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. 



