THE 
EDINBURGH 
PHILOSOPHICAL JOURNAL. 
Art. I . — On Black Lead from Cast-Iron. In a Letter to Dr 
Brewster from J. MacCulloch, M. D. and F. R. S., &c. 
Communicated by the Author. 
Dear Sir, 
In compliance with your request, I send you 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- 
VOL. VII. NO. IL OCT. 18SS. 
o 
