jSS On ihd AJJiiying cf Ores Ij Fu/ion^ 



thofe of iron-done. When aflayed with a v'ltreOus flux, 

 either of falls, alkalies, or filex, the rcfults are rendered very 

 uncertain and erroneous : when pot-afh, tartar, &c. are ufed, 

 the crucible is often deftroyed, and the compound entirely 

 !oft : when bottle glafs and a mixture of thefe are ufed, the 

 fcoria formed is fo very black and ponderous as to give the 

 moll prefumable indication of the fecretion of metallic 

 oxyde : this is afterwards verified by fufing the mafs with a 

 mixture of dried chalk and charcoal, a globule of metal will 

 be obtained, which evinces the richnefs of the fcoria ; this, 

 having loft its colourmg principle (the metal), becomes clear 

 and tranfparent. The refults from thefe ores by fufion afford 

 various produfts, and lead to different conclufions : I iliaB 

 mention feveral of them. 



The Cumberland iron ore, when introduced into a cru- 

 cible without any additional mixture, fufes eafily, and forms 

 ah opaque fcoria, internally of a black colour, but towards 

 the furface covered with fine fliades of brown : this arifes 

 from a partial oxygenation of the femi-revived metal while 

 cooling, and is often injured by a frefli combination of 

 ox3gen. If the crucible remains found, and the melted 

 hiafs is kept in a ftate of extreme divifion for jhi hour, a 

 confiderable quantity of metal will be found precipitated, 

 but fo highly oxygenated as to fliiver to pieces if expofed to 

 air before it is entirely cooled. If, when the crucible is taken 

 from the furnace, it be {lightly inclined to one fide, and the 

 vitrtfied fluid entirely removed from the furface of the metal, 

 a violent deflagration will immediately enfue, the eje£led 

 globules will be thrown three feet upwards from the mouth 

 of the crucible : if the quantity of metal does not exceed 

 500 grains, it will totally difappear, except a rough dark- 

 blue oxyde m the bottom of the crucible, not above i-4th 

 of the original weight. The metal thus oxydated will be 

 found in fniall fpherules of a blackifh colour, and fpongy 

 around the fpot occupied by the crucible. 



This curious appearance is in faft a combuftion of iron 



by 



