- a b c d The square Stone at the top, covering the whole Furnance. This is indeed the Furnance.
- a d, b c The breadth two Foot and one Inch.
- a b, c d The Length two Foot three Inches. Into the Breadth and Length about the whole Stone, is let in even with the top of the Stone a square Iron Band two Inches deep, and a quarter and half quarter of an Inch thick to preserve the Edges of the Stone from battering.
- e The round hole the Pan stands in, which hath an Iron Plate let into it eight Inches diameter, an Inch and half broad and one quarter of an Inch thick.
- This Iron-Plate fits the inside of the Hole so far as it is Circular, and consequently is a Segment of a Circle. But where the Smoak-vent breaks off the Circularity of the Stone, there ends this Plate of Iron, that the Smoak may have the freer vent. Its Office also is to preserve the Edge of the Hole from battering, with the oft taking out and putting in the Iron Pan.
- f The Funnel seven Inches high, and five Inches wide.
- g The Stoke-Hole four Inches wide, and six Inches long.
- h h The height of the Furnance two Foot ten Inches.
- i The Air-Hole just underneath the Hearth to let in Air that the Fire may burn the freer.
- k The Ash-Hole where the Ashes that fall from the Hearth are taken away.
- l m n o The Bench two Foot broad, three Foot long, and two Foot eight Inches high. The Bench is to empty the Letters out of the Mold upon, as the Founder Casts them.
The Hearth lies seven Inches below the top of the round Hole, and hath under it another round Iron-Ring of the same demensions with the first, on which straight Iron-Bars are fastened that the Fire is laid on.
In the round Iron-Ring (or rather Segment) on the top of the Furnance is set the Pan, which is either a Plate Ladle, or a small Cast-Iron Kettle that sinks into it within two Inches of the Brims of the Pan.
¶. 2. Of making Mettal.
The Mettal Founders make Printing-Letters of, is Lead hardned with Iron: Thus they chuse stub-Nails for the best Iron to Melt, as well because they are asured stub-Nails are made of good soft and tough Iron, as because (they being in small pieces of Iron) will Melt the sooner.
To make the Iron Run, they mingle an equal weight of Antimony (beaten in an Iron-Morter into small pieces) and stub-Nails together. And preparing so many Earthen forty or fifty pounds Melting-Pots (made for that purpose to endure the Fire) as they intend to use: They Charge these Pots with the mingled Iron and Antimony as full as they will hold.
Every time they Melt Mettal, they build a new Furnance to melt it in: This Furnance is called an Open Furnance; because the Air blows in through all its sides to Fan the Fire: They make it of Bricks in a broad open place, as well because the Air may have free access to all its sides, as that the Vapours of the Antimony (which are Obnoxious) may the less offend those that officiate at the Making the Mettal: And also because the Violent Fire made in the Furnance should not endanger the Firing any adjacent Houses.
They consider before they make the Furnance how many Pots of Mettal they intend to Melt, and make the Furnance sizable to that number: We will suppose five Pots. Therefore they first make a Circle on the Ground capable to hold these five Pots, and wider yet by three or four Inches round about: Then within this Circle they lay a Course of Bricks close to one another to fill the Plain of that Platform, with their broad or flat sides downwards, and their ends all one way, and on this Course of Bricks they lay another Course of Bricks as before, only the Lengths of this Course of Bricks lies athwart the Breadths of the other Course of Bricks: Then they lay a third Course of Bricks with their lengths cross the Breadth of the second Course of Bricks.
Having thus raised a Platform, they place these five Pots in the middle of it close to one another, and then on the Foundation or Platform raise the Furnance round about by laying the Bricks of the first Lay end to end and flat, close to one another: On the second Lay, they place the middle of a Brick over a Joynt (as Brick-layers call it) that is where the ends of two Bricks joyn together, and so again lay Bricks end to end till they Trim round the Platform. Then they lay a third Lay of Bricks, covering the Joynts of the second Lay of Bricks as before: So is the Foundation finisht.
Then they raise the Walls to the Furnance on this Foundation; But do not lay the ends of their Bricks close together. But lay the ends of each Brick about three Inches off each other, to serve for Wind-holes till they Trim round about: Then they lay another Lay of Bricks leaving other such Wind-holes over the middle of the last Lay of Bricks, and so Trim as they work round either with half Bricks or Bats that the Wind-holes of the last Lay may be covered: And in this manner and order they lay so many Lays till the Walls of the Furnance be raised about three Bricks higher than the Mouths of the Melting-Pots, still observing to leave such Wind-holes over the middle of every Brick that lies under each Lay.