1, < /span>< span style="font-size: 16px;">hourglass maximum time is unknown , but the average hourglass has a nominal working time of 1 minute.

2. The hourglass is also called the sand clock, which is a device for measuring time. The western hourglass consists of two glass spheres and a narrow connecting pipe. Time is measured by the time it takes for a glass ball filled with sand to flow from above through a narrow tube into the bottom glass ball. Once all the sand has flowed to the bottom glass ball, the hourglass can be turned upside down to measure time.

most famous HourglassIt was created by Zhan Xiyuan in 1360 The "five-wheeled hourglass". The quicksand flows from the funnel-shaped sand pool to the sand bucket beside the primary wheel, drives the primary wheel, and then drives the mechanical gears at all levels to rotate. The last stage gear drives the middle wheel that rotates on the horizontal plane. There is a pointer on the axis of the middle wheel, and the pointer rotates on a scaled instrument disc to flash the time. This flashing method is almost the same as that of modern clocks. The surface structure is exactly the same. In addition, Zhan Xiyuan also wonderfully added a mechanical toggle device to the middle wheel to remind the two wooden figures standing on the five-wheeled hourglass when the drum was cut. Every hour or quarter, the two wooden figures would come out on their own, cutting drums to report the time. This Hourglassout of aid The astronomical instrument has independently become a mechanical clock structure.
Hourglass is more accurate than stencil due to waterless wire system