different Earths for Carbon. 141 



This mixture fused, and vieldcd a very perfect glass, ac- 

 companied by a metallic button which weiglicd 98 grains : 

 equal to 24-y percent. The glass obtaint^d" was green, and 

 possessed a flinty fracture. 



Mxp. IV. 400 grains of roasted ironstone, 

 80 of charcoal, or l-5th. 



This mixture was fused at a heat of l6o°, and when cold 

 was examined, and found as follows : 



23 grains of charcoal were found upon the 

 surface of a light green coloured glass, which 

 covered a nictallic button weighing - 108 strains. 



Globules extracted from the class - 6 



Produce equal to 28',- per cent. , - 114 



Exp. V. 400 grains of roasted ironstone, 

 133-,^(,- — of carbon, or l-3d. 

 This mixture was exposed to a heat of 162° of Wedge- 

 wood. When cold it was found imperfectly reduced. 

 About 50 grains of metallic globules were obtained. A 

 portion of glass was formed in perfect spheres, entirely co- 

 vered v.ith carburated globules of cast iron. The pulveru- 

 lent matter that remained unfused was of a deep black co- 

 lour mixed with spheres of vcrv brilliant crude iron. This 

 experiment was repeated as follows: 



Exp.Yl. 400 grains of roasted ironstone, 

 133-rV — of charcoal, or l-3d, 

 120 — of raw chalk.; 

 This mixture was exposed in a much inferior heat, and a 

 very perfect reduction of the compound obtained. A me- 

 tallic button was found, and some globules, which weighed 

 145 grains; equal to 35-^ per cent.: which amounted to 

 within l-l- grain of the whole contents of iron contained in 

 the ore. 



These, with many other experiments, prove that when 

 clay enters greatly into the compound of any ore, that car- 

 bon alone is not capable of reviving its metallic contents 

 whether the ore is used in the raw or roasted state, and that 

 calcareous earth, in almost every case, can be applied as a 

 substitute in part for carbon in consequence of the curious 

 relation it hears lo both. 



The difference betwixt the quantities of revived iron with 

 l-40th of carbon is sufficiently accounted for by the roasted 

 ironst(me containing 31 per cent, more of iron ; of course 

 the additional affinity exerted by this iron required an extra 

 dose of carbon before any iron was let fall. 



xxirr. On 



