Ewing 6c Rosenham. 
Phil. Trans., A., Vol. 195, Plate 9 . 
Fig. 24.—Same after 5 days 16 hours at 200° C. with 
incidence of light altered. 
Fig. 25.—Same after 40 days at 200° C. 
Fig. 26.—Same specimen as Fig. 25 (after 40 days at 200° 
C.) with incidence of light altered, x 8. 
