the Manvfacl.iirc of Crude Iron. 4_5 



xmderftood, it will be eafily coinprchended, tiiat as iron ilor.es 

 and ores pofl'efs widely different proportions of mixture, their 

 fuiion will be produAive of vitrid fcorise, various in their 

 deprees of divifion and tcnacitv. This leads to a conclufion, 

 the juftice of which cannot be doubted, that fince the various 

 mixtures of iron ores are produi^tive of lava, which tends 

 more or lefs to keep the iron from feparation, it becomes a 

 necelfary ftudy to obviate the imperfe6tions of fueh mixtures, 

 and at all times to regulate the proportion of the calcareous 

 earth, from a knowledge of thefe mixtures and their effect;?, 

 and not from an implicit reverence to the cuftoms of a fenior 

 eftablidiment. 



If the various claffL's of iron ftones are fufcd in contact 

 with charcoal, without the addition of a flux or folvcnt, the 

 rcfult is, from calcareous iron (lone, a larger portion of iron 

 proportioned to the intrinfic richncfs of the ore, than from 

 arcillaceous iron ftonc; and from the latter, a larger produce 

 of iron, than from an ore whofc chief niixture was (ilex: the 

 fcoria produced in the rcfpeclive operations always demon- 

 ftratcs, from its colour and opacity, the probable quantity of 

 iron which ftill remams to be taken up. 



There are fome calcareous iron ftones which contain lime 

 almoll fuuicient to form the nccefifary quality of fcoria, the 

 colour of which, when freed from the metal, poflelfes a con- 

 fiderable degree of tranfparcncy. When a number of thefe 

 iron ftones are ufcd in the blaft furnace, a much Icfs quantity 

 of calcareous earths is neccflary. It fometimes happens jt 

 iron w jrks, whofc cliief fupply is derived from a calcareous 

 field of iron (lone, that, by ufing a great proportion of an in- 

 dividual ore furchargcd with lime, the operations of the 

 furnace are obllruiled, and confequences entailed fatal to the 

 intereft of the manufacturer. From an excefs of pure calca- 

 reous earth being prefent in tlie furnace, the fcoria, thick and 

 curdled, becomes attached to tlie (ides and bottom of the 

 furnace J the quantity hourly incrcafcs, till it has accumu- 

 lated to fuch a degree as to intercept the afccnt of the blaf^, 

 7 and 



