different Earths for Carlon. 85 



Uniformly we find that argillaceous ore lets fall its first por- 

 tion of metal with the smallest quantitv of carbon ; or, what 

 amounts to the same thing, with equal portions of carboa 

 it yields a greater produce in metal than the siliceous iron- 

 stone. On the contrary, we find tliat the calcareous ores 

 require a greater dose of carbon to separate the first portions 

 of iron; or, what is similar, with equal portions of carbon 

 less metal is revived from the ores of this class than from 

 any of the other two ; with this limitation, however, that 

 calcareous ironstones in general never become infusible, 

 even with a very high proportion of carbon, until nearly 

 the whole metallic contents become revived. This, by a 

 strict examination of the tables, will not be found applicable 

 to the argillaceous and siliceous, one-half of the metallic 

 contents of which are either not separated or not revived. 



The general results of these experiments are sufficient to 

 establish an operation of affinity directly betwixt crubon, 

 clay, and silex, in temperatures of fusion, or approaching 

 thereto. Thev are also sufficient to establish the operation 

 of a principle still more powerful, when these enter into the 

 composition of ores of iron and become subjected to the 

 heat of the assav furnace. Under these circumstances we 

 find calcareous earth, the affinity of which for carbon, by 

 fusing them together, could not be detected by any altera- 

 tion of -colour or combination, operatins; as a stimulus to 

 the well known affinity that exists between iron and carbon, 

 and by its simple agency alone doul)ling the produce from 

 an argillaceous or siliceous ore. In some of these cxperi- 

 Oients we find the result accompanied by a small portion 

 of iron, and a large proportion of the carbonaceous matter 

 originally introduced, if the same experiment is repeated 

 with the addition of l-3d or l--lth of calcareous earth, the 

 charcoal will be no longer found, the metallic contents, will 

 be considerably increased, and the glass, tVom being black 

 and spongy, will exhibit a mass of uniform colour, density, 

 and comparative transparency. 



As numerous experiments have forlnerly been given to 

 point out the effect which the addition of calcareous earth 

 has in reviving the meiallic produce from an ore, the tbl- 

 lowing experiments will prove its secreting powers in the 

 early sta<ies of separation. 



il.rp. T. I took a quantity of the same oxide of iron used 

 iu former exjieriments upon this subject 3 1 weiixhed 



'JOO grains, 

 and added 1 -loth part of charc(xU dust, or - 2Q 



F 3 The 



