees. See Malenders. SELENEUSIACA terra, earth of Seleneufia, in the materia medica of the antients, a light fungous earth called by later naturalifts agarkus mineralis, and when found in form of powder, or in a difcontinuous ftate, lac luna. It is an earth common enough, wherever there are {tone quarries, all over the world ; but the fineft ever met with, is that from Sicily, the place where the antient Selmeufia, or Selimts flood, and from whence the antient phyficians had it. Some of them have called it the creta Seleneufiaca ; but all their defcriptions agree in proving it to be this very earth now found there. Diofcorides and Galen mention its remarkable diftufibility in water, and Pliny mentions its melting into a kind of juice, or fmooth homogene fubftance with it; properties fo very applicable to this earth, and fo little fo to any other, as to leave no doubt of their having been originally applied to the very fame fubftance. The antients gave it internally as an aftringent ; but its principal ufe was external, as a cofmetic among the ladies. And Dr. Plot recommends our lac luns, on pcribnal experi- ence, for the fame purpofes. Hill's Hift. of Foflils, p. 40. See the article AgaRICUS mineral;*. SELENIACON, a name for a kind of amulet worn for the

epilepfy. SELENITES, (Cycl.) in natural hiftory, the name of a large clafs of foflils, the characters of which are thefe. They are bodies compofed of flender, and fcarce vifible filaments, ar- ranged into fine, even, and thin flakes ; and thofe difpofed into regular figures, in the feveral different genera, ap- proaching to a rhomboide, or hexangular column, or a re£tan°-led parallellogram : fiflile, like the talcs, but that not only in a horizontal, but alfo in a perpendicular direction : they are flexile in a fmall degree, but not at all elaftic : they do not ferment with acid menftrua, but readily calcine in the fire. See Tab. of Foflils, Clafs 2. Of this clafs there are feven orders of bodies, and under thofe ten genera. The felenita of the firft order are thofe compofed of horizontal plates, and approaching to a rhom- boidal form. Of the fecond are thofe compofed of horizon- tal plates, arranged into a columnar and angular form. Of the third are thofe whole filaments are fcarce vifibly arranged into plates, but which, in the whole manes, appear rather of a ftriated, than of a tabulated firucture. Of the fourth arc thofe which are flat, but of no determinately angular figure. Of the fifth are thofe formed of plates, perpendicu- larly arranged. Of the fixth are thofe formed of congeries of plates, arranged into the figure of a ftar. And of the feventh, are thofe of a complex and indeterminate figure. Hill's Hift. of Foil", p. 1 19, 120.

Of the firft of thefe orders there are three genera. I, The hptodecarhomles. Thefe are thin felenita of a rhomboidal figure. 2. The pachodecarbombes. Thefe are thicker fele- nita of a rhomboidal figure. The fcknitee of both thefe ge- nera confirt of ten planes each. 3. The tetradecarhombes. ' Thefe are felenlta of a rhomboidal figure, but confifting of fourteen inftead of ten planes. See the articles Leptode- carhombes, Pacodecarhombes, and Tetradeca-

RHOMBES.

Of the fecond order there are alfo three genera. The firft the ifchnambluces. Thefe are felenita of a flatted columnar octohaedral figure, confifting of fix fides, and two broken ends. 2. The ifambluces. Thefe are felenita of an odto- haedral columnar form, but not flatted. 3. The oxueige. Thefe are felenita of a columnar form, but not truncated, or with broken ends, but tapering off at each end to a point. See the articles Ischnamblucis, Istc. Of the third order there is only one known genus, the mam- blacxa. Thefe are columnar felenita with abrupt ends, and of a fibrofe, not tabulated texture.

Of the fourth order there is alfo only one known genus, the fanulia. Thefe ate felenita of no determinate figure, but of a tabulated ftructure, and refembling the foliaceous tubes. See the articles Inamblucia andSANiDiA. Of the fifth order there is alfo only one known genus, the tathdolipes. Thefe are octohaedral felenita with perpendi- cular plates, and obtufe angles! HilPsHlft. of Foff. p. 121, 122, 123.

Of the fixth order there are two genera. 1, The kpaftra. Thefe are felenita compofed of filaments, arranged into plates, and difpofed in form of a ftar. 2. The iricheftra. Thefe are felenita compofed of filaments, fcarce vifibly ar- ranged into plates, but difpofed in threads into the form of a radiated ftar, and appearing merely of a ftriated texture. See the articles Lepastra and Trichestra. Of the feventh order there is only one genus, the fymplexia. Thefe are felenlta compofed of various irregularly connected bodies, of the ftructure and general figure of one or other of the former genera. See the article Symplexium. ■ The ftructure of the felenita of all the genera of the firft

order is exactly alike, they arc all compofod of a great num- ber of broad flakes or plates, in a great meafure externally refembling the flakes of the foliaceous talcs. Thefe are of the length and breadth of the whole mafs. The top and bottom being each only one fuch plate, and thofe between them, in like manner, each compleat and fingle, and the body may always be cafily and evenly fplit, according to the direction of thefe flakes. Thefe differ, however, ex- tremely from the talcs; for they are each compofed of a number of parallel threads, or filaments, which are ufualiy difpofed parallelly to the fides of the body, though fome- times parallelly to its ends. In many of the (pecies they are alfo divided by parallel lines, placed at a coniiderable Jiftance from each other, and the plates in fplitting often break at thefe lines : add to this, that they are not elaftic, and that they readily calcine. Hill's Hift. of FoiT. p. 120. The ftructure of thofe of the fecond order is the fame with that of the firft ; but that in many of the fpecimens of them, the filaments, of which the plates are compofed, run in two directions, and meet in an obtufe angle j and in the middle there is generally feen in this cafe a ftrait line, running the whole length of the column, and fmall parcels of clay infinuating themfelves into this crack, represent in it the figure of an ear of grafs fo naturally, as to have de- ceived many into a belief, that there was really an ear of grafs there. The other orders confifting only of fingle ge- nera, the ftructure of each is explained under the gcnerical name. Hill's Hift. of Foff. p. 121. See the articles Lep-

TODECARHOMBIS, &C.

SELF (Cycl.) — Self opens, a term ufed by the miners in the north of England to exprefs certain natural cavities, or chambers, which are frequently met with, fome near the furface, fome at very great depths, fome fmall, and others very large.

Thefe are of various figures, and often run into Arrange fi- nufes. Dr. Lifter, in accounting for the origin of earthquakes, fuppofes the whole cruft of the earth to be more or lefs hollowed in this manner; which he alfo argues for, from the ftreams of waters which arife in large quantities from the fides of mountains, and muff, have communication with thefe J elf opens and fupplies from them. Thefe natural hollows the doctor thinks to be the means of continuing, and propagating earthquakes ; the firft caufe of which he afcribes to the breath of the pyrites, which he al- fo fays is the pyrites itfelf tota fnbftantia. This he obferves takes fire of itfelf, on being expoied to the air in our fight, and may do fo, from various other caufes, underground. The fulphureous fmell of the air and waters, before and after earthquakes, in the places where they happen, feems a proof that they owe their origin to fome fuch fulphureous matter as this ftone ; and the rolling, and defultory noife of an earthquake, feems alfo to fhew that it is not expanded every way at once, but is propagated through a chain of thefe fubterranean hollows.

It is not necelTary that we mould fuppofe a continued chain of them, from the place where the earthquake be- gins to be felt, to the fpot where it ends 5 but if there are many of them irregularly fcattered about the earth, the force of the explofion will be fufikient to burft through the folid parts between, and open a paiTage from one to the others, which may continue open no longer than the force continues, and after the lhock is over clofe together again, fo as to leave no trace where it was.

Our miners not only find the natural caverns, but they alfo find them often full of what they call fire damps, which are inflammable vapours, of the very nature of thofe which occafion earthquakes, and when fired make the fame explo- fions, and caufe the fame effects in a certain degree. Thefe fometimes require a candle, or other actual fire, to come in contact, in order to kindle them ; but fometimes they are found kindled of themfelves, and flaming on the furface of the waters, in the bottoms of the pits, or at the fiflures of the coal. Philof. Tranf. N° 157. SELI, in botany, a word formed by an abbreviation of the word fefili, and fignifying the fame plant. See the article Seseli. SELICHA, a name given by the Arabians to a kind of cin- namon. -See the article Cinnamum. SELIGONION, in botany, a name by which fome authors

have called piony. Ger. Emac. Ind. 2. SELION of land, fella terra, is derived from the French, fell- Ion, which fignifies a ridge of land, or ground arifing be- tween two furrows, and contains no certain quantity, but fometimes more and fometimes lefs. Therefore Crompton fays, that a felon of land cannot be in demand, becaufe it is a thing uncertain. ' Crpmpt. Jurif. 221. Terms of Law. SELKIE, the name in Zetland for a feal. Many of thefe are

found in that ifland. Philof. Tranf. N 3 473. fea. 8. SELL bed, in mining, a term ufed in fome parts of England to exprefs fome particularly rich parts of the vein of ore. In Cornwall they fometimes find the tin ore fo pure-, that it requires only bruifmg to drefs it, without the warning and reparation by grates, launders, and the like means : they call thefe collections of ore the fell beds of tin ; and it is ob- 3 ferved.