Quote by Carl D. Anderson
Measurements of the specific ionization of both the positive and negative particles, by counting the number of droplets per unit length along the tracks, showed the great majority of both the positive and negative particles to possess unit electric charge.
Summary
This quote explains that through measurements of specific ionization, scientists have discovered that the majority of both positively and negatively charged particles carry a unit of electric charge. By counting the number of droplets per unit length along the tracks, researchers were able to determine that the vast majority of these particles possess single-unit charges.