(ss)

free his Stone from all Sand er Grit, be-fore he attempts to smelt it, otherwise hewill find his Labour too frequently unsuc-cessful.

What has been here related of the Con-comitants of Copper and Iron Ore, fre-quently attend that of Ttn ; for whichReasons the Smelters, should mind not toroast such Ore too long, otherwise a greatPart of the Metal will be lost by its beingformed or turned with the Iron 'Earth,into such like strong Concretes or Scoriæwhich the Fire cannot master, so that itought to be separated by washing, as be-fore noticed; and this is more especially tobe regarded, as Tin is seldom found with-out them.

Lead Ore is not always exempt fromthese Impediments, and the worst SteelOre, which yields no Silver, is the mostliable to them ; I therefore judge it to bevery necessary, that the Smelters shouldmake themselves acquainted with these na-tural impeding Causes attending Ores, andthe Means to rectify them; for whichthere is the more Reason, because From theSymptoms which now appear to me, I ap-prehend it will fiot be long before theymeet with such Kind of Ores in theirMines.

lothly, Since I have entered upon a De-tail of these abstruse Ores and Minerals, ID 4 cannot