Page:Cyclopaedia, Chambers - Volume 1.djvu/832

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In China it is only a huge wooden Mallet, ftruck by Force of Arm againft the Bell : Whence they can have but little of thae Concordancy fo muchad mir'd in feme of our Rings of Bells. The Chinefe have an extraordinary way of increas- ing the Sound of their Bells, viz. by leaving a Hole un- der the Canon; which our Sell Founders would reckon a Defect.

The Proportions of our Bells differ very much from thofe of the Chinefe. In ours, the modern Proportions are to make the Diamerer fifteen times the Thicknefs of the Ledge, and twelve times the Height.

The Manner of cafting great Guns, or Pieces of Artillery.

The Cafting of Canons, Mortars, and other Pieces of Ar- tillery, is performed like that of Statues and Bells: Efpe- cially as to what regards the Mould, Wax, Shell, Fur- naces, &c.

As to the Metal, it is fomewhat different from both ; as having a Mixture of Tin, which is not in that of Statues ; and only having half the Quantity of Tin that is in Bells, i. e. at the rate of ten Pound of Tin, to an hundred of Cop- per. A Canon is always fhap'd a little Conical, being thickeft of Metal at the Breech- where the greateit Effort of the Gunpowder is made, and diminifhing thence to the Muzzle : So that if the Mouth be two Inches thick of Me- tal, the Breech is fix.

Its Length is meafur'd in Callipers, /. e. in Diameters of the Muzzle. Six Inches at the Muzzle require 20 Calip- pers, or ten Feet in length : There is about £ of an Inch al- lowed Play for the Ball.

Letter Foundry, or the Manner of cafting Printing Letters-

The Invention of Printing Letters we ihall fpeak of under the Articles Printing, and Letter.

Their Difference, Kind, &c. has already been explain'd under the Articles Character, &c.

The two Things principally to be regarded in the cafting of Letters, are the Matter, and the Matrices.

The Matter is a Compound Metal; partly Copper, and partly Lead, mix'd in a certain Proportion, which every Letter Founder regulates at his own Difcretion, and to which lie frequently adds a certain Quantity of fome other Metal or Mineral, as his Experience directs him, to render his Compofition the harder.—* —

The moll ufual Proportion of the two Metals, is a hun- dred Pound of Lead to twenty or twenty five Pound of Brafs. Some (tho 1 not the beft Founders) ufe Iron, inftead of Brafs; in the Proportion of a hundred Pound of Lead, to thirty, or thirty five of Iron.—

Thefe Metals are melted feparately in large* Crucibles ; the Brafs, or Iron with Antimony, and the Lead by it felf. When in Fufion, they are mix'd together : This Fufion, and Mixture are the molt laborious Parts of the Letter Foun- ders Art.

The Matrices of the Letters are Pieces of Copper, where- on the Impreffion of the intended Character has been cut, or ftruck in Creux, by means of Punchions, &c. graven in Relievo. See Matrice, Punchion, &c.

Each Letter has its proper Matrix ; and there are parti- cular ones for Points, Virgula's, Figures, Rules, Head-pieces and other Ornaments of Printing : Excepting the Quadrats, which being only of L-ead, and not intended to leave any , Impreffion, are caft: without Matrices, and only in Moulds : And each Matrice has its Punchion, made of Steel, or Iron, well temper'd. See Engraving in Steel.

The Matrices being ftruck, and touch'd up, or repair'd, where needful, are put each at the End of an iron Mould, inclos'd between two thin pieces of Board, two or three In- ches fquare; the two upper Angles being cut off, fo as to compofe an irregular Hexagon.

The principal Parts of thefe Moulds, which, as already mention'd, are hid between the pieces of Wood ; are i° Two Steel Plates, with each its Screw, to keep them faft, at a diftance from the Boards. 2 Long Pieces. 3 A Piece calPd the Blank, which is what properly forms the Body of the Character, and at the Extremity whereof the Matrice is put. 4 A Jet ; which is a fort of little Funnel, to re- ceive and convey the melted Matter to the Matrice. 5 A Regtfter, ferving to rejoin the two Parts of the Mould, af- ter they have been open'd to take out the Letter, when caft.

On the Outfide of the Moulds are three other Pieces, p/S. the Bow, at bottom ; and two Hooks atop. The Bow is a thick Steel Wire, two or three Lines in Diameter j and eight or ten Inches long, bent in a manner of a Bow, or Arch; whereof the lower piece of Wood is as it were the Chord, or String. One End is faften'd to the Board, and the other, which is left at liberty, ferves, by its Spring, or Elafticity to prefs and retain the Matrice of the Chara-

cter againft the Extremity of the Blank, where the meftetJ Matter running in, makes the Impreffion.

The Hooks a-top of the Mould are alio of Wire, about the fame Size with the Bow, and about an Inch and half long; being faften'd, one of thetri to one Board, and the other to the other. Their Ufe is, to open the Mould, and. to take out the Character when caft, fo as the Workman may not be incommoded with the Heat.

Every thing belonging to the Mould being thus difpos'd, they begin to prepare the Matter.

The Furnace, whereon the Bafon is plac'd for the Metal to be melted in, is made of the fame Matter as Cruci- bles. It is ufually 18 or zo Inches high, and ten or twelve in Diameter. An iron Grate horizontally plac'd, divides it into two : The lower Part ferves to hold the Afhes, and is furnifh'd with a Hole to let in Air. The Wood is put in the upper Part, thro' an Aperture made over the Grate. An earthen Pipe ferves to carry off the Smoak out at a Win- dow, near which the Furnace is ordinarily plac'd. Laftly, a Stone, or wooden Stool ferves to fupport the Furnace, and raife it to a proper Height for the Workman, to work ftana- ing.

Over the Furnace is plac'd the Melting Bafon, or Copper. It is about nine Inches in Diameter, and takes up the wnol6 Aperture a-top ; being even luted to it all round, with Pot- ters Earth. Its Matter is a kind of Pot Metal ; and that it- may be fit for melting both hard and loft Metals, it is di- vided into two equal Parts, by a perpendicular Partition.

In this Bafon they melt only the Matter already prepar'd; that is, the Mixture or Compofition made in the Crucibles' above mention'd. A little iron Ladle ferves to ikim off the Scoriae or Impurities from the Surface of the melted Me- tal. Thefe Scoria: are not all loft, but ferve to melt over again.

Two Workmen are ufually employ'd at each Furnace- Each of them has his Part of the Bafon to empty; and they have a Table or Bench in common, where they lay the Cha- racters as fall as they are caft.

To run the Metal into the Mould, the Founder holds it in his left Hand ; and in his right a little iron Ladle with a wooden Handle, containing juit enough for one Letter.

Having now fill'd this Ladle with liquid Metal, he pours it into the Jet, or Funnel, whofe Aperture is in thcMiddla of the two Hooks of the Mould; and thrufting his Hand brifkly forward wherewith he holds the Mould, makes the Metal run into the Matrix of the Character; which without fuch Motion might grow cold before it arrived there.

He then unbends the Bow, opens the Mould, and with one of the Hooks takes out the Character; and without Lofs of Time fhuts it again, replaces the Matrice, and cafts a new Letter. 'Tis incredible with what Expedition and Addrefs all this is done.

The Letter being caft, they view it, before they breakj off the Jet ; to fee whether it be perfect; other wife to throw it among the Refufe of the Fount.

If it be found com pleat, the Jet is broke off; the fuper-^ fluous Metal occafion'd by the Mould's not being exactly clofed, taken off with a Knife ; the lcmg-tail'd Letters, as / and /hollow'd at bottom, to give room for the Maffivd of the other Letters to be plac'd underneath.

With the fame Knife they fcrape the Letter, to fmooth its two broadeft Sides, or Faces, and fit them to be rub'd on the Stone.. They take care only ro rub thofe Sides ; for fear of damaging a Notch on one of the other Sides, whichv is to fliew the Sides to the Compofitor when he fets hia Forms.

The Stone they grind them on, is a fort of hard, coarfe- grain'd Free-ftone, plac'd horizontally; before which the Workman fits. To fave his Fingers from the Friction, he*. has a kind of Finger-ftalls, made of fome old piece of Lea- ther; with which he covers the two Fingers next the Thumb : With thefe he works each Side of the Letter backwards acid forwards : To fhift Sides, he makes ufe of the Thumb, but without difcontinuing the Motion ; fo that the By-ftander would eafily be deceiv'd, and be ready to fwear they had all the while rub'd on the fame Side.

The Letters thus ground are plac'd on the Compofitor, to be fcrap'd and brought to the proper Thicknefs on the two other Sides, viz. that of the Notch, and its Oppofite. This they call Compofition.

The Compofitor is a wooden RuTer, with a little Ledge' at Bottom, againft which the Letters are rang'd. On the, fame Inftrument the Quadrats, Rules, Borders, &c, are ad- jufted.

When the Letters are compofed T they remain to be-jtt'j ftified, both as to Thicknefs and Height. In order to this,, they ufe a little Copper-plate, which is their Level. The Juftification, as to Thicknefs, is made on a piece of Marble j and that for the Height, on an iron Compofitor. The Ju- ftification of the Height, is guided by the m of fome Bouy of Characters already juftified.


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