28 Mr. Smith aiid Dr. Brett's Additioiial Remarks 



part of Mr. Smith." This ill agrees with the statement in 

 pp. 240-1 of the Transactions, where, after directing the para- 

 cyanide of iron to be inclosed in a luted crucible and stucco 

 powder, and then " the fiercest heat of a powerful wind furnace 

 to be apj)lied for two hours," Dr. Brown states, that " it is 

 evident that the ferrocyanide may be substituted for the para- 

 cyanide in this formula, the cyanide being sublimed away by 

 the heat of the furnace." Ferrocyanide of potassium is ob- 

 viously meant here, as he speaks of the sublimation of the 

 cyanide. In die same paragraph he continues, " In one cru- 

 cible, of the capacity of an ounce and weighing 500 grs., one 

 operation produced 165 grs. of the semicrysta'line siliciuret of 

 iron, and the third repetition raised the weight above that of 

 the crucible itself:" yet forsooth the experiment just alluded 

 to " is entirely original" on our part, whereas it really is an 

 exact repetition of his own process, even to the capacity of 

 the Berlin crucible employed. 



The tangible objections made by Dr. Brown to our experi- 

 ments apply, first, to the paracyanogen employed by us, and, 

 secondly, to the apparatus. Armed \\'\\\\ the first objection, 

 he endeavours to destroy the force of our most decisive ex- 

 periments, by declaring, that it " renders almost all their ex- 

 periments of no value," and this because our paracyanogen 

 was obtained from the decomposition of an aqueous solution 

 of hydrocyanic acid, instead of the ignition of bicyanide 

 of mercury ; and from this argues, that if our paracyanogen 

 " were not prepared in exactly the same way as my own," 

 our results cannot challenge the correctness of his statements, 

 and therefore conveniently avoids making any observations on 

 the majority, and the most important of, our experiments. 

 Now seriously, it appears to us that this author would have 

 been equally justified in objecting to the nitric or hydrochloric 

 acids employed by us, supposing that we had chosen to obtain 

 the former from nitrate of barytes, and the latter from chlo- 

 ride of calcium, instead of using these acids obtained from the 

 same sources in all probability as those employed by Dr. 

 Brown, — nitrate of potash and chloride of sodium. What 

 can it signify from what source we obtained paracyanogen, if, 

 as we state, it possessed all the known properties of paracy- 

 anogen ? In fact, Dr. Brown himself admits that we employed 

 paracyanogen, though he terms it a " low hydrate" of that 

 substance, since it was obtained from an aqueous solution of 

 hydrocyanic acid. Now supposing that it is this low hydrate 

 of paracyanogen so vastly insisted upon by Dr. Brown in the 

 *' Observations," — which is likely to be the purer preparation ? 

 paracyanogen combined with a very small quantity of water, 



