_In which is described the Nature of the Fourth Furnace; by the help whereof, Minerals and Metals are tryed, and examined after a more compendious way, than hitherto after the common manner; also the separation of Metals by the force of Fusion, and other necessary things that are done by the power of Fusion or Melting. Most profitable for Chymists, Tryers, and Diggers of Minerals._ Of making the Furnace. In the first Figure, A. _represents the Ash-hole with its door_. B. _The Register appointed for governing the fire._ C. _The Hole with its door assign’d to receive the Crucibles and Coals._ D. _The Hole with the door of the First Story._ E. _The long Pipe of Iron in the top of the Furnace._ The second Figure, _A Cone or Casting Vessel belonging to this Furnace_. This furnace may be made greater, or smaller, as you please, according to the matter to be tryed: and if the _Diameter_ thereof within, be but of one foot, you may set in it a crucible containing two or three pound; but greater crucibles require a greater furnace. Now this furnace must be quadrangular, and be built of stones, and lute, such which abide the fire, of the height of one or two foot from the bottom to the grate, which must be such as may be cleared from the dross mixed with coals, or such as was the grate of the first furnace, consisting of too strong cross iron bars fastned in the furnace with certain distances for the receiving of 5, 6, or 7. other lesser iron bars which are to be moveable, so that when they are obstructed they may be removed, and cleared from the dross; the lower part of the furnace must have near the bottom a hole (in the forepart) of the heighth, and breadth of a little span, with an iron or copper door, shutting close: the lower part also must have another hole near the grate on the other side with its register for the government of the fire, and for the attracting of wind. Above the grate, and a hand breadth from the grate must be another hole for putting in of coals, and crucibles, sutable to the proportion of the furnace, and the height thereof must be of one foot, and the latitude of half a foot, if the inward Diameter of the furnace be of one foot, whereby the crucibles may be the more conveniently handled, and the coals be cast in with a fire-pan: Let this hole also have a very strong door of stone covered over with lute, either of which may endure the fire, and shut very close, that the fire may thereby (when the crucible is placed in the fire) attract air, but only from the collateral hole under the grate. Let the height of the furnace (being coated above) from the hole appointed for the putting in of coals and crucibles, be of one great span: Let there also be a round hole in the furnace, having the third part of the intrinsecal diameter of the furnace, appointed for the flame and smoke; to which if you will use a very violent fire, put to it a strong iron pipe of