BULL. GEOL. SOC. AM. VOES O89 pe 2o 
Ficurer 1 
CONCENTRIC WEATHERING IN THE SHALE ON BLOCK HOUSE RUN AT NEW BRIGHTON, 
PENNSYLVANIA 
Figure 2 
CONCENTRIC WEATHERING IN FLINT FIRE-CLAY (THE BOLIVAR CLAY) AT BOLIVAR, 
PENNSYLVANIA 
