Hydroscope vs. Hygroscope — What's the Difference?

The word hydroscope is used to mean any of several instruments related to water. One kind is an instrument for making observations below the surface of water, such as a long tube fitted with various lenses arranged so that objects lying at the bottom can be reflected upon a screen on the deck of the ship that carries it.

An instrument that indicates changes in atmospheric humidity.

An optical device used for viewing objects far below the surface of water.

An instrument that indicates changes in atmospheric humidity

A device for viewing objects below the surface of the water.

An instrument which shows whether there is more or less moisture in the atmosphere, without indicating its amount.

(historical) A kind of water clock consisting of a cylindrical graduated tube, from which the water escaped through a hole in the bottom.

Hygrometer that shows variations in the relative humidity of the atmosphere

An instrument designed to mark the presence of water, especially in air.

A kind of water clock, used anciently for measuring time, the water tricking from an orifice at the end of a graduated tube.