This loss is proportional to the length of the wire.
As the source of monochromatic light a bright sodium burner is used, and the rotation, which is exactly proportional to H, is measured by an accurate polarimeter.
The proportional rent is from I% to 5:/.
So if a battle today were similarly costly, the proportional number of casualties would be 230,000.
To take a reading the torsion-head is turned until an aluminium pointer attached to the coil is brought to the zero position on a small scale; the strength of the field is then proportional to the angular torsion.