Vicing &f Rosenham 
Phil. Trans., A., Vol. icjj, Plate 7 . 
Same after 30 minutes further at 200° C 
Fig. 17.—Same after 48 hours further at 200° 0, 
Fig. 19.—Sheet lead. X 12. Another part of the same 
specimen as Fig. 18. 
Fig 18.—Same after 4 days further at 200° C 
