I-.LACK I.KAI) FROM CAST-IKON. 



In a Letter to l)r /{HKU s'i K/?. 



Ity J. MACCULLOC'II, M. 1) & I\ U S fcc. 



From Me Edinburgh Philosophical Journal. 



DEAR SIR, 



J_N compliance with your request, I send yon the following 

 statement respecting the Black Lead which is obtained from cast- 

 iron, various detached notices of which has already appeared in 

 your Journal. 



It is more? than twenty years since I was in the frequent 

 habit of examining the metal of the iron guns delivered by the 

 contractors to the Ordnance, by solution, according to Berg- 

 man's suggestion on this subject. No useful results, as far as 

 our particular objects were concerned, were, however, obtained 

 in this way ; as it was found that the quantity of plumbago in 

 the iron bore no relation to the strength or goodness of the 

 metal, which, I need not say, is metal of the second fusion, or 

 from the reverberatory. The results were, however, sometimes 

 curious, from the very variable quantity of this substance con- 

 tained in different specimens of iron. 



It has been imagined that the worst, or weakest metal, was 

 that which contained most plumbago ; but the trials were far 

 from confirming this opinion. On one occasion, in particular, 

 a gun had been condemned for some fault in the bore, (a screw 



