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Feature Article: The Compass
The ancients recognized the pole star as being a constant
reference for determining direction. The Norsemen in the 11th
century used a needle of magnetic iron inserted in a straw and
floated on water to point to the pole star. Petrus Peregrinus
de Maricourt invented the pivoted floating compass with lubberline
and sight for bearing. The modern compass is little more than
one hundred years old.The compass card, due to wind rose origins
is older than the magnetic needle. Names of the cardinal compass
points are from the ancient terms for wind direction.
Variation was understood by 1800 as a problem. Edmond Halley
at end of 17th century mapped lines of variation and drew isogonic
lines (lines of variation) on his maps. George Graham showed
that variation was subject to diurnal (seasonal) changes with
variation being less in winter.
John Smith wrote about deviation in 1627 by John Smith. He
saw it as a problem encountered through use of metal nails in
his compass box. Captain. Mathew Flinders in 1801-2 found way
to correct by use of "Flinder's Bars as did Lord Kelvin
through use of Kelvin spheres. Placement of soft iron spheres
at sides of compass could be used to correct deviation.
The magnetic compass depends on the horizontal component of
the earths' magnetic field. The directional properties of the
lodestone were known to early man. The term magnet comes from
the name of a region in southern Europe which was a major source
for lodestone. The development of the magnet grew form a floating
needle in a straw, to the needle in a cork, a pivoted needle,
the pivoted card, the pivoted card in a bowl, to the use of gimbals,
and finally the liquid chamber with a pivoted card.
Compasses were in use as early as the 12th century but their
operation was imperfect and not fully understood. About 18090
Mathew Flinders discovered a solution to the problem of local
attraction. Deviation as used in aviation. Flinder's Bars, large
masses of unmagnetized iron, are universally used on ships. In
1838 Sir G. B. Airy used magnets and iron to neutralize effects
of iron ships.
The initial dry card compass was developed by Lord Kelvin
who determined that a cards steadiness depended on the natural
period of vibration of card and needle. A light card with a heavy
rim was suspended by a pyramid of threads to a central pivot
point. This produced a steady card. The use of a liquid float
chamber with the buoyancy of the magnet and card only slightly
less than weight to reduce fraction. The liquid has a dampening
effect as well.
The development of the gyro compass began in 1851 when Leon
Foucault used suspended cannon shot on a long wire pendulum to
show the rotation of the earth as well as the inertia of the
free swinging ball. By 1852 he had created the gyroscope but
had trouble applying continuous power. By 1900 the electric gyroscope
was invented by both Elmer A. Sperry and Anschutz-Kampfe of Germany.
By 1911 gyro compasses were in use soon to be followed by gyro
repeaters (selysn(sp) units) flux-gate compasses and gyro pilots..
Last Modified October 17, ©2025 TAGE.COM
