Geophysical investigations preliminary maps. 3, pl. 1. Map of part of Iron County, Mich., showing part of area of aeromagnetic survey and magnetic trend lines, prepared by H. E. Hawkes, jr., from magnetic data compiled by J. R. Balsley, jr., H. Jenson, J. P. Fitzsimmons, M. E. Hill, V. S. Neuschel. Scale 1 m.=0.5 in. n. p.