TRANSACTIONS OF THE SECTIONS. 6/ 



II. Another is compact and crystalline, not unlike the dark-coloured mountain 

 limestone of South Wales in appearance. 



III. The third variety is similar in structure to the first-named. The granules, con- 

 sisting of iron pyrites, are mixed with coal, and apparently cemented together by a 

 mineral substance of like composition to the two foregoing. 



It is from the yellow colour of this last variety that the name 'brass' has been 

 given to the ores by ihe miners. 



The following is their composition : — 



I. II. ' 



Carbonate of iron 68-71 = iron 33-3 5973 iron = 28-83 



Carbonate of manganese 0-42 0-37 



Carbonate of lime 9-36 11-80 



Carbonate of magnesia .. 11-80 15-55 



Iron pyrites 0-22 trace 



Phosphoric acid 0-17 0-23 



Coaly matter 8-87 9-80 



Clay 2-70 



99-55 100-18 



III. 



Carbonate of iron 17-74 



Carbonate of lime 14-19 



Carbonate of magnesia , 12-06 



Iron pyrites 49-72 



Phosphoric acid trace 



Coaly matter 010 



99-81 



The ores I. and II., to which attention is directed as being those to which 

 the remarks apply, may be classified with the spathose carbonates of iron. The 

 absence of clay, and the difficulty, from ignorance of this fact, that would in conse- 

 quence be experienced in smelting these ores, sufficiently explain the reason of the 

 disrepute in which they have hitherto been held; for when judiciously treated in the 

 blast-furnace, they smelt with the greatest facility, and afford an iron equal to that 



f)roduced from the argillaceous ores. It will be evident, from the large amount of 

 ime and magnesia which they contain, that their employment must be advantageous 

 in an economic point of view. 



An interesting feature in these ores is their fusibility during calcination on the 

 large scale. When this process is conducted in heaps, the centre portions are inva- 

 riably melted. This, considering the almost entire absence of silica, is apparently an 

 unexpected result. 



The fused mass is entirely magnetic and crystalline. Treated with acids, it dis- 

 solves with great evolution of heat. 

 The following is its composition : — 



Protoxide of iron 38-28 



Sesquioxide of iron 32-50 



Protoxide of manganese 0-38 



Lime 12-84 



Magnesia 13-87 



Phosphoric acid 0-17 



Sulphur 0-23 



Silicic acid 1-20 



Alumina 0-51 



100-08 



From the above analysis, it is probable that its fusibility is owing to the magnetic 

 oxide of iron acting the part of an acid. 



When thoroughly calcined and unfused, the ores retain their original form, and if 

 exposed to the air for any length of time, crumble to powder from the absorption of 

 water by the alkaline earths. _____ 



5* 



