.
The next step in advance in the attempt at the determination of
was made in 1903 by H. A. Wilson,[37] also in the Cavendish Laboratory.
III. H. A. WILSON’S METHOD
Wilson’s modification of Thomson’s work consisted in placing inside the chamber A two horizontal brass plates 3½ cm. in diameter and from 4 to 10 mm. apart and connecting to these plates the terminals of a 2,000-volt battery. He then formed a negative cloud by a sudden expansion of amount between 1.25 and 1.3, and observed first the rate of fall of the top surface of this cloud between the plates when no electrical field was on; then he repeated the expansion and observed the rate of fall of the cloud when the electrical field as well as gravity was driving the droplets downward. If
represents the force of gravity acting on the droplets in the top surface of the cloud and
the force of gravity plus the electrical force arising from the action of the field