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ber os Instances have fallen within my Ob-servation since my coming hither; manyhave assay’d Metals under my Direction,who, when I was present, always suc-ceeded ; but, when they attempted it with-out me, and managed the Fire themselves,they always failed, at least their Processnever answered their Expectation whereashad they had a true Notion of the different:Degrees of Fire, and thoroughly under-stood its Force of Action, they would un-doubtedly have succeeded. No one, inJustice, can presume to undertake the Ma-nagement of a Smelting-work, who is notwell acquainted with the chief Agent,since, upon it, the whole Art depends.

2 dly, What we read in Books concern-ing the different Degrees of Fire, is of someUle to the young Smelter, as a Body ofMustek is to the initiated Musician; neithercan the one, nor the other, be afcertain’dbut by Experience ; a patient, and constantPractice, is absolutely requisite. Give metherefore leave to advise all commencingStudents in Metallurgy, not to rely uponimaginary Theory or Conjecture, nor tobelieve any Thing but what has been con-sirm'd by his own Hand Labour • for itrequires the Employment and Satisfactionof all the Senses, to judge rightly of it.

^dlv, A Smelter must be acquainted withthe Nature of Clays, and endeavour as much

as