Ewing &" Posenhain 
Phil. TransA., Vo!. 795 , Plate 6 
Pig 13 
.—Same after six months. 
Pig. 12.—Same after four months. 
Pig. 14.— Sheet lead. X 12. 
Pig. 15.— Same sheet lead. X 12. After 
30 minutes at 200° C. 
