M. Karstcn's Observations and 



constantly keeping the sand-bath at the same degree of tempera- 

 ture. It was in the rapid carbonization that the results differed 

 most from each other, because, in this case, it is still more diffi- 

 cult to regulate the temperature. The quantity of charcoal ob- 

 tained by means of the rapid carbonization varies, for 100 parts 

 of the matter employed, between 1 1 .90 (the produce of old oak), 

 and 16 39 (that of young oak) ; but, in the slow carbonization, 

 the quantity of charcoal obtained is nearly double, or at the least 

 one-half more. It varies from 24.20 (the produce of lime-wood), 

 to 27.50 (the produce of young Norwegian spruce). In both 

 modes of carbonization, the quantity of ashes remains the same : 

 it varies, in general, from 2.75 (the produce of fern) to 0.11 

 (the produce of old oak wood) ; but, in most cases, it is below 

 0.4. 



Like unaltered vegetable fibre, fossil wood, on being carbo- 

 nised, retains its external form completely, and only undergoes a 

 diminution of size. This preservation of the external form after 

 carbonization, that is to say, after a complete decomposition, is 

 a phenomenon without example in inorganic nature, and one ex- 

 clusively peculiar to unaltered vegetable fibre, fossil wood, brown 

 coal, and some sorts of black coal. Other kinds of coal, i-n the 

 process of decomposition by an ardent heat, lose more or less 

 their form ; and, by the difference which they thus exhibit, they 

 already afford an indication beforehand of what their composition 

 must be. 



It may be -without rashness asserted, that fossil wood and lig- 

 nite, or brown coal, are still at the present day, so to speak, in 

 a train of developement. This is proved by the frequent oc- 

 currence, in brown coal mines, of pieces of coml-ustible, which 

 present an evident transition from fossil wood to brown coal,— 

 one extremity of the specimen being fossil wood, the other brown 

 coal. With regard to black coal, there is not equal reason for 

 supposing that the formation of that combustible is still going 

 on, or that a change of relation in its elements still continues to 

 be effected, although this is not improbable. 



From the frequent variations which fossil wood presents in its 

 passages into brown coal or lignite, it might already be expect- 

 ed not to afford, as the residuum of its carbonization, a constant 

 quantity of charcoal, as was seen to be the case with regard to 



