| 摘要 |
A plumb-line, for measuring water depth in a well or reservoir, is graduated in meters, centimetres and millimetres and has a weight at its end. After immersion to the bottom of the water and determination of the line length, the other end of the line is attached to a float, the base of which establishes the depth read-off line. Inversion of the plumb-line gives the water depth at the read-off line.
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