on the different hinds of Coal. 331 



each the numbers 93, for the remains in pure charcoal obtained 

 from the mineral charcoal, the table would bear the number 

 87.9 of coke, in reference to the coal of the same points, as well 

 in the case of No. 2. as in No. 1., if, in both, the coal had fur- 

 nished a pulverulent coke ; but, in the second case, the coal has 

 furnished an intumesced coke, a coke which is always less abun- 

 dant when the contents in carbon are the same. This is the 

 reason why, in No. 2., there are only 81 parts of that residuum 

 in charcoal which is called coke. The same reasoning will ap- 

 ply to the other numbers of the table. 



It is remarked, moreover, that, in mineral charcoal, the con- 

 tents in carbon vary from 78.03 to 95.74 per cent. ; while, in 

 the coals of the same localities (Nos 6. and 3.), they vary from 

 41, in contumesccd coke, to 91.4, in pulverulent coke. M. 

 Karsten concludes from this, that mineral charcoal often con- 

 tains much less carbon than many coals. The pulverulent state 

 of the residuum which the carbonization of the former affords, 

 sufficiently indicates, continues the author, that in mineral char- 

 coal, the proportion of oxygen must be much greater than that of 

 hydrogen. Lastly, The examination of mineral charcoal appears 

 to him to prove that, in the formation of coal, some parts of the 

 vegetable fibres have advanced more rapidly than others to- 

 wards carbonization. 



M. Karsten then states considerations calculated to furnish 

 the means of ascertaining in some measure the composition and 

 properties of coals by their mere aspect. The following are 

 the principal ideas of the author : 



It is only in coals which are very rich in carbon, that a cer> 

 tain homogeneousness of the mass is observed. All the fossil 

 coals, with a small proportion of carbon, consist of a mixture of 

 charcoals, of which some are rich, and others poor, in carbon. 



When a mass of coal is interrupted, whether by alternating 

 beds of combustible, richer or poorer in carbon, or by walls of 

 fissures, or by interposed beds of mineral charcoal, these cir- 

 cumstances may frequently decide as to the employment of such 

 coal for a particular object. It is from this important conside- 

 ration, from the circumstances of a mass of coal in this respect, 

 that mineralogists have distinguished different sorts of this com- 

 bustible by names, which it will suffice just to mention here : 



