Page:Cyclopaedia, Chambers - Volume 1.djvu/285

 BUR

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BUS

cording to Schottus, burnt Pieces of Wood, at the Diftance of 15 or 16 Paces.

M. rfebimbaus's Mirror, at leaft, equals the former, both in Bignefs and Effect : The following Things are no- ted of it in the AtJa Eruditorum. 1. Green Wood takes tire ir.frantaneoufly, fo as a ftrong Wind can't extin- guish it. 2. Water boils immediately, and Eggs in it are prefently edible. 3. A Mixture of Tin and Lead, three In- ches thick, drops prefently : An Iron or Steel Plate becomes red-hot prefently,and a little after burns into Holes. 4. Things not capable of melting, as Stones, Bricks, £5?c. become foon red-hot, like Iron. 5. Slate becomes firft white, then a black Glafs. 6. Tiles are converted into a yellow Glafs, and Shells into a blacki/h yellow one, 7. A Pumice Stone emitted from a Volcano., melts into a white Glafs : And, 8. A piece of a Crucible alfo vitrifies in eight Minutes. 9. Bones are foon turn'd into an opake Glafs, and Earth into a black one. The Breadth of this Mirror is near three Leip- Jick Ells, its Focus two Ells diftant from it : It is made of Copper, and its Subftance is not above double the Thick- nefs of the Back of a Knife.

Villette, a French Artift of Lyons, made a large Mirror, bought by 1'avernier, and prefented to the King of Per- Jia ; a fecond, bought by the King of ^Denmark 5 a third prefented by the French King to the Royal Academy ; a fourth has been in England, where it was publickly ex- pos'd. The Effects hereof, as found by Dr. Harris and Dr. 1)efaguliers, are, that a Silver Sixpence is melted in 7" and I $ a King George's Halfpenny in 16", and runs with a Hole in 34. Tin melts in 3", Caft Iron in itf 1 ', Slate in ■$"; a foffile Shilling calcines in 7" 5 a piece o^Pompey's Pillar at Alexandria, vitrifies in the black Part in 50", in the white in 54 ; Copper Ore in 8": Bone calcines in 4", vitrifies in 33. An Emerald melts into a Subftance like a Turquois Stone $ a Diamond weighing 4 Gr. lofes \ of its Weight : The Asbeftos vitrifies ; as all other Bodies will do, if kept long enough in the Focus : When once vitri- fy'd, the Mirror can go no further with them. This Mir- ror is 47 Inches wide ; and is ground to a Sphere of 76 Inches Radius : fo that its Focus is about 38 Inches from the Vertex. Its Subftance is a Compolition of Tin, Cop- per, and Tin-Glals.

Every Lens, whether Convex, Piano Convex, or Con- vexo Convex, collects the Sun's Rays, difpers'd o'er its Convexity, into a Point, by Refraction 5 and is therefore a burning Glafs. The moft considerable of this kind known, is that made by M. de 'Tfcbimhaufen : The Diameters of his Lenfis are three and four Feet 5 the Focus at the Dif- tance of 12 Feet, and its Diameter an Inch and half. To make the Focus the more vivid, 'tis collected a fecond time by a fecond Lens parallel to the firft 5 and plac'd in that Place where the Diameter of the Cone of Rays form'd by the firft Lens, is equal to the Diameter of the fecond : So that it receives 'em all ; and the Fccus from an Inch and a half, is contracted into the Space of eight Lines, and its Force increas'd proportionably. Its Effects, among others, as related in the Atla Erudit. Lipfii, are, That it lights hard Wood, even moiiten'd with Water, into a Flame, in- ftantly 5 that Water, in a little VefTel, begins to boil pre- fently 5 all Metals are melted 5 Brick, Pumice Stone, tDelpht Wares, and the Asbeftos Stone, are turn'd into Glafs ; Sulphur, Pitch, &c. melted under Water: The Afhes of Vegetables, Woods, and other Matters, tranfmuted into Glafs. In a word, every thing apply'd to its Focus, is ei- ther melted, turn'd into Calx, or into Smoak ; and the Colours of Jewels, and all other Bodies, Metals alone ex- cepted, are chang'd by it. He obferves, that it fucceeds heft when the Matter apply'd is laid on a hard Coal well ■burnt.

Tho the Force of the Solar Rays be here found fo Stupen- dous 5 yet the Rays of the Full Moon, collected by the fame Burning Glafs, don't exhibit the leaft Increafe of Heat.

Further, as the Effects of a Burning Lens depend whol- ly on its Convexity, 'tis no wonder that even thofe pre- paid of Ice produce Fire, £<&. A Lens of that kind is ea- fily prepar'd, by putting a piece of Ice into a Skuttle, or hollow Segment of a Sphere, and melting it over the Fire, till it accommodate it felf to the Figure thereof

Kor will thofe ignorant of Dioptrics, be lefs furpriz'd to fee Flame, and the ErFc&s thereof, produced by means of the Refraction of Light in a Glafs Bubble fill'd with Water. See Lens.

Wolfius tells us, that an Artift of %)refden made burn- ing Mirrors of Wood, bigger than thole of M. tffebirn- haus or Villette, which had Efrefts at leaft equal to any of 'em. Traherus teaches how to make burning Mirrors of Leaf Gold ; viz. by turning a Concave, laying its Infide equally with Pitch, and covering that with fquare Pieces of the Gold, two or three Fingers broad, fattening 'em on, if need be, by Fire. He adds, that very large Mirrors may .be made, of 30, 40, or more Concave Pieces, artfully join'd in a turn'd wooden Difh or Skuttle 5 the Effects of

which will hot be much lefs, than if the Surface was cofc tinuous.

Zahnius adds, further, that Newman, an Engineer at Vienna, in itfjjji, made a Mirror of Paftboard, cover'd with- in fide with Straw glu'd to it 5 by which all kind of Metals* &c. were melted. See Mirror.

Burning of Land, call'd alfo vulgarly 2)enjhiring, quafi 2)evonJhiring, or Denbyjfriring, as being moft ufed there : A Method of preparing and fertilising Lands barren, four, heathy and rumy, for Corn ; by paring off the Turf; and drying, and burning iton the Ground. The fame Method alfo obtains for Meadows and Pafture Ground, moift, claiey, or ruihy.

Burning Mountains. See Vulcano, Earthquake* Mountain, &c.

BURNISHING, the Aaion offmoothening orpolifhing a Body, by a violent rubbing it with any thing. Thus Bookbinders burnijh the Edges of their Books, by rubbing 'em with a Dog's Tooth. Gold and Silver are bumijhd with a Wolf's Tooth, a Dog's Tooth, or the bloody Stone, Tripoli, a piece of white Wood and Emery. Hence Bur- nijloer, is a round polifti'd piece of StceJ, ferving to fmooth and give a Luftre to Metals : Of thefe there are various Kinds, of various Figures - 3 ftrait, crooked, \$c. Half .£??»"- nijhers, are us'd to folder Silver, as well as to give it a Luftre.

Deer are faid to burnijh their Heads, when rubbing off a white downy Skin from their Horns againft a Tree, they thruft 'em into a reddifh Earth, to give 'cm a new Colour and Luftre.

BURR, or BURR-DOCK, is an Herb, whofe broad Leaves, Roots, and Seeds, are fometimes us'd in Phyfick.

Burr-Pump, or Bildge Pump, a kind of Pump lb call'd, becaufe it holds much Water ; fee Pump.

BURSARS, in Scotland, are Youths chofen, and fent as Exhibitioners to the Univerfities, one each Year, by each Presbytery ; by whom they are to be fubfifted for the Space of four Years, at the Rate of 100 /. per Annum, Scots.

BUSHEL, a Meafure of Capacity for things Dry 5 as Grains, Pulfe, dry Fruits, &c. Th.zEngUfhBujhcl contains 4 Pecks, or 8 Gallons, or £ of a Quarter. See Measure.

At Paris, the Bujhel is divided into two half ' BuJIj- els ; the half Bitjhel into two Quarts 5 the Quart into two half Quarts 5 the half Quart into two Litrons j and the Litron into two half Litrons. Bya Sentence of the Pro' voft of the Merchants of Paris, the Bujhel is to be eight Inches, two Lines and a half high, and ten Inches in Dia- meter 5 the Quart four Inches nine Lines high, and fix Inches nine Lines wide 5 the half Quart four Inches three Lines high, and five Inches -Diameter $ the Litron three Inches and a half high, and three Inches ten Lines in Dia- meter, Three Bujhels make a Minot, fix a Mine, 12 a Septier, and 144 a Muid : See Muid. In other Parts of France the Bujhel varies : 14 | Bujhels of Amhoife and 'Tours, make the Paris Septier. 2.0 Bujliels of Avignon, make three Paris Septiers $ 20 Bujhels of Slots, make one Paris Septier 5 2 Bujhels of Bourdeaux, make one Pa- ris Septier; 32 Bujhels of Rochel, make 19 Paris Sep- tiers; Note, Oats are meafur'd in a double Proportion to other Grains $ fo that 24 'Bujhels of Oats make a Septier, and 248 a Muid. The Bujhel of Oats is divided into four Picotins, the Picotin into two half Quarts, or four Litrons. For Salt, four Bujhels make one Minot, and fix a Septier. For Coals, eight Bujhels make one Minot, 16 a Mine, and 320 a Muid. For Lime, 3 Bujhels make a Minot, and 48 Minots a Muid.

2)u Cange derives the Word from Bufellus t or BuftelluSt or Bifellus, a diminutive of Buz,, or Bttza, us'd in the corrupt Latin for the fame thing. Others derive it from Buffulus, an Urn wherein Lots are caft.

BUSKIN, Cothurnus, a kind of Stocking among the Antients, in manner of a little Boot, covering the Foot and Mid-leg, and ty'd beneath the Knee ; very rich and fine, and us'd principally on the Stage by the Aftors in Trage- dy. The Buskin is faid to have been firft introdue'd by Sophocles : It was of a Quadrangular Form, and might be wore indifferently on either Leg. It was fo thick, as by means hereof Men of ordinary Stature might be rais'd to the Pitch and Elevation of the Heroes they perforated: In which it was diftinguilh'd from the Sock, wore in Co- medy ; which was a low, popular Drefs. ^Dempfier ob- ferves, that it was not Aclors alone who wore the Buskin, but Girls likewife us'd 'em to raife their Height 5 Travellers and Hunters to defend themfelves from the Mire, &>c As the Buskin was the dittinguilhing Mark of Tragedy on the Stage, we find it in Claflick Authors frequently us'd to fig- nify Tragedy it felf.

BUST, or BUSTO, in Sculpture, &c. a Term us'd for the Figure, or Portrait ofaPerfon in Relievo ; Ihewingonly the Head, Shoulders, and Stomach ; the Arms being lopp'd off: ordinarily placed on a Pedeftal, or Confole. Felibien obferves, that 'tho in Painting one may fay a Figure appears