Gouy balance
Amongst a wide range of interest in optics, Brownian motion, and experimental physics, Gouy also had a strong intrigue for the phenomena of magnetism. Gouy derived a mathematical expression showing that force is proportional to volume susceptibility for the interaction of material in a uniform magnetic field in 1889. From this derivation, Gouy proposed that balance measurements taken for tubes of material suspended in a magnetic field could evaluate his expression for volume susceptibility. Though Gouy never tested the scientific suggestion himself, this simple and inexpensive method became the foundation for measuring magnetic susceptibility and the blueprint for the Gouy balance.
