Surveying - Carpenter's and Builder's Math, Plans, and Specifications - page 204

2. Revolve the instrument horizontally by a one-half revolution.
3. If the bubble moves, correct it halfway by means of the support
screws (at the foot of the Ys). If the rings become worn and
unequal, use the two-peg method of the dumpy level.

Dumpy Level Adjustment
Figure 6-3 shows the dumpy level (so-called because of its com-
pactness). It is used mostly in England, although it is used to
some extent in the United States because of the better stability
of its adjustments over the wye level. The dumpy level differs
from the wye level mainly in that the telescope of the dumpy
level is permanently attached to the supports or uprights, but
these uprights are adjustable. The two-peg adjustment method is as
follows:
1.

Drive two stakes (pegs) several hundred feet apart.

2.

Set the instrument approximately halfway between them.

3.

Level up and sight the rod that is held in succession on each
stake. The difference in the readings is the true difference of the

Figure 6-3 A dumpy level.