184 On the AJfaying of Iron Ores 



ad, I fubje£led to a fimilar treatment 875 grains of an ar- 

 gillaceous iron-ftone, which contained a ul'ual proportion of 

 lime ; the fufion of this powder was more difficult than that of 

 the former, though the phenomena exhibited by both during 

 reduction were alike. The crucible was withdrawn from the 

 furnace in forty minutes after introdu(3:ion, and the furface 

 of the button expofed to combuftion as before. The de- 

 flagration differed little in point of appearance from that 

 effefted with the filiceous iron-ftone : the button of crude 

 iron was found oxygenated, and weighed 249 grains j a pro- 

 duce in iron from the raw ftone — 28.5 per cent. : the 

 vitrid mafs was found to weigh 354 grains; the lofs of vo- 

 latile mixtures was therefore 373 grains, or 31 fcr cent. 

 The frafture of the regulus now obtained was ftill white, 

 though not allied to any degree of cryftallifation, and its 

 furface fmoother and lefs oxydated. The glafs produced in 

 this experiment was of a deep brown fhining colour, in many 

 places porous, and enriched with fine ti^^s of colouring. 



3cl, The fame experiment was repeated upon 875 grains 

 of a fine calcareous iron-ftone. The fufion of this required a 

 violent heat of feventecn minutes, during which time the 

 difengagement of a gafeous fubftance was moft evident ; ia 

 other rcfpedlis it exhibited the fame features, when in fufion, 

 as the two former : the degree and length of heat conveyed 

 was nearly the fame ; and the refult obtained was a button 

 of carbo-oxygcnated crude iron * weighing 361 grains ; a 



produce 



* Aldiough in th's experiment a true carbonatlon is efFefted by means 

 of tho prefgnce of lime ;.lone, yet experience has never confirmed this in 

 the large way ; nor fliewn, after a juft proportion of materials was in the 

 furnsce, that additiqnal lime alone conferred any additional degree of car-!- 

 bonation. The widely different manner in vvhich the heat is excited, and 

 the fubftances which are operated upon expofed to its aftion, may account 

 for this want of coincidence of efleft. It is the fame principle that 

 e.Cloutthas lately ingenioufly applied to the fabrication ofcaft ftee! from 

 bar iron. To the decompofuion of the carbonic acid alone, I attribute 

 the a4vantagi:s derived from the ufe of li.Tie in the manufacturing of crude 



iron. 



