This large rheostat (potentiometer) was made between 1900-1920 by the noted French firm of Clemancon and would have been used in a Cinema or Theatre to dim their many lights down. Clemancon began supplying gas lighting fixtures for theatres and travelling stages from around the 1840s but during the 1880s was quick to recognise the shift to electrification. As well as theatres the firm also helped electrify some of the French metro stations and were one of the first firms in France to help light the new Cinemas that emerged in the early part of the century.
As rheostats go this is a particularly nice example and a great imposing display piece for any collector. Although smaller examples would usually be mounted flat to the wall or in boxes, larger industrial pieces such as this would be mounted spaced apart in banks vertically from the wall to allow the mass of heat that was always created to dissipate better. While most rheostats used a long coil of wire wrapped over a metal ring or core to work, this one is unusual in that it employed meshed wire of varying grades that was laid ontop of each other and individually secured to a black marble (or slate?) insulating ring. This arrangement probably helped the cooling process and increased the accuracy of the device.
It is offered in original yet untested condition and apart from the alloy brush connection arm that feels loose (or possibly damaged?) appears all good and rotates smoothly. It has a 47.5cm diameter ring and being cast iron and black marble is extremely heavy as already mentioned. For this reason international shipping is not included in the price of the item so please get in touch for a quote.
