32 On the AJJinit'ies of 



XI. Pure silex - • - 120 grs* 



Oxide ot iron - - - 80 



Charcoal 1 -20th of the compound, or 20 

 Pure chalk - - - 30 



The fusion of this mixture afforded a very beautiful glass 

 of a rich brown blackish colour, possessed of great smooth- 

 ness and lustre. Eeuoath was found an elegant crystallized 

 iiiflallic button which w eighcd 50 grains ; equal to 25 per 

 cent, from the mixture. 



In this experiment again, as in others formerly recorded, 

 wc have a direct proof of the useful agency of calcareous 

 eartli in the reduction and separation of iron from its earth}'' 

 combinetions. 



Recapitulation of experiments with siliceous matter and 



oxide of iron in the proportion of six of the former to 

 tour of the latter. 

 Exp.W. l-40thof charcoal yielded 1-^% per cent. 



III. l-25th ditto ' 7^^ 



IV. l-20th ditto Q 



V. 1-IJtli ditto 13 



VI. 1-lOth ditto. not fused \2-f^ 

 VII. Being No. VI. repeated, with tbe addition of 



80 grains of chalk, 20^0 

 VIII. With pure silex, 



1 -40th of charcoal yielded 6 per cent. 



IX. l-20lh ditto ' 11 



X. 1-lOth ditto not fused 13 

 XI. Being No. X. repeated, with the addition of 

 30 grains of pure lime, 25 per cent. 

 One very obvious fact marks this table, namely, a great 

 UifFcnencc betwixt the qviantity of iron revived when sand 

 and pure silex were used. It may be proper here to remark, 

 that Exp. VIII, IX, X, XI, where p'sre silex was used, 

 were performed in crucibles made of Cornwall clay. If, 

 tiierefore, there exists any tendency in clay under high 

 temperatures to absorb the oxygen of the oxide, which I 

 have suspected sometimes to have been the case ; and if 

 this affinity is exerted )ti proportion to the purity of the 

 clay; a partial deoxidatiou of the oxide in these experi- 

 ments may account for a larger portion of metal being re- 

 rived witli the same proportion of charcoal. 

 Third class of compounded ores consisted of 

 Well prepared chalk, six pans, 

 U.'iiile, four parts. 



I. Mixture 



