This book presents a decade of earth-current measurements recorded at the Tucson Magnetic Observatory. It details the data collected between 1932 and 1942, focusing on the geophysical phenomena observed. The work is a compilation of raw observational data, likely intended for scientific analysis and archival purposes.

This volume serves as a direct archival record of geophysical measurements. Its value lies in the raw data it provides for researchers studying earth currents and magnetic phenomena during the specified period. The work is likely regarded as a foundational data set for historical geophysical studies.