406 ILtinois Naturat History SuRVEY BULLETIN Vol. 26, Art. 5 
Fig. 19.—Part of the cliff at Principia, near Elsah, Jersey County, with sharp rock salients 
that project beyond the spur fronts above. 
Fig. 20.—An upper slope of a cove of Principia hill prairie with a mixture of prairie plants, 
Rhus glabra, and small oaks. 
