prism to swing freely into a position so that a horizontal line of sight is achieved. This horizontal line of
sight is maintained even when the telescope is unlevel or the instrument is disturbed because the prism
swings freely with gravity.
Figure 5-3. The dumpy level
Figure 5-4. The automatic level
(3) Hand Levels. The hand level, like all surveying levels, is an instrument that combines a
level vial and a sighting device (see Figure 5-5, page 5-6). It is a very simplistic device that is used for
taping and for rough determinations of elevations. The basic principle is that if the bubble is centered
while sighting through the tube, the line of sight is horizontal.