Loránd Eötvös
These changes mirrored Rankine's shift in interests from optics to the newly emerging field of geophysics. His interest in this area developed in the late 1920s and early 1930s, and from 1927 onwards he became an advisor for the Anglo-Persian Oil Company (later the Anglo-Iran Oil Company, and later still British Petroleum). It was in 1934 that the School of Applied Geophysics was established at Imperial College, with Rankine directing the research. His work in this area included improving the gravimeter invented by Loránd Eötvös (the "Eötvös gravimeter") and constructing a magnetometer "of great sensitivity".