L., 4. Gilbert H., 10. Colorado, South Silverton area: Expanding horizons: Lay, R. L.,L Geophysicist in...the future: Just, E. ing: Burwell, E. B., Jr., 4. Mining geology, retrospect and Index fossils: Stephenson...Forresgeologic processes: Perry, ter, J. D., 3. T. G., 3. Mississippi River and Gulf Industrial minerals: Gillson,...Alvarez, M., Jr.,6. Mountain-building, chronology, Iowa, ground water, geologic reand nature of geologic...Barstow quadrangle: Trenton group, Ordovician: Bowen, O. E., Jr. , 5. Clark, T. H., 10. Canada, arctic |