ClipArt ETC
"Various methods have been devised for measuring electrostatic quantity, one of the simplest of which is with the Kinnersley electrical air-thermometer. When a spark passes between the balls within the larger tube, the confined air is expanded, and the liquid column in the smaller communicating tube rises, and thus approximately indicates the quantity of the charge." — Avery, 1895

Kinnersley electrical air-thermometer

"Various methods have been devised for measuring electrostatic quantity, one of the simplest of which…