Page:Cyclopaedia, Chambers - Volume 2.djvu/867

 T H U

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T H U

THKEK-Lcgged Staff, an Inftrument confiding of three Wooden Legs, made with Joints, fo to fhut all together, and to take off in the Middle, for the better Carriage ; and ufually having on its Top a Ball and Socket, ferving to fupport and adjuft Inftruments for Aftronomy, Surveying, gfc. See Ball and Socket.

THRENGUS, in our ancient Cufloms. See Drenches.

Quia veronal erant adhnc tempore Regis Willielmi Mill- ies m Anglia, fed Threnges ; prtecipit Rex tit de eh Milites fierent ad defendendam terrara : fecit autem Lanfrancus Threngos fuos Milites, ckc. Somn. Gavelk.

They were.Vaffals, but not of the lowed Degree of thofe who held Lands of the chief Lord.

The Name was impos'd by the Conqueror ; for when one Edieyn Sharnbourn of Norfolk, and others, were ejected out of their Lands; they complain'd to the Conqueror ; infiding, that they were always on his Side, and never oppos'd him : which, upon Enquiry, he found to be true ; and therefore he commanded that every one mould be reftor'd to their Lands, and for ever after be call'd 'Drenches. Spelm.

THRENODY, Threnoeia, a mournful, or Funeral Song, See Funeral.

THROAT, the Part of an Animal between the Head and the Shoulders, wherein is the Gullet. See Gullet.

Phyficians include under the Word Throat, all that Hol- low or Cavity which may be feen when the Mouth is wide open.

It is ibmetimes alfo call'd Ijlhmus, by Reafon it is narrow, and bears fome Refemblance to thofe Streights call'd by the Geographers Ifthmi.

Throat, in Architecture, Fortification, g?c. See Gorge and Gula.

THRONE, from the Greek *£?r©-, a magnificent Seat or Chair ; is a Royal Seat, inrich'd with Ornaments of Ar- chitecture and Sculpture, made of fome precious Matter, rais'd on feveral Steps, and cover'd with a kind of Canopy.

Such as are in the Rooms of Audience of Kings and other Sovereigns.

THROWS of Women, the Pains of Child-Birth. See Delivery, &c.

THROWSTER, one who throws, i. e. winds or rolls SiUc. See Silk.

THUNDER, a Noife in the loweft Region of the Air, excited by a fudden kindling of fulphurous Exhalations. See Air, Atmosphere, Exhalations, &c.

Seneca, Rohault, and other Authors, both ancient and modern, account for 'Thunder, by fuppofing two Clouds impending over one another, the uppet and rarer whereof be- coming condens'd by a frefh Acceffion of Air rais'd thither by Warmth from the lower Parts of the Attnofphere ; or dri- ven upon it by the Wind; immediately falls forcibly down upon the lower, and denfer Cloud : By which Fall, the Air interpos'd between the two being comprefs'd; that next the Extremities of the two Clouds is fqueez'd out, and leaves Room for the Extremity of the upper Cloud to clofe tight upon the under : Thus a great Quantity of Air is inclos'd, which at length efcaping thro' fome winding irregular Vent or Paffage, it occafions that Noife we call Thunder. See

Cloud, ££c

But this only reaches to the Phenomena of Thunder heard without Lightening ; and, in effect, we have now a better Solution : Thunder is not occafion'd by the falling of Clouds; but by the kindling of fulphurous Exhalations, in the fame Manner as the Noile of Aurum Fulminans.

« c There are fulphurous Exhalations, fays Sir Ifaac Ne-zv- " toft, always afcending into the Air when the Earth is dry ; " there they ferment with the nitrous Acids, and fbmetimes " taking Fire, generate into Thunder, lightening, e?c.

That, befide the Vapours rais'd from Water, l£c. there are alfo Exhalations catry'd off from Sulphur, Bitumen, Volatile Salts, f£c. is pad all doubt ; the vaft Quantity of fulphurous and bituminous Matter all over the Surface of the Earth, and the Volatile Salts of Plants and Animals, afford fuch an ample Stock thereof; that 'tis no Wonder the Air Ihould be fiU'd with fuch Particles, rais'd higher or lower, according to their greater or lefs Degree of Subtility and Activity ; and more copioufly fpread in this or that Quarter, according to the Direction of the Winds, ££c. See Sul-

Now, the Effects of Thunder are fo like thofe of fir'd Gunpowder, that Dr. Wallis thinks we need not fcruple to afcribe them to the fame Caufe : But the principal Ingredi- ents in Gunpowder we know are Nitre and Sulphur ; Char- coal only ferving to keep the Parts fepatate, for the better kindling. See Gunpowder.

Hence, if we conceive in the Air a convenient Mixture of nitrous and fulphurous Particles, from the Sources above- mention'd ; and thofe, from fome Caufe, to take Fire ; fuch Explofion may well follow, and with fuch Noife and Light, the two Phenomena of Thunder; as in the firing of Gunpowder: and being once kindled, it will run from Place to Place, this Way or that, as the Exhalations happen to lead it 5 as in a Train of Gunpowder.

This Explofion, if high in the Air, and remote from us, will do no Milchief ; but if near us, may deftroy Trees, Ani- mals, e?c as Gunpowder would do in the like Circumftances. This Nearnefs or Fatnels may be eflimated by the Interval of lime between the Flafli and the Noife : Dr. Wallis 00- ferves, that ordinarily the Difference between the two is about feven Seconds; which, at the Rate of 11 42 Feet ma Second of Time, gives the Diftance about a Mile and half: But fometimes it comes in a Second or two, which argues the Explofion very near us, and even among us. And in fuch Cafes, the Revd. Doctor affures us, he has more than once foretold the Mifchiefs that befell.

Upon the whole, that there is in Lightening a fulphurous Vapour, appears from the Sulphur which attends it, and from the fultry Heat in the Air which ufually precedes it ; and that there is a nitrous Vapour along with it, the fame Author con- cludes hence, that we know of no other Body fo liable to a fiid- den and violent Explofion. And as to the kindling of thefe Materials, we know that a Mixture of Sulphur and Steel Filings, with a little Water, will break forth into aSual Flame. Nothing therefore is wanting to the Explofion, but fome Chalybeat, or Vitriolic Vapour ; and amono the various Effluvia from the Earth, the Doctor does not doubt, but there muft be fome of that : But what he leaves as a Pro- bability, we can produce a kind of Proof of.

In Hiltory we meet with Indances of its raining Iron in Italy, and Iron Stones in Germany : Jul. Scaliger tells us, he had by him a Piece of Iron rain'd in Savoy. Cardan re- ports 1200 Stones to have fallen from Heaven, fome of them weighing 30, fome 40, and one an hundred and twenty lound, all very hard, and of the Colour of Iron.

The Matter of Fact is fb well atteded, that Dr. Liller, in the <Philofophicsl TranfaRions, builds a whole Theory of Thunder and Lightening on it; maintaining, that they both owe their Matter to the Breath or Exhalation of 'Pyrites. See Pyrites.

That Rattling in the Noife of Thunder, which makes it feem as if it pafs'd thro' Arches, or were broken varioufly, is doubtlels owing to the Sound being excited among Clouds hanging over one another, and the agitated Air parting be- tween them. See Lightening.

THUNDER-.2W/. If what we call Lightning, act with extraordinary Violence, and break orfhatter any thing ; it is call'd a Thunder-bolt ; which the People, to fit it tor fuch Effeas, fuppofe to be a hard Body, and even a Stone. See Lightening.

But that we need not have recourfe to a hard folid Body to account for the Effects commonly attributed to the Thunder- bolt, will be evident to anyone, who confiders thole of Pulvis Fulminans, &c. of Gun-powder. See Fulminans.

The Phenomena of the 7 bunder-bolt are, that it' oftener ftnkes on high Places than on low : That it frequently burns Peoples Cloaths, without touching their Bodies : That it fometimes breaks their Bones, without hurting their Flefli or their Cloaths; that it has even melted the Sword without touching the Scabbard, £gc.

The Firft is eafily accounted for, from the ordinary Height of the Clouds, out of which the Lightening darts : As to the reft, fince Exhalations may be very different from one an- other ; fome, e.gr. coming nearer! the Nature of Sulphur, may only yield a very flight lambent Flame, which will only affect fuch things as take Fire the fooneft. And others on the contrary, fb fubtile and penetrating, as to come near the Nature of Volatile Salts or Aqua-fortis, which fpare fbft Bodies, and fpend their whole Force on hard ones.

The Chevalier de Louville of the French Academy of Sciences, accounts for fome of the Effeifs of Thunder upon a new Principle ; as to killing of Animals, without burning or wounding them, 'tis naturally enough afcribed to the Sulphur, which falling near enough the' Perfon, the Fumes thereof flop hisRefpiration. As to Trees, Building., t£ c. fplit or beat down, there mud be another Caufe. M. di ' Louville therefore, fuppofes, that when theThunder is fohigh, its Flame is diffipated e'er it arrive at the Earth : And that the Air being violently driven along by the impetuous Motion of the Flame, and of conlequence exceedingly condenfed. becomes a kind of hard Body, capable of producing terrible Effects.

Places ftruck with Thunder-bolts, were held Sacred among the Ancients. Nigidius has a very curious Treatife on the Thunder-bolt.

Marcilius Ficinus, and fome others, maintain, that Coral diffipates panic Fears, and keeps off Thunder-bolts and Hail : Fortunat.Licetus has endeavour'd ro account for it phyficaily. F. le Brim proves very eafily, that thofe Philol'ophers are miftaken.

On Medals, the Thunder-bolt is fometimes found to ac- company the Emperors Heads ; as that of Juguftus. In which Cafe, it is a Mark of Soveraignty, and of a Power equal with the Gods.

Appian informs us, that the Thunder-bolt was the principal Divinity of Seleucia ; adding, that it was adored even in his Time, with various Hymns and Ceremonies. See Goo

THUS.