Daily Republican., 1884-08-28
THE CAUSE or Many wnEox..

Asofbipy VI thc ouiOu HttaIn-
ship Wyoming, was stand ing In his
cabin door reading an evening paper
when tribune reporter came up the
thatchway and stumbled over q pile OF
rope to dig his fingers into some fresh
paint.
| I'm going to the theatre" the cap.
tain said but not for twenty minutes
yet. Sad story about the Amsterdam. u
| Yes. How is IL that Captain Lucas
was thirty Aye miles out ia his reckon.
imagine. You see the Gulf stream cuts
| across the Atlantic before IL gets to
Newfoundland, leaving a gap as il
were, between it aud land. Tn Is gap IL
filled up By the Arctic current that
flo Wa down the coast in the opposi to
direction. The conflict Of these cur
rents at times is aggrava,ing, aud their
influence just at that point makes Sable
| Island dangerous place. There have
been 10 many ships lost there that we
always give it "a good berth, and espe-
cially in heavy weather"
Could not the compass have thrown
Captain Lucas out?'
That Is hardly probable. / never
knew of there being any unusual de-
Walton Of the compass in passing Sable
Island, and to got thirty.five miles out
OF his course in thirty three hours in
creases my belief that it was the cur.
rent that kept beating him off till he
struck"
The deviation of the compass is the
problem that continues to vex the sea-
man, and with every loss OF a vessel
cnriosity concerning this matter IL
aroused. Oniy those connected with
a ms HUI 70, ...,A x~,tt
there Is no deviation on wooden YES
sci unless she be loaded with cargo of
iron OF steel. Captains of tie large
ocean steamships are required in Eng
land to sign declaration that they
both understand the deviation and can
apply their knowledge. A well.known
hip-instrumept maker in this CITY,
speaking on this subject, said:
II have seen IA points deviation in the
compass Of an iron steamship, that is to
say, the needle lacked only two points
of being reversed. A popular vessel
left this port one Tuesday morning and
steamed through mist and fog for AZ
hours before the captain could take an
observation. When he did so, he found
himself 152 miles out Of his course
Didn't understand deviation, or there
were some unusual magnetic influences
which deceived him. Deviation of the
compass is caused by polarity OF iron
and steel used in the construction of the
vessel. 1t begins with the laying of the
keel and clings to the vessel ever after
ward.
The first thorough practical expert.
ments on this subject were made by
Frederick j. Evans, superintendent of
the compass department of the British
Navy, upon the Great Eastern, built in
1857. She lay, during construction,
with her head s. go 80 f , and after
launching her position was changed
100 from her original direction, placing
Der head $3.50 Z. superintendent Evans
drew the following conclusions from
his experiments and observations that
prior to a newly built iron ship being
sent to sea, her head, while being
equipped, should be secured In an op.
posite direction TO that In which
she was built The plan was adopted
by all the iron steamship builders Of
since. Go to the shipya ards there and you
will see the bows OF the new vessels ali
pointing north.
" But why is this ?"
because the magnetic lines OF force in,
the earth run north aud south, and
thus induce positive and negative poles
at the bow and stern. In the case of
an iron vessel built in England, head
south, the north end Of the needle is
drawn to the bow,or the bow Is positive.
The steam machinery has the same eff
feet. When an iron vessel Is built 80 A.
to head north, the north end of the
needle Is drawn to the stern, or the bow
is negative. 1t may be taken as rale
that those vessels with the bow positive
have, taking size and other conditions
of compass positive into consideration,
large compass deviations."
But why is the ship reversed after
she il built 2"
In order that antagonistic lines of
force may counteract the influ ence OF
the magnetism already inclined by the
first position. You rub your hand up a
cats back and ruflle the hair. You rub
1t the other way and smooth 1t down"
Do physical forces affect the mag
netism of the iron ?''
think the driving and hammer
ing Of red. hot rivets has great deal to
do with 1t. Anyway, know that If a
vessel has to be hauled on the docks for
repairs her compass deviation Is consid-
erably changed by the hammering."
Where is the proper position for q
ships compass ?"
That can only be found by practi-
cal experiment, iO,it is different in all
vessels. The position OF the compass
with reference TO the machinery in an
iron vessel has an important bearing
practically and theoretically, for lift is
placed in proximity to the funnel,
which may be considered as the zero or
measuring point for the machinery in
general, the inductive magnetism of
the machinery is added to the perma-
nent magnetism of the hull. Large
steamships carry six or more com
passes, distributed from stem to stern,
and generally there is one at the mast
head. There is what is called neutral
point in every ship-a point at which
there Ia the least possible deviation of
the compass-and it sometimes requires
two or three years Of shaking down of
the magnetic lines by the vibrations of
the machinery to fully and accurately
determine this point. The. compass
situated at that point Is called the
standard compass and becomes the
one by which the vessel IL navigatsd.
In the Louisiana, when she was shaken
down, 1t was discovered that her neu-
trail point was exactly over a hatch. 1
believe she met with trouble ON her
first trip"
What are the different kinds of de-
viation?"
The first and mostimportant il that
caused by the magnetism of the hull
and machinery. Then there is heeling
deviation, caused by the rolling of the
ship. The compass, swinging always
in a horizontal plane, when the vessel
heels it is brought fraction nearer the
higher side, which OF course exerts an