drosometer

A drosometer (from Classical Greek , drosos, dew + , metron, measure) is an apparatus for measuring the quantity of dew formed in a unit of time per unit area of surface.

==Description== The surface may be either a horizontal metal plate or a leaf hanging naturally, or a bit of wool or cotton representing a large surface of fine fibres. The unit of time is usually one hour, and the measurement is made in the early morning, before the rising sun evaporates the dew. When the apparatus is made self-registering, the surface, with its accumulating dew, hangs at one end of a delicate balance, or from a delicate spiral metallic spring, and by its gradual sinking moves the index that makes the record on a moving sheet of paper.