Thermograph

Thermograph records air temperature continuously on a chart. Two metals of different alloys are welded together in a coil form. The different in the coefficient of expansions will uncoil or tighten the coil when subjected to temperature changes. The movement is then magnified by a lever system to a horizontal pen which is attached to the coil with a pen nib slightly rested on a chart. The scaled chart is wrapped around a drum. A clock is build inside the drum.