PYROPHYSALITfi PYRRHO. 



763 



It is formed from heating a mixture of three parts 

 lampblack, four calcined alum and eight pearlashes, 

 in a gun barrel. The mixture is maintained at a 

 cherry-red heat about one hour, or until it ceases 

 to give off inflammable gas at the orifice of the 

 tube, after which it is withdrawn from the furnace, 

 and closely corked from the air. When cold, if 

 poured from the gun-barrel into the air, it imme- 

 diately glows and takes fire; and more especially if 

 breathed upon, or slightly moistened. This py- 

 rophorus may be preserved in its full activity for a 

 year or more, if well corked up from the air, but it 

 requires much caution in disengaging it from the 

 tube ; for it has been known to explode, with great 

 violence, simply on introducing into it an iron ram- 

 rod. This compound appears to owe its energy to 

 its containing the sulphuret of potassium. 



PYROPHYSALtTE. See Topaz. 



PYROSMALITE; a lamellar substance, found 

 also in six-sided tables, of a shining lustre; trans- 

 lucent; brittle; specific gravity 3.08. It is soluble 

 in muriatic acid, with a residuum of silex. It gives 

 out the odour of chlorine when heated before the 

 blow-pipe, and becomes attractable by the magnet. 

 Its constituents are peroxide of iron 21.81, protox- 

 ide of manganese 21.14, sub-muriate of iron 14.09, 

 silex 35.85, lime 1.21, water and loss 5.9. It oc- 

 curs in a bed of magnetic iron ore, along with cal- 

 careous spar and hornblende, in Bjelke's mine in 

 Nordmark, in Wermeland. 



P YROTECHN Y is properly speaking, the science 

 which teaches the management and application of 

 fire; but, in a more limited sense, and as it is more 

 commonly used, it refers chiefly to the composition, 

 structure and use of artificial fire-works. The in- 

 gredients are, 1. saltpetre, purified for the purpose; 

 2. sulphur; and, 3. charcoal. Gunpowder is like- 

 wise used in the composition of fire-works, being 

 first ground, or, as it is technically termed, mealed. 

 Camphor and gum-benzoin are employed as ingre- 

 dients in odoriferous fire-works. The proportions 

 of the materials differ very much in different fire- 

 works, and the utmost care and precaution are ne- 

 cessary in the working them to a state fit for use, 

 and then in the mixing. When stars are wanted, 

 camphor, alcohol, antimony, and other ingredients, 

 are required, according as the stars are to be bine, 

 white, &c. In some cases, gold and silver rain is 

 required; then brass-dust, steel-dust, saw-dust, &c., 

 enter into the composition. Hence the varieties 

 may be almost indefinite. With respect to colour, 

 sulphur gives a blue, camphor a white or pale 

 colour, saltpetre a clear white yellow, sal-ammoniac 

 a green, antimony a reddish, rosin a copper colour, 

 and sulphate of strontia that beautiful purple light 

 so often exhibited in theatres. (See Rocket.) 



PYROXENE, OB AUGITE. See Augite. 



PYROXYLIC SPIRIT. When wood is distilled, 

 the products are water, acetic acid, pyroxylic acid, 

 empyreumetic oil, and a black matter, which is con- 

 sidered as analogous to pitch, or, rather, tar. When 

 the watery portion, freed as well as possible mechan- 

 ically from the tar, is distilled at a low heat, the 

 fiist portion that comes over is the pyroxylic acid, 

 which may be freed from acetic acid by agitation 

 with lime or magnesia, and subsequent distillation 

 at a low temperature ; but it is still impure from 

 the presence of empyreumatic oil. To free it com- 

 pletely from this impurity, it must be mixed with 

 its own weight of sulphuric acid, and the mixture 

 be subjected to distillation. Thus purified, it is a 

 transparent and colourless liquid, having a strong 

 and pungent smell, which has been compared to 

 that of ants, and also to the odour of acetic ether, 

 fts taste is strong, hot, pungent, and very disagree- 



able. Specific gravity, in its most concentrated 

 state, 0.8121. Its boiling point is 150. When 

 completely freed from acetic acid, it does not redden 

 vegetable blues. It burns with a very pale yellow 

 flame, inclining to blue, but the light is consider- 

 ably greater than that given out by alcohol. It 

 burns all away, without leaving any residue, and 

 the only products are carbonic acid and water. It 

 dissolves in alcohol in any proportion. With water 

 it becomes opaque, owing, probably, to a small 

 quantity of oil it still contains. It dissolves readily 

 in oil of turpentine, and in liquid potash, acquiring, 

 at the same time, a yellowish colour. When the 

 solution of this spirit in potash is distilled, we are 

 able to obtain it perfectly pure from every portion 

 of oil. When this spirit is mixed with nitric acid 

 and distilled, an ethereal liquid comes over, pos- 

 sessed of an exceedingly pungent smell, and acting 

 strongly on the nose and eyes. It burns with a 

 bluish flame. The specific gravity of this vapour 

 is 1.94. Pyroxylic spirit is now very commonly 

 used instead of alcohol in the spirit lamp for chemi- 

 cal purposes. 



PYRRHA. See Deucalion. 



PYRRHICHIUS. See Rhythm. 



PYRRHO, a Grecian philosopher of Elis, founder 

 of the Tyrrhenian or ancient sceptical school, flour- 

 ished about 340 B. C., and was probably born about 

 the 101st Olympiad. In his youth he studied the 

 art of painting, but was early led to apply himself 

 to philosophy by the writings of Democritus. He 

 accompanied his master, Anaxarchus, to India, in 

 the train of Alexander the Great. During this 

 journey, he became acquainted with the doctrines 

 of the Brahmins, Gymnosophists, Magi, and other 

 Eastern philosophers. His doubts concerning posi- 

 tive knowledge (or his scepticism) were strength- 

 ened as he proceeded in his studies, until at length 

 he came to hold all knowledge useless, and consid- 

 ered virtue alone as valuable. In all disputes, his 

 answer to his opponents was, " What you say may, 

 or may not, be true; I cannot decide;" and he 

 taught in his school, that truth could not be attain- 

 ed, but we must be content to suspend our judg- 

 ment on all subjects. He spent a great part of his 

 life in solitude, and, by abstaining from all decided 

 opinions (ja-^x) concerning moral and physical 

 phenomena, he endeavoured to attain a state of 

 tranquillity not to be affected by fear, joy or sorrow. 

 He bore corporal pains with great fortitude, and no 

 danger could disturb his equanimity. In disputa- 

 tion, he was distinguished for acuteness of argu- 

 ment and clearness of language. His countrymen 

 made him high priest, and exempted all philoso- 

 phers from the payment of taxes. Pyrrho died in 

 the ninetieth year of his age. The A thenians erec- 

 ted a statute in honour of him, and his countrymen 

 raised a monument to his memory. His scepticism 

 is easily accounted for. He early became acquaint- 

 ed with the system of Democritus, who held that, 

 except the immediate elements of bodies (atoms), 

 nothing was real, and that all perception was sub- 

 jective. (See Objective.) He was confirmed in 

 these views by the doctrines of Socrates, to whom, 

 in his character, he bore a great resemblance. 

 Cicero mentions him expressly among the disciples 

 of Socrates, and his scepticism is allied to the irony 

 of that philosopher. Led, by his temperament and 

 and his manner of life, to esteem an uninterrupted 

 tranquillity the great object of all philosophy, believ- 

 ing that nothing tended so much to destroy this 

 quiet as the interminable disputes of the schools of 

 the Dogmatists, and that uncertainty was increased 

 by their contentions, he determined to seek, in some 

 other way, the peace which he despaired of finding 



