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Hourglass / Sand Clock

An hourglass, also known as a sand clock or sand timer, is a device used to measure time. It consists of two glass bulbs connected vertically by a narrow neck that allows a regulated trickle of sand from the upper bulb to the lower one. The sand takes a specific amount of time to flow from one bulb to the other, marking the passage of time. Hourglasses have been used historically as simple, reliable timekeeping devices. They have been replaced by more accurate timekeeping instruments like clocks and watches but are still used for decorative purposes.