on the alleged Conversion of Carbon into Silicon. 31 



substituted a tube made by rolling up platinum foil for the 

 crucibles or shreds of platinum foil mentioned in pp. 237-8 

 of the Transactions; and that a copper tube and paracyanogen, 

 and copper in a minute state of division and paracyanogen 

 were employed, instead of " a copper tube packed with bi- 

 cyanide of mercury," which salt, according to Dr. Brown's 

 own showing, must be converted into mercury and paracyano- 

 gen before any reaction could take place between the latter 

 substance and the copper; so that this objection must also fall 

 to the ground, unless this discoverer chooses to contend that 

 our non-success was owing to our employing a tube made 

 by rolling up thin sheet copper, whilst he used a cast copper 

 one. 



In the " Observations," Dr. Brown remarks, " Even so late 

 as last November and December I tried to effect the alleged 

 transformation before a celebrated physician and chemist six 

 weeks in vain ; but at last succeeded, or, as I must now say, 

 appeared to succeed." As we before observed, we do not 

 find in the original memoir a single recorded case of failure, or 

 even a distant hint of the slightest difficulty being experienced 

 in effecting the alleged transformation, which we are now in- 

 formed was tried in vain for six weeks before a celebrated 

 physician and chemist : may we in our turn be allowed to ex- 

 press our " respectful conviction" that such repeated unsuc- 

 cessful attempts, say an average of one experiment per diem, 

 should have rendered both the experimenter and the cele- 

 brated physician and chemist extremely cautious in recogni- 

 zing that experiment, attended with success, as the true and 

 proper result; and might have recalled to their recollec- 

 tion the unfortunate result of the laborious experiments, 

 sometimes accompanied with apparent successful results, re- 

 specting the identity of palladium and an amalgam of mercury 

 and platina? This unsuccessful attempt to effect the alleged 

 conversion is not only not alluded to in the original papers, but 

 the very reverse obtains; there "simplicity," "freedom from 

 any intelligible source of fallacy," "infallible and easy of ex- 

 ecution," are the terms applied to the various experiments. 

 As to the six weeks' trial, we scarce know which to sympathize 

 with most, the experimenter doomed for that period to con- 

 stant failure and repeated disappointment, or the celebrated 

 personage, whose patience, which is evidently great, was put 

 to so severe a test. 



We have now stated all that we conceive to be necessary 

 in reply to Dr. Brown's observations in the last Number of 

 the Philosophical Magazine ; we trust that our remarks, both 

 at present and in our ibrmer communication, have never vio- 



