The next class of wave or oscillation detector is the magnetic detector depending upon the power of electric oscillations to affect the magnetic state of iron.
During a gale a slight oscillation is noticeable on the bridge itself and from the shore.
As in the rest of the Mediterranean, tides are scarcely observable; but at several points on the west and south coasts a curious oscillation in the level of the waters, known to the natives as the marrobbio (or marobia), is sometimes noticed, and is said to be always preceded by certain atmospheric signs.
It is the oscillation which Mill manifests between the conception of his formula as it is actually applicable to concrete problems in practice, and the conception of it as an expression of a theoretical limit to practical procedure.
To find the forced oscillation due to a periodic force we have tl+k+ux-f cos(rjt+e).
