Geophysical investigations, maps. Total intensity aeromagnetic map [and accompanying aeromagnetic profiles] of western part of Itasca County, Minn., aeromagnetic survey 1947 by J. R. Henderson and M. E. Hill. Scale 1 m. = 1 in. for map and 1 m. = 0.5 in. for profiles, contour interval 50 gammas, n. p.