hourglass
two bulb-shaped glass or plastic chambers connected by a narrow waist one chamber on the top and one on the bottom the chambers are filled with sand or other material a narrow opening at the top and bottom of each chamber a frame or stopper at the top to control the sand's flow markings on the outside to measure time
hourglass which has two bulb-shaped glass or plastic chambers connected by a narrow waist hourglass which has one chamber on the top and one on the bottom hourglass which has the chambers are filled with sand or other material hourglass which is a narrow opening at the top and bottom of each chamber hourglass which is a frame or stopper at the top to control the sand's flow hourglass which has markings on the outside to measure time