The sight drops through a socket in a pivoted bracket which is provided From Treatise on Service Ordnance.
These coils are placed with their axes at right angles to one another, and at the point where the axes intersect a small pivoted needle of soft iron is placed, carrying a longer index needle moving over a scale.
With that, he pivoted on one heal and walked away.
In the other gap are pivoted two coils wound on an iron core and connected at nearly a right angle to each other.
The small pivoted iron needle ns placed in their common field therefore takes up a certain position, dependent on the relative value of these fields.