Chap. 40.] Black Lead. 16 j 



is cut into a thin plate, the edge of which, being fitted 

 into a groove in a femi-cylinder of wood, is then fawed 

 off, fo as to leave the cavity entirely filled. The 

 black lead is retained in its place by the other half 

 of the cylinder, which is glued on. The makers of 

 fmall mot polifh and blacken its furface by agitating 

 or rolling it in a calk with powder of plumbago. This 

 mineral is likewife ufed in the manufacture of razor- 

 ftraps. 



S 4 



