First, a Type or Mold is to be made of Wood, answering to the bigness of the Test, but not with one Handle, as those are made for the purifying of silver, but with two oblong Necks, and without Chaps or Chinks, which otherwise are wont to happen, that so the Cover may remain entire. Then to this wooden Mould the Earth is to be applied, and the Cover to be wrought in the usual manner.
Of the Figure of the Furnace.
The Furnace is so to be built, that it may have within-side the space of an hands breadth all round the Test from its Walls, for Coals, the Test standing in the middle; so that the magnitude of the Furnace is to be proportionable to that of the Test, and may be either round or square, provided it be built with good Bricks, or fit Stones, and Lute, or Earth rightly prepared. There ought to be at least a span between the bottom and the grate, which also ought not to be fastened to the Furnace, but standing upon four Feet, that it may be taken in and out by the foreside of the Furnace (when need requires) being alwaies open. Let the Furnace rise above the Grate the heighth of a span, being every way close, having no door. Upon this heighth of a span a hole is to be left of an hands breadth and heighth, by which the Test may be inspected, and the mixed Metals put in and taken out, and the Fire may have its passage. NB. But if the Test should be above a span over, which would also cause the Furnace to be the greater; then that hole being too little, would not allow a sufficient passage for the Fire; therefore the hole is to bear a due proportion to them. From this hole, nourishing the Fire by its ventilation, the Furnace is yet to be carried up the heighth of two spans, to its upper hole or top, where the Coals are to be put in. Moreover, an Iron Cover is to be made with hollow Superficies, with Iron Buttons, or little Knobs infixed, by which the Lute being put on, may stick fast; the Convex or upper part of the Cover must have a Handle, by which it may be lifted up when the Coals are to be put in, and afterwards put down again to shut the Furnace. See the Figure of this Furnace, in all its parts, at the beginning of this Continuation of Miraculum Mundi, noted at the top with [Pag. 62].
A, The Furnace, as it is working.
B, The lower part of the Furnace open.
C, The upper part of the same.
D, The Grate.
E, The Hearth or Test.
F, The Muffle that belongs to the Hearth.
G, The Cover of the Furnace, with which it is to be covered when the Coals are in and at work.