The weekly Thibodaux sentinel and journal of the 8th Senatorial District. [volume] (Thibodaux, Lna. [i.e. La.]) 1875-1898, 1895-09-28
n MARINE COMPASS.

The Reason Why 1t Varies During Thun-
de@storIns and IN FoSs.
Apparently tie compass is L simple
instrument, q needle Of steel suspended
on ii pivot. the needle ulaglIetized either
byaElaGaet crl4ttezF. 50 that its points
are attracted nafth and south. What at
tracts and determines the position OF the
needle, whether 1t be currents Of cleo
tricity from north aud south passing
round the earth, OF, us vulgar sea Euowl-
edge has it. tie north pole, scientists
yet are in dosot. Of course every school
child knows that tie cClap2Ss is useless
as it approaches the north pole, the dip
Is so greet. although Instruments have
been nlada for tie Use Of vessels destined
for vo"2.es Of discovery. But this COM
nicrcs;.! 80 requires that all things
should re practical.
- TIE r!st:esn steel ard iron vessels
have cilae it IL necessity that there
should he .so;..e test fer t~hecompasS. Ii
fact. upon I'll Ira1 vessel tie compass is
useless ul!cSs tire Iced attraction If the
iron II the vessel can be centralized or
cGUiiter"cted This is done bv placing
small magnets III the p]ilothousc, which
can Only Ee done correctly by swinging
the vessel Exactly corth and south, then
by Sna@li magnets overcome the local at
traction, until the needle Of the mp
Is correct. There the danger begins. In
a month CT 50 the magnets lose part OF
their power; the iron Of the vessel alb
serbs It. The consequence is that the
vessel is II danger. Another thing, a
dense fog VIII neutralize on rather
weaken the magnetic power Of tie nee
die OF the compass, SO if there be the
least friction III the pivot the needle
SWINGS upoa, the compass is faulty and
the vessel is ashore. 1t Is a singular.
unexplained fact that coming TO and
passing the straits of Mackinac the local
attraction Of the shore is such that the
compass cannot be depended upon for
safe navigation. Many a vessel might be
saved, II IL 4 foe, by placing a compass
at the masthead and ''con'' the corrsa
by the call Of the man placed there to
observe 1T. II the ship isnear the shore.
say within u mile, the needle of tie
l' - ~ 1tlIttlth 6IlI-kDOrTn CT |
a point; the shore attracts it. A thun-
derstorm VIII change the poles Of the
compass at times, and summer light
nlng or any electric disturbance will
make a difference. In the fall j bril-
liant dlspla.- OF the northern lights IAN
boreabs) will play hob with your
compass. Sometimes the point, cspe-
clally IN the spirit compass, may become
very blunt cit is made of brass) and the
cord will hang. 1t is Il good
plan Tor every captain navigating the
lakes to test his compass. Take a piece
of steel or a long knife, chiscl or file:
apply 1t opposite the north pole of the
compass and gradually try to pull the
either way. If after releasing the
needle from the influence of the article
1sed 1t swings back and points to the
forth, the compass is correct-that is. if
he needle is placed right on the card.
But when within a mile or more of
he shore the lead is the instrument to
depended upon. venture to say that
very shipinaster will tell you that at
INES the compass has its moods. But
when we take into consideration the
many surrounding influences that in our
modern iron ship bear upon the eficien-
y OF the compass we wonder there are
lot more errors.-E. r. P. Shurly in
chicago Inter Ocean.