Kew pattern dip circle by Barrow with Creak total force attachment.

Made:
1848-1864 in London and England
maker:
Henry Barrow
designer:
Ettrick William Creak

Kew pattern dip circle by Barrow with Creak's Total Force attachment

Dip circles are used to measure the angle between the direction of the earth's magnetic field and the horizontal at any point on the earth's surface. A magnetic needle on a horizontal axis lies horizontally only at the magnetic equator, where the attraction to the poles is equally balanced. Elsewhere, the needle will dip to an angle which depends on the distance from the nearest magnetic pole. At the north and south magnetic poles the needle dips vertically. Dip circles were frequently taken on scientific expeditions from the 18th century onwards. This example has total force attachment designed by Creak to clamp a second needle outside the box for measuring magnetic intensity or strength.

Details

Category:
Terrestrial Magnetism
Object Number:
1980-1879
Measurements:
overall: 270 mm x 210 mm x 200 mm,
type:
dip circles
credit:
Meteorological Office