Description of the C. I. W. Marine Earth Inductor

Abstract

One of the problems encountered in ocean magnetic work covering an extensive area has been that of the satisfactory determination of the variations in the reductions of dip observations to standard with change in magnetic latitude. The problem has been the more difficult because of the mechanical impossibility, despite the most skillful and careful workmanship, of producing a perfect axle. Up to the present time the corrections on standard have been obtained with the aid of the observations at the ports visited where intercomparisons were secured between a standardized earth inductor and the dip circles employed at sea. As these stations are often widely separated and as the conditions aboard ship, where the instruments and needles are in constant motion, are so very different from those on shore, it became desirable that some form of instrument should be devised for the purpose of securing standardizations and the required control on board ship, i. e., in transit from port to port.