ihe ManufuSlure of Crude Iron. 4^ 



the fcoria flo:iting upon the furfacc of the precipitated metal, 

 changes its colour, and in iHuInfr from the furnace conveys 

 a complete change of form and dcpofition. 



Should it, however, happen that an extra quantity of lime 

 is dddcd when the iron is alriiady richly Carbonated, then the 

 metal loll is no longer in the (late of a fufed oxyde incorporated 

 with the fcoria, but in fmall metallic globulesj completely 

 enveloped, unable to penetrate the curdled mafs and find their 

 ^vav to the bottom of the furnace. This curious pherlome- 

 noil arifos from the peculiar nature of fufed calcareous earth, 

 which, while it poni-ircs no great degree of tenacity as a fluid, 

 yet forms a confidcncy through which irbn with all its fupe- 

 rior denfity is not able to penetrate : when cold, fuch fcorise 

 have no appearance of vitrification, but are of a ftraw colour, 

 rough fraclure, and very ponderous. I have fome fpecimens 

 of this fcoria, obtained from the blaft furnace, with triple 

 ftrata of regularly depofitcd globules of fuper-carbonated 

 crude iron, from h^lf an inch to the fmalleil diameter. 



The \\x\d: analogy exifting betwixt lime ftones and ores, 

 in the variety aiid proportion^ of the earths combined with 

 each, renders the inveftigation of both equally neceflary, and 

 requifite to be performed in connexion with each other. 



There arc advantages to be derived from a thorough 

 knowledge of the component parts of iron ftones, which 

 may not at firli fight firlke the mnnuiafturer : where a 

 variety pf fituations ofier, this knowledge will direft him 

 to an eftabliflimcnt where the iron ftones are of a nature 

 moll likely to fuit his views. Where mtlting pig iron for 

 fale is tile chief objeit, calcareous iron ftc nes mixed with 

 filcx and nearly deftitute of clay poUefs the greatell advan- 

 tages. Inm made from this dal-j of ores never pofielfes any 

 great degree pf ftrength; this, however, in the cafting bufi- 

 nefs in general, is reckoned its greateft property; it becomes 

 fufed with kTs fuel, lefs walle of metal, and the articled made 

 from it exceed tljole made from ftronyvr iron, in the fmoothf 

 nefs of their furface and in the folidity oi' iheir pans. 



\'oL. IV, r; Analo^oas 



