P Y K 



Fermenting cataplafms are of fervicc chiefly as they fiipply 

 fixed air to the part. In cafes of putridity, fixed air Ijas 

 been fuccefsfully applied to the lurfacc of the body, cxpoled 

 to ftreams of it. It is alfo found an excellent cooling as 

 well as ilrengthening beverage in hot relaxing weatiier, and 

 has the advantage of being pleafant to the tafte. Sec on 

 the fubjeft of this article Frieilley's Exp. and Obf. on Air, 

 vol. ii. p. 263, &c. 298, &c. Phil. Tranf. vol. Ixv. part i. 

 p. 59, &c. Magellan's Defcription of a Glafs Apparatus 

 for making Mineral Waters, &c. p. I, &c. Prieftley's 

 Exp. and Obf. vol. v. Appendix, p. 389, &c. Elliot's 

 Account of the Nature and medicinal Virtues of the princi- 

 pal Mineral Waters, &c. 1 781. Henry's Account of a 

 Method of preferviiig Water at Sea, &c. 1781. p. 19, &c. 

 PYROBOLOGY, or the art of miffile fires, is derived 

 from the Greek cti-j, Jire, and ^cXXhv, to throiu. See Pv- 



KOTECHNY. 



PYRO BOLUS, in Natural Hi/lory, a name given by 

 many authors to the itoiie more generally called pyrites ; 

 others have called it fiderllcs, pyrobalanui, pyropus, and othoniia, 

 and the Greeks mylias. 



PYROCHROA, in Entomology. See Lampyris. 

 " PYROCTOGONIUM, in Natural Hi/lory, the name 

 given by Dr. Hill to a genus of foffils ufually compre- 

 hended by authors, with many other bodies of a different 

 figure and flrufture, under the general name pyrites. 



The charafters of the pyroftogonium are thefe : it is a 

 compound, inflammable, metallic body, of a regular o£lo- 

 Iiedral figure, or compofcd of eight planes. 



There is only one known fpccits of this genus, which is 

 a very fingular and elegant fofTil, being compofed of eight 

 i triangular planes ; thefe being the fides of two quadrilateral 

 pyramids, with broad bafcs, which being joined bafe to 

 bafe, conftitute the pyroftogonium. 



It is found very frequently in Cornwall, Devonfhire, and 

 moft other of our counties where there arc mines. It is 

 fometimes met with loofe m the earth, fometimes lodged in 

 the bodies of marcafites, or in the fohd foflils, and varies 

 fometimes from its iron colour to a dufliy yellow. It is 

 fometimes alfo found with many fpecimens connedled into a 

 mafs ; thefe are feldom uniform in fize, and cohere in vari- 

 ous direftions, often greatly injuring one another's figure. 

 Sometimes alfo, as in the cafe of the cryifals, they form a 

 large mafs, of which the outer furface only is concreted into 

 or covered with regular figures, the whole inner part being 

 a confufed fubitancc. 



Mailes of this kind are not unfrequently found of a regu- 

 lar orbicular figure, and befet all over with regularly figured 

 pyroftogonia of various fizes. Hill. 



PYRODMALITE, in Mineralogy, a mineral difcovered 

 forae years .igo in the mine of Bjelke, in Vermeland, a pro- 

 vince of Sweden, fituated on the N. fide of the lake Venner, 

 which was obferved to have the property of giving out the 

 odour of muriatic acid when heated, and hence dillinguifhed 

 by the name of pyrodmalite. J. G. Gahn of Fahlun has 

 given the following defcription of it. Its colour is com- 

 monly yellowifh-brown, pafling into greenifh : internally, it 

 is light greenifli-yellow. It occuri cryilallized in regular 

 fix-fided prifms, without any terrriinating pyramids. It is 

 compoled of plates lying on each other in a diretlion per- 

 pendicular to the axis of the prifm ; principal frafture, 

 refplendent ; crofs fratlure, uneven and without luitre ; 

 opaque ; femi-hard ; fcratched by fteel ; the cryftals are 

 often feveral inches long; fpecific gravity 3.081. Before 

 the blowpipe it becomes dark reddiih-brown, and emits the 

 odour of muriatic acid. It then melts into a black flag, 

 and at laft a fmall bead is obtained, more or lefs attratled 

 Vol. XXIX. 



P Y Pt 



by the magnet. It diffolves readily, and in confiderable 

 quantity in glafs of borax, and gives a colour indicating the 

 prefence of mangancfe and iron : — in phofphate of ammonia 

 and foda it diffolves with great difficulty. Its conflituents 

 are filica, lime, iron, manganefe, aiid muriatic acid. In 

 the mine of Bjelke 'it occurs mixed with iron ore, calcare- 

 ous fpar, and black cryftallized malacolite. Pyrodmalite 

 was lately analyfed by Mr. Hifinger, who found its confli- 

 tuents to be as foUow : 



Silica - . . 

 Oxyd of iron 

 Oxyd of manganefe 



Alumina 

 Muriatic acid 

 Lofs - - . 



35-4 



32.6 



23.i 



0.6 



6-5 

 1.8 



1 00.0 



The efcape of the acid by heat feems to indicate the 

 prefence of a portion of water amounting to about two- 

 thirds of the lofs Hated as fuftained in the analyfis. Annals 

 of Philofophy, N° 12. 



PYROENUS, formed of i^vc, Jire, and oiyo;-, •ivine, is a 

 term fometimes ufed for rectified fpirit of wine ; thus called 

 becaufe made by fire, or rather bccaufe rendered of a fiery 

 nature. 



PYROET, PyroueT, or rather Pirouette, in the Ma- 

 nege. See Pirouette. 



PYROLA, m Botany, a name adopted by Linnaeus from 

 the old authors, but not one of their bcfl. It is a diminu- 

 tive of Pyrus, and alludes to the refemblance of the leaves, in 

 this pretty genus, to thofe of a pear-tree. — Linn. Gen. 221. 

 Schreb. 297. WiUd. Sp. PI. v. 2. 621. Mart. Mill. Dift. 

 v. 3. Ait. Hort. Kew. v. 3. 58. Purfh 299.- Sm. Fl. 

 Brit. 443. Prodr. Fl. Graec. Sibth. v. i. 274. Juff. i6l. 

 Tourn. t. 132. Lamarck Illullr. 1.367. Gscrtn. t. 63. 

 (Chimaphila; Purtli 300.) — Clafs and order, Deeandria 

 Mcnogynia- Nat. Ord. Bicornes, Lmn. Ericit, Juff. 



Gen. Ch. Cal. Perianth inferior, frnaU, in five deep 

 fegments, permanent. Cor. Petals five, roundifh, concave, 

 fpreading. Stam. Filaments ten, awl-fhaped, fhorter than 

 the corolla ; anthers drooping, large, with two horns at 

 the bafe, each difcharging the pollen by a terminal orifice. 

 Pift. Germen fuperior, roundifh, angular ; flyle cylindrical, 

 permanent, various in length and diredtion, fometimes fcarcely 

 any ; ttigma thickifli, varioufly fliapcd. Perie. Capfule 

 roundifli, deprefled, five-fided, of five cells, burfling at the 

 angles. Seeds numerous, chaffy. 



Eff. Ch. Calyx in five deep fegments. Petals five. Cap- 

 fule fuperior, with five cells, burfling at the angles, and 

 many feeds. Anthers with two pores. 



Obf. In fome fpecies the flamens and flyle are ereft ; 

 in others inchned to one fide or the other ; in fome the 

 former fpread every way. The form of the lligma is dif- 

 ferent in different fpecies. In two American ones the fligma 

 is nearly, or quite, feffile ; on which mark Mr. Purfh's 

 genus Chimaphila is founded, its name being nearly fynoni- 

 mous with Winter-green, the Englifh appellation of Pyrola. 

 SeftioH I. Style elongated. Pyrola of Pnr{h. 

 I. P. rotundifolia. Round-leaved Winter-green. Linn. 

 Sp. PL 567. Willd. n. I. Ait. n. i. Purfh n. I. Engl. 

 Bot. 213. (Pyrola; Ger. Em. 408. Camer. Epit. 723. 

 Rivin. Pentap. Irr. t. 136. f. 2. P. vulgatior ; Cluf. Hift. 

 V. 2. 116. Limonium ; Fuchf. Hift. 467. L. fylveifre ; 

 Trag. Hift. 707.) — Stamens afcending. Style twice as 

 long, deflexed and recurved. Clufler rrrany-flowered. Calyx 

 as long as the flamens. — Native of thickets, for the mofl 



L part - 



