Robert Mann Grogan

Short papers on geologic subjects: Present state of knowledge regarding the pre-Cambrian crystallines of Illinois, by Robert M. Grogan; Factors affecting measurement of permeability of unconsolidated glacial material, by Robert D. Knodle. Facies analyzes of the Niagaran rocks, by Heinz A. Lowenstam. Physical characteristics of the oölite grains of the Ste. Genevieve formation, by Raymond S. Shrode

Structures due to volume shrinkage in the bedding-replacement fluorspar deposits of southern Illinois

Beads of meteoric iron from an Indian mound near Havana, Illinois

Illinois surface clays as bonding clays for molding sands

Agricultural limestone resources of Cumberland, Effingham, Clay, Richard, and Jasper counties