Telluric current

A telluric current (Latin: tellūs, "earth"; hence: earth current, the name by which it was more commonly referred in the 19th century), also known as ground current or terrestrial current, is a flow of electric charge (current) that travels through the surface layers of the Earth (lithosphere) and through bodies of water, being generated by various natural and artificial causes.

Research

J. E. Burbank's Earth-Currents: and a Proposed Method for Their Investigation (1905), on the origin of the study of earth current:

Sir Humphrey Davy appears to have been the first to suggest the possibility of currents of electricity flowing in the earth, and states that the variation in the declination may be caused by the variations of these currents. Christie carried the suggestion still further in his "Theory of the Diurnal Variation of the Earth's Magnetism" and argued that the heat of the sun was the cause of these currents; he constructed a model to test this point. Becquerel made some experiments in 1844 to find whether the Earth's magnetism had an electrical origin, but his results seem to indicate effects due to the electrochemical action of the plates and the soil. W. H. Barlow from his observations on the English telegraph lines in 1847 appears to have been the first to prove that the currents which often interfered with the sending of messages actually came from the Earth and were always present. He found the general direction of these currents was in the N-S line.

Reading

Historical

• Burbank, J. E. (March-Dec. 1905), "Earth-Currents: and a Proposed Method for Their Investigation", Terrestrial Magnetism and Atmospheric Electricity (Baltimore, Maryland: John Hopkins Press) 5 (1): 23-49, https://babel.hathitrust.org/cgi/pt?id=chi.36506308&view=1up&seq=41 

Modern

• Helman, Daniel S. (2013), "Earth Electricity: a Review of Mechanisms Which Cause Telluric Currents in the Lithosphere", Annals of Geophysics 56 (5), https://doi.org/10.4401/ag-6184