390 Dr. Brown on Dr. Brett and Mr. Smith's Experiments. 



ignigenous paracyanogen gives off cyanogen when heated ! 

 The last but one is wholly exceptionable on account of the ma- 

 terial ; and consequently, the last paragraph but one (p. 305) 

 is not to the point. The last of all is a feeble trial, made on 

 a wrong subject, and attended by no significant result. 



In conclusion, this is all I can oppose to the authority of 

 Dr. Brett and Mr. Smith. I trust it is enough to preserve 

 the right-minded scepticism of chemists on the subject at issue, 

 which is either so momentous as to be worth a world of cau- 

 tious inquiry, or so unimportant as not to merit even condem- 

 nation. Meanwhile, I beg your leave to take this opportunity 

 of offering a few suggestions on the right repetition of my ex- 

 periments, which I confess to be necessary on account of the 

 extreme condensation of my memoirs ; a quality, which must 

 be attributed to my inexperience on one hand, and a settled 

 aversion to many words on the other. 



If the apparent transformation be real, it is manifest that 

 the rationale must be very subtle to find, however simple it 

 may yet be found to be, and that it is very likely that the suc- 

 cess of the processes may depend on contingencies which are 

 the least obvious. I often failed ; at length far oftener suc- 

 ceeded; and have described the operations in successful cases, 

 trusting that I have included the essential circumstances of 

 success, but knowing very well that I may not have done so. 

 Hence the necessity of copying the very letter of the text ; 

 and, hence, too, my humble right of suggesting the propriety 

 of not concluding too hastily against my special positive re- 

 sults. Chemists, who are willing to work, will not easily be 

 deluded by silicated vessels, dirty crucibles, or foul potassa. 

 In chemical investigation it is very difficult to discover new 

 truth ; but for every one who feelingly knows thftt it is so, it 

 is also difficult to be very much misled. 



As it is evident that, so far as I was led to perform these 

 experiments by hypothetical insight, true or imaginary, the 

 likelihood of success depended on the correctness of the view 

 of the constitution of paracyanogen exhibited in the paper on 

 that substance, scrupulous care must be taken not to infringe 

 on that constitution by any experimental accident, such as 

 ever so slight access of air during the prolonged heatings; 

 inasmuch as for every equivalent of carbon that may be sur- 

 reptitiously drawn offi say in the form of carbonic oxide, three 

 equivalents are lost for conversion, and one less of silicon can 

 be produced. I have wasted a great deal of paracyanogen in 

 this way : and it was only last week that I hit upon a lute ca- 

 pable of hindering the paracyanide of a certain metal from 



