282 M. Karsten's Observations and 



where yet been found in a natural deposit of true or black coal, 

 any more than true or black coal has been found in a deposite 

 of brown coal. 



The transition of black coal to glance coal or anthracite, is not 

 less insensible than that of brown coal to black coal. True 

 glance coal, as well as graphite, is a formation of rare occur- 

 rence ; and, it would be difficult to point out any instances of 

 their being associated with black coal. Yet this could never be 

 a reason for rejecting^ as improbable, the idea that glance coal 

 and graphite may have arisen from the alteration of vegetable 

 fibres, if there be nothing in the intimate nature of these bodies 

 contrary to such an idea. 



In unaltered vegetable fibres, the quantity of carbon is less, 

 while the proportion of oxygen and hydrogen is greater, than 

 in vegetable fibres that have undergone alteration. It is from 

 a necessary consequence of this fact that the former, when put 

 in contact with other bodies in a heated furnace, are so differently 

 affected by them from the latter. The greater the alteration the 

 fibres have experienced, the more apparent does the difference 

 become ; in other terms, this difference keeps pace with the in- 

 crease of the relation which the quantity of carbon has to the 

 quantity of the other constituent parts. In glance coal and 

 graphite, this relation appears to have obtained its maximum ; 

 and these two substances, or at least the latter, are regarded as 

 a carbon entirely deprived of oxygen and hydrogen. 



According to the ideas generally admitted, graphite is a car- 

 bon, and its difference of chemical character from carbon is ex- 

 plained by considering it as a chemical combination of ninety-five 

 parts of carbon with five parts of iron, whence result 100 parts 

 of graphite or percarburet of iron. As to the difference be- 

 tween glance coal and pure carbon, this is less obvious. It ap- 

 pears, in reality^ that it is a difficult problem in chemistry, to 

 explain the difference which exists between diamond, graphite,, 

 glance coal, and pure charcoal. 



Peat, brown coal, and black coal, submitted to distillation in 

 the dry way, almost always afford more or less distinct traces of 

 ammonia. Such a result is not obtained from the distillation of 

 unaltered vegetable fibre. Thus, azote appears to present itself 

 as a new constituent part of altered vegetable fibre. However, 



