These bobbins can have let down into them an E-shaped piece of laminated iron, so as to complete the magnetic circuit, and thus raise the inductance of the bobbin.
"Hertzian Wave Wireless Telegraphy"
John Ambrose Fleming
If, therefore, electromotive impulses are applied to one end of the bobbin at regular intervals, electrical oscillations will be set up in it, and, as already explained, if these are timed at a certain rate, the bobbin will act like a closed organ-pipe to air impulses and oscillations of potential will be accumulated at the opposite end, which have much greater amplitude than the impressed oscillations at the end at which they are applied.
"Hertzian Wave Wireless Telegraphy"
John Ambrose Fleming
The cardboard box contained a bobbin, to which a second string was tied, and concealed in the same manner as the first.
"The Manor House School"
Angela Brazil