Page:Cyclopaedia, Chambers - Volume 2.djvu/985

 VOL

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VOL

the meaning is, he (hail upon his Oath fpeak or declare the Truth, whether he (hall get or lofe by the Matter in Con- troverfy.— If he be unconcern'd, his Teftimony, is allow'd; otherwife, not. See Oath, Witness, S£c.

"VOL, among the French Heralds, fignifies the two Wings of a Fowl born in Armoury as being the whole that makes the Flight : Accordingly, a Demivol is a fingle Wing.

VOLA, the Palm of the "Hand. See Hand.

VOLANT, in Heraldry, is when a Bird in a Coat of Arms is drawn flying, or having its Wings fpread out.

VOLATILE, in Phyficks, is commonly ufed to denote a mix'd Body whofe integral Parts are eafily diflipated by Fire, or other heat ; but is more properly ufed for Bodies whofe Elements, or firft component Parts, are eafily fepara- ted from each other, and difpers'd in Air. See Body, Co- hesion, Element, $$c.

For, as any mix'd Body is faid to be fix'd in a double Senfe ; fo may it be faid to be Volatile two ways : whence the fame Body, e. g. Mercury, is both volatile and fix'd at the fame time.

Since, as its integral Parts, or thofe which flill retain the Nature of Mercury, are eafily feparable by Fire, and readily fly away ; it is faid to be Volatile : And yet as 'tis very difficult to deflroy its Contexture, and refolve it by Fire, or any other Menftruum, into its firft Elements, it is faid to be fix'd.— The fame may be faid of Sulphur, Antimony, t§c.

Minerals, for the generality, are iefs volatile than Vege- tables, and Vegetables lefs than Animals. See Fix'd.

The Chymifts diftinguifti between Volatile Salts, and Fix'd Salts. See Salts.

The Capitals of Alembicks flop and collect the Volatile 'Parts of Subftances in Sublimation ; and make what we call Flowers. See Flowers.

' The Particles of Fluids which do not cohere very ftrong- ■ ly together, and are of fuch Smallnefs, as renders them

• moft fufceptible of thofe Agitations which keep Liquors in ' a Fluor, are eafily rarify'd into Vapour ; and, in the Lan-

' guage of the Chymifts, are Volatile. Thofe which are

' groffer, and fo lefs fufceptible of Alterations ; or cohere by

• a ftronger Attraction, do not evaporate without a ftronger 1 Heat, or perhaps not without Fermentation : Thefe are « what the Chymifts call Fix'd Bodies' Neivton. Optic.

V- ii*- ^

Volatile, in Chymiftry — When the Fire decompounds any mix'd Body, the Parts molt difpofed to receive a great Motion, are fooneft loofen'd, and rife up in the Order which the differences of that Difpofition give them 5 the reft re- maining immoveable at the bottom of the Veffel. See A- nalysis, Fire, &c.

Thofe that rife firft, are called Volatile Tarts ; fuch are 'Phlegm., Oil, Spirits, and Salts, both urinous and alkalious. See Spirit, Phlegm, and Salt.

The Parts remaining, viz. Earth, and Lixivial Satis, are call'd Fix'd. See Earth, and Volatilisation.

For the making of Fix'd Salts volatile ; fee Volatili- sation.

VOLATILISATION, the Aft of rendering Fix'd Bo- dies Volatile ; or of refolving 'em by Fire into a fine, fub- tile Vapour, or Spirit, which eafily diflipates, and flies away. See Volatile.

All Bodies, even the moft fix'd, as Gold may be vola- tiliz'd ; either of themfelves, or with the Admixture of fome volatile Subftance, or Spirit ; by Diftillation, or Subli- mation. See Distillation, and Sublimation 5 fee al- fo Gold, Burning-Glass, Z$c.

In the Memoirs of the French Academy, we have a Dif- courfe on the Volatilifation of the fix'd Salts of Plants, by M. Homberg. — That admirable Chymift, it feems, by an odd Ac- cident, found fix'd Salts fpontaneoufly volatiliz'd in Soap : Now Soap, we know, is a Compofition of Oil, and the al- kalous lixivial Salts of the Plant Kali. — Upon this, M. Hom- lerg conjectur'd, that the Oil from which the volatile Salts feem to derive rheir Volatility, being intimately mix'd with the fix'd Salts of the Kali in the Soap, had render'd them Volatile : So that they ceafe to be Alkalious, by reafon their Pores are now fill'd with the Oil which they have abforb'd. — Oil, in effect, has always fomewhat of an Acid in it j which Acid, being join'd to the Alkali, the whole is render'd a kind of intermediate Salt $ which yet, as the Acid and Alkali were only join'd by means of the Oil, is ftill oily or ful- phureous.

In confequence of this View, he made divers chymical Operations, whereby he found, that to difpofe the fix'd Salts of Plants to volatillfe, the Procefs is to be begun by making them into a Sapa, and letting that Sapa moot out little fa- line Points, or Cryftals on its Surface ; which Cryftals are no other than fix'd Salts already volatiliz'd. — Then, the Re- mainder of the Matter is to be fet over the Fire, after being well imbib'd and penetrated by fbme new Liquor, proper to aflift in a new Sublimation of more fix'd Salts to be vo- latiliz'd : and this to be repeated till no more Salts will rife.

The Choice of the Liquor wherewith the Sapa is to be faturated, is not indifferent — Water is, of all other, the leaft fit for the Effeft : Oil docs well ; yet diftill'd Oil better than that drawn from Exprcffion : and Spirit of Wine bell of all.

By fuch means, M. Homberg volatiliz'd almoft half a Quantity of Salt of Tartar, which is a fix'd Vegetable Salt. See Tartar.

VOLATILITY. See Sublimation.

VOLCANO, or Vulcano, in Natural Hiftory, a Name given to Mountains that belch, or vomit Fire, Flame, Aftles, Cinders, Stones, Ssc. See Mountain.

Such are Mount JEtna in Sicily, Mount Vefuvitts near Na- ples, &c. See Eruption.

Near Guatimala in South America, are two Mountains, the one call'd Volcano of Fire ; the other of Water. — Out of the firft, huge pieces of Rocks are frequently hurl'd with as much vehemence as Balls out of a Canon j and a written Letter may be read by the Light of its Flames, at the dif- tance of three Miles.

Out of the other, vaft Quantities of Water are continually fpued up. See Earthquake.

Volcanos and Ignivomous Mountains, thofome of the moft terrible Phenomena in Nature, have their Ufes ; being a kind of Spiracles, or Tunnels, whereby to vent the Fire and Vapour, that would otherwife make a more dreadful Havock by Convulfions and Earthquakes.

Nay, if the Hypothefis of a central Fire and Waters, he admitted ; thefe Outlets muft be abfolutely neceffary to the Peace and Quiet of the terraqueous Globe. — According- ly, Dr. Woodward oblerves, there is fcarce any Country much annoy'd with Earthquakes, but has one of thefe fiery Vents ; which are conftantly obferved to be all in Flames, whenever an Earthquake happens ; by which means, they difgorge that Fire, which while it was underneath, was the Caufe of the Difafter. — He adds, that were it not for thefe "Diverti- cula, whereby the central Fire has an Exit, 'twould rage in the Bowels of the Earth much more furioufly, and make much greater Havock than it does ; and that there are not wanting Inttances of Countries that have been wholly freed from Earthquakes, by the Eruption of a new Volcano there, See Earthquake.

VOLERY, a great Bird-Cage, fo large, that the Birds have room to fly up and down in it. See Aviary.

VOLITION, the Aft of Willing. See Will.

VOLLEY, a military Salute, made by difcharging a great number of Fire- Arms at the fame time.

In the Pbilofophical T'ranfaffiom, Mr. Robert Clarke gives us an Account of a very remarkable Effect of firing ibme Volleys of final! Shot : ' Upon proclaiming the Peace in

' Centre whereof was againft a Butcher's Door, who kept ' a very large, couragious Maltiff Dog, the biggeft in the ' Town.
 * 1697, two Troops of Horfe were drawn in a Line, the

' Upon firing of the firft Volley, the Dog, who before lay ' a-fleep by the Fire, ftarted up, ran into an upper Room,


 * and hid himfelf under the Bed.- The Servant being

' Stairs) a fecond Volley came ; which made the Dog rife, ' run feveral times about the Chamber, with violent Trem-
 * about to beat him down, (as he had never ufed to go up

' blings, and ftrange Agonies. But immediately a third

1 Volley came; upon which the Dog run once or twice abour, ' fell down, and died immediately ; throwing out Blood at ' Mouth and Nofe.'

VOLO, in Antiquity, a Name which the Romans gave the Slaves, who, in the fecond Tunic War, offer'd them- felves to ferve in the Army 5 upon a want of a fufficient Number of Citizens. See Slave.

The Names Volo, Volones, they are faid to have had from their offering themfelves voluntarily.

Feftus fays, 'twas after the Battle of Cannce that this hap- pen'd : Macrobius, Sat. Lib. I. cap. ii. places it before that Battle.

Cafitolinus tells us, that Marcus Aurelius form'd Troops or Legions of Slaves, which he call'd Voluntarii ; and that the like Forces in the fecond Punic War had been call'd Volones. — But before M. Aurelius, Augufius had given the Name Voluntarii to Forces which he had raifed out of Li- berti, or Freedmen ; as we are affur'd by Macrobius, Sat. Lib. I. cap. ii.

VOLUME, Volumn, Volumen, a Book, or Writing, of a juft bulk to be bound by it felf.

The Library of Ptolemy King of Egypt, contain'd, ac- cording to Aldus Gellius, three hundred rhoufand Volumes ; and according to Sabellicus, feven hundred thoufand. See Library.

Raymond Lully wrote above four thoufand Volumes ; whereof we have divers Catalogues extant. — 'Tis held, that 'Trifmegifitts wrote fix thoufand five hundred twenty five Vo- lumes 5 others fay, thirty fix thoufand five hundred twenty nine ; But 'tis much more rational to fuppofe, with la Croix,

that