On the Ajfaylng of Ores hj Prijion. 385 



when rubje(^ed to the gauge, much fuperior In ftrength ; 

 arid if the experiment be accurately performed, the metal will 

 be but a little reduced in point of carbonation. The follow- 

 ing proportions will give accuracy to the refult : — Oxyde of 

 iron, 4 parts — Lime, a — Clay, i — Glafs, 3= 10 parts. By- 

 mixing clay with the flux in all experiments, the ftrength of 

 the crude iron is improved. This point may be urged fo far 

 as to form, by an extra-addition of clay, a flux of difficult 

 fufion; in which the iron becomes fufpended in globules, 

 which are partially malleabilifed apart from each other. 

 Crude iron, obtained with a fuperior mixture of clay, in all 

 its ftages of quality, poflefles a greater degree of ftrength than 

 iron from calcareous iron-ftones. Iron from argillaceous 

 iron-ftone is reckoned ftrongeft when carbo-oxygenated ; 

 that extrafted from calcareous iron-ftorie is reckoned to 

 pofTefs moft ftrength when oxygenated, mottled. I would 

 far exceed the limits of the prefent communication, were I 

 to enter fully into this curious fubjed, and particularife the- 

 different refults obtained by the hifion of ores with different 

 earths in various proportions : all my experiments have fully 

 proved to me, that originally the quality of the iron, fimply 

 confidered, -was the fame j that, as it underwent change by 

 decompofition and new combination, it became united to 

 foreign fubftances, poffefl'mg widely different properties ; and 

 which mixture, by a general fufion, imparts to the metal va- 

 rious properties, feldom homogeneous, but frequently other- 

 wife : in ftiort, that the numberlefs mixtures with which it 

 is combined are not neutral in fufion, but convey an altera- 

 tion to the quality of the reduced iron. I hope to refume 

 this fubje6t when my experiments will be more extended by 

 the examination of a vaft variety of iron-ftones, and ftiall 

 then point out the confequent effcfts of their application to 

 the manufacture of caft and malleable iron. 



The affaying of primary ores comes next under confidera - 

 tion. Thefe, I have already faid, poffefs a much greater di- 

 verfity of external charaaer, as well as internal variety, than 



Vol. IV, C c thofe 



