The hourglass is sometimes referred to as a sand timers or a sandglass. Hourglass, an early device for measuring intervals of time. It is also known as a sand timers or a log glass when used in conjunction with the common log for ascertaining the speed of a ship. It consists of two pear-shaped bulbs of glass, united at their apexes and having a minute passage formed between them. A quantity of sand is enclosed in the bulbs, and the size of the passage is so proportioned that this media will completely run through from one bulb to another in the time it is desired to measure— an hour or a minute. Each hourglass contained different amounts of sand.