St. Tammany farmer. [volume] (Covington, La.) 1874-current, 1898-07-02
MARINE CHRONoMETERs.


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be seen in commission, at home or
abroad, she carries q minute instru-
ment, in comparison to her guns, her
most essential prerequisite Of safety.
Whether on q smooth sea. in q storm,
or in battle, the unerring device keeps
u sleepless vigilance over the position
of the vessel. The marine ecnronometer,
the production of many Ingenious men.
nm instrument of peculiar construction
and great workmanship, by which time
is measured with extremesaccuracy in
determining geographical longitudes,
is said to be the most valuable gift that
astronomical science has given to man.
kind in the progress Of navigation and
the increased security of life and prop
erty.
One of the most essential and prac-
tical features of the United States naval
observatory is to keep in hand, for the
use of the navy, thoroughly tested
chronometers, q work which requires
much care and attention six months in
tie-year. A temperature Room tx.nans
nected with the chronometer and time
service department of the observatory.
in which the testings are made, under
the influence of hygrometric condition
of the atmosphere. Comparisons are
made daily between II and IL 40 o'clock
q. m, with the meantime standard
clock, and the errors and rates are
worked up once a week. From these
mean rates calculations are made to the
nearest quarter of a second. The tenn
perature is closely observed each day
and recorded for the previous "a hours.
by chronometric thermometer, and
by self-registering maximum and mini
mum thermometers.
The room is heated by circulation Of
hot water, the fuel being gas, controlled
by electricity, and is cooled by an ice
refrigerator when temperature is re-
quired below that of the outside at
mosphere. For the six colder months
of the year the temperature room is
kept within a range of two degrees, and
often for 4s hours within one degree.
Chronometers received are placed on
trial for six months before purchased
by the government, and are tested at
three temperatures between As and &c
degrees Fahrenheit. Fifty-fve, 10 and
IS degrees are good temperatures to use,
as between these extremes are included
all degrees of heat and cold chronom-
eters will pass in ordinary navigation.
Chronometers are suspended in gimbals
on the ship, SO that whatever angle the
deck of the vessel may form with the
horizon the chronometer will always
maintain the same position.
Chronometers for service are selected
| with a view to the climate in which they
are to be used. Those for tropical nav.
| igation should have their point of com
putation highest, and those for cold
climates the reverse. When called fol
they are transported direct from the
observatory, through the equipment OF
the navy department, to their destina-
ton, while stHl running, with the great.
est care. The marine chronometer diff.
iers from the ordinary watch in the
mechanism of its escapement, which is
90 constructed that the balance is en-
firely free from the wheels during the
greater part of its vibration, and also
In bsing fitted with compensation adj
justment to prevent the expansion and
contraction Of the metal by action OF
heat and cold. They are delicate and
costly instruments. Yet every ship that
sails a United States naval pennan,
.nust carry from one to five chronome-
sers for the purpose of checking one an
other and to guard against the effect.
Of accidental arrangement in any single
one. They cost from s375 to $3.50 apiece
Since the war preparations have been In
progress there has been the greates'
run ON the observatory for them since
the late war.-Washington Post.