The evaluation of magnetic anomalies by means of scales

At the 1939 meeting of the Union [Fundamental research in geophysics relating to prospecting, Trans. Amer. Geophys. Union, 1939, pp. 302 and 390], the writer described a set of scales for aiding in the evaluation of the magnetic anomaly due to a selected magnetized body. During the past year, these scales have been modified in several minor details. The revised forms are shown by typical scales illustrated in Figure 1.