Hydrometer

[Sarah]

An instrument for determining the specific gravities ofliquids, and thence the strength spirituous liquors, salinesolutions, etc.

[Luis Fok]

A glass cylinder with a suction bulb on one end ,that is used to measure the salt level of a lobster tank.

[Luis Fok]

a piece of equipment used to measure the density (= amount of matter in a particular quantity) of liquids, especially a long glass tube, closed and with a weight at one end so that it floats vertically