Edwin Hall’s discovery at JHU in autumn of 1879, which came to be called the “Hall Effect,” may be one of the most underappreciated achievements in the history of Hopkins. Over the past 140 years, the Hall effect has become an indispensable tool for measuring the strength of electromagnetic fields. In a new article in the Krieger School of Arts & Sciences Magazine, Professors N. Peter Armitage and Chia-Ling Chien reflect on Edwin Hall and the Hall Effect.