different Earths for Carhon. .333 



being equal to 32-i- per cent. This is 4 per cent, less than 

 in No. V, and is no doubt occasioned by part of the com- 

 pound forming an infusible residuum at the teinperature at 

 which the mass entered into fusion. 



Recapitulation of experiments made with roasted calcarcoiig 

 ironstone, first variety. p^-r ^^^^^^ 



Exp. I. 1 -30th of carbon yielded of metal 17 grs. or 4^ 



It would appear to result from these experiments, that 

 when a large portion of carbonaceous matter is used, there 

 results an ^imperfection in the reduction, which,' though 

 neither of the same magnitude nor importance as was ex- 

 perienced in the argillaceous con)pouuded ore, or with that 

 compounded of siliceous matter, yet is equally extensive 

 with the dcMciency remarked in t]ie argillaceous ironstone 

 treated of in the last comnumication. The metallic produce 

 \xi the case of the argillaceous ironstone appears to be re- 

 t.i-.ded by a quantity of the iron still remaining in the state 

 of glass of iron, over which the carbonaceous matter does 

 noi seem to act during the short period of reduction with 

 full effect. 



In the case of the calcareous ironstone, the want of com- 

 jilete reduction, or the dfticiency of 'Lhe metallic product, 

 arises I'rom a very different cause. The glasses are found 

 perfect, containing little or no iron ; but a portion of the 

 compound is formed, by means of the agency of the calca-^ 

 rcous carih, into a dull magnetic- carburet ol iron, which re- 

 sists the highest heat of the furnace. 



If this riTasoning upon facts that seem sufficiently esta- 

 blished by experiment be correct, then the present calca- 

 reous ore either contains too much lime or too small a pro- 

 portion of iron to make a perfect reduction without the ad- 

 dition of another earth. To prove this the following expe- 

 riments were made: 



Exp. I. This was No.M, with raw calcareous ironstone, 

 repeated in the following manner : 

 200 grains of ironstone, 



28t^ of carbon, or 1 -7th nearly. 



.50 of sand, very pure. 



This inixturc was completely reduccil without an atom of 



any 



