This is a recording psychrometer made by Jules Richard of Paris, it records the wet bulb and dry bulb temperature.  It has two bi-metal temperature sensors, the lower of which would be covered with a wetted cloth wick.  I'm not sure of its age, I suspect the 1930s. ​ I don't have the right temperature chart for it, it came with a relative humidity chart. If anyone has the correct chart please contact me.

​Go to Home Page.