RESUME, AND GENEKAL DISCUSSION. 



541 



V 



and the formation of the material in gas retorts, are striking instances 

 of this. 



The most abundant source of artificial graphite, however, is in con- 

 nection with the manufacture of soda by the Lc JManc process ; for 

 here the quantity produced is so large that it has been seriously pro- 

 posed to use it for the manufacture of lead pencils. This graphite, 

 according to R. Wagner, is formed at a certain stage of the process of 

 converting the caustic soda into the carbonate ; at which time the 

 cyanogen present — which must have resulted from tlie preceding treat- 

 ment of the saline mass at a high temperature in the reverbcratory 

 furnace — nndergoes decomposition, the carbon separating out in the 

 form of graphite. The same origin is claimed by AVagner for the 

 graphite occurring in cast-iron. According to him, it is not the carbon, 

 dissolved in the iron itself, which separates out when the latter cools and 

 solidities, but tliat which is derived from the decomposition of the cya- 

 nides present in large quantity in the iron as well as in the slag. These 

 cyanides undergo decomposition, the carbon appearing as graphite, and 

 the nitrogen going off in the form of ammonia, well known to be one 

 of the products of blast-furnace operations.* 



Thus it appears that we know of no other way in which graphite can 

 be artificially formed than indirectly in connection with, or as one of 

 the results of, some process or operation carried on at a very high 

 temperature. 



The position assumed by Bischof with reference to the diamond is also 

 based on imperfect knowledge of the facts connected witii the occur- 

 rence of this most remarkable su\)stance. It was Bischofs idea that 

 the diamond was formed in the superfu^ial dctrital material of recent 

 age, in which tliis gem had until within a few years been exclusively 

 found. He believed that it was simply a result of the decomposition of 

 organic matter, \mder conditions which prevail everywhere ; so that, if 

 his view were tlie correct one, the diamond, instead of being the most 

 precious of gems and being found in exceedingly minute quantity, should 

 be literally "as common as dirt." 



The facts in regard to the diamond, from the standpoint of our 

 present Imowledge, arc simply these : Wherever dc:flritus of crystalline 

 rocks occurs unconsolidated, so that it can be cheaply " handled," — 

 tliat is, moved and washed, — there gold either has been in former times 

 or is now being obtained, although not by any means always in remu- 



* See Sitzungsberichte der pliys.-med. Gesells. zu Wiirzburg, 1869, p. xxii. ; also, 

 Wngiicr's Jahrcsboiicht, 1872, p 57. 



