100 
the graphite modification, can only take place in presence of 
cyanogen compounds, and that no carbon whatever is taken 
up by the iron when this metal is heated with other carboni- 
ferous gases* The mode of the production of graphite 
noticed in this communication appears to be an intermediate 
reaction between that from the carbide of iron and from the 
nitride of carbon. 
As in the process of cementation it is seen that the carbon 
of the cyanogen is taken up by the iron without being set free, 
so this reaction proves that cyanogen can be split up into its 
constituent parts without either of them combining with a 
third body. 
Despretz asserts, that the carbonization of iron is always 
preceded by a combination of this metal with nitrogen, a pro- 
cess which makes it porous and more fit for the unition with 
carbon. The correctness of this supposition has, however, 
become rather doubtful, by Caron’s recently published experi- 
ments (“ Comptes Rendus,” No. 15 and 24, 1860). 
To conclude, I beg to say some words about the formation 
of native graphite ; I do not think that this body has been 
formed from coal or diamond, but I rather believe it has been 
separated out of carbon compounds as graphite, by processes 
perhaps analagous to those above described. 
