STANDARD - Survey Instrument Antique Center!

14
Additional Suggestions Pertaining to the Care and Pro*
tection of Instruments in Field Use.
In field use, an instrument has to be necessarily exposed to the heat of the sun,
and to the action of dust and water; all of these, however, singly or combined, ha/e
a tendency to affect its accuracy and endurance. While our instruments in particular
have been designed to guard against injuries resulting from exposure of this kind,
yet glaring abuses, such as to allow it to stand for hours in the hot sun, etc., without a
covering or shelter of some sort, may often lead to a permanent injury to its most vital
parts. To preserve the finer qualities of an instrument, viz., the telescope slide, the
lenses, the edge of the graduation and verniers, the centers, etc., any undue unequal
expansion of the different parts should be prevented. A bag thrown over the instrument
when not in use, or any shelter that can be had, is to be recommended. Wi ile
in use, an umbrella or screen held over it will insure greater permanency of its adjustments,
and the results obtained will be more accurate and uniform than when
carelessly exposed.
To protect an instrument from the effects of salt water, when used near the sea
coast, a fine film of watch-oil rubbed over the exposed parts will often prevent
the appearance of oxyd. To remove such oxyd-spots as well as possible, apply
some watch-oil and allow it to remain for a few hours, then rub dry with a soft piece
of linen. To preserve the outer appearance of an instrument, never use anything for
dusting except a fine camel's hair brush. To remove water and dust spots, first use
the camel's hair brush, and then rub off with fine watch-oil, and wipe dry to let the
;
oil remain would tend to accumulate dust on the instrument.
Lubricating, etc. An instrument used in a tropical or semi-tropical country,
or during the warm season in a northern latitude, requires more frequent cleaning,
and oiling than in the more temperate climes and seasons ; but so long as an instru.
ment works well and the centers revolve freely, it is best not to disturb it. However,
If necessary, proceed as described under "Care of Centers, etc." A few additional
remarks we give here : Should the centers or the object-slide commence to fret, they
should be examined as soon as possible. Once commencing to
fret, it grows worse rapidly
and oftentimes is then beyond repairing. Never use emery or emery-paper on them, as
this will cause everlasting trouble afterwards. After a thorough cleaning of the slide
and tube (taking care not to break the endeavor to smooth
cross-wires}, carefully
the injured parts with the back of a pen-knife, ana barely apply enough tallow to
grease the surface of the injured part. If this does not remove the trouble, a little
scraping of the roughened parts on the slide, and, if accessible, on the inside of the
tube, may become necessary, and apply a mere trifle of finely-powdered pumice
stone moistened with oil. Replace the slide and grind a little by moving it in and
out; clean thoroughly, and with a piece of charcoal moistened with oil smooth the parts
thus ground on the slide. This process of grinding is a most precarious operation,
and generally requires the hand of a skillful workman; it should be resorted to only
in case of utmost necessity. Whenever permissible, recourse should be had to a
maker. These remarks apply equally to the centers.
The centers of a transit should always be lubricated with fine watch-oil only, and
after a careful cleaning; never apply fresh oil before thoroughly wiping off old
grit and oil. Rendered marrow is a most excellent lubricant for instruments made o\
brass and the many kindred alloys of copper and tin. In the varying climes of oui
northern latitudes this lubricant becomes rigid in cold weather, and an instrument so
treated will often become unmanageable in the field. Its application, particularly
to the centers of a transit, is therefore restricted to the wanner zones. The use of
watch-oil for the finer parts of an instrument, involving freedom of motion, is
imperative in our latitudes.
Many parts of an instrument, especially those whose metal compositions are
closely related to each other, may sometimes cause trouble if simply oiled. If they
begin to fret and grind, but are otherwise free from grit, etc., the judicious application
of a little marrow may prove very beneficial, but it should be cleaned off again as
much as possible. The rack and pinion motion and the telescope clamp should
always be greased with marrow, but the clamp, tangent and leveling screws, should
receive as little of it as possible in the Northern States.
Vaseline, not having as great a tendency to rigidity under similar circumstances,
may prove an excellent substitute for marrow, and may often be applied to leveloenters,
where watch-oil would not give the necessary rigidity in the use of the more