cur when such Adits are wrought or driven inward upon a Level, or near it, 20, 30, or 40. fathom, more or less; Aswel because of the expence of money, as of time also, in the Ordinary way of preventing or remedying those inconveniences; which is, by letting down shafts from the day (as Miners speak) to meet with the Adit; by which means the Air hath liberty to play through the whole work, and so takes away bad vapours and furnishes good Air for Respiration. The Expence of which shafts, in regard of their vast depth, hardness of the Rock, drawing of water &c. doth sometimes equal, yea exceed the ordinary charge of the whole Adit.
Amongst the Expedients that have been devised to remedy this, there is one practised in the Coal-mines, near the Town of Liege (or Luyck) that seems preferable to all others for Efficacy, Ease, and Cheapness: the description whereof followeth.
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 foot broad; and the other two, 5. foot: the wall 11 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