Hourglass

A device for timekeeping, with two glass bulbs connected by an extremely thin tube. One bulb is filled with grains of fine sand. When the Hourglass is turned upside down, the sands slowly fall through the tube into the other bulb, allowing a steady flow that makes it possible to predict the passage of time. The hourglass is most often secured by a wood or metal stand built around it, binding both ends to a flat surface.