A highly important and unusual French scientific thermograph

A highly important and unusual French scientific thermograph, invented by M. Hervé Mangon and manufactured by A. Redier in 1877. The changes of temperature are derived from the difference in coefficient of expansion between an iron and a zinc rod of 1 meter and registered on a paper placed on a rotating cylinder. The accuracy of it’s measurement was revolutionary for the time. There were very few constructed, a similar one is currently exhibited in the ‘arts et métier’ museum in Paris, this is number two manufactured. Besides the complicated mechanism it’s a highly decorative object.
Description in the old French scientific journal ‘La Nature’ of the first semester of 1878, page 140 and 141.