upon the Diamond, Anthracite, and Plumbago. 1 35 



Addiiiotial Notice on the Fused Carho7uicemis Bodies *. 



If melted charcoal, plumbago and anthracite do really ap- 

 proximate towards the character of diamond, we ought to ex- 

 pect that, in consequence of fusion, there would be a diminu- 

 tion of conducting power, with respect both to heat and to 

 electricity- This I find to be the fact. As soon as the point 

 of charcoal is fused by the deflagrator, the power of the instru- 

 ment is very much impeded by it ; but as soon as the melted 

 portion is removed, the remaining charcoal conducts as well as 

 before; and soon, for any number of repetitions of the experi- 

 ment, with the same pieces of charcoal. 



The globules of melted plumbago are absolute non-conduct- 

 ors, as strictly so as the diamond. This fact is very pleasingly 

 exhibited, when a point of prepared charcoal, connected with 

 the zinc pole of the deflagrator, is made to touch a globule of 

 melted plumbago, however small, still adhering to a parallelo- 

 piped of plumbago, in its natural state, sci*ewed into the vice 

 connected with the copper pole : not the minute?t spark will 

 pass ; but if the charcoal point be moved ever so little aside, 

 so as to touch the plumbago in its common state, or even that 

 which has been ignited, without being fused, a vivid spark will 

 instantly pass. This fact is the more remarkable, because it 

 is equally true of the intensely black globules which are sensi- 

 bly magnetic, and therefore contain ii'on, as of the light co- 

 loured and limpid ones, which are not attractable. 



The globules of melted anthracite are also perfect non-con- 

 ductors. This may appear the less remarkable, because the 

 anthracite itself is scarcely a conductor; at least, this is the 

 common opinion, and it certainly is strictly true, of that of 

 Wilkesbarre and of that of Kilkenny; for, when both poles are 

 tipped with those substances, there is only a minute spark, 

 which is but little augmented when charcoal terminates one of 

 the poles. But the fact is remarkably the reverse widi the 

 lihode-Ishmd anthracite; this conducts quite as well as })lum- 

 bago, and I think even better, giving a very intense light, and 

 bright scintillations. I have now no doubt, that the deflagra- 

 t )r will melt it, but have not had time to complete the trial. 



If it should be said that the conducting power of the R. I. 

 anthracite may be owing to iron, we are only the more er.ibar- 

 rassed to account for the fact, that its black melted globules 

 are insensible to the magnet, and are perfect non-conductors. 



It will now probably not be deemed extravagant, if we con- 

 clude that our melted carbonaceous substances approximate 

 very nearly to the condition of diamond. — April 23, 1823. 



• Silliinan's Joiirnul, vol. vi. p. 37b. 



XXVIII. Ob- 



