on the alleged Conversion of Carbon into Silicon. 25 



on one occasion only, but at least half-a-dozen times. The plug 

 only loosely went into the orifice, and the luting was a thin 

 layer of china clay, more for the purpose of preventing dirt, 

 &c. getting into the tube than for anything else ; it appears, 

 therefore, to us out of the question to talk about there not 

 being free enough exit for nitrogen ; besides, we find in the 

 original memoir, p. 231 of the Transactions, thefollowing state- 

 ment: — " A little crucible of Berlin porcelain was filled with 

 paracyanogen, and after the lid had been tightly luted on, it 

 was imbedded in stucco paste within a larger crucible. The 

 gypsum having set and dried, the apparatus was kept at a 

 white heat for an hour and a half; the residue of this process 

 resembled the last, only that it was denser and darker." Now 

 in this experiment Dr. Brown asserts, that the transformation 

 was effected; but will any candid observer maintain, that 

 greater opportunity for free exit of nitrogen obtained in 

 this experiment than in our experiments with the iron tube 

 and plug ? Again, at p. 286 of the Edinburgh Transac- 

 tions, we are informed that a siliciuret of copper was obtained 

 when bicyanide of mercury was heated for more than an 

 hour to whiteness in a double copper tube : if reference be made 

 top. I?* of the Transactions, a description of this double 

 copper tube will be found, and it is there stated that the open 

 ends of these tubes terminate, the one in a male screw, the 

 other in a female screw : and the section in which this tubular 

 apparatus is described closes with the following remark, of 

 considerable importance, we imagine, as regards the subject 

 immediately under discussion : — " The latter," speaking of one 

 of the tubes, " thrice as long as the former, is charged, and 

 the two are firmly screwed together, so as to give vety great 

 kit not fixed joressure, for the screws alwayspermit gaseous pass- 

 age in such circumstances^ 



We must therefore be allowed to think, that the objection 

 raised by Dr. Brovvli to our employment of an iron tube and 

 plug, and gun-barrel, is answered by himself, seeing that in 

 his own recorded experiments the alleged transformation of 

 carbon into silicon was brought about in tubes, and in a cru- 

 cible so contrived, that no greater, and we very much doubt 

 il the same amount of freedom ^ov gaseous passage, was allowed 

 as in the instruments employed by us. 



It is therefore incumbent upon Dr. Brown to look for other 

 reasons to account for our failure: he will not say we did not 

 hit upon the right temperature, for in certain experiments the 

 temperature at which we i'ailed was the same as that at which 

 he succeeded. Will Dr. Brown still continue to maintain that 

 the alleged transformation, wlien the materials operated upon 



