w a r m , dry storage areas and by the use of desic-
2-34. Operation in Dusty or Sandy Areas
cants. Dry the instrument thoroughly after use and
S p e c i a l care must be taken of an instrument being
wipe the metal parts with a soft cloth lightly
used in areas where dust and sand occur. Both dust
moistened in watch oil. DO not get any of the oil on
and sand are highly abrasive. If they are allowed to
t h e lens, prism, or level vial surfaces.
remain
on
threaded
or
sliding
surfaces,
moving
p a r t s of the theodolite will soon bind, and the in-
2-36. Operation in Salt Water Areas
s t r u m e n t will become inaccurate or inoperable. The
Salt air is highly corrosive to many metals, par-
theodolite should be brushed frequently and
ticularly brass from which many theodolite parts
c a r e f u l l y wiped clean. B e extremely careful not to
a r e made. Salt, combined with brass, may produce
scratch lens and prism surfaces during cleaning
a green deposit (verdigris) which must be guarded
operations. Always protect the instrument from
against and removed as soon as it is noticed. Wipe
b l o w i n g dust and sand. Hood it when not in use.
the instrument frequently with a soft cloth
moistened in fresh water, and dry thoroughly.
2-35. Operation under Rainy or Humid Con-
D a i l y , after cleaning, rub the metal parts with a
ditions
cloth lightly moistened with watch oil. If the
In humid areas,
a slight lowering of the tem-
theodolite is exposed to direct salt spray it should be
will cause condensation of moisture
perature
b e cleaned thoroughly, and should be returned to
a n d fogging of lenses and prisms. Try to keep the
an instrument shop for overhauling and cleaning as
theodolite warmer than the surrounding air. In-
soon as conveniently possible. Cleaning intervals
ternal fogging can usually be removed by taking the
should be shortened
considerably
for
the
theodolite into a warm, dry place. Corrosion, due to
t h e o d o l i t e s when subjected to salt air exposure.
high humidity, can be partially eliminated by using
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