P Y R 



P Y R 



52. Neft of ferpents. 



53. Two double cones illuminated. 



34. Regulating piece of ieveii mutations, viz, 



1. Vertical wheel illuminated. 



2. Golden glory. 



3. Ottagon vertical wheel. 



4. Porcupine's quills. 



5. Crofs fires. 



6. Star piece with brilliant rays. 



7. Six vertical wheels. 



35. Brilliant fun. 



36. Large flight of rockets. 



When water-works are to be exhibited, divide them into 

 feveral fets, and fire one fet after every fifth or fixth change 

 of land and air-works. Obferve this rule in firing a double 

 fet of works ; always to begin with iky-rockets, then two 

 moveable pieces, then two fixed pieces, and fo on ; ending 

 with a large flight of rockets, or a maroon battery : if a 

 fingle coUeftion, fire a fixed piece after every wheel or two, 

 and now and then fome air and water-works. Jones's Fire- 

 works, 8vo. 1776. 



PYROTECHNICAL Spunge. See Spunge. 



PYROTICS, nufoinxct, formed from ■ujvfyjire, in Medi- 

 cine, cauftics, or remedies, either aftually or potentially hot ; 

 and which, accordingly, will burn the fleih, and raife an 

 efchar. 



PYROUET. See Pirouette. 



PYROXENE, in Mineralogy. See AuGlTE and Lava. 



According to Haliy, the mineral called augite by Werner 

 is the black or greenifh-black variety of pyroxene found is 

 volcanic countries and in bafalt. The primitive form of the 

 cryitals of pyroxene is an oblique rhomboidal prifm. 



The greyifh-green tranfparent pyroxene, with the forms 

 of the cryftals diltinftly marked, from the department of the 

 Po, is the alalite of Bouvoifin. Journal des Mines, N'^ 115. 



The greyifh-green, or whiti(h-grey variety, the primitive 

 cryitals of which are mdiflinA, from the fame deparment, 

 were called by Bouvoifin mallite. Both thefe varieties have 

 been called by fome mineralogifts diopfide. 



The greyirti-green and obfcure green perioftahedral va- 

 riety of pyroxene, is the fahlite of Werner, called alfo ma- 

 locolithe by Haiiy. The mineral called coccolite, difcovered 

 by Dandrada at the iron mines of Sudermannland and Nerika, 

 in Sweden, and Arendahl in Norway, is alfo brought under 

 the fpecies pyroxene by Haiiy. Tableau Comparatif. 



By reducing many varieties of minerals under one fpecies, 

 Haiiy may be confidered as having rendered an additional fer- 

 vice to mineralogy, already too much loaded with pedantic or 

 unmeaning terms ; but the term pyroxene itfelf may be juftly 

 ©bjetled to, as being founded not on anydiilinft character, but 

 on the hypothetical ailumption that thefe cryftals are foreign 

 to the igneous produfts in which they are imbedded, an af- 

 fumption for which there does not appear fufficient proof. 

 The conftituent parts of pyroxene, its fpecific gravity and 

 hardnefs, fo nearly agree with thofe of bafaltic hornblende, 

 that thefe- fubftances ought perhaps to be claded as varieties 

 of the fame fpecies, without regarding the fmall difference 

 of their crylialline forms. See Hornblende. 



Pyroxene en Roche, or Rr,ch Pyroxene. In the Journal 

 des Mines, Nov. 1812, a defcription is given of entire 

 -rocks compofed of pyroxene, difcovered by J. Charpentier 

 in the Pyrenees. The fubftance is homogeneous, of a tex- 

 ture commonly granularly lamellar, which in fome pieces 

 becomes flaty. Its molt common colour is green of various 



• ftiadcs, from an olive green to an emerald green, fometimes 

 cloudy but often clear. From a greenifli-grey it pafies to a 



• reddifi) brown and ochre yellow. It is amorphous. The 



luftre is fplendent. Its fratturc is lamellar, and has a tvyo* 

 fold cleavage equally pcrfeit, crolling at an angle of about 

 92°. In other directions the frafture is cither impcrfdtly 

 lamellar or csnchoidal. It fcratches glafs, and gives fome 

 fparks with fleel. It melts with gruat difficulty by the 

 blowpipe, but with borax it eafily forms a green glafs. 

 M. Vogel has analyfed tliis mineral, and difcovred chrome 

 in the green fpecimen. From the detailed defcription of 

 this rock, it appears nearly allied to fchiilole, fpar, and fer- 

 pentine. It is frequently intimately combined with talc, in 

 which ftate it is not eafy to dillinguilh it from ferpentine. 

 Rock pyroxene 15 found in beds in the primitive limcllone, 

 tliat forms vaft mountains fuperincumbent on granite, ex- 

 tending from the valley of VicdefTos, in the department of 

 Arriege, to St. Beat, in the valley of Garonne. The maffes 

 of rock pyroxene are of extraordinary fize, extending in 

 length 5000 toifes. Its thickncfs is difficult to determine, 

 but is fuppofed to exceed 300 toifes. Charpentier is dif- 

 pofed to clals rock pyroxene as an intermediate rock be- 

 tween hornblende and ferpentine, and fubordinate to primi- 

 tive limeftone. It neither contains foreign beds nor mineral 

 veins, and is lefs liable to decompofition when pui-e, than 

 almolt any other rock. When intermixed with talc it de- 

 compofes rapidly. 



PYRRHA, in /Indent Geography, a town of the ifle of 

 Lefbos, between the promontory Sigrium and the town of 

 ErefTus, according to Ptolemy. The town took its name 

 from a llrait between Afia Minor and the ifle of Lefbos, 

 and gave it to a foreft in the fame ifle. — Alfo, a town of 

 Macedonia, in Magnefia. Pliny. — Alfo, a town of Afia 

 Minor, in Lycia. Pliny. — Alfo, a town of Afia Minor, 

 in Ionia, fituated at the entrance of the northern part of 

 theLatmic gulf, E.N.E. of the town of Miletus, and S.S.E. 

 of that of Myus. Strabo places it at 100 lladia from 

 Heraclea — Alfo, a promontory of Theflaly, upon the coalt 

 of the Phtiiiothide. Strabo fays, that before this promon- 

 tory were two ifles ; one called Pyrrha, and the other Deu- 

 calion. — Alfo, a town of Greece, in the Phocide. Pliny. 

 — Alfo, a town fituated in the vicinity of the Palus-M^otis ; 

 fubmerged according to the relation of Phny. — Alfo, a 

 town of Afia Minor, in Caria. 



PYRRHICHA, Uv^'f^x^, in Antiquity, a kind of ex- 

 ercife on horfeback ; or a feigned combat, for the exercife 

 of the cavalry. 



It was thus called from its inventor Pyrrhicus, or Pyr- 

 rhus, in Cydonia, who firft taught the Cretans to march 

 in meafure and cadence to battle, and to obferve the pace 

 of the Pyrrhic foot. Others derive the name from Pyr- 

 rhus, fon of Achilles, who inltituted this exercife at the 

 obfequics of his father. Ariftotle fays, that it w as Achilles 

 himfelf who invented it. 



The Romans alfo called it ludus Trojanus, the Trojan 

 game ; and Aulus Gellius decurfus. It is doubtlefs this 

 exercife, that we fee reprefented on medals, by two cava- 

 liers in front, running with lances, and the word decurjio in 

 the exergum. 



PYRRHICHIUS, n^pf.;^!'..:, in the Greek and Latin 

 Poetry, a foot confitting of two fyllables, both fhort ; as deus. 



Among the ancients this foot is alfo called periambus ; by 

 others hegemona. 



PYRRHICUS, in Ancient Geography, a town of La- 

 conia, upon the flream of Scyrax, S. of Hypfus. Here 

 were two temples, one of Diana Aftratia, and another 

 of the Amazonian Apollo. The ftatues of thefe deities 

 were of wood, and it is fuppofed they were placed here by 

 the Amazons themfelves. 



PYRRHO. See Pyrrhonians. 



PYRRHO- 



