{{Refimprove, date=November 2011 Dip circles (also ''dip needles'') are used to measure the angle between the

horizon The horizon is the apparent line 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 line divides all viewing directions based on whether ...

and the

Earth's magnetic field Earth's magnetic field, also known as the geomagnetic field, is the magnetic field that extends from Earth's interior out into space, where it interacts with the solar wind, a stream of charged particles emanating from the Sun. The magneti ...

(the dip angle). They were used in

surveying Surveying or land surveying is the technique, profession, art, and science of determining the terrestrial two-dimensional or three-dimensional positions of points and the distances and angles between them. A land surveying professional is ...

mining Mining is the extraction of valuable minerals or other geological materials from the Earth, usually from an ore body, lode, vein, seam, reef, or placer deposit. The exploitation of these deposits for raw material is based on the economic ...

and

prospecting Prospecting is the first stage of the geological analysis (followed by exploration) of a territory. It is the search for minerals, fossils, precious metals, or mineral specimens. It is also known as fossicking. Traditionally prospecting rel ...

as well as for the demonstration and study of

magnetism Magnetism is the class of physical attributes that are mediated by a magnetic field, which refers to the capacity to induce attractive and repulsive phenomena in other entities. Electric currents and the magnetic moments of elementary particle ...

. 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 ...

dipped towards the north

hemisphere Hemisphere refers to: * A half of a sphere As half of the Earth * A hemisphere of Earth ** Northern Hemisphere ** Southern Hemisphere ** Eastern Hemisphere ** Western Hemisphere ** Land and water hemispheres * A half of the (geocentric) celesti ...

. Rather than explore this phenomenon, Hartmann sought ways to eliminate it. However,

Robert Norman Robert Norman was a 16th-century- English mariner, compass builder, and hydrographer who discovered magnetic inclination, the deviation of the Earth's magnetic field from the vertical. Work Robert Norman is noted for ''The Newe Attractiv ...

around 1576 investigated 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 (motion), sliding against each other. There are several types of friction: *Dry friction is a force that opposes the relative la ...

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. Improvements which made the dip circle a practical aid for polar navigation were made by Robert Were Fox FRS, who developed in the 1830s the first dip circle that could be used on board a moving ship. Another important improvement to the instrument was developed in the 1830s by the

Dublin Dublin (; , or ) is the capital and largest city of Ireland. On a bay at the mouth of the River Liffey, it is in the province of Leinster, bordered on the south by the Dublin Mountains, a part of the Wicklow Mountains range. At the 2016 ...

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 change the motion of an object. A force can cause an object with mass to change its velocity (e.g. moving from a state of rest), i.e., to accelerate. Force can also be described intuitively as a ...

(by seeing the extent to which the right-angle needle deflected the dip-needle). By

World War I World War I (28 July 1914 11 November 1918), often abbreviated as WWI, was List of wars and anthropogenic disasters by death toll, one of the deadliest global conflicts in history. Belligerents included much of Europe, the Russian Empire, ...

the most advanced dip circles were being made. With the development of electronic systems dip circles became obsolete.

References

External links

The dip needle
Geomagnetism Navigational equipment zh:磁偏角

See also

References

External links