li^^ On the JJje of Calcareous Slohcs hi 



and the clefcent of the materials. The fource of this evil \i 

 juftly attributed to the nature of the iron ftone; but in place 

 of attempting to obviate its impcrfeAions of mixture, it is 

 either totally rcjeded, or ufed in the moll fparing quantities : 

 whereas, had the quantity of calcareous earth been propor- 

 tioned to that contained in the iron ftone, the fame ore might 

 have been advantageoufly fmclted, and a confiderable quan- 

 tity of lime faved. The fame happy effefts might alfo have 

 been produced by combining with the calcareous iron ftone, 

 one containing a large proportion of clay or fand ; in fome 

 fituations, where a variety of lime ftones are found, the fame 

 confequences may be cffc<5lcd by applying orie lefs pure, 

 mixed with a proportion of elay and filex. 



A ftmilar excefs of clay in th<s argillaceous genus of iron 

 ftones, is fraught with the fame fatal clVeiils to the produce 

 in metal from the blaft furnace ; and maiiv fuch ores of iron 

 are totally rejected, merely bccaufc tl>eir improper application 

 was found produftlve of confcqucnt cH'ci-^s. The fufibllity 

 of lime and clay, individually, is much fecilitated by the ad- 

 dition of f;md ; and in all cafes where thefe earths exift to' 

 excefs in the ores, they ought either to be combined in the 

 blaft furnace with filiceous iron ftone, or treated with a lime 

 ftone containing a confiderable portion of fand. 



Again, inftanccs occur in the manufacturing of crude iron^ 



where ores fuflicientlv rich in iron are totally rejeiSled, a:s 



being incapable of aft'ording a quality of crude iron for the^ 



purpofe of melting. It is found that an excefs of fuch iroi"^ 



ftone always changes the colour of the fcoria, and that ai 



confiderable portion of the metal goes to efioftuate this 



change in the ftate of an oxyde united with the fufed earths^ 



Thefe ores are of the moft fufible nature, combined with a; 



heavy proportion of filex ; but ItiH capable of being treated 



in fuch a manner as to afford their iron of a valuable quality.. 



When this mixture is fldly afcertained, the fufibility of the 



iron ftone is little impaired, and the quality of the iron 



xncndcd with an increafe <?f quantity. 



5 From 



