The field-line was built of seven twisted, rubber-coated wires which were hastily strung on trees or fences.
|line of force |
A line used to indicate the direction of a field, especially an electric or magnetic field, at various points in space. The tangent of a line of force at each point indicates the orientation of the field at that point. Arrows are usually used to indicate the direction of the force. See Note at magnetism.