Holtz's Influence Machine

The action of the Holtz machine is rather complex. The picture is of a later version of the original machine. A is a glass plate fixed by its edges. Plate B can be rotated at speed by turning the handle. Plate A has two holes or windows cut in it (P & P'). Sectors of varnished paper are stuck to this disk (above P and below P'). These pieces of paper are on the reverse side of the plate to the moving plate. The paper sectors have tongues or points which pass through the windows so that the tips nearly touch the moving plate. The disc must rotate in the opposite direction to the direction that the tongues point. On the front side of the moving disc, and opposite the leading edge of the paper sectors is an oblique conductor (D) fitted with metal combs or spikes. On the right and left are a pair of comb collectors mounted on glass rods. An adjustable spark gap is provided between the collectors.

To operate this instrument an initial charge must be given to one of the paper sectors, this was commonly done using an electrophorous. When the disc is rapidly rotated it is found that after a few turns more effort is required; at the same time brush discharges are seen from the points, and sparks discharge across the spark gap.