Note 46 — Chapter IX · CATHODE RAYS AND RADIOACTIVE BODIES
Reading edition
In reality M. Sagnac operated in the converse manner. He took two equal weights of a salt of radium and a salt of barium, which he made oscillate one after the other in a torsion balance. Had the durations of oscillation been different, it might be concluded that the mechanical mass is not the same for radium as for barium.