Fox dip and intensity apparatus by George
circa 1840
Dip circle by Nairne and Blunt
1775
Kew pattern dip circle by Henry Barrow
1851-1864
Dip circle by Dover
1891
Kew pattern dip circle by Dover, c.1870
1870
Dip circle
1904
circa 1840
1775
1851-1864
1891
1870
1904