At the mouth or entry of the _Adit_ there is a structure raised of _Brick_, like a _Chimney_, some 28. or 30. foot high in all: at the bottom, two opposite sides are (or may be) some 51/2 foot broad; and the other two, 5. foot: the wall 11/2 _Brick_ thick. At the lower part of it, is a hole, some 9. or 10. inches square, for taking out of the Ashes, which when it is done, this Ash-hole is immediately stopt so close, as Air cannot possibly get in at any part of it. Then, some 3. foot above ground or more, there is on that side, that is next to the _Adit_ or Pit, a square hole of 8. or 9. inches every way, by which the Air enters to make the Fire burn: Into this hole there is fixed a square _Tube_ or _Pipe_ of Wood, whereof the Joints and Chinks are so stopt with Parchment pasted or glewed upon them, that the Air can no where get in to the Pipe but at the end: And this Pipe is still lengthened, as the _Adit_ or Pit advanceth, by fitting the new Pipes so, as one end is alwaies thrust into the other, and the Joints and Chinks still carefully cemented and stopt as before. So the Pipe or Tube being still carried on, as near as is necessary, to the wall or place, where fresh Air is requisite; the Fire within the Chimney doth still attract {81} (so to speak) Air through the Tube, without which it cannot burn, which yet it will do, as is obvious to conceive (all Illustrations and Philosophical Explications being here superfluous,) and so, while the Air is drawn by the fire from the farthest or most inward part of the _Mine_ or _Adit_, fresh Air must needs come in from without to supply the place of the other, which by its motion doth carry away with it all the ill vapors, that breath out of the ground; by which meanes the whole _Adit_ will be alwaies filled with fresh Air, so that men will there breath as surely as abroad, and not only Candles burn, but Fire, when upon occasion there is use for it for breaking of the Rock. Now that there may be no want of such fresh Air, the Fire must alwaies be kept burning in the Chimney, or at least as frequently as is necessary: For which purpose there must be two of the Iron Grates or Chimneys, that when any accident befals the one, the other may be ready to be in its place, the Coals being first well kindled in it: but when the fire is neer spent, the Chimney or Grate being haled up to the dore, is to be supplied with fresh fuel. The Figure of the Fabrick, Chimney, and all the parts thereof being hereunto annexed, the rest will be easily understood. [Illustration] _Figure_ 1. A. The _Hole_ for taking out the Ashes. B. The _Square-hole_, into which the Tube or Pipe for conveying the Air is to be fixed. C. The _Border_ or _Ledge_ of _Brick_ or _Iron_, upon which the _Iron-grate_ or _Cradle_, that holds the burning Coals, is to rest, the one being exactly fitted for the other. D. The _Hole_ where the _Cradle_ is set. E. The woodden _Tube_, through which the Air is conveyed towards the _Cradle_.