Experiments upon Diamond, Anthracite and Plumbago, 353 



of carbon. If the former be true, it proves that no existing 

 analysis of plumbago can be correct, and would still leave 

 the remarkable white fume, so abundantly exhaled between 

 the poles of the deflagrator, and so rapidly transferred from 

 the copper to the zinc pole, entirely unaccounted for. I 

 would add, that for the mere fusion of plumbago, the blow- 

 pipe is much preferable to the deflagrator, but a variety of 

 interesting phenomena in relation to both plumbago and 

 charcoal are exliibited by the latter and not by the former. 



Hoping that if these subjects have not already engaged 

 your attention, they will speedily do so, I remain my dear 

 Sir, as ever, your friend and servant. 



B. SILLIMAN, 



Postscript, April 18. Fusion of Anthracite. 



The anthracite of Rhode-Island is thought to be very 

 pure. Dr. William Meade, (See Bruce's Journal, pa. oQ) 

 estimates its proportion of carbon at ninety-four per cent. 

 This anthracite 1 have just succeeded in melting by the 

 compound blow-pipe. It gives iarge brilliant black globules, 

 not attractable by the m-rsgnef, but in other respects not to 

 be distinguished from the dark globules of melted plumbago. 

 The experiment was entirely successful in every trial, 

 and the great number of the globules and their evident flow 

 from, and connexion with, the entire mass, permitted no 

 doubt as to their beins; really the melted anthracite. 



The Kilkenny coal gave only white and iransparent.glob- 

 uit': but it seems ralher difficult to impute this to impuri- 

 ties, since this anthracite is stated to contain ninety-seven 

 per cent, of carbon. 



I have exposed a diamond this afternoon to the solar fo- 

 cus in a jar of pure oxygen gas, but observed no signs of fu- 

 sion, nor indeed did I expect it, but I wished to compare 

 this old experiment with those related above. 



The diamond is noAv the only substance which has not 

 been perfectly melted. 



I inserted a piece of plumbago into a cavity in quick lime, 

 and succeeded in melting it down by the blow-pipe into two 

 or three large globules, adhering into one mass, and occupy- 

 ing the cavity in the lime; these globules were limpid, and 

 nothing remained of the original appearance ofthe p]umba-= 

 go except a few black points. 



Vol. VI.— No. 2. 45 



