LEVELLING-STAVES, instruments used in levelling, serving to support the marks to be observed, and at the same time to measure the heights of those marks from the ground. They usually consist of mahogany staves ten feet long, each being in two parts, which slide in upon
one another to about 5 feet, for the more convenient carriage. They are divided into small equal parts, and numbered at every tenth division by 10, 20, 30, &c. as in figure 6; and on one side the feet and inches, or tenths, are also sometimes marked. These staves are likewise frequently called levelling poles, station-poles, or station-staves.
A vane A slides up and down each of these staves, and by brass springs will stand at any part. These vanes are about ten inches long and four inches broad; and are painted with stripes of white and black alternately. They have each a brass wire across a square hole in the centre, which serves to point out the height correctly, by coinciding with the horizontal wire of the telescope of the level.