An Earth Inductor (Delzenne's Circle) by Elliott Brothers of London. Circa 1910.
The rotating circle is mounted with a brass backed mirror.
The right hand side of the frame has a gilt brass circle divided by an 180 degree scale, subdivided by 90 degrees from the horizontal.
The base has an inset ivorine label: THE ELECTRICAL STANDARDIZING TESTING AND TRAINING INSTITUTION LONDON.
Height: 51 cm.
Width: 45.5 cm.
Depth: 39 cm.
Designed by Charles Edouard Joseph Delzenne in the 1840s, the circle is used to measure the magnitude and direction of the earth’s magnetic field.