( 5i ) 'them, then they are converted into perpetual -Springs of Water ; the like Effctft whereof we fee in every common Still ; but if when they pafs through the Rocks they meet with thofe two Juices, namely the Firc-ftone, or Brimftone clarify’d and confolidated, as hath been faid a little before, then it diffolves the faid Juices, mixing itfelf with them, and after boiling together a convenientTime,it thickens and hardens in the Mine ; this is the Doctrine of Bracefco in his Comment upon Getro ; but the greateft Number of Alchymifts do affirm the immediate Matter of Metals to be Quick silver and Sulpur, and that from the different Proportion of their Mixture, and greater or lefl'er Purification, refults the Difference that ^ found in Metals. CHAP. XIX. The Opinion that gh/ickfdver and Sulphur are the Matter whereof Metals are made, is defended. T HOSE that think nothing can be eftecftcd that comes not within die Compafs of Bicir own Capacity, a Prefumption very un worthy of learned Men, and much dimi- n| ihing their Credit, who are pofleffed tlie- re with, from Rcafons that neither convince f 101 ; are of any Force to deny, hold, that 4 f x n0t P 01 ^ c ty Art to change one fort Metal into another. It is not proper in Place to examine all the Arguments D 2 of