32 On the alleged Co7iversion of Carbon into Silicon. 



lated the rules of courleous disputation, for, in common with 

 Dr. Brown, we feel that truth is most likely to be arrived at 

 by calmness in discussion. Time, which always does so much 

 both in fixing scientific facts on a firm and solid basis, as well 

 as in dissipating errors which will inevitably creep into ex- 

 perimental research, will, it is hoped, ere long settle this at 

 present, perhaps, quiestio vexata. If Dr. Brown be right, 

 then chemistry must undergo a i-evolution; our present notions 

 must suffer a complete change in respect to all we understand 

 concerning elementary bodies ; and we feel assured, that we 

 shall not be severely condemned by chemical philosophers, for 

 expressing strong doubts as to the correctness of experiments 

 which are more startling in their results than any which are 

 recorded in the annals of chemical science, especially as those 

 doubts are borne out by our own experience. 



We shall refrain, Sir, from again addressing you on this 

 subject, at least for the present; we feel that we have not 

 judged hastily, nor without good grounds for forming an opi- 

 nion. For our own parts, we are satisfied of the erroneous 

 nature of Dr. Brown's views ; but should the results of other 

 experimenters serve to confirm them, should further experi- 

 ments be made on the subject, we will reconsider our judge- 

 ment, and should we have reason to believe ourselves in error, 

 we will without hesitation acknowledge the truth of that which 

 we at present firmly believe to be " a plenary mistake." 



J. Denham Smith. 



Liverpool, Nov. 16, 1841. R. H. Brett. 



P.S. Through the kindness of Professor Johnston our 

 attention has been directed to a paragraph in his paper on 

 paracyanogen in the Edinburgh Philosophical Transactions, 

 which completely confirms our views as to the constitution of 

 the black powder produced by the decomposition of aqueous 

 hydrocyanic acid, after it has been exposed to an elevated 

 temperature, which proves that the composition of the sub- 

 stance is then identical with cyanogen, in short, that it is para- 

 cyanogen. We subjoin the paragraph, vol. xiv. p.33: — "When 

 strong prussic acid is set aside it speedily decomposes and 

 deposits a black powder in considerable quantity. Dried in 

 vacuo over sulphuric acid, or at 212° Fahr., this substance 

 still gives off, when heated in close vessels over a lamp, water, 

 carbonic and hydrocyanic acids, and ammonia. The black 

 matter that remains, burned with bichromate of potash in 

 large excess, gave a mixture of carbonic acid and nitrogen in 

 the proportion of 2 to 1." 



