44 On the Uj'c oj Calcareous Stones hi 



Before this principle was undcrftood and generally ailed 

 v.pon, the refult ia iron, from a given (luantity of ore, mull 

 have been very uncertain, and its real value in the fmelting 

 furnace falfely appreciated : even at this advanced period of 

 improvement, and attainment of fcientlfic kno-wleclge, it is 

 much to be doubted if the principle of cippllcation of calca- 

 reous earths, in the blaft furnace, is radically undcrftood. 



If an almoii: total want of knowledge concerning the na- 

 ture, proportions, and variety of the earths united to the ores, 

 prevail at the various manufaftorics of iron in Britain, we 

 are not to wonder that the application of lime-ftonc is fi'.bjeft 

 to great error, and produ6live of hurtful c'onfequences. 



In the fmelting proccfs the three great fprings of action 

 and government in the manufaAure ought to be — a com- 

 plete revival of all the metal contained m the ore — to confcr 

 value upon it, by reviving it fatura,ted with a fufficieut quan- 

 tity of carbon — and to ufc every endeavour to inercafe the 

 OjUantity : ftill, however, keeping in eye the produce of iron 

 from the ore, and its quality; both of which may be calil^- 

 impr.ired by too much cagernefs after quantity. 



To deprive an ore of its iron, fo that no portion of it flialj 

 cfeape in the fcoria unrevivcd, two things arc Indifpenfible : 

 3 . The metal contained in the ore mull be prefented to a 

 portion of fuel fufiicient to take up the oxygen from the 

 metal. 2. As this revivification gpcs on in the manner of a 

 metallic perfpiration upon the foftcned furfaces of the ore, 

 another agent ought to be prefent to fecilitate the feparation, 

 bvvmitingwith the earthy parts of the ore; forming a thinly 

 divided lava, no longer capable of retaining the globules of 

 metal, or of preventing the congenial affinity of the carbonic 

 principle from taking full eftc^^t for the improvement of the 

 quality of the iron. 



Experience has flicwn, that an exccfs of any particular 

 earth may be corrected by applying one oppofite in its 

 effects ; and that the addition of lime, in various proportions, 

 js found in mcft cafes to anfwer the defircd end : this once 



ur-c-'criloo4^ 



