Geophysical investigations maps, GP (series). 48. Total intensity aeromagnetic map [and accompanying aeromagnetic profiles] of part of Becker County, Minn., aeromagnetic survey 1947 by J. R. Balsey and M. E. Hill. Scale 1 m. =1 in. for map and 1 m.=0.5 in. for profiles, contour interval 50, 250 and 1000 gammas, n. p.