196 Mr. J. Napier on Coppei' Smelting. 



conflagration takes place, cover with a tile or any convenient 

 article till tlie burning ceases ; then grind what is left, and keep 

 in a stoppered bottle as it is liable to deliquesce. 



By the results of the assays both the buyer and seller of the 

 ores are guided, and the regular agreement of the various assay- 

 ers in their results is a proof of general accuracy. When, week 

 after week, not less than a dozen assayers, every one separately 

 assaying the same sample of ore two or three times over, are all 

 found to agree within y^fth of a per cent., it must be a source of 

 confidence to all parties. Nevertheless many of the assayers know 

 as little of the principles of their operation as the miner or seller ; 

 consequently the whole process, as it is practised, is a mecha- 

 nical operation, and one that has undergone little or no change 

 these two centuries, as will be evident by a few extracts from 

 the works of the celebrated Lazarus Erckern, published in this 

 country in 1683. Indeed so accurate are his processes and de- 

 scriptions, that an edition of his works, with our improved no- 

 menclature and apparatus, would be a valuable addition to the 

 library of every chemist and metallurgist. 



" To make Flux to prove Copper Ores. 

 " Take two parts of argal and one part nitre, grind them small 

 and mingle them, and put the whole into an unglazed pot, and 

 put a little live coals in it, when it will begin to burn ; when the 

 burning gives over, put away the coals, and grind the flux and 

 keep it in a warm jdace ; if set in a cool or moist place it deli- 

 quesces. This flux is to be used to good copper ore ; but for 

 flinty or other ores hard to melt, this flux is too weak of itself; 

 there must be something additional added." 



" Hoio to prove easily flowing {melting) ores. 



"Rich good copper ores (not flinty and speiry) arc proved 

 thus : grind the ore small, and weigh two centners (200 parts), 

 and put them in a ci'ucible with three times as much of the 

 before-mentioned flux well mixed ; then cover this with a layer 

 of common salt a full finger thick, press it down, cover the cru- 

 cible luted with clay to prevent coals falling in or the contents 

 flowing over ; place the crucible in the fire or oven, then cover 

 with coals about an handbreadth high, and blow through the 

 hole under the grate that the wind may go alike round the cru- 

 cible until in perfect fusion ; let it stand awhile in the fusion, 

 then take the upper fire oft" and lift out the crucible, and set it 

 on a plain tile that the grains of copper may settle. When cool, 

 the crucible is broke, and a button of copper is found at bottom. 

 You must observe in proving, the heat be not too high, for the 

 copper will burn and drive itself into the slack (slag). If the 



