4^4 
BLACK LEAD. 
they are now opened more frequently, and that the 
persons employed are watched very narrowly to pre- 
vent their stealing the mineral. 
Some years ago, says Magellan, this mine appeared 
to be almost exhausted ; but by digging a few yards 
through the strata underneath, according to the 
advice of an experienced miner, whose opinion had 
been long unattended to, the workmen discovered 
a very thick and rich vein of black lead, to the 
great joy of the proprietors and advantage of the 
public. The lead from this mine is acknowledged 
to be the best in Europe ; Magellan having seen 
various specimens from different countries, but 
none of them were either of a texture or quality to 
compare with the lead of Borrowdale. 
The lead is prepared for pencils by being cut into 
a proper shape, and placed in quadrangular grooves 
made of cypress wood, over which a slip of the 
same is placed, and the wood worked into small 
cylinders like quills. But the use of black lead is 
not confined to the manufactory of pencils ; it is of 
great service to chemists, either in the shape of 
crucibles, or mixed with different ingredients for 
covering the retorts and other vessels which are 
intended to resist a strong fire. Fourcroy considers 
its power to prevent iron from rusting as one of 
its most important properties. The pipes of stoves, 
the back parts of grates, and other utensils exposed 
to the action of fire and air, are coated with powder 
of black lead to preserve them from rusting, which 
is applied to their surface by simply rubbing with 
