Dip Circle
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Dip circles (also known as ''dip needles or inclination compasses'') are used to measure the angle between the
horizon The horizon is the apparent curve that separates the surface of a celestial body from its sky when viewed from the perspective of an observer on or near the surface of the relevant body. This curve divides all viewing directions based on whethe ...
and the
Earth's magnetic field Earth's magnetic field, also known as the geomagnetic field, is the magnetic field that extends from structure of Earth, Earth's interior out into space, where it interacts with the solar wind, a stream of charged particles emanating from ...
(the dip angle). They were used in
surveying Surveying or land surveying is the technique, profession, art, and science of determining the land, terrestrial Plane (mathematics), two-dimensional or Three-dimensional space#In Euclidean geometry, three-dimensional positions of Point (geom ...
,
mining Mining is the Resource extraction, extraction of valuable geological materials and minerals from the surface of the Earth. Mining is required to obtain most materials that cannot be grown through agriculture, agricultural processes, or feasib ...
and
prospecting Prospecting is the first stage of the geological analysis (followed by Mining engineering#Pre-mining, exploration) of a territory. It is the search for minerals, fossils, precious metals, or mineral specimens. It is also known as fossicking. ...
as well as for the demonstration and study of
magnetism Magnetism is the class of physical attributes that occur through a magnetic field, which allows objects to attract or repel each other. Because both electric currents and magnetic moments of elementary particles give rise to a magnetic field, ...
.


Uses

Dip circles typically consist of a magnetised needle swinging freely vertically within a case. The needle will dip to follow the lines of
Earth's magnetic field Earth's magnetic field, also known as the geomagnetic field, is the magnetic field that extends from structure of Earth, Earth's interior out into space, where it interacts with the solar wind, a stream of charged particles emanating from ...
. As the dip angle varies by latitude (0° at the equator and 90° at the poles), a dip circle can be used to determine latitude when compared against a chart of dip angles. As the variation is not constant, this is not an exact measurement. Dip circles can also be used in locate ore, and they were the first scientific instrument to be used for this purpose. They were used to find magnetite in Sweden in the Middle Ages, and have been used extensively in iron mining. They were still in use in the 1930s, but modern
magnetometers A magnetometer is a device that measures magnetic field or magnetic dipole moment. Different types of magnetometers measure the direction, strength, or relative change of a magnetic field at a particular location. A compass is one such device, o ...
are more sensitive and have taken their place in ore prospecting. When prospecting with a dip circle, miners would map the prospective site using the needle and a compass, noting disturbances. Dip would occur over ore bodies, with a greater inclination at the south magnetic pole of the deposit.


History

Georg Hartmann first discovered dip angle in 1544, when he noticed the needle on a
compass A compass is a device that shows the cardinal directions used for navigation and geographic orientation. It commonly consists of a magnetized needle or other element, such as a compass card or compass rose, which can pivot to align itself with No ...
dipped towards the north
hemisphere Hemisphere may refer to: In geometry * Hemisphere (geometry), a half of a sphere As half of Earth or any spherical astronomical object * A hemisphere of Earth ** Northern Hemisphere ** Southern Hemisphere ** Eastern Hemisphere ** Western Hemi ...
. Rather than explore this phenomenon, Hartmann sought ways to eliminate it. However, around 1576 Robert Norman investigated the dip angle further and in 1581 described in print a device to measure this phenomenon.Norman, Robert; Borough, William. (1581). ''The newe attractiue, containyng a short discourse of the magnes or lodestone, and amongst other his vertues, of a newe discouered secret and subtill propertie, concernyng the declinyng of the needle, touched therewith vnder the plaine of the horizon. Now first founde out by Robert Norman. Herevnto are annexed certaine necessarie rules for the art of nauigation, by the same R. N.'' London: Ihon Kyngston for Richard Ballard
WorldCat record.
OCLC: 181712334.
Early dip circles were not accurate and gave poor results. Over the next 300 years many improvements were made, including reducing the
friction Friction is the force resisting the relative motion of solid surfaces, fluid layers, and material elements sliding against each other. Types of friction include dry, fluid, lubricated, skin, and internal -- an incomplete list. The study of t ...
between the needle and its pivot and encasing the circle in glass. Between the late 18th century and late 19th century the design approached its peak. Robert Were Fox FRS developed in the 1830s the first dip circle that could be used on board a moving ship, making the dip circle a practical aid for polar navigation. Another important improvement to the instrument was developed in the 1830s by the
Dublin Dublin is the capital and largest city of Republic of Ireland, Ireland. Situated on Dublin Bay at the mouth of the River Liffey, it is in the Provinces of Ireland, province of Leinster, and is bordered on the south by the Dublin Mountains, pa ...
physicist Humphrey Lloyd, who devised a way of attaching a magnetic needle at right-angles to the dip needle in order to measure the intensity of
force In physics, a force is an influence that can cause an Physical object, object to change its velocity unless counterbalanced by other forces. In mechanics, force makes ideas like 'pushing' or 'pulling' mathematically precise. Because the Magnitu ...
(by seeing the extent to which the right-angle needle deflected the dip-needle). By
World War I World War I or the First World War (28 July 1914 – 11 November 1918), also known as the Great War, was a World war, global conflict between two coalitions: the Allies of World War I, Allies (or Entente) and the Central Powers. Fighting to ...
the most advanced dip circles were being made. With the development of electronic systems, dip circles became obsolete.


See also

*
Magnetic dip Magnetic dip, dip angle, or magnetic inclination is the angle made with the horizontal by Earth's magnetic field, Earth's magnetic field lines. This angle varies at different points on Earth's surface. Positive values of inclination indicate t ...


References


External links


The dip needle
{{Webarchive, url=https://web.archive.org/web/20080127021924/http://physics.kenyon.edu/EarlyApparatus/Electricity/Dip_Needle/Dip_Needle.html , date=2008-01-27 Geomagnetism Navigational equipment zh:磁偏角