Detecting small electric charges was not possible in the eighteenth century. Therefore, a trick was devised: by means of an electric doubler the charge to be measured was increased. The instrument shown here, was devised by William Nicholson. It can detect very small charges through induction: by means of an electric charge, an electric field is generated in a nearby conductor without touching it. One of the disks of the device can rotate vertically. Thus it can make contact with the sphere and come close to the other two disks. After the initial charge is applied to the sphere, each revolution of the rotatable disk ensures that the charge is increased by a factor of 1½. So, after 20 revolutions, the initial charge is increased by a factor of 3000! Eventually, an electrometer connected to the instrument, will deflect, even though the initial charge was extremely small.