Page:Cyclopaedia, Chambers - Volume 2.djvu/543

 PYR

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PYR

the Glory and Magnificence of Princes : but as they are the Symbol of Immortality, they are more commonly ufed as funeral Monuments. See Mon ument.

Such is that of Cejiius at Rome $ and thofe other cele- brated ones of Egypt, as famous for the Hugenefs of their Size, as their Antiquity.

Thefe laft are all fquare in their Bafes 3 and 'tis a thing has been frequently propofed, to eflablifti a fixed Meafure

from them 3 to be thereby tranfmitted to Pofteriiy.

See their Defections, Meai'ures, gfc. in P'hevenot, Pietro delta Vallc, &c.

Among the Egyptians* the Pyramid is faid to have been a Symbol of human Life 3 the Beginning whereof is re- prefented by the Bafe, and the End by the Apex : On which account it was, they ufed to erect them on Sepul- chres. Herodotus.

Some derive the Word from w4&h Wheat, and dwla, coliigoj pretending that the Exi\ Pyramids were built by

the Patriarch Jofeph for Granaries. But Villalpandus,

with much better reafon, derives the Word from <avg } Fire; becaufe ending in a Point like Flame.

When they are very narrow at bottom, i. e. their Bafe very fmall 3 they are call'd Obelisks and Needles. See Obelisk.

Scenography of a Pyramid. See Scenography. Optic Pyramid. See Optic Pyramid. PYRAMIDAL Mirrors. See Mirror. PYRAMIDAL Numbers, are the Sums of Polygonal Numbers, collected after the fame manner as the Polygon Numbers themfelves are extracted from Arithmetical l'ro- grefTions. SeePoLYGoNAL Number, &c.

Thefe are particularly call'd primo pyramidals The

Sums of firtt 'Pyramidals we ca.\V6feco7id Pyramidals

The Sums of thofe third Pyramidals, gfo ad infinitum.

Particularly thofe arifing from triangular Numbers are call'd prime triangular Pyramidals h thofe arifing from Pentagonal Numbers are vaW A prime pentagonal Pyrami- dals, &c;

From the manner of fumming up polygonal Numbers it appears evidently how the prime Pyramidal Numbers are (a — *)#* +3K 1 — (a— 5)«,

found 3 viz, — expreffes all the

6 prime Pyramidals.

PYRAM1DALF, Corpus, in Anatomy, a Plexus of Blood- Veffels on the back of the Telticles } thus call'd from its Form : and from its Structure alfo call'd Corpus Varico- fum, and P amp ini -forme. See Corpus and Varico- sum.

Ir confids of innumerable little Veins, communicating with each other 5 and forming a kind of Net-Work j which, at length, uniting, terminate in one Vein; by which the 31ood is convey e into them all.

TheOrigin of this Plexus is from the fpermatic Veins, which, a little above the Tefticles, fplit into feveral Bran- ches 3 which again uniting, feveral times, form the Corpus Tyramidale. See Testicle and Spermatic Veins. PYRAMIDAI..ES Papilla, fee Pafillje "Pyramidales. PYRAMIDALIS, in Anatomy, a fmall Mufcle of the Abdomeri, lying on the lower part of the Retlus — It has its Name from its Figure 3 and its Origin from the Margin of the Os P&hiSjViith a pretty broad fieflbyHead, whence it grows gradually narrower till it end in a fmall round Tendon in the lama alba 3 fometimes almoft at the Navel.

This Mufcle is fometimes fingle, fometimes it has its fellow 3 and fometimes they are both wanting.

PYRAMIDOID, call'd alfo Parabolic Spindle, a folid Figure form'd by the Revolution of a Parabola round its Bafe, or greateft Ordinate.

Thus, if youconfider it according to the Method of In- divifibles, you may conceive its Solidity to confift of an in- finite Series of Circles, whofe Diameters are all parallel to the Axis of the revolving Parabola. See Parabolic Spindle.

PYRATE, fee Pirate.

PYRENOIDES Proceffus, in Anatomy, a Procefs of the fecond Vertebra 3 thus call'd from its pear-like fhape 3 as alfo for the like reafon, Qentiformis, or Tooth-like Pro- cefs. See Process and Vertebra.

The Word is compounded of Pyrum, Pear, and «JV, Figure.

PYRETICS, Medicines good againfl Fevers. See Fe- ver.

The Word is form'd from the Greek tv^t©-, Fever, of Tup, Fire.

PYR1FORMIS, in Anatomy, a Mufcle of the Thigh, receiving its Name from its Figure, which refembles that of a Pear. — It is alfo call'd Iliacus externus, from its Si- tuaton. See Iliacus.

Its beginning is round and fJeflry, from the inferior and internal part of the Os Sacrum, whers it refpecls the Pelvis of the Abdomen 5 and defcending o\bliquely in the great

Sinus of the Os Ilium, above the acute Procefs of the Ifchium, and joining with the Gluteus medius, it inferted by a round Tendon into the fuperior part of the Root of the great Trochanter.

This moves the Os Femoris fomewhat upwards, and turns it outwards.

PYRITES, in Natural Hiftory, aSemi-metal, fu^pofed to be the Marcafite of Copper 3 or the Matrix or Ore where- in that Metal is formed. SecMARCAsiTE, Ore, Copper, &c.

From this Marcafite it is that the Roman Vitriol is pro- cured. See Vitriol.

The Word is form'd from the Greek fl-uf, in regard it

takes fire more readily than any other Stone —It is alfo

call'd J%?tis.

Antiently it was ufed in lieu of the Flints in Fire-Locks.

Dr. Slarc tells us of a Heap of Pyrites confiiting of two

or three hundred Tons 5 which being cover'd up from the Air five or fix Months, took fire, and burnt for a Week. Some of it look'd like melted Metal, others like red' hot Stones. He adds, it emitted a moft noifome Smoke.

Dr. Lifter attributes Thunder, Earthquakes, &c. to the fulphureous and inflammable Breath of the Pyrites, See Thunder, Earthquake, Exhalation, &c.

Pyrites, in a more general fenfe, is ufed tor the Mar- cafites of all Metals 3 the Names whereof are varied ac- cording to the Metals they partake of. See Marc asite.

ThusChryfites is that of Gold 3 Argyrites that ofSdver; Siderites that of Iron 3 Chalcites thai of Copper 3 Molyb- dues that of Lead, &c See Argyrites, Chrysites, Siderites, &c.

PYROBOLOGY, fee Pyrotechnta. PYROENL'S, from wPf, Ignis, Fire, and oiwr, Vinwn, Wine 5 is a Term fometimes ufed lor recliiy'd Spirit of Wine 3 thus call'd becaufe made by Fire, or rather becaufe render'd of a fiery nature. See Spirit and Rectifi- cation.

PYROET, or Pirouet, or Pyrouet, in the Manage. See Pi rouet.

PYROMANCY, a kind of Divination, perform'd by meansof Fire. See Divination.

The Antients imagined they could foretel Futurity by in- fpefiing Fire and Flame : To this end, they confider'd its Di- rection, or which way itturn'd. — Sometimes they added 0- ther Matters to the Fire 3 e.gr. a Veffel full of Urine, with 'its Neck bound about with Wool 3 watching narrowly on which fide it burft, and thence taking their Augury.

Sometimes they threw Pitch on it 5 and if it took fire immediately, efteem'd it a good Augury. (• PYROTECHNY, Pyrotechnia, the Art of Fire ; or a Science which teaches the Management and Application of Fire in feveral Operations. See Fire.

The Word is form'd from theGreek tvc, Fire, and te^cjj, Am

pyrotechny is of two kinds, Military, and Chymical. Military 1 j yrotechny is theDocirine of Artificial Fire- W^orks and Fire- Arms 3 teaching the Structure and Ufe both of thofe ufed in War for the Attacking of Fortifications, &c. as Gun Powder, Camions, Bombs, Granadoes, Carcajfes, Mines, Fufees, Sic. and thofe made for Amufement-fake, as Rockets, Stars, Serpents, &c. See FiRE-^raz, Ord- nance, &c.

Some call Pyrotechny by the name Artillery 5 tho' that Word feems confined to the Instruments ufed in War. See Artillery.

Others chufe to call it Pyrobology, q. d. the Art of MuTiIe Fires 5 from the Greek ^up, Fire, and QaKhsiy, to caft, throw. SeeGuNNERY, Projectile, &c.

Wolfius has reduced Pyrotechnia into a kind of mixt Mathematical Art : Indeed, it won't allow of Geometrical Di'monftraticns j but he brings it to tolerable Rules and Reafons 3 whereas, before, it had .ufed to be rreated by Authors at Random and without any Reafon at all. See Mathematics.

Seethe Elements of Military Pyrotechny under the fe- veral Instruments and Operations 3 Cannon, Bomb, Roc- ket, Gun-Powder, %£c.

Chymical Py rot -ecuni a, is the Art of managing and applying Fire, in Diftillatfons, Calcinations, and other Ope- rations of Chymiflry. See Chymistry and Operation.

Some reckon a third kind of Pyrotechnia, viz. the Art of fufing, refining, and preparing Metals. See Metal, Fusion, Refining, ££c.

PYROTICS, in Medicine, Remedies either aaually, or potentially hots and which, accordingly, will burn the Flefh, and raife an Efchar. See Caustic and Esciia- rotic. The Word is form'd from the Greek •&£?, Fire. PYRRHIC, Pyrrhica, in Antiquity, a kind of Exer- cife on Horfe-back 3 or a feign'd Combat, for thi Exercife of the Cavalry. See Exercise.

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