on the different kinds of Coal 3^7 



foreign substances, which, from the effect of carbonization, are 

 ' inclosed in the mass ; and, in consequence, cause these cokes, 

 under a strong pressure, to fall more easily into fragments. 

 Then they become altogether incapable of being used for the 

 fusion of iron-ore in great furnaces. And further, the abun- 

 dance of foreign mixtures which the combustible must also bring 

 into fusion, renders these cokes unfit for being employed in the 

 fourneaux bas a cuve, commonly called Jburneaux a mancJie. 



On the other hand, coke prepared with the small debris of a 

 coal with vesicular coke, when this coal is perfectly pure, and as 

 exempt as possible from foreign mixtures, may answer quite as 

 well as coke produced from the same kind of coal, had it been 

 in large pieces. It might happen, however, that a coke coming 

 from coal in large pieces, might present more firmness than one 

 that would result from small debris. Then, consequently, the 

 former would be less exposed to break down into small pieces in 

 the fourneaux a cuve, at least in very high furnaces, and under 

 a great pressure of ore. 



If pyritous coals are carbonized, the coke which results con- 

 tains in general so much the more sulphur in proportion to the 

 larger quantity of iron pyrites that occurs in the mass of com- 

 bustible ; but M. Karsten asserts, that hitherto he has not ob- 

 served that the mixture of a great quantity of pyrites rendered 

 a coal incapable of being converted into coke, nor the cokes pro- 

 duced by it incapable of being employed in metallurgic opera- 

 tions, from the idea that the quantity of sulphur contained in 

 them would have too prejudicial an influence upon the quality 

 of the product to be obtained. According to the author, this 

 no doubt is an inconvenience, but it does not furnish a sufficient 

 reason for entirely excluding pyritous coals from the preparation 

 of cokes for metallurgic purposes. 



The case is different with respect to lighting by gas. When 

 * the pureness of the coal is very much altered by the presence of 

 iron pyrites, this inconvenience may entirely prevent the em- 

 ployment of such a combustible, if the object in view be to dis- 

 till it in the dry way for the purpose of obtaining from it a gas 

 adapted for lighting. As we have already seen from the com- 

 position of the different sorts of coal, the employment of a coal 

 for this purpose does not depend solely either upon the quantity 



