BULL. GEOL. SOC. AM. 



VOL. 28, 1916, PL. 20 



FlGUKE 1. DUWN.STKKAM E\D OF "DeKP."' SHOWING NU.NrEROT.S AKUTICAL POT IIOLES OX 



Side Wall (left) 



Figure 2. — View showing great iuregularity in Detail of Gorge Erosion 

 DETAILS SHOWING MANNER OP EP^CSION IN "DEEP" AT HOLTWOOD, PENNSYLVANIA 



